( ber of species were lost. Studies o...)Fish extinctions alter critical nutrients in water, study shows

Studies of complex ecosystems, especially those involving large, highly mobile fish, are almost impossible to carry out in the wild, but new methods are helping researchers better understand these systems.

"Computer simulations provide a means to assess patterns of species loss in a system in which we just cannot do complex experiments," said co-author Alex Flecker, Cornell associate professor of ecology and evolutionary biology, who served as McIntyre's adviser. "But we have to be aware that there is a whole set of assumptions that goes into simulating species loss."

For example, it is unknown whether surviving species can truly compensate for extinctions. In a study of two species of fish in the Venezuelan river that eat mud from the river bottom, Flecker found that the rarer of the two species was unable to make up for the loss of the more common one. Thus, it appears that human overfishing of the common species, coporo (Prochilodus mariae), may have large effects on the ecosystem, in part because of its large contribution to nitrogen recycling.

The current study also revealed that species that heavily recycle nitrogen are not always the same ones that recycle the most phosphorus. These differences would make it difficult for conservationists to prioritize species to protect.
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Source:Cornell University News Service