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The Ocean School

Life Science - GOM Life Forms Through Time - Conservation, Pollution, and Exploitation

Concepts of Exploitation

By Susan Kynast

 

Life forms have to eat to live. Every predator species and every grazer that’s ever lived on this planet is so driven. Generally a balance exists between the organism which eats and the one which gets eaten. A predator which drives its prey to scarcity will be faced with starvation. Its numbers decline, the prey species recovers, and the cycle starts anew. A specialized predator walks a narrow line on the edge of extinction. Should its prey species not recover, it will also die. A predator which is more of a generalist can afford to drive certain species to extinction, and evolutionary history is full of cases where slower, easier to catch prey species went extinct and other, faster ones evolved. Eventually the ecosystem finds balance between many predator and prey adaptations – the predators might be superb hunters, but the prey will be superb at escape. This process is called co-evolution.

 

Humans are omnivores, are ‘opptunivores’. We can afford to drive almost any food source in our environment to extinction – there will always be something else to eat. From the moment we entered the evolutionary theater, we’ve destroyed many of our prey species. Not only do we kill to eat, we also kill to kill, the mark of a species which fears neither the energy used in the hunt nor the extinction of its prey. Furthermore, we no longer evolved, we learned, and we not only learned, we became able to communicate increasingly complex concepts. Our ability to hunt and kill no longer needed to be imprinted in the genes of our offspring – we could use language to convey it directly. Coevolution of our prey with us became impossible, as we improved our hunting methods over timespans as short as millennia, then centuries, decades, and finally years, while evolutionary adaptation takes thousands of years. There is little difference between the wooly mammoth we drove to extinction with fire and sticks, the fur seals which we clubbed into extinction after using sailing vessels to reach their breeding grounds, and the last of the groundfish which we will exterminate using 40-mile-long gillnets made out of indestructible plastic.

 

We now have the ability to kill every last animal of every species on this planet – but do we have the wisdom to choose not to? We need to eat to live, but what to eat is our choice. The earth – the land or the oceans – are not the unlimited ‘breadbasket’ we consider it to be. Instead they are a balanced system of predator and prey which developed over millions of years. If we remove some of the predators, there will be excess prey individuals for us to eat. If we however remove too many prey individuals, the predators might decrease in number until a new equilibrium with their food sources is reached, or the delicate system might not be able to return to a balance, and either predator or prey will go extinct. So what if we eat the excess, those who would die anyways? The salmon after spawning, the really old whales, the eels in the Sargasso sea? Then we move from the predator to the scavenger category, and enter a completely new field of competition. Anything that dies in the oceans slowly sinks into the abyss and sustains every lifeform from the surface down to the sea floor thousands of feet below. On the ocean floor energy is the limiting factor and population densities are low because there is simply not enough to eat. We do not even know what lives in the abyss of most of the world’s oceans, and yet we are probably driving whatever it is to extinction by reducing the biomass in the worlds oceans by so much that there simply aren’t enough dead animals left to sink.

There are 6 billion of us on this planet. We can all choose to live our life in the predator slot of the foodchain, or we can make responsible choices.

 

The Tragedy of the Commons

 

The tragedy of the commons owes its name – and concept – to the middle ages, where a certain patch of ground in every town was held in common. This meant that every individual had the right and opportunity to graze his lifestock on that particular pasture. The result however was a complete degradation of the ground to the extent where it became non-usable, even though every individual involved had a thorough understanding of the principles of animal husbandry, and number of animals that could be pastured on a field without destroying it, as demonstrated by the fact that their own fields were never overgrazed. So what happened? The problem was that if farmer A decided that the common was getting overgrazed and would remove some of his sheep, farmer B would profit and now put more of his sheep into the vacated space – and if he didn’t farmer C would. Conservation of the resource in other words would not pay of because you weren’t conserving it for yourself – you were merely helping somebody else profit. Centuries later, the same principle emerged in fisheries management (or non-management). There was no incentive for fisherman A to throw back the smaller fish because fisherman B would simply catch and sell them. There was no incentive for one ship to limit the number of hooks or miles of net, or trips made to conserve the resource if the next ship over simply made up for it simply by being there. There was no incentive for any one country to limit its number of ships or tons of catch when the ship from another country simply gobbled up what was left. Instead, fisheries became a race. If you didn’t get every last fish out there, somebody else would. Governments extended their territorial waters to keep out foreign ships but then subsidized their own increasingly large and advanced fleets to get every last fish presumably before it could get out of the territorial waters and get caught by someone else. The frenzy was only comparable to our ancestors putting every sheep they had onto the common on the first day of spring and watching them turn the grass into a puddle of mud.

 

I recently stopped at a gas station in the middle of the night somewhere on the coast of Maine. A commercial fisherman was also fueling up, and we got to talking. He worked on a commercial tuna boat, and had been all over the world fishing. I told him that I am a science educator and write about fishing. “This is how it is,” he told me. “You get to some new and beautiful place and the fish are large and beautiful. You start out with fishing real careful. You only take the really big ones and let all the little ones go, because they are beautiful, and well, we want them to be here forever. But then the guy next to you puts out his nets. And maybe he’s from another country where they don’t think that much about conservation, or maybe there are just too many boats and too few big fish, but pretty soon you see him hauling up the little ones and keeping those too. And you don’t like it, but the next time you are back all the big ones are gone, and then you take the little ones too, because if you don’t the next guy is, and you’ve got to make a living. And if there aren’t any more of any reasonable size and you don’t want to be part of wiping that whole population out you leave the fishing there to the other guys and you move on to some other place where nobody has been before and the fish are still big and beautiful. You know,” he said, “I love the fish, and I love the ocean, but out on the open sea there are no regulations, and what you don’t get, the next guy will. And so you have a helicopter on board, and all the electronics, and you find the fish if they are there. And then you let the little ones go, just because you want them to be there forever. But then the next guy shows up…”
That is the tragedy of the commons. You know, I really wanted to keep the grazing good. So I took my sheep off when it got ragged. But then my neighbor, he didn’t care, he put his on, and pretty soon it was all mud…

 

The tragedy of the commons got exasperated by the fact that technology advanced. Subsistence fishing is unlikely to significantly reduce population numbers. When fishing was done by handline from shore or from wooden boats, simply not enough fish could be taken to have an impact. Even fish traps near shore probably did not noticeably decrease the population. But then longer and better nets were invented, and suddenly a lot more fish were being caught. At that point economic factors became important, and new markets had to be developed for those fish. As always if you flood a market, prices drop, so you need to catch and sell more fish to make the same amount of money.

 

This is how the herring industry in Downeast Maine was described to me: “First, we had the herring traps, and the nets. So herring were being caught, and canned, and everybody was making a living. Then somebody came up with the purse seine. That is a big net which you can pull around a school of fish, close it on the bottom, and haul it up, catching the whole school. All of a sudden fishermen were catching a lot of fish. New canneries opened, but there were still more fish. So they ground them up and sold them as fertilizer. And there were still more fish. So they used the scales for paint and threw the rest away. And then all of a sudden the fish were all gone. And the factories closed.” Now you can see abandoned herring weirs and crumpling factories standing like monuments to the destruction of a species all over Downeast Maine – and all because of a single invention: the purse seine.

 

Once everybody started catching a lot of fish, the fish started to become scarce, so you needed better technology to find and catch them. Faster ships, equipped with weather fax, Doppler, fishfinders, temperature probes, and even helicopters started scouring the oceans. Technology costs money, and fishing vessels became increasingly expensive to operate. But if you didn’t have the technology, the guy in the next boat over who did would find all the fish. Once you find the fish, you’ve got to catch them. Invisible nets made out of practically indestructible plastic, chemical lightsticks, Styrofoam floats and lures, electronic gear markers… thousands of dollars worth of gear were put into – and lost – in the ocean. Gear became increasingly good at catching – and killing – anything. Bycatch started to approach actual catch in quantity. When the fish were all gone on the surface, gear was developed to reach down to the bottom. When that wasn’t enough, gear was used that actually dragged the bottom. We basically threw all the advances of civilization into our quest to catch every single last fish. When it became clear that species severely declined, quotas were created.

 

Now the race was really on: once a certain number of fish were caught, everybody had to stop, so now you not only needed to get your fish, you needed to get them quick. One can easily imagine that considerations such as bycatch went out of the window in the quest to fill the hold. Once the quota was filled, the expensive ship was lying around unused. The solution: let’s go after another species where there are no quotas yet. There are some species which were and still are commercially fished right after their discovery simply because if you don’t know anything about the species, it won’t be regulated, and somebody will eat it, and if not it can be sold as fishmeal. And if you can’t find anything else to catch in your backyard you take your now any-weather any-ocean vessel and go anywhere on the world’s oceans where there are still fish.

 

The solution to the tragedy of the commons are quotas – worldwide, indisputable, clear quotas for all oceans and all ships. The quotas have to be specified by fishing ground, vessel, and size of individual. And since only a few individuals can be taken we might as well return to selective fishing gear which will only take the target species. It does not matter now if it is slower or more labor intensive since once the quota is filled there won’t be anything else for the ship to do so it might as well take its time. If captains want to use technology to find the best fishing grounds that is fine – but unless our fishing fleets will be dramatically reduced any vessel will be underutilized under any kind of sensible quota, so time once again will not be important, and less advanced methods might work just as well. If there are so few individuals of a species left that it takes you technology to find them, then they shouldn’t be harvested anyways. Yes, the price of fish will increase under this system, but it will now reflect the true price of the piece of protein we have on our plate. The prize is extinction. Fish now is a luxury item.

