In lakes and streams, fish and insects can help protect aquatic plants that gobble up greenhouse gas

By Janet Raloff

Web edition: February 21, 2013

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This freshwater stickleback eats the tiny animals in stream water that graze on plants and algae.

Credit: Nicole Bedford, UBC

Too few bugs or fish could affect Earth’s climate in a big way, by contributing to the buildup of heat-trapping gases in the atmosphere, a new study finds. It’s a surprising example of what can happen when communities in nature become unbalanced.

Freshwater fish and insects normally feed on smaller aquatic animals. These include microscopic organisms called zooplankton. Those smaller guys in turn graze on algae and plants in the water. Those plants and algae don’t just sit at the bottom of the food chain. They also remove carbon dioxide from the water and release oxygen. It is a byproduct of photosynthesis. Algae alone produce about half the oxygen we breath.

Trisha Atwood of Canada’s University of British Columbia in Vancouver wondered what would happen to carbon dioxide levels in an aquatic environment if there were too few fish and insects at the top of this food chain. Her new tests show the impacts can be dramatic..

Visit the new Science News for Kids website and read the full story: Predators as climate helpers