Parasites outweigh predators in Pacific Coast...( In a study of parasites living in th...)

In a study of parasites living in three estuaries on the Pacific coast of California and Baja California, researchers have determined that biomass of these parasites exceeds that of top predators, in some cases by more than 20 times.

Their findings, which could have significant ecological and biomedical implications, appear in this week's issue of the journal Nature.

Biomass is the amount of living matter that exists in a given habitat. It is expressed either as the weight of organisms per unit area or as the volume of organisms per unit volume of habitat.

Until now, scientists have believed that because parasites are microscopic in size they comprised a small fraction of biomass in a habitat, while free-living organisms such as fish, birds and other predators make up the vast majority.

"We quantified the biomass of free-living and parasitic species in three estuaries and discovered that parasites have substantial biomass in these ecosystems," said Armand Kuris, a zoologist at the University of California at Santa Barbara (UCSB), and a lead author of the paper.

"Parasites have as much, or even more, biomass than other important groups of animals--like birds, fish and crabs," said Ryan Hechinger, a marine scientist at UCSB and co-lead author of the paper.

The results are part of a study supported the National Science Foundation (NSF) and the National Institutes of Health through the agencies' joint Ecology of Infectious Diseases (EID) Program.

"Unlike large animals, such as birds, parasites are tiny and often easy to overlook," said Sam Scheiner, NSF program director for EID, co-funded by NSF's Directorates for Biological Sciences and Geosciences. "These results will cause ecologists and other scientists to completely reconsider their views."

Other principal investigators include Kevin Lafferty, a marine ecologist with the United States Geological Survey and Andrew Dobson,
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