 

Rate of Replacement and Population Mining

 

A concept which is essential to responsible wildlife and fisheries management is managing stocks of any species based on their rate of replacement, not their absolute numbers. This is especially applicable to species which have no natural enemies, and whose life strategy therefore is based on growing to a large size before reproducing, and having a therefore higher quality offspring. Let us consider the difference between rabbits, turtles, and elephants. Rabbits, since they are everybody’s prey, have a natural lifespan in the wild which frequently does not even reach a single year, let alone 10 or 20. If you are a rabbit in order to propagate your genetic material you therefore have offspring as early in life as possible – or you might never have a chance to have offspring at all because you will be dead. Never mind that having offspring that early – and lots of it, since offspring also gets eaten – will reduce your long-term survival. Chances are you won’t escape becoming somebody’s dinner long enough to even have to worry about your long-term survival. So as a rabbit you have lots of babies in your first season at the expense of your body’s wellbeing. You might make it for a little while longer, but that doesn’t really matter, since your genes will live on in your offspring. Since the generation time is so short, species like rabbits – called r-selected species – are able to exploit their habitat phenomenally well. In a year where there are no predators and a lot of food all the offspring will survive and go on to have offspring itself, and the population explodes, populating their habitat to a point where resources will run out.

 

This point is called the habitat carrying capacity and the species will be at carrying capacity. Because food resources will now become limited, the health of individuals will decline, and less energy will be available for reproduction. In the first case the population might crash from disease or starvation, in the second case it will adjust its reproductive output downward to hold at carrying capacity. R-selected species at carrying capacity are ideal species to exploit, especially if the species is holding at carrying capacity, so that every individual you remove is immediately replaced. In fact you might even remove slightly more individuals to ease the pressure on their food species. However, if a species goes through alternating cycles of explosion and population crashes, things may not be as easy. We have to consider first that something happens to their biomass as they crash. Most likely they are feeding a large number of scavengers after their death which may well rely on that food source. Also the food source of the species itself – vegetation in the case of rabbits – will have a chance to recover during a population crash. If we keep the species from cycling through harvesting, we are disrupting this process and may in fact be damaging the system.

 

If you are a turtle, your outlook on life is somewhat different. Generally if you make it above a certain size you have it made – nobody and nothing will kill you. It is therefore advantageous to get to that size quickly, and you do that by holding off with reproduction until you have arrived there. In fact you can now afford to wait even a bit longer with reproduction since if nothing will kill you, you can maximize your reproductive output by having offspring at a time when your body is large enough so that the energy drain of reproduction no longer decreases your life expectancy. So this type of species – called k-selected – will maximize lifetime reproductive output by delaying reproduction until a large size is reached, and by then having smaller numbers of offspring throughout life. Many turtles will start producing offspring when they are around 20 years of age and will continue to do so for centuries! Since your offspring gets killed by everyone, you produce lots of it at a very small energy investment (i.e. very small, very fragile offspring), so that those few which by chance make it will propagate your genes. In many turtles the ratio of surviving offspring is one in a thousand or so. Because your offspring is so fragile, literally everything will eat or kill it. Even a reduction in the numbers of any one predator will likely not affect the survival rate of your offspring in any significant manner. K-selected species have no density-dependent reproductive response.

 

There are several reasons for that. In species which produce lots of low-investment offspring the offspring is so much smaller than the adult that it usually exploits a completely different environment with different food sources, so even if the adults of the species are at carrying capacity this would have no impact on survival of the offspring. Another reason is that adults never reproduce at their full capacity, i.e. their energy investment in reproduction is low compared to the energy budget of the organism. Consequently a reduction in the amount of energy available to the adult will not translate itself into a lower reproductive output as it does in species where a major amount of the mother’s energy is used for reproduction. Also consider that reproductive output is reduced by a factor of thousand to arrive at actual adult replacement rate. An adult which would produce 10 more eggs in a good year would only add 1/100 of an offspring to her lifetime output, and chances are that this particular clutch might be destroyed by environmental factors anyways, so the extra effort would be wasted. In k-selected species lifetime reproductive output is maximized by a long reproductive lifespan and can therefore e reduced by untimely death, but never increased, while in an r-selected species lifetime reproductive output is maximized through a maximum number of young as early as possible. In r-selected species any young that are produced because the adult lives unexpectedly long or has more energy available are an added extra and will lead to a population increase. Generation time is another key factor.

 

True population explosions operate on an exponential curve, with generation one having ten offspring, all of which have another ten offspring in generation two, and so on. In k-selected species generation times are extremely long, so whatever factors might have led to better juvenile survival in one year will be long gone by the time those juveniles reach adult size. Population explosions are therefore not possible, and instead good and bad years for offspring survival will average out over the several centuries of reproduction to produce a sufficient number of offspring to replace the adults. K-selected species are therefore the ideal climax species (species living in an environment which will remain stable for centuries) since they will not overpopulate their environment in the boom-and-crash cycle of many r-selected species. Instead they are superbly adapted to their environment and able to exist in it without overusing it. Even though k-selected species can exist well at carrying capacity, most of them are no longer anywhere near those population numbers today.

 

In fact many of the threatened, endangered, and critically endangered species today are k-selected. The reason is that the number of surviving offspring is usually just high enough for replacement of those adults which die of old age. However, if the adults of a k-selected species begin to die, a horrible effect happens: first of all, since the species is incapable of a density-dependent reproductive response, there is no increase in offspring production or survival. So the adult that is removed from the population is not only not replaced, but also the 2000 offspring it would have needed to replace itself and its mate are never born. This adult individual is therefore being mined from the population. A population which has grown to its current population level over millennia is now one individual smaller. It is also important to remember that the reproductive lifespan of any k-selected individual is extremely long, and that it will only reproduce enough offspring to replace itself and its mate after often a century of reproduction. Therefore any adult individual which is killed might easily die without ever having produced a single surviving offspring.

 

If a population of a k-selected species is not at carrying capacity, a very simply calculation can be made: determine the age of the species (in the case of turtles 50 million years). Determine if there ever was any source of adult mortality other than old age. If not, determine the total population number. A simple mathematical calculation will now allow you to determine the number of excess individuals generated per century. This is the number of adult individuals which can be harvested each century without reducing population levels. Another calculation would involve taking a total population number – let’s say of 50 mature turtles in a bay with a natural lifespan of 100 years. Let’s say that maturity is reached at age 10 and natural mortality between age 10 and age 100 is 0. The age distribution of such a population is therefore a flat line, i.e. there are equal numbers of individuals for each age. In the case of our sample population, every other year one turtle would die of old age. So the replacement rate would be half a turtle per year. If only 5 turtles are killed each year, our population will go extinct in just under 11 years.
 
Elephants are another example of a k-selected species with a slightly different reproductive strategy. Here the adults maximize lifetime reproductive output also by only reproducing late in life but instead of having many low-energy investment offspring they have very few offspring but assure through a significant energy investment (feeding and parental care) that this offspring survives. Here the adult ensures offspring survival through a very tight family structure and parental care over many years, so now the loss of either the parent or the offspring is catastrophic. Again, because actual energy invested into reproductive output is low, there is no density-dependent reproductive response. Generation time is once again extremely long, so even if by chance conditions are favorable in one year, they will not be throughout the time of the offspring growing up and will likely not be by the time that individual itself reproduces. Intensive parental care instead of high numbers of offspring compensates once again for chance environmental fluctuations instead of exploiting them. If an adult individual is removed, it will therefore not be replaced.

 

Whales are the elephants of the sea. When whaling first started, the ocean was ‘full of whales’, and yet, there was no indication that the whales were at carrying capacity. And that meant that the rate of reproduction equaled the rate of natural death. Therefore no excess individuals were being produced, and every whale taken was mined from a population which had grown to its current size over millennia. No k-selected species can sustain adult mortality, and today virtually no k-selected species is at carrying capacity simply because humans are causing precisely that adult mortality. K-selected species have a k-selected life history strategy because nothing naturally kills their adults. They are on the top of the foodchain or superbly equipped with defensive armoring, so generally they have no fear. And that is precisely why they are so easy to kill for us.

 

Threshold Densities and Effective Population Size

 

Sexual reproduction biologically takes two individuals, a male and a female. We therefore expect that if a male and a female of a species exist in their natural and reasonably undamaged environment, we will arrive at persistence or population growth. There are however obvious and not-so-obvious fallacies with the one-of-each-kind concept. If the last surviving group of a species is very small, accidental death might kill off all individuals or all individuals of one gender. A certain size group, flock, herd, or school might also be necessary to procure food, escape from predators, migrate, or respond to adverse climatic conditions (for example group hibernation). In species with more complex behaviors minimum population sizes may be necessary for communication, socialization, and learning behaviors. For example the great whales communicate across ocean basins. Loosing their communication partners may irreversibly disrupt their social structure and consequently their ability to function. Even if the population is large enough to function and display some behaviors, large numbers of individuals might be necessary to sustain the full potential for behaviors.

 

Just consider humans. In a small group advanced scientific, cultural, and social knowledge will be invariably lost. Finally, genetic factors are also important. A sizable group of individuals will have certain differences in their genome which convey no survival benefit. Those mutations are called neutral. However, if the population is exposed to a novel disease, toxin, or environmental shift, the previously neutral mutation might suddenly become advantageous and allow the few individuals with that mutation to survive when the rest perishes. In a population which is large enough, the incidence of neutral mutations is high enough that a remnant of the population will survive any number of threats. If the population however becomes too small, it will likely be exterminated by any novel disease since there is simply not enough diversity that by chance a few protected individuals could exist. This situation is called a population bottleneck. Even if reproduction is increased again after a population has gone through such a bottleneck (for example through targeted intensive breeding or restocking programs), genetic diversity is not, at least not for many years. The concept works not unlike lottery tickets – the more you buy, the greater your chance to have winning numbers. Throw most of your tickets away, and your chances decrease dramatically. Make a hundred copies of the one ticket you have left, and your chances won’t increase at all.

