Marine Food Webs Collapsing Due to Climate Change

(Paul B. Hillman/NOAA Fisheries via AP)

(CN) – Rising sea temperatures reduce the critical flow of energy from the bottom to the top of marine food webs, according to a new study showing the threat climate change poses to aquatic species.

The report, published Tuesday in the journal PLOS Biology, examines how energy transfer issues can potentially limit food availability for top predators, which in turn can affect other species within marine food webs.

“Healthy food webs are important for maintenance of species diversity and provide a source of income and food for millions of people worldwide,” said lead author Hadayet Ullah, a doctoral candidate at the University of Adelaide in Australia. “Therefore, it is important to understand how climate change is altering marine food webs in the near future.”

For the study, the researchers built 12 large 423-gallon tanks that simulated predicted levels of ocean temperature and acidity caused by rising man-made greenhouse gas emissions. The tanks featured snails, sponges, shrimp, algae, fish and other marine species.

The small-scale food web was exposed to future climate conditions for six months, during which the team assessed the productivity, biomass, growth and survival of all plants and animals.

The researchers then used these findings in an advanced food web model.

“Whilst climate change increased the productivity of plants, this was mainly due to an expansion of cyanobacteria (small blue-green algae),” Ullah said. “This increased primary productivity does not support food webs, however, because these cyanobacteria are largely unpalatable and they are not consumed by herbivores.”

Understanding how ecosystems react to global warming is a challenge in ecological research. Most research on ocean warming focuses on basic, short-term experiments on one or a few species.

“If we are to adequately forecast the impacts of climate change on ocean food webs and fisheries productivity, we need more complex and realistic approaches, such as large mesocosms that provide more reliable data for sophisticated food web models,” said project leader Ivan Nagelkerken, a marine ecology professor at the University of Adelaide.

Marine ecosystems already face major impacts from climate change, making it important to examine how these results can be applied to ecosystems worldwide.

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