Impacts of environmental changes on southern ocean food web

In January of this year, a comprehensive study of animals in the Southern Ocean was completed, showing that the region is under threat from climate change. The scientific journal Deep Sea Research Part II: Topical Studies in Oceanography featured the findings of an international group of researchers who wrote over 20 papers about the effects on the Scotia Sea food web by above average water temperatures. Primary producers, also known as autotrophs like phytoplankton, are organisms that make their own food from a primary energy source like the sun or deep sea vents. These organisms are eaten by zootrophs, such as krill, and then eaten by fish, and so on. The study outlined how this food web is currently structured, how it has changed over time, and provides insight as to how it will respond to future climate change. The research team took three years and three separate expeditions at various times of year to study this complex web, using techniques ranging from net sampling to hydro-acoustics. The team was lead by the British Antarctic Survey (BAS), one of the world's leading environmental research centers. Dr. Geraint Tarling, lead researcher from the BAS said, "The Scotia Sea has some of the highest levels of productivity in the Southern Ocean. With impacts like ocean temperature change and krill fishing taking place it’s essential we understand exactly who eats who." Recordings around the island of South Georgia — a British territory in the southern Atlantic Ocean - showed that this region has some of the strongest carbon dioxide (CO2) absorption rates compared to the rest of the Southern Ocean.  When more carbon dioxide is absorbed by the ocean from the air, it can disrupt the natural balance of marine life and upset the food web. This is because while the oceans can help mitigate global warming by absorbing CO2, excessive dissolved CO2 can have a negative effect on marine life. CO2 is an acidic gas, which can cause the surface ocean pH to drop, which in turn makes the water itself more acidic. According to National Geographic, the increase in acidity makes it more difficult for animals that create their own shells and some algae to gather carbonate ions from the seawater, which is crucial for them to form their shells. Many of these shell-forming animals are key links in the food web. In the Scotia Sea, it was found that there are short and long food chains in various areas. This observation is important because compared to findings from the Discovery Investigations - which took place over 80 years ago to investigate the biology of whales in the area - there were predominantly short food chains present. This is an indication of the changing nature of the environment as well. "Our research shows there is likely to be regional extinctions of some species and the introduction of others so there will be winners and losers. This will have implications for the management of the Southern Ocean ecosystem in the face of the joint pressures of environmental change and the commercial harvesting of key species such as Antarctic krill," says Dr. Tarling.