Climate change and the collapse of marine food chains

"We know relatively little about how climate change will affect the marine environment," said Sean Connell, a professor in ecology and environmental science at the University of Adelaide, according to Science Alert. "Until now, there has been almost total reliance on qualitative reviews and perspectives of potential global change. Where quantitative assessments exist, they typically focus on single stressors, single ecosystems or single species." 

This is the first time that scientists have analyzed over 600 different studies covering a wide range of ocean environments, ecosystems and marine species and the effect that global warming has on ocean life. According to Connell, this is the first time scientists will be able to study the combined effects of multiple stressors on whole communities. These factors include interactions among different species and different responses to climate change, covering tropical to Arctic waters, as well as a range of ecosystems from coral reefs to kelp forests to open oceans.

"This is the first time scientists will study the combined effects of multiple stressors on whole communities."

The correlation of these studies was published Oct. 12, 2015, in the journal Proceedings of the National Academy of Science. The research gave the first large-scale data showing that ocean acidification and warming temperatures have decreased marine diversity and the number of marine organisms left in the world's oceans. The study went on to conclude that the data is directly correlated to increased anthropogenic carbon dioxide emissions.

The breakdown of the food chain
All ecosystems have intertwined food chains, which create larger and bigger food webs. Researchers have predicted that many, if not most, marine species will not be able to acclimate to the increased water temperatures or the higher levels of acidification. Over time, this will lead to a decrease in the marine species diversity and the number of organisms living in the sea.

Warm waters cause an increase in an organism's metabolic rate, which has created a greater demand for food, especially for larger carnivorous marine organisms. Most species of phytoplankton (primary producers) will still be successful at the bottom of the marine food webs depending on where they are located, but the changes in the water temperature and acidity will not help the organisms further up the food web, including zooplankton and other small fish (primary consumers). The large fish that fisheries are based around are not surviving because there is less food available for them. This causes them to starve before they are able to reproduce. 

Further research into the coral reef habitats has shown that high levels of acidity impact habitat-forming calcifying species such as mussels, oysters and coral. The results of acidification on coral reefs greatly impacts the many different types of marine organisms that call the reef systems their home, causing even more damage to the number and diversity of marine life. Acidification has also lead to a decline in dimethylsulfide gas (DMS). This gas is produced by ocean plankton and helps in cloud formation, which in turn, helps the Earth control heat exchange with space.

Marine food chains may be immensely impacted by climate change, and soon. Marine food chains may be immensely impacted by climate change, and soon.

The future of the world's oceans
Ivan Nagelkerken, an associate professor at the University of Adelaide said, "This 'simplification' of our oceans will have profound consequences for our current way of life, particularly for coastal populations and those that rely on oceans for food and trade."

In recent years, fisheries have seen a decrease in many marine organisms, including large fish like tuna all the way down to shellfish species. Local shell fisheries on the U.S. West Coast have had near total loses of oysters in both the natural environments and aquaculture facilities (marine farms). Research collected over the last few years has shown that an increase in pH (acidity) has caused a drastic decrease in the development of the larval oysters. Recent observations are indicating that the increase in acidity is not from natural carbon dioxide vents, but from anthropogenic carbon dioxide, which is contributing to the seasonal decrease of oysters and other shellfish species.

Coastal communities heavily rely on the marine ecosystem, especially when it comes to the local and regional economy. The oyster business brings in over $100 million dollars a year to California and Washington. More needs to be done to take care of the oceans that support us with food and other resources. Water quality consultants and ecological consulting services can help local communities with monitoring and tracking carbon dioxide in the oceans at various depths and distances offshore.

This will not only provide the U.S. Environmental Protection Agency (EPA) with more data, but also allow fisheries to start identifying significant changes that occur in the oceans. Right now, there is no way to predict how the marine ecosystems will fully be impacted with the current acceleration of warming ocean waters and increased acidification, but it is important that local communities track their anthropogenic and natural carbon dioxide emissions and hopefully find ways to decrease these emissions in the future.