Winners, losers among fish when landscape undergoes change

Date: February 21, 2017

Source: University of Washington

A new study by the University of Washington and Simon Fraser University finds that some fish lose out while others benefit as urban and agricultural development encroaches on streams and rivers across the United States. Having a diversity of species, each with different land-use sensitivities and ecological functions, helps buffer ecosystems from failing in the face of development. The findings were published online in December in Global Change Biology.

"Human activities operating across the landscape don't randomly impact biodiversity, that is, species survival is not determined by a flip of the coin. Species have different traits and ecologies that determine their sensitivity environmental change," said co-author Julian Olden, a UW associate professor of aquatic and fishery sciences.

"Our research suggests that every player in a community is important, to varying degrees, for ecosystem functioning into the future."

This study is the first to take a national-level look at the effects that land-use changes can have on a major ecosystem role that freshwater fishes serve in streams and rivers. The authors analyzed data on more than 500 fish species taken from about 8,100 locations within streams across the U.S.

The authors specifically looked at the magnitude of nutrient recycling by fish, either by urinating or excreting through their gills. In any given stream, important nutrients like phosphorus and nitrogen that keep the ecosystem healthy are locked up in the bodies of plants and animals. When fish eat, they acquire some of these nutrients from prey and excrete the rest back into the water, essentially serving as giant recyclers in the ecosystem.

The researchers took data on the amount of nutrient recycling by different fish species, then paired that with fish populations in each area to map the geography of recycling occurring in streams and rivers across the entire U.S. Once they identified and counted the fish that contribute the most nutrients in any given stream, they were able to use predictive models to forecast what would happen to these ecosystems if urbanization increased into the future. Broadly, they found that having a diversity of species appears to help ecosystems maintain balance.

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