 

The concept of effective population size is closely related to the above. In most advanced species the female produces the offspring while the male merely contributes his sperm – and lots of it to many different individuals. In a population consisting of one female and one male, the effective population size is therefore two. With one fem,ale and ten, onehundred, or fivehundred males, it is still two – just because there are more males, the females will not be able to produce more offspring. How much increased genetic diversity the increased number of males will be able to generate will then depend on the mating system. If mortality in a species is increased for females, effective population sizes will rapidly drop but be tragically masked by the high surviving number of males. This happens especially in species where females expose themselves to humans during reproduction, sea turtles being one example.

Finally barriers and population fragmentation have to be considered. Pollution, physical barriers, and habitat degradation can split a population into several pieces. Consider the situation of a series of shallow bays on a shoreline and a coastal species whose distribution is continuous along that shoreline. Now pollute the middle bay to an extent where it is dead. Even though all individuals might have escaped the disaster by moving to the bays at the end, they can no longer get together. Each now forms its own individual population with total and effective population size constraints and a decrease in genetic diversity.
Sometimes however there are substantial total and effective population sizes and the population still does not reproduce. As individuals are lost to old age and accidents, the population consistently decreases without any new recruitment. The most frequently cited example is that of the passenger pigeons. Once there used to be millions, and hugen numbers were harvested. Pigeons are an r-selected species, so reproduction while not compensating for the losses should at least have slowed the decline. Instead reproduction – stopped. Natural and unnatural death whittled away on the remaining population until the last individuals – a male and a female – finally died in a zoo and the species was extinct. Only much later was it determined that in order to reproduce passenger pigeons needed the behavioral stimulus of thousands of individuals being in one place. This may have been evolutionarily advantageous for a variety of reasons including communal nesting, better protection from predators, or a good choice of site reinforced by many individuals. Whatever the reason, once the large numbers no longer existed reproduction stopped, and extinction occurred.

 

This or similar threshold effects can be seen especially in species with complex social structures and behaviors. Whales for example employ complex communication patterns prior to reproduction and the reproductive process itself can involve large numbers of individuals. If there are not enough conspecifics to communicate with or involve into the mating, reproduction will cease. Other threshold density events might involve juvenile survival to recruitment into the adult population. In species where adult and juvenile sizes, habitat use, and behaviors are vastly different, and growth to adult size is slow, juveniles have to learn certain behaviors such as migrating or hibernating from individuals which are just slightly bigger than they are.

 

Once a discontinuity is introduced into the population structure, i.e. total reproductive failures occur for a number of years so that the population is only made up of adults and newborn individuals, those newborn individuals will then be unable to learn certain essential behaviors and will therefore die. No new recruitment into the adult population will take place, and extinction will follow. Even very ‘primitive’ organisms can have threshold events involved into their reproduction. Clams are broadcast spawners, i.e. they put their gametes into the water column where fertilization takes place. This process only works if there is a sufficient number of gametes in the watercolumn, so every clam over a whole area has to spawn at once. In order to synchronize the spawning event, the spawning individuals will also put a hormone into the water column which entices others to spawn, again putting more hormone into the water, and so on. If the density of the clams is no longer high enough, the level of hormone in the water will also never be high enough to initiate the mass spawning cycle. Each clam will then spawn on its own timetable, gamete concentrations in the water column will not become high enough for fertilization, and no new generation will be created.

 

Threshold densities of this nature could exist in almost any mass-spawning or mass-mating invertebrate or vertebrate species, and often threshold densities may be extremely close to existing population densities. Consider for example the problem of an individual of a species which exists at a very low densities such as the predators of the total darkness of the abyssal plain. At ‘natural’ densities any one individual may only have one encounter with an individual of the opposite sex during its lifetime. Reduce the densities through population stresses such as pollution or bycatch and it may have none. This means that if any species is to be considered for harvesting, we have to understand not only its life history but also its behaviors. Threshold density considerations should be used primarily for species restoration and conservation programs. Using the concept to then reduce a species to a density just above its threshold density through harvesting is unethical. All harvesting should only remove what can be regenerated in a single reproductive cycle. The reduction of total population numbers is only acceptable in a case where habitat degradation has progressed to a point where other species will suffer unless all individuals are culled to a level of what the habitat can support.

 

Keystone Species and Inter- and Intra-Specific Interactions

 

Every organism on this earth is part of a foodchain. Plants get eaten by animals, animals get eaten by other animals, and in the end the biomass gets converted back to energy, carbon dioxide, and water by bacteria. The most important processes are grazing, which is a herbivore eating a plant, predation, which is an animal killing and eating another animal, and scavenging, which is an animal eating another dead animal. Animal and plant species can also closely interact in four basic manners: parasitism, in which one organism profits at the detriment of another, commensalisms in which both organisms profit or at least have no detrimental effects from the relationship, symbiosis, in which both organisms profit, and amensalism, in which one organism modifies the situation so that only itself can profit.

 

A food web is a depiction of who eats who in any environment or community. The key here is that every individual has to be supported. If the herbivore overgrazes its environment and consequently starves, the food chain looses its basis which allows the conversion of energy for use by predators. If the top-level predators decrease in number the lower-level predators will survive in greater numbers, kill of the herbivores, and the whole net collapses again. Finally there need to be enough dead individuals of any group for the scavenger to have enough to eat.

 

Ecology used to subscribe to the concept of keystone predators. A keystone predator was any top-level predator which allowed the ecosystem to remain at its greatest possible diversity. The classical example is that of starfish. Starfish eat blue mussels and therefore determine the downward extent of the blue mussel band in the rocky intertidal. Below the blue mussel band a variety of invertebrate species which are not eaten by starfish survive. If the starfish are artificially removed and excluded, The blue mussel band will quickly grow lower down, displacing all the other sessile invertebrate species. The existence of the starfish alone therefore determines biodiversity in this habitat, the mark of a keystone species. However, if we examine any ecosystem more closely and you will find that virtually every species is a keystone species. Remove the barnacles and certain organisms might never be able to gain a hold on the smooth rock surface. Remove the blue mussels and the starfish would starve and disappear. Remove the plankton from the water and neither blue mussels nor barnacles would have anything to eat, which would lead to their disappearance and consequently that of the starfish.

 

The pattern is further complicated by the fact that different species fit into different parts of the foodchain during different stages of their life. A top-level predator might have a planktonic form which along with all other species in the plankton would form the bottom level of the foodchain for every one. After leaving the plankton the same species might now have a benthic (bottom-living) form which has moved up in the world of predator-prey relationships. It can now itself feed on smaller invertebrates but still gets eaten by the larger species. Finally it might reach a size which makes it the top-level predator for its habitat. Any species might also be its own worst enemy by eating its own young under certain conditions. It is also important to determine a species’ feeding habits. Species can be either specialists or generalists. Specialists are generally dependent on a single food source and if that food source declines, so will they. Generalists can utilize a variety of food sources, but if one food species declines, the pressure will shift to another species, possibly putting too much pressure on it.

 

For fisheries management this poses a set of complicated problems. First of all the complete life cycle of an organism needs to be understood. Removing an organism which is a top-level predator as an adult might affect recruitment for that species, which in turn might remove an important food source for mid-level predators which might be feeding on a smaller life stage of the organism. Next all the dependencies have to be understood. If we are removing a top-level predator, how will that affect the mid-level predators? Will they overpopulate and overeat the grazers? If we are removing a mid-level predator, what will the top-level predators feed on? If we are removing a grazer, which species will act the intermediary between the plant material and the carnivore food chain. And most importantly, what are the density levels at which those effects occur. Removing one individual might not have an impact, but what about removing 10, 100, 1000?

 

We also have to determine populations and their boundaries. In the ocean this is a lot harder than on land. We have basically benthic (bottom) and neritic (water column) organisms, however, they might switch between the two types during their live cycle. Most organisms start out as part of the nekton and then drop into the benthos later in life. However, they might also start out in the benthos, become part of the nekton for a while, and then become part of the benthos again. Furthermore, physiology and behavior determines he boundaries of populations. As part of the plankton an organism might disperse widely until it settles out on a very specific piece of sea bottom where it and its conspecifics remain relatively isolated from other species, or the planktonic stage might grow up to become a strong-swimming neritic organism which might have a very small or a very large home range. Each distinct population can be isolated or there can be interactions with other populations in the form of immigration or emigration. If the former is the case, any impact on the population, even if small in terms of numbers removed, might have a significant impact on genetic diversity. If the latter is the case, then any impact on one population will also impact all other populations with which individuals are exchanged.

 

Habitats, Ecosystems, Migration, and Life Cycles (and Fisheries Regulations)

 

As we have said, it is essential that we understand the full and complete life cycle and interactions of any species we consider for harvesting. A further consideration is that every life stage of every species has different habitat requirements, any one of which will be subject to different disturbances. If we for example want to protect a beautiful reef system we need to know how large an area around that reef system the planktonic life stages of the reef inhabitants and the plankton which forms the basis of its food chain are using. Depending on current systems that area might be hundreds of miles. Different threats obviously act on different life stages. While the reef itself can be damaged by pollution, mechanical damage, and overexploitation, the major threat to plankton is pollution. So in order to protect a single reef, the plankton over a large area has to be protected from oil pollution. The organisms on the reef might be using the reef at very different life stages as well. Perhaps young fish live here, but as adults they might migrate halfway around the world. Now we need to protect that species wherever they go from exploitation, pollution, and also habitat degradation. Migrations might be undertaken to feed or to reproduce. If feeding, sufficient food species need to be available. If breeding, the breeding habitat cannot be degraded.

 

Of special concern are species which utilize both freshwater and saltwater habitats during their lifecycle. Anadromous fishes start and end their life cycle in freshwater, while catadromous fishes start and end it in saltwater. For both conditions in freshwater rivers become as or more important as those in the ocean. Dams, pollution, siltification, and water level fluctuations due to reduced watershed retention are just some ways how terrestrial factors can influence riverine environments. The same factors can also directly or indirectly impact our ocean habitat. Pollution and silt are transported by the rivers into the ocean, where they can change habitats and kill organisms outright. Shoreland fortification and beach development changes current and temperature pattern besides affecting species which use those beaches for reproduction. Some species quite simply use almost the whole globe as their habitat, traveling through and utilizing hundreds of food webs and habitats on their way, every one of which has to be intact for the species to persist.

