Loss of One Species Makes Big Difference

U.S. scientists say removal of just one important freshwater species can seriously disrupt how such an ecosystem functions.

The finding by researchers at Dartmouth College, Cornell University and the University of Wyoming contradicts theories that other species can jump in and compensate for the loss.

Brad Taylor, a research associate in the department of biological sciences at Dartmouth, and colleagues studied a fish called the flannelmouth characin (Prochilodus mariae) native to South American rivers. That fish eats detritus, the fine organic matter on the river bottom and plays a critical role in regulating the breakdown and transport of carbon in the rivers.

This fish species is a popular food source; it is harvested regularly, and in some cases, it’s overfished, said Taylor, the study’s lead author. We learned that removing this particular fish greatly altered the metabolic activity of the river ecosystem. Other fish species did not compensate for the lack of (the fish) an effect consistent with observations from other rivers where they have been excluded much longer by dams.

Taylor’s research, funded by the National Science Foundation, appeared in the Aug. 11 issue of the journal Science.