A starfish and other marine organisms in an underwater ecosystem.

Marine communities filled with diverse life forms could be devastated as ocean water warms and acidifies. Credit: Sean D. Connell

Ocean sciences

Bustling seascapes risk collapse as the climate changes

A marine food web recreated in the laboratory provides a sobering look at ocean life in a warming world.

Global warming could degrade the ocean’s food webs and lead to their collapse, according to experiments that used oversized fish tanks to simulate the waters of coastal Australia.

Ivan Nagelkerken at the University of Adelaide, Australia, and colleagues recreated a marine ecosystem in a series of 1,800-litre tanks that held everything from algae to invertebrates and fish. The team then increased acidity and temperatures to reflect conditions projected for the ocean at the end of the twenty-first century.

Faced with acidification alone, the food webs’ composition and function did not change significantly. Waters warmer than current temperatures, by contrast, bolstered productivity and biomass of weedy algae and other photosynthetic life forms at the bottom of the food chain; molluscs and other organisms that consume these low-level producers suffered. These trends were even more pronounced in food webs exposed to both warming and acidification.

Predatory invertebrates and fish proved relatively resilient to these changes, but the authors note that their experiments lasted for only four to five months, and warn that longer-term changes at lower levels of the food web could eventually harm species at the top.