Generally, more highly structured habitats with firm attachment points which are within the photic zone (the zone through which light penetrates) support the highest biodiversity. They are therefore the best nnursery habitats since they offer shelter and a variety of foods to juveniles of various species which allows them to grow large enough to venture as top predators onto the open submarine plains or into the water column.

 

The problem is that human exploitation of bottom-living animals has ruined precisely those habitats. Generally in order to fish for groundfish a bottom-trawl is used which is a giant net that is dragged over the sea floor by means of weights. It scrapes up and flattens everything in its path. What it brings up besides groundfish is then dumped back overboard as bycatch, usually dead. Only more destructive are actual drags which are used to remove invertebrates such as scallops from the bottom. Those often consist of a series of metal rings. Bycatch is not an issue since they crush anything that will not fit the drag. Bottom drags literally plow furrows into the sea floor, plowing under any sort of hard structures with their communities which have evolved over millennia, and leaving a muddy, featureless bottom not unlike a plowed field which would offer no protection to the juveniles of any species. Because of modern GPS technology draggers will plow furrow after furrow after furrow next to each other, effectively denuding huge patches of seafloor. Reefs, both natural and human-made often offer great habitat. However, because of their very existence those prime nurseries are often shrouded in ghost nets, which we will take a look at below.

 

Two examples of fisheries management not considering life cycles and migration were the Atlantic Salmon and the American lobster.
Atlantic Salmon populations have been consistently declining in rivers on the North American East Coast. Pollution, dams, and habitat destruction certainly played a role in this decline. Expensive and necessary measures were taken to remedy those problems, including stocking programs and fishways around dams. Some dams were even completely removed. However, the numbers of salmon continued to decline because there was an ongoing intensive salmon fishery off Greenland, where all the salmon from the rivers we were restocking and restoring went during every summer. Considering the pricetag for salmon restoration projects, each salmon which migrated up to Greenland might have been worth a significant amount of money, potentially much more than the commercial salmon fishermen who complained that salmon fishing was their livelihood, actually got for each salmon on the wholesale fish market after their costs for fuel, boat, and crew was considered. We were essentially at considerable expense subsidizing the Greenland salmon fishery. It might have been cheaper for us in the long run to in fact pay that money directly to the salmon fishermen for not fishing…

 

Lobsters are another fisheries management failure story. Maine has a very tightly regulated lobster fishery which is designed to ensure that enough large lobsters are kept alive as breeding stock and that females are not taken. So every lobster that is over a certain size limit gets thrown back by Maine lobstermen. Lobsters however also migrate through the Gulf of Maine in a circular pattern which takes them down to Massachusetts, over the banks, to Nova Scotia, and back over to Maine. Massachusetts has no upper size limit on lobsters, so the large breeding stock conserved by Maine lobstermen invariably ends up on the fish markets of Massachusetts.

 

Bycatch

 

Bycatch is every organism that comes up in your net or on your hook that is not a target species at the target size. In other words it is an organism that is too small, too large, or not the animal you are after. Bycatch can be anything from a too-small lobster to a highly endangered leatherback sea turtle. Bychatch can also simply be bycatch because you caught too many of the species you want and went over the quota, or if your quota is very small, you might just be going after the ideal-sized individuals and might consider everything else, even though it is legal-sized, bycatch. What happens to bycatch depends on the type of gear you are fishing and the type of animal.

 

Consider for example lobster traps. Almost perfectly harmless, they are boxes that sit on the ocean floor. Since presumably anything that wanders around on the bottom at that depth is gill breathing, the traps are reasonably safe for all kinds of organisms. They walk in, can’t get out, and are released by the lobsterman when he hauls his traps. The traps are only hauled up over a relatively short vertical distance, and are only exposed to air for a fairly short time, so whatever gets thrown back likely survives. But even here we have problems. First of all most species that get caught in a lobster trap are bottom-living, i.e. benthic. When they are released from the trap they float for a few minutes in the water column where they potentially become prey to any animal that happens to be swimming by. And finally, at least the smaller, slower-moving species had a specific home place in the bottom habitat from which they now have been displaced, which may mean that there is a higher chance that they will be killed by something else as they attempt to return to their home base. The trap itself becomes a lot more dangerous if it has caught something. Now you have a big lobster sitting in a box from which there is no escape. Any animal that happens to be in the trap already or happens to walk into it while it is occupied will likely end up as lobster food. Also as lobster traps are set and hauled a rather heavy structure is dropped onto the ocean floor, crushing whatever they land on. Ad finally, the trap is connected with the float on the surface by a rope.

 

Here is where the interests of conservationists and lobstermen diverge. Traditionally, natural fiber rope with a very low breaking strength was used to mark and haul one light trap. As technology  evolved, heavier traps were developed which stood up better to abuse, but which also necessitated the use of stronger rope. Since stronger rope was being used anyways, several traps were now tied together under water in a ‘string’ to facilitate hauling. In the end, the rope connecting the trap to the surface became essentially indestructible, with a breaking strength of several thousand pounds. And that was when large, airbreathing animals such as whales and sea turtles became bycatch as they became entangled in the ropes and frequently drowned. So even a low technology harvesting technology like a lobster trap can generate bycatch ranging from small, benthic organisms to whales.

When nets are being used, air-breating animals such as turtles and dolphins die in increasing numbers. Especially as material gets more advanced and stronger, nets can be hauled less frequently since they can hold more weight and volume, so drownings become more frequent. More advanced materials also make the nets nearly invisible to target species and bycatch alike, so entanglement in the net material itself becomes more frequent. The drowning of air-breathing animals such as sea turtles and dolphins in nets can be reduced through the use of technology. Many tuna boats now employ scuba divers to remove dolphins from the nets before hauling. Shrimp trawlers, which are one of the most dangerous fishing technologies for sea turtles, can use so-called TEDs (turtle excluder devices) which allow sea turtles to swim free of the net. Acceptance of those devices and techniques is however low. For example TEDs do not reduce the effectiveness of a shrimp trawl, but fishermen still refuse to use them. Scuba net-checks get the dolphins out, but cost time and money. Bycatch is legal and an accepted side-effect of fishing – there is no incentive to reduce it. Consumers have a significant amount of power to demand bycatch reductions. Due to worldwide protest, most tuna is today caught without dolphin bycatch. TEDs had been mandated by the US government on all boats selling shrimp to the US. However, a protest at the WTO alleging discrimination against a product based on means of manufacture removed this requirement, and sea turtles continue to die a horrible and unnecessary death. Besides air-breathing animals, fish also die as bycatch. Especially deep trawls bring up fish quickly through several hundred vertical feet, exposing them to rapidly and dramatically dropping pressure. Just like a human diver, those animals suffer massive cell and tissue damage in the process. They are then dropped in a heap onto the deck of a boat, sorted, and thrown back. Most of those fish are dying by the time they hit the water. This is especially tragic in the case where they were the target species but too small.

 

Other damage can occur with a variety of fishing equipment. Long-lines catch animals on hooks, leaving depending on the method of release  either a hook to rust out or an open wound in the animals mouth or if it swallowed the hook a stomach which is torn to shreds, a certain death sentence. The fight and the hauling itself has exhausted the animal, and in the final stages it will be banged against and dragged along the hukll of a ship, even if the crew is as careful as possible. Any animal which is caught on a longline will also defenselessly be exposed to sharks and other predators while on the hook, and likely bleeding, disoriented, and exhausted and therefore easy prey for sharks after it is released. Nets, especially gillnets, can kill an animal simply be entanglement, especially when the net is hauled and the animal now hangs suspended from its gills or neck in a material which easily cuts through tissue. Animals dropped on deck are exposed to crushing injury, abrasions, asphyxiation, and other injuries. If you consider how carefully a dolphin or a sea turtle is handled if caught or transported on purpose for research, you can easily sea why one accidentally hauled up on fishing gear has little chance to survive. And finally the big bottom drags and trawl roll over the seabed, leaving deep furrows and leveling the ocean floor and its essential habitat.

 

Consider the following story:

 

“I was dragging for scallops off the coast. I made a couple passes and brought up quite a few scallops. I made a couple more, and still brought up scallops. Now I could see on my depthfinder that I had dug down quite a bit with the drag – about 6 feet, and I was curious why I was still finding scallops. So we sent a diver down.” The diver found a sight which he described as a “moon landcape” The drag had torn repeated 6-foot-deep furrows into the ocean floor, plowing under scallops, mud, and marine life indiscriminately. The reason why the dragger still brought up scallops was that they had been literally plowed under feet deep by the first passes.

 

Many fishes are bottom-living (benthic), which is why bottom trawl are being used for them. However, even their small life stages are benthic, and they can only survive in a healthy bottom habitat with food species and plenty of cover. The bottom drag and trawl destroys all this, so not only are the adults taken, but replacement is made impossible through destruction of the very habitat the juveniles would live in.

 

Ghost Netting

 

Fisheries have traditionally used to most advanced technology available to catch fish. Fishing is one of the most dangerous occupations on earth, and running a boat is expensive, so you need to catch whatever you are after fast and effectively. Having a net, trap, or line break when fully loaded means lost catch. Having a net that is visible to fish means that you have to work so much harder to get fish into it, and that the biggest, smartest, and oldest individuals will be likely to ‘get away’. As plastic materials became available, nets and lines started to be made from them quickly. Plastics are virtually indestructible, virtually invisible, and could be made thin enough that they can actually entangle and kill instead of just confine fish. Monofilament line – a single stand of plastic – became the standard for fishing lines and nets. Haul lines started to be made out of materials capable of withstanding thousands of pounds of force. The problem however is that plastics are virtually indestructible. If a net snags on the bottom – such as a wreck or an underwater reef – there is practically no way to retrieve it. The ship will cut it and write it off as a loss – an operating expense of fishing. However, the expense only starts. Plastic generally only breaks down under the influence of ultraviolet light. If a net is lost below the photic zone, it will not break down for millennia, and it will go on fishing for all that time, killing untold millions of marine organisms including the highly endangered sea turtles and even whales.

