Ocean Acidification To Bring Collapsing Food Web

Ocean acidification created by continuing anthropogenic climate change will result in a collapsing food web, according to new research from the University of Adelaide. The new findings are the result of analysis focused around determining the effects of climate change on the world’s fisheries, and on overall marine biodiversity.

Image via NOAA

“Humans rely heavily on a diversity of services that are provided by ocean ecosystems, including the food we eat and industries that arise from that,” commented project leader Professor Ivan Nagelkerken, from the University of Adelaide’s Environment Institute.

“Our understanding of what’s likely to happen has been hampered by an over-reliance on simplified laboratory systems centred on single levels of the food web. In this study, we created a series of three-level food webs and monitored and measured the results over a number of months to provide an understanding of future food webs under climate change.”

The work based these constructed marine food webs on the algae, base invertebrates (krill, shrimp, etc), and small fish that form the foundations of the world’s marine food webs.

To this end, the researchers put together 12 large aquaria, each stocked with various species meant to approximate sea grass, risky reef, and open sand marine habitats. Tidal movements were mimicked with artificial current creation.

These approximated habitats were then subjected to the levels of ocean acidification that are (conservatively) estimated for occur by the end of the century — over the course of several months.

“Elevated carbon dioxide concentrations boosted plant growth; more plant food meant more small invertebrates, and more small invertebrates, in turn, allowed the fish to grow faster,” commented PhD candidate Silvan Goldenberg, who is supervised by Professor Nagelkerken and Professor Sean Connell.

“However, ocean warming cancelled this benefit of elevated carbon dioxide by causing stress to the animals, making them less efficient feeders and preventing the extra energy produced by the plants from travelling through the food web to the fish. At the same time, fish were getting hungrier at higher temperatures and started to decimate their prey, the small invertebrates.”

In other words, the net-effect is severely “negative.”

“The consequences for marine ecosystems are likely to be severe,” stated Professor Nagelkerken. “Oceans in the future may provide less fish and shellfish for us to eat, and larger animals that are at the top of the food web, in particular, will suffer. We hope this study will provide predictive understanding which is critical for effective fisheries management.”

That would be the case, of course, if most of the world’s fisheries weren’t expected to collapse over the coming decades anyways, as a result of overfishing.

The new research was detailed in a paper published in the journal Global Change Biology.

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