Over-fishing: Global Warming’s fuel

Photo courtesy worldwildlife.org

The oceans cover almost three-quarter of the Earth’s surface and contain over 80% of all known species of living things, many of which are yet to be discovered. It is no surprise therefore that much of our dependence would be placed on these vast bodies of water that surround us and the different resources that they contain. There are over 3 billion people worldwide who depend on fish as their primary source of protein, which has also given room for the over 35 million full time and part time workers in the fishing sector around the world. Fish has been known to produce high levels of protein, the necessary macro-nutrient for body tissue construction and repair, as well as the building block of all genetic material. Other resources from fish, such as their liver oils, have proven to be good sources of vitamins and minerals for hair, skin and general organ health. Exploration and general human curiosity has also led to fishing incorporating once unconventional animals. Crustaceans and Molluscs are now harvested regularly, bring greater variety to the food we eat. However, Over-fishing has been deemed as a serious problem in recent times, with some connecting it to various issues that once seemed unrelated. One such issue is the phenomenon of Global Warming. Is Over-fishing a fuel to Global Warming?

Global Warming has always been associated with Carbon dioxide emissions

When mentioning Global Warming, the first thing that would occur in the mind of anyone would/might be Carbon emissions. Factors that have been known to cause Global Warming include Carbon dioxide emissions, Deforestation, Algal blooms in the oceans and Mining, among others. Many (if not all) of these factors, in actuality, incorporate Carbon dioxide emissions. Therefore, rising smoke or spraying aerosols would seem to be the obvious sources of a warming effect throughout the globe. What about fishing?

According to the FAO, in the year 2000, total fish captures amounted to 94.8 million tons, the highest level ever reached. The year before (1999) saw atmospheric carbon dioxide levels reaching as high as 367 parts per million (ppm). This was a huge increase from the 280 ppm which was recorded in the year 1759. Approximately 75% of these emissions were due to immediate emissions from industrial sites, primarily in the United States and China. However, the oceans must be considered. The oceans can be labelled as the Earth’s “carbon deposit bin”. Here, Carbon sequestration occurs on a large scale. This is where Carbon dioxide is taken from the atmosphere or the surrounding environment and stored in solid or liquid form. The oceans absorb over 22 million tons of Carbon every day. This shows that they play a major part in “assisting” the atmosphere in holding carbon to bring about a consistent cooling effect on the Earth. This means that carbon released from factories, cars, chemicals, burning, and respiration, are gathered and sent either into the atmosphere or into the oceans. In curbing this immense entrance of carbon, the oceans rely on a frequently overlooked factor, a secret weapon rather; Phytoplankton. This is where fishes would play their part.

Phytoplankton as seen under an electron microscope (Photo courtesy the Smithsonian magazine)

Phytoplankton are microscopic plant-like forms of plankton, having animal-like features but with photosynthetic capabilities. They act as the primary producers in oceanic food chains, being a direct or indirect source of food for whales, dolphins, seals, sea lions and other large (and small) animals. Their main function also involves the fixing of Carbon and the use of that Carbon in Photosynthesis. During Photosynthesis, light energy is used to split water into Hydrogen and Oxygen. The Oxygen is released by the Phytoplankton and made available for respiration for the survival of other animals. The Hydrogen is then combined with Carbon dioxide to form Glucose, the main food substance used by plants for various processes. When the oceans absorb Carbon, Phytoplankton absorb the Carbon. When fishes eat Plankton they also “eat” the fixed Carbon. These fishes would then deposit the Carbon in the form of waste into the deep parts of the ocean, thus alleviating the Carbon that was absorbed, separating that Carbon from the atmosphere safely for many centuries. In theory, it sounds like there isn’t a problem, especially when one can view the fish population as a “limitless resource”. However, over-fishing has led to less animals being available for consuming Phytoplankton. Also, Global warming has led to a decrease in the Plankton levels, as it offsets the chemical processes involving Nitrogen, Carbon and Phosphorus which keep Phytoplankton alive. Research done by the universities of East Anglia and Exeter have found that Phytoplankton would tend to produce more ribosomes in cooler water than in warmer water. Ribosomes are structures that help to connect protein molecules together to build genetic material. They are also made up (and therefore rich) of phosphorus. An increase in oceanic temperatures would result in a decrease in Ribosomic production in Phytoplankton, which would increase the amount of Nitrogen in the ocean in comparison to the amount of Phosphorus. This can result in the death of much Phytoplankton and the subsequent rise in Carbon levels in the ocean, creating warmer seas.

So, to recap, how are they all linked? Most Carbon emissions are taken up by the atmosphere and by the oceans. The oceans also receive Carbon from the atmosphere itself. When the Carbon enters the ocean, Phytoplankton absorb it and use it for Photosynthesis for the production of Glucose. Fish depend on Phytoplankton heavily for food, both directly and indirectly. Therefore, when they consume Phytoplankton they also consume Carbon and would help in disposing of the Carbon in deep oceanic territories and on sea floors. However, Over-fishing can lessen the amount of fish in the oceans which would limit the amount of Carbon that could be safely deposited in biological waste form at deep oceanic levels. This, overtime, would (and has been causing) cause an increase in oceanic temperatures which can result in the death of more marine life. The Phytoplankton themselves would also be affected, as increased temperatures would offset the Nitrogen-Phosphorus ratio, killing Phytoplankton and erasing the ocean’s secret weapon in the process of Carbon sequestration.

Over 50% of all fishing is done by developing countries. Therefore, simply relinquishing fishing on a whole would be anything but beneficial. Also, the global fishing industry produces a first sale value in fish captures of about US$76 billion with the fish trade worth over US$50 billion. This therefore shows that fishing is a necessary block in the economic foundation of various countries and individuals. However, methods must be put in place to curb the issue of Over-Fishing, as it not only affects marine biota and aquatic feeding relationships, but it also plays a part in the general stability of life on the planet. Therefore, when you go fishing, fish wisely!



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