 

Nets made out of natural materials used to fall apart within a few weeks or months of being lost, so regulations for lost nets have not yet caught up with reality. A lost net is not lost equipment, a lost net is an unregistered fishing vessel operating below the surface of the ocean. We currently have the technology to tag fishing gear for retrieval. For example long-liners attach radio beacons at regular intervals to their mainlines in case they break. This stems not so much from a concern over ghost fishing, but rather from the fact that gear is expensive. Once a broken section of mainline is found again through the use of the radio transmitter, it can be easily retrieved. Lost nets, especially bottom trawl, are not easily recovered. Generally it takes an ROV, a remote-operated vehicle to go down to the bottom and cut the net free. An operation of this sort would costs tens of thousands of dollars. However, again the cost of the net continuing to fish has to be considered. Raising a single sea turtle up from an egg to maturity can cost several thousand dollars depending on the method used, the survival rate to maturity of the juveniles released, medical costs, etc. If that sea turtle is then killed in a ghost net, the cost of our sea turtle recovery program is essentially subsidizing the fishing industry.

 

The only sensible solution is to radio-tag all fishing gear and to require every fishing vessel to return exactly the amount of gear they set out with to land. Vessels which loose gear will have to GPS mark the position where the gear was lost for recovery. While recovering a deep-ocean trawl from a snag will initially bankrupt the operator of the vessel, it will do several things. First, technology to recover nets will become cheaper and more available as the demand for its availability increases. Vessel operators will also become more careful as to where they will trawl. Trawling in areas of underwater wrecks, ridges, and other outstanding bottom features is popular since those are areas of high biological productivity. They are however also areas where fishing gear causes a maximum of damage to delicate communities of organisms, and which should not be fished out of principle. Finally requirements to recover all gear will promote the use of devices on nets which will allow recovery by the vessel itself. Again, the true costs of every economic activity have to be considered. Traditionally, chemical companies discharged their waste into rivers, and the public bore the costs for the environmental damage and cleanup. Today laws have changed, and the company itself has to pay for the cleanup. Yes, the price of fish will go up if we adopt a ‘clean up after yourself’ stance, but the price to the public for endangered species restoration will eventually go down.

 

Ghost trapping is not as much of a problem as ghost netting since traps are stationary, heavy, and generally not deployed in water so deep that it cannot be dragged for recovery. Lobster traps in Maine today are required to have corrosion points which will cause the trap to fall apart after a certain number of months if it is lost and cannot be relocated. Still, even here a ‘bring back what you set out with’ policy should be adopted. Currently the recovery of a trap is an economic decision. If the cost of recovery exceeds to value of the trap, it will be left, even though most traps are set within the depth limit accessible to scuba divers and could be potentially fitted with a transmitter so that they can be relocated.

 

Direct and Indirect Impacts

 

All marine organisms and ecosystems can be destroyed by direct or indirect forces or changes. The easiest to identify and most obvious are the direct impacts. A tour boat which anchors on a coral reef tears a hole into the coral with its anchor. A fast vessel hits and kills a logging whale. A powerboat runs over a manatee. An oilspill wipes out a whole coastal ecosystem. A trawler brings up any number of marine organisms dead in its nets. Direct impacts are what often creates public outrage, and a call to stop the activity. The less direct the impact, the harder it is to stop the activity. A ship may dump garbage overboard which gets eaten by sea turtles which die. A net is lost overboard and later entangles a whale which drowns. The individuals involved in the activity might understand that the activity by itself is not a good practice, but they might never see the actual impact of it. There are also the impacts of activities which seem completely innocent but after a long chain of events cause impacts just as bad or worse than the direct impacts we can see. A child plays with a mylar balloon which gets blown away by a gust of wind. Months later a sea turtle in the open ocean finds it, eats it, and dies. A camp owner builds a floating dock using styrofoam billets and a few foam crumbs float off into the lake. Years later a baby sea turtle in the gulf stream mistakes the little crumbs for food and dies. And finally there are impacts which only cause a problem when they are cumulative. A homeowner fertilizes his lawn near a lake. So does every other homeowner on that lake. Months later, an algal bloom in the bay into which the watershed drains consumes all the available oxygen and a large number of fish suffocate. A fishing vessel washes some motoroil into the ocean with a deckhose. In conjunction with the millions of gallons of oil lost by all vessels on all oceans over a year it contributes to the monomolecular oil film covering the world’s oceans which reduces phytoplankton production and therefore global oxygen production and oceanic energy fixation, which in turn affects the complete oceanic foodchain. And finally there are the impacts we cause by things our consumer choices support.

 

We may go on a cruise because we want to enjoy the ecological splendor of carribean coral reef systems. However, unless we very carefully select the ship we will use, we will likely impact those very ecosystems because the ship will be dumping raw or minimally treated sewage directly into the ocean. We might buy beef because we do not want to impact the ocean foodchain, but unless we select organic beef the cattle might have been grown on a plot of land cleared out of the Argentinian rainforest with the exposed soil draining into an oceanic environment where it too smothers coral reef communities. The greatest challenge in that area is to get individuals to see the impacts they have. Who is going to believe you if you tell them that the burger they just ate probably killed a thousand tropic fish?

As a species and as individuals we will have impacts on our environment. It is up to us to make educated choices to minimize those impacts. The camp owner might have been just as happy with floatation barrels for his dock, the child with a ball instead of a balloon, the cruise tourist with a ship which does have a sewage treatment plant, and the deckhand on the boat with wiping the oil up with a rag. The oceans are the ultimate downstream of every single one of our activities – whether it is antibacterial soap used in the bathroom (the chemicals don’t get filtered out in the wastewater treatment plant and end up directly in the ocean) or the new hardwood floor we install in our home (hardwoods are generally harvested in tropical countries where they contribute to deforestation and consequent erosion and siltification). The greatest tragedy are the senseless impacts where one material, item, or activity could have easily been substituted for the destructive one.

 

Energy Conversion and Biomass Harvesting

 

Lifeforms on our planet generally fall into two categories: heterotrophs and autotrophs. Autotrophs use energy from the sun to generate complex organic compounds out of carbon dioxide. This process in called photosynthesis and it fixes energy in chemical bonds. Photosynthesis is considered an endothermic reaction which means that energy is put into it, much like rolling a rock up a hill. Plants are the main group of autotrophs on our planet. Heterotrophs are those organisms which use the energy found in chemical bonds to live by basically burning the complex organic compounds in a series of controlled reactions. The end result is the oxidation of carbon to carbon dioxide in a process called respiration. The burn process is however not perfect. Heat is lost to the environment – whether you are a bacteria or a complex mammal. Heat is also needed to function. In order to convert carbon compounds to carbon dioxide in a controlled reaction you need catalysts.

 

Catalysts in living systems are called enzymes, and enzymes only work over a very specific range of temperatures. Generally if it is warmer, they work better, until they get too hot and fall apart. This is why bacteria don’t grow well in the refrigerator. Ectotherms, animals which draw their body heat from the environment, are somewhat efficient at energy conversion. Their only source of waste heat is from energy burned in muscle contractions, and even that heat is efficiently retained in many species and used to heat up the body. If ectotherms get cold, they find a sunny spot and use the sun’s energy to heat up. If that is not enough, they hibernate, i.e. their bodies cool down, enzymes don’t work, and they don’t use any energy at all. Endotherms, animals which heat their body up from the inside, are horribly inefficient at energy conversion. Most of what they eat has to be converted to heat to keep the body – and its set of enzymes – at a very specific temperature. If an endotherm cools down, it generally dies.

 

So what does that have to do with us? We, like all other heterotrophs, have to eat to live. If we eat an autotroph  (i.e. plant material), we directly use fixed solar energy. However, if we eat animal material, we consume the energy that is contained in the material we eat plus the energy which the animal used during its lifespan to get to the size it was before we ate it. That is, if the animal is a grazer, i.e. it uses plant material as its food source. If the animal however is a predator, then in consuming it we consume the energy in its tissues plus the energy it lost through respiration, plus the energy it took its prey to grow to the size where they were eaten (both fixed in tissue and lost to respiration). The higher up on the foodchain we eat, the more energy we waste – especially if we eat anything warm-blooded.

 

Having said that, what are the implications for us? Considering limited food resources on our planet, eating vegetarian is the smartest choice. On the other range of the spectrum are concepts which convert one form of animal protein to another. Having fished out most palatable fish species in the ocean, companies are turning to biomass harvesting, which basically means taking any living animal and grinding it up into fish meal. Besides the obvious conservation implications of killing species we know little to nothing about without perhaps even an effort to identify what we are in fact killing, the problem is that nobody would eat the product. So it gets turned into animal food and gets fed to cows, chickens, and fish, whose protein we then eat. All of those animals of course respirate, so it takes many pounds of fishmeal to generate one pound of steak.

 

Diseases

 

Marine life is increasingly dying from disease. The papilloma virus which is decimating sea turtle populations is probably the most tragic issue, but other mass die-offs due to disease have been recorded, including the loss of a majority of the European seal population to canine distemper and the current threat of infectious salmon anemia jumping to wild salmon populations. The primary reason for disease outbreaks appears to be immune suppression due to persistent environmental chemicals which accumulate in the tissues of especially the top-level predators, as well as environmental stresses.

 

Organisms which are weakened due to partial clogging of their digestive system from the ingestion of garbage or oil, hungry because of a lack of food due to overfishing of their food resource and habitat degradation, exhausted because their traditional migrating stopovers are no longer usable due to human development or human impacts, and stressed because they are constantly attempting to escape from human activity will simply be more likely to contract a disease. In general disease can be caused by parasites, bacteria, and viruses and spread by direct, indirect, or vector-borne transmission. Direct transmission involves a diseased animal coming into direct contact with a healthy animal. Indirect transmission can occur over inanimate objects such as ship hulls and fishing gear. Vector-borne transmission requires an intermediate host, usually an invertebrate, to harbor the pathogen or parasite for a certain amount of time. Viruses are generally more species-specific than bacteria or parasites because the utilize the cell’s own replication machinery to replicate themselves. Retro viruses are viruses which are transmitted as RNA and have to be converted back to DNA by the cellular machinery. They are therefore most likely to mutate during infections which can enable them easily to jump from species to species. Herpes is an example of a retro virus which has jumped from humans to animal populations. Viruses which are perfectly harmless in one species can by a tiny mutation become very deadly in another species.

 

Human activity is a major factor in spreading viruses and bacteria to animal populations. When canine distemper jumped to the European seals it was due to a person walking a dog with distemper on a beach where it bit a seal. First the seal must have been habituated to humans, or it would have never allowed the dog to get close. Second, a non-domesticated canine would have likely never been hunting on the beach, especially when ill. Other bacteria and viruses are being spread by ship’s ballast water, which frequently transports marine organisms which can act as vectors for diseases, and by marine equipment (commercial and recreational) which is quickly moved from one population to another without disinfection. This is a major concern as fishing vessels rapidly move between the world’s oceans to exploit seasonal fisheries and also as recreational divers jet-hop between various exotic locations. No research has been done on the persistence of most viruses on wet or dry equipment, but for example herpes is extremely contagious and could easily be transmitted between various populations. Further issues are the release of diseased pets or animals acting as vectors for diseases into the wild, and farming operations which use non-native stock.

 

All populations of all organisms have co-evolved with certain pathogens and therefore have natural resistance against them. If individuals from this population or other mechanisms however transport those pathogens to populations which have previously not been exposed and therefore have no natural resistance, an epidemic will result and might kill the majority of individuals in a population. The greatest concern is that co-evolution may be so effective that one population may be completely asymptomatic while still carrying the pathogen. If this seemingly healthy individual is introduced into a new population, it can still spread the disease. It is virtually impossible to test an organism for all possible pathogens. As previously discussed a reduction in genetic diversity (population bottlenecks) will make impacts of disease more dramatic since the population is lacking the genetic variability which might make a few individuals more resistant to the pathogen.

 

Farming

 

A solution which was put forward to produce seafood in a sustainable manner was fish farming. The idea was to grow your own fish in pens (similar to what a farmer does on his fields), and then to kill them when they were big enough. Nothing wrong with the concept – it’s worked throughout human history in agriculture. Except that fish are not plants. Instead of autotrophs they are heterotrophs. They don’t fix energy, they consume it. In short, the fish need to eat to grow. And because most species which we like to eat are carnivores, they need to eat animal protein, which is a horribly inefficient way to get energy. So in order to feed the fish in the pens, two major food sources are being used: beef and pork byproducts and fishmeal. The problem with the former is that we now essentially grow plants to feed cattle to then feed the cattle two the fish. The problem with the latter is that we kill any number of fish species which are still reasonably healthy because nobody liked to eat them only to convert them to fish protein we like to eat. Both processes loose huge amounts of energy simply for the purpose of a different item on the dinner plate.

While energy is lost in the process of converting one type of animal protein to another, chemical contaminants are not – they bioaccumulate, and do so primarily in the fatty tissue. Since farm-raised fish are grown fast with minimal space to exercise to create the greatest economic benefit, they generally have a relatively high amount of body fat. Fish raised on terrestrial food sources tend to accumulate dioxin and heavy metals (fallout from industrial sources ingested by the cows), while those raised on aquatic food sources tend to accumulate methylmercury and PCBs (persistent environmental chemicals which accumulate primarily through aquatic food chains). Even if the fish were lean or the fatty tissues were avoided, the levels of toxicity would still be a health risk to humans. The solution here is to feed plant-based protein such as soy. Not only does this effectively move the fish down the foodchain to the position of a herbivore, causing much more effective energy use, it also avoids issues with bioaccumulation especially if the plant protein is organically grown. And once commonly used, plant protein should be a cheaper food source than animal protein. Even if for some reason the fish becomes more expensive when fed on a vegetarian food source, its true cost will actually decrease if we take the delayed costs associated with ingestion of toxic materials into account.

A further issue with aquaculture is crowding. Pens are expensive, so a maximum number of fish are placed in each pen. This means that contact is intimate, and fungal, bacterial, viral, and parasitic infections become common. Probably one of the biggest threats to salmon, the most common fish aquaculture species is infectious salmon anemia, a highly contagious viral disease which can rapidly spread from pen to pen on contaminated feed barges and other equipment. In case of ISA outbreaks, all fish are killed, but the true environmental impact results from the resulting disinfection of all equipment which is generally done with bleach. In fact, during one outbreak it was reported that an attempt would be made to ‘sterilize the bay’, which was fortunately never done but would have obviously caused a tremendous environmental impact. A further concern is that since many of the salmon aquaculture facilities are located in the mouths of rivers where natural salmon runs are taking place, ISA could spread to the endangered remnants of the wild populations, driving them to extinction.

 

Of an even greater concern that ISA are those diseases which are treatable and are being treated. Pens with ill fish are generally sheeted in plastic tarps and medications are subsequently introduced into the pens. Once the medications had time to act, the plastic sheeting is removed and the remainder drains into the surrounding bays. Medications which are active against parasites such as fish lice are often also detrimental to invertebrate organisms of the same group (such as crustaceans), even in extremely small concentrations. Antifungals in general are often very toxic, and low-dose antibiotic use brings with it the same issues with resistance that occur on farms. Besides the environmental impact there is also a human health cost associated with having those substances in the meat. And finally, while not as contagious as ISA, the transmission of any one of those diseases to wild populations might also potentially have significant impacts on those populations.

Another concern with fish aquaculture operations is water pollution from fecal matter and leftover food. Aquaculture pens should ideally be located in areas of high water flow so that pollutants can be quickly washed away. However, those areas are also generally areas which are wind and wave exposed and therefore not desirable due to gear damage. So aquaculture sites are often located in relatively sheltered coves. Here food and fecal matter builds up in a several-foot-thick sludge underneath the pens which quickly turns anoxic. Even detritus feeders generally avoid those areas since there is no longer any firm surface to cling to but instead a sticky mess which would quickly suffocate any organism venturing into it. Pathogens naturally accumulate in this material and can spread back into the pens. If there is some wave action, but no true water exchange, eutrophication of the bay from food and fecal matter can also occur with the inherent low oxygen levels and possible fish mortality.

 

One possible solution for this problem is better siting of the pens in areas with higher water flow. As better technology has become available, pens have become increasingly sturdy and able to resist wave action, so they can no be placed in less protected areas. Aquaculture firms have also experimented with improved computerized feeding systems to reduce food waste. A possible idea to reduce waste and eutrophication has been the concept of multiple levels of aquaculture organisms, with detritus and/or filter feeders being grown underneath the pens. This would probably become a more viable option if aquaculture could reduce its dependence on pharmaceuticals which in many cases are incompatible with invertebrate aquaculture. As always, the bottom line comes down to economics. Larger pens with lower densities of fish which are sturdy enough to withstand significant wave action are certainly within the realm of technological possibilities, but they are not economically feasible. Sturdier pens have for years been proposed to combat the problem of fish escapes due to seal ‘attacks’. Certainly there are many types of mesh which are impenetrable for seals. However, the cost for such pens would be ‘prohibitive’, so aquaculture operations practice predator control (i.e. frequently the shooting of ‘nuisance’ seals) instead. As regulations in the US become stricter for fish aquaculture businesses, many relocate to third-world countries which will frequently sell out their environment for the short-term profit of having the business provide jobs. In another example of the tragedy of the commons, fisheries which are an integral part of the global ocean food chain will now be destroyed in those countries, and their effects will likely impact species we care about and attempt to preserve.

At the same time a concern and a solution in fish aquaculture are genetics. First, aquaculture providers like to utilize European salmon strains in the US since those strains have been selectively bred for use in aquaculture for years, and have many favorable traits, including disease resistance. However, the migration behavior of salmon appears to be genetically imprinted. A salmon from any specific river will return to exactly that river to mate and reproduce. If farmed salmon escape they will likely also move upriver and mate with the wild salmon, which might create offspring incapable of finding the right river to spawn in in a process called outbreeding depression (two organisms with very different distinctive traits interbreed resulting in offspring with and intermediate and therefore useless form of that trait). Because of that issue it is generally better to use wild-stock salmon specific to a river in the pens. However, in fish aquaculture possibilities to dramatically modify a fish’s traits also exist. Fish can be made to mature quicker, have less body fat, or be more disease resistant. This can be done either through direct genetic manipulation or through hybridization of one fish species with another. Obviously it would be a complete disaster if any of those ‘modified’ fish ever escaped into the wild and contributed their genetic material to wild stock fish. Traits which are advantageous for a farm-raised fish such as reduced body fat could be horribly deleterious in wild fish, and once bred into a wild population could never be removed again. The producers of hybrid or GMO (genetically modified organisms) stock assure their buyers that those fish are sterile, but depending on the method used, 100% sterility might not be achieved. While GMOs are not toxic or dangerous on principle, as many opponents claim, abuses can certainly happen such as the insertion of pesticide-type-substance producing genes into plants, or the use of invertebrate genes with unknown effects on humans in animals.

 

Finally there is the issue of shellfish aquaculture. Here many of the problems found in fish aquaculture are not seen. Most species of shellfish are filter feeders, so they feed on naturally occurring plankton and do not require additional feed. Shellfish also occur naturally in beds or other dense aggregations, so crowding and the associated diseases are also not an issue. Confinement is easy since the species are only minimally mobile. In fact most shellfish aquaculture can be conducted below the surface, so waves also do not even impact the gear. The only potentially detrimental impact would be an extremely high stocking rate which might critically reduce plankton levels downstream of the area. Care also must be taken not to introduce non-native or GMO species. Otherwise shellfish aquaculture might just be one of the few marine-related success stories.

 

Concepts of Pollution

 

We tend to treat the ocean at the same time as a garbage dump and as a food pantry. The idea is that the ocean is ‘endless’ and that any pollutant dumped into the ocean will be diluted sufficiently so that it won’t be a problem. Under this premise cities empty their sewers, factories their chemical effluent, and ships their holding tanks into the world’s oceans. The first problem with this premise is that the ocean is not a featureless hole. Pollution from land or river-based sources will first flow through the coastal zone and through river deltas before even reaching the continental plain and finally dropping down into the abyss. In some shallow landlocked seas such as the North Sea and the Baltic, the maximum depth is as little as 100 feet and water exchange with the world’s oceans takes decades or centuries. In others inland seas such as the Black Sea, the depth may be significant but water exchange with the rest of the world’s oceans virtually non-existent. So the polluted effluent will initially hit the water at a high concentration and might not get significantly diluted for a long time or distance depending on coastal topography and water exchange rates. And worst of all, the locations of the most concentrated pollution are the shallow, photic areas where the highest marine productivity occurs, and where the pollutants can have the highest impacts. Those impacts can be direct poisoning of animal life, a reduction in dissolved oxygen due to a high bacterial load leading to fish mortality, or increased turbidity (water cloudiness) which blocks light penetration and therefore kills any plant life which not only provides the basis for the food chain but also oxygen for the water column.

 

A similar effect occurs when pollutants are dumped in the open ocean. Here a toxic plume can form which kills everything in its path until dilution finally occurs. This is especially an issue with radioactive materials which are ‘buried’ at sea. Here no dilution is taking place. Instead a zone of intense radioactivity exists near the material which presumably kills everything in its path. Once the item such as an old reactor sufficiently disintegrates, radioactive material could possibly enter the food chain in sublethal amounts, reducing viability of animal populations as well as eliminating any chance of any marine specie’s suitability as human food. A further problem is that mixing is not as likely as some people think. Only extremely cold, dense, heavy water sinks into the abyss. Warm and possibly fresh water gets transported on the surface instead. So instead of sinking, sewage effluent and chemical-laden freshwater will travel on the surface of the world’s ocean currents, killing plankton and productive surface communities, and possibly even washing back on shore killing coastal ecosystems. There are also currently proposals do deep-pump some gaseous pollutants, primarily carbon dioxide. Deep pumping relies on the principle that below a certain water depth the water pressure is great enough to keep a gas as a liquid which would spread out in basically a giant ‘puddle’. Deep pumping also relies on the principle that basically nothing lives in the deep ocean, which is completely untrue. The liquid carbon dioxide lake would form a death trap for deep-sea species we do not even know exist.

When classifying pollutants and their impacts, it is important to look at their characteristics. First of all it needs to be determined whether the pollutant will eventually break down or whether it is persistent, i.e. immortal. If it can break down, the conditions under which it can do so need to be considered. Will it only break down if it has contact with UV light, or can it break down in the dark, cold ocean environment. Also, if the compound can break down or get metabolized (changed by living organisms), all its breakdown products need to be considered. Frequently the end-product is more persistent as well as more toxic than the original. Is the chemical reactive, i.e. will it react with other natural or artificial chemicals. A huge problem is the mixing of chemicals for deep ocean disposal. If any of those chemicals are reactive, they can react with others in the process to create possibly much more persistent and much more dangerous compounds. Related to the question of reactivity is the question whether the material can be chemically converted to an organic compound which can accumulate throughout the food chain.

 

We next need to consider solubility of the substance. Light insoluable substances tend to clump or form films like an oilslick which suffocate or coat marine organisms, while heavy insoluable substances also clump but sink to the bottom where they will likely be mistaken for food and eaten. If the substance is a solid, floating versus non-floating also needs to be considered, with floating substances presenting a far greater risk to marine life due to ingestion. Finally we need to consider whether the substance is organic or chemical in nature. While sewage presents a significant disease and eutrophication risk, it will eventually biologically disintegrate, while a chemical might stay in the ocean environment for decades, centuries, or millennia. The break-down times for each substance under oceanic conditions have to be considered when assessing the seriousness of the problem.

 

The following was told to me by a whale researcher on the St. Lorenz seaway. “We would,” she said, “get those beluga whales. When they came to the beach they would be dead or dying. We would dissect them, but in order to do that you had to wear full chemical protective gear because of the level of toxins in their tissues. In fact once you found them, you had problems getting them anywhere. They needed to be dumped on a toxic waste dump, but you couldn’t transport them on a ship because the ship would need a special toxic waste transport permit. In fact if living whales would fall under maritime law, they wouldn’t be allowed to swim up that river – they are too toxic.”

 

Solid Marine Waste

 

Solid and liquid pollutants have very different effects on marine ecosystems. Solid pollutants include all kinds of garbage and items lost overboard or on beaches. Some are obviously and inherently dangerous such as fishing gear lost overboard. Almost as dangerous are lines and rigging that are lost off boats, fishing gear, or docks. Most marine rigging floats and gets quickly tangled with other debris into a mess of loops. Marine life swimming through those loops can get easily entangled. The ropes will then proceed to drag the animal down, keep it from using its fins or flippers, and strangle or suffocate it.

 

Polypropylene ropes persist for hundreds of years in the marine environment. Monofilament recreational fishing line which gets lost into rivers, bays, or the ocean acts in exactly the same manner except that due to its thinness it actually can cut the organism it entangles. More common household items can have similar effects. Sixpack plastic rings for example can entangle smaller organisms. Kite string is the same type of monofilament line as fishing line. If a kite breaks its line and drops into the ocean, nobody tends to give much thought to the environmental effects. However, kite string can just as effectively entangle and choke marine organisms as any gillnet.

Styrofoam, especially the cheaper kind which breaks down into little beads is another extremely dangerous slid pollutant since small organisms, especially sea turtles, ingest the floating beads and die from digestive system obstruction. Dock floatation, packing material, and disposable coolers are all sources of this material. While everybody would agree that it is bad to dump Styrofoam packing material into the ocean, few people would worry about a foam cooler lid that gets blown off the beach. Fully disintegrated, that lid could however kill thousands of sea turtles!

Open ocean dumping of medical garbage used to be another well publicized issue which was stopped due to public outrage. In fact MARPOL, the international marine pollution treaty makes it illegal to dump plastic in any waters worldwide. When medical garbage was still dumped at sea, IV bags which strongly strongly resemble jellyfish, and get ingested by adult sea turtles, which subsequently die of GI obstruction were the main problem. However, plastic bags, balloons, and small inflatable beach toys can have exactly the same effect. Many of those materials are indestructible enough that after the animal which died has decomposed they will go on floating in the ocean to kill again and again.

A big source of solid pollutants are containerships which loose deck containers overboard. While some losses might greatly contribute to our understanding of ocean currents and actually be rather funny (such as the release of thousands of bathroom toys from a container ship), others contribute to the amount of possible ingestion and entanglement hazards floating in the open ocean. Solid sinking objects are not nearly as hazardous as floating or neutral buoyancy (suspended) objects. A solid object which sinks will in many cases actually provide structure and attachment places for marine life on the ocean floor. Environmental groups and diving organizations will in fact often sink decommissioned warships and other military equipment as artificial reefs. Even in the cold water of the deep ocean non-plastic materials will rapidly break down, as can be seen in the case of sunken ships such as the Titanic.

 

The problem with solid objects is however that they might leak toxic chemicals or that corrosion might introduce such chemicals into the water column. Batteries will leak any number of toxic chemicals, as will computer components and electronics. Glues, paints, stains, oils, and other surface treatments can dissolve off the item and act as chemicals in the water. Mercury thermometers pose a huge hazard since the mercury can actually enter the organic food chain. Lead as found in sinkers on fishing lures or in lead shot will not dissolve but if the sinker or the lead shot is ingested, the animal will die of lead poisoning. The dead animal will then get ingested by a scavenger, which will also die, and so on.

 

Lead is another substance which will go on killing. Besides sinkers and lead shot that finds its way to the river or ocean bottom from loss or simple hunting activity, fish which get dumped back into the water after having swallowed a lead sinker and birds which are wounded by lead shot might pose even greater hazards since they will invariably die and get eaten. In the case of relatively inert solid objects the ethical question remains what we want to bottom of our oceans to look like. Do we want beer bottles, porcelain plates, pieces of bathroom mirrors, rubber boots, bricks, hard plastic boxes and casings, and the occasional piece of titanium hardware to be found everywhere on earth including in the rift communities of the deep ocean?

 

Point-Source and Non-Point Source Liquid Pollutants

 

Liquid pollutants again include the obvious gross abuses of our oceans such as dumping oil overboard. When I was a child in Germany in the late 70s and early 80s, it used to be legal for tankers to dump oil from dirty tanks overboard outside the 5-mile territorial limit. As a consequence the beaches were coated with clumps of oil which got all over you, your beach toys, and your clothing. However, it was considered a fact of life and an acceptable side effect to commercial shipping. Today of course we know what that oil did to marine life, and the practice is highly illegal. The shipping industry which clearly did not want this easy way to clean their tanks banned objected at that time, but if there was any intention today to re-legalize the practice, public outrage would be great.

 

Every one of us decides what is acceptable, and every one of us has the power to stop abuses of our ecosystems. Obvious gross abuses today include open ocean dumping of chemicals and straight-piping of wastewater from commercial and private ships, factories, and even cities. Gross and clear pollution is considered point-source pollution, which means that we know where it is coming from. The problem with liquid wastes is that they can be toxic in extremely small amounts, and that they invariably follow the water downhill. Gasoline remnants from streets can get washed into storm drains and from there into the ocean. Soap from washing down anything in your driveway, fertilizer, pesticides and herbicides applied to fields, gardens, and parks, all eventually enter the ocean. Even chemicals which enter the wastewater system in your house such as all the compounds in your dish and laundry detergent, shower gel, toothpaste, and liquid soap will frequently not get removed in a wastewater treatment plant.

 

Wastewater treatment plants generally remove solids and the biologically degrade the sewage. Any substance that is not biodegradable will likely enter the ocean. In this category are also medications which are used in homes and flushed down toilets, or used on farms and seep into the runoff. Those types of pollution are because they are difficult to trace called non-point-source pollution. From a personal point of view doing something against non-point-source pollution does not appear to matter much. Why should you as an individual restrict your activity which only adds a tiny amount of pollution compared to the big point-source polluters. First, because it gives you the moral power to politically attack the point-source polluter. Second, because you set an example for others to follow. Third, because you buy time until a policy will change. Every bit of toxin or excess nutrient entering the marine environment drives that environment one step closer to dying. Every bit that is kept out will delay that process.

 

Bioaccumulation and Biomagnification of Persistent Environmental Chemicals

 

Liquid pollutants generally fall into two categories: hydrophilic (water-loving) and hydrophobic (water-hating). Hydrophobic compounds are often lipophilic (fat-loving), which means that they dissolve in body fat. Organic compounds including Polychlorinated biphenyls (PCBs), Dioxins, and many pesticides and herbicides are lipophilic. Mercury, which is a metal and insoluble in water, gets converted by bacteria to Methylmercury, another organic lipophilic compound. Especially lipophilic compounds can get biomagnified, especially if they are so-called persistent compounds which means that they generally do not react with anything and therefore continue to exist in their original form basically forever. Remember the issue with trophic levels and energy conversion.

 

The majority of energy gets lost in the conversion from one level of the foodchain in the process of metabolizing complex organic compounds through the use of oxygen. However, if a lipophilic compound enters the food chain the opposite happens. Lets say an aquatic plant takes up a small amount of a persistent lipophilic toxin in its tissue. The herbivorous snail eats 1000 plants over its lifetime. The complex carbon compounds get metabolized, but the persistent chemical remains in its fatty tissues. At some point the snail gets eaten by a fish, as part of perhaps 10,000 snails the fish eats over its lifetime. Now the fish has a concentration of 100 x 10,000 units of toxin in its fatty tissue. The fish gets then eaten by a tooth whale as part of perhaps 1,000,000 fish over a lifetime. The whale has now accumulated 100 x 10,000 x 1,000,000 units of toxin in its tissue. There is almost no way to remove the toxin from the body. Even if fat is metabolized, only the carbon is burned, while the toxin remains. Tragically the only mechanism by which fat and toxins leave the body is reproduction. Egg yolk, the baby fat in mammalian offspring, and mother’s milk are all extremely fatty to sustain the offspring, and combined with the fat are the toxins. The mother therefore literally loads her offspring with toxins during the process of reproduction.

Persistent environmental chemicals are man-made compounds which are today found in every organism and every ecosystem on earth, including us. A study looking at toxicity levels in human populations required a control group, and a tribe of Inuit living on an Alaskan island were chosen since they were presumed not to have had any contact with civilization. However, testing found that they actually had the highest levels of persistent environmental chemicals of any human population in their tissues. The reason it was determined was that they were eating almost exclusively meat from marine predators such as seals, which themselves had bioaccumulated toxins to an extremely high level.

 

Mechanisms of Toxicity: Cytotoxins, Neurotoxins, Mutagenics, Hormone Mimetics, and Immunosuppressors

 

Different toxins act differently on the body. Cytotoxins or cell-poisons in some way disrupt cell function. This can occur through a loss of respiratory function on the cellular level, leakage of fluid from cell walls, a disruption of cell metabolism, or a variety of other mechanisms. Cytotoxicity is usually immediate, the best-known example is Cyanide poisoning. A ship or a factory which dumps a cytotoxin into the water will generally cause an immediate fishkill at the site. Marine life also produces cytotoxins. Jellyfish and sea anemones inject cytotoxins with their stinging cells to predigest their prey.

Neurotoxins attack the nervous system. There are a variety of neurotoxins out there, and some are naturally created. Red tide, a marine organism, produces a neurotoxin, and so do several poisonous marine species. The main purpose and action of a neurotoxin is paralysis of the nervous system. The toxin may attack the nerves themselves or the neurotransmitters which are chemical messenger compounds within the brain or nervous system. One of the problems with neurotoxins is that different species have different neurotransmitters, which makes some of them not only non-susceptible to the toxin, but also allows them to bioaccumulate it to levels that are much higher than those in the surrounding water. A clam for example will accumulate red tide toxin to a level where eating that clam can be deadly for a human while swimming in water polluted with the red tide organism would be relatively harmless (depending on the intensity of the outbreak). Certain species of turtles can accumulate environmental toxins to extremely high levels without any ill effects, while causing massive problems for the unlucky organism which eats them. Methylmercury is a neurotoxin which readily accumulates in the marine foodchain and is found in many species of fish. Methylmercury disrupts brain function causing at high concentrations the so-called Minimata disease which resembles a permanent and irreversible state of extreme intoxication.

Mutagenics are substances which if they get into the body disrupt the genetic material within the cells or the developmental process of the fetus, causing birth defects and cancer. Obviously radioactive materials fall into this category, as do hormone mimetics (discussed below) and certain other chemicals.
Hormone mimetics are persistent environmental chemicals which can mimic the action of hormones, especially estrogen, in the body. Especially if this happens during the development of the fetus, dramatic abnormalities can occur such as feminization up to and including a complete lack of male sexual characteristics or male sexual behavior in organisms which are genetically male, and the inability to reproduce in both male and female organisms. DDT, the chemical featured in Rachel Carson’s Silent Spring is a hormone mimetic which disrupts the formation of eggshells in birds. Hormone mimicking effects of both PCBs and Dioxins have been documented in multiple species ranging from seagulls and turtles to humans. In adults hormone mimetics can promote or possibly cause hormone-sensitive cancers and lower male sperm counts up to and including total reproductive failures have been documented in many mammalian predator species (including humans).

 

Immunosuppressors are persistent environmental chemicals which somehow affect or block the immune system. While the exact mechanisms are unclear, we do know that immunesuppression played a huge role in massive disease outbreaks which decimated whole populations of marine life such as the canine distemper outbreak in European harbor seals and the papilloma virus in sea turtles.

 

Whatever the mechanism, toxins eventually kill. The real tragedy lies in those toxins which like PCBs are immortal and will go on killing for as long as life on earth exists – and we as a species created them. The lesson to be learned is this: never create chemicals for frivolous purposes. There is no real need for most of the agricultural chemicals we use today, nor for many of the chemicals used in homes. Chemicals which are necessary for industrial processes need to be tested under all condition including living systems and food chains to see their effects. It then needs to be assured that the chemicals do not get from the factory to the environment. Dilution, whether in air or water, is no longer an option.

 

Non-Chemical Pollution

 

Besides chemicals there are other sources of pollution which may be just as detrimental. Visual pollution means the visual changes human activities cause in the environment. Marine species which see a vessel or a swimmer approaching generally flee. Species which would normally use an area for overwintering or reproduction will avoid it if it has people and structures on it. Many species navigate visually, with some species using the stars as navigation aids. Both air and water are getting murkier through pollution, and our city lights alone prevent a view of the stars in many coastal areas. For some species the attraction of lights is fatal. In undeveloped areas the brightest spot is the ocean, and this is where for example hatchling sea turtles head. However, in today’s world the brightest spot is in many cases the lit-up street where confused sea turtle hatchlings get killed by vehicles. Many visual organisms navigate using the coastal skyline – but exactly that we have dramatically changed over the last centuries. We do not know how many migrating animals might get confused because of those changes, but there are frequent reports of ‘lost’ sea turtles found way outside their range. Sediment and other solids in the water cut down on light penetration, so besides causing very real biological changes to photosynthetic organisms, the murkyness must also cause great difficulty for organisms which navigate, hunt, and escape visually, or which use visual communication signals such as some species of squid. Some species which visually forage for food might be distracted by objects of certain colors.

Noise pollution means the sound we are putting into air and water. If you want to know exactly how loud something is under water, put your head under water when a powerboat passes. Water conducts sound extremely well. Whales for example used to communicate across ocean basins with their songs. Today that is impossible due to all the ship noises. Humans speaking or screaming and radios blaring on coastal beaches and ships will also deter many animals from coastal environments or at least cause a significant energy drain and disruption of normal behaviors from repeated flight responses. And then there is underwater and over water military testing which creates significant amounts of noise. The greatest problem in this regard is for echolocating species which use certain low-frequency sounds to navigate, avoid collisions, and hunt. The same frequencies are also used in our sonar equipment, with unknown consequences.

Finally there is electromagnetic pollution. We have been saturating the atmosphere with radio waves and have recently also added transmitters which will penetrate both earth and water. Many marine organisms are extremely sensitive to electric fields. Sharks for example can ‘feel’ the electrical activity in the heart of their prey, or the electrical field caused by the corrosion of a very small amount of metal. Many sharks in fact navigate by following anomalies in the earth’s magnetic field. It is unknown if or how the human-created electromagnetic fields in the atmosphere affect those species. The ocean is deep, and extinctions could be taking place which we will only notice far too late.

 

 

 

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