Article

Strong top-down control in southern California kelp forest ecosystems.

National Center for Ecological Analysis and Synthesis, 735 State Street, Santa Barbara, CA 93101, USA.
Science (Impact Factor: 31.48). 06/2006; 312(5777):1230-2. DOI: 10.1126/science.1128613
Source: PubMed

ABSTRACT Global-scale changes in anthropogenic nutrient input into marine ecosystems via terrestrial runoff, coupled with widespread predator removal via fishing, have created greater urgency for understanding the relative role of top-down versus bottom-up control of food web dynamics. Yet recent large-scale studies of community regulation in marine ecosystems have shown dramatically different results that leave this issue largely unresolved. We combined a multiyear, large-scale data set of species abundances for 46 species in kelp forests from the California Channel Islands with satellite-derived primary production and found that top-down control explains 7- to 10-fold more of the variance in abundance of bottom and mid-trophic levels than does bottom-up control. This top-down control was propagated via a variety of species-level direct and indirect responses to predator abundance. Management of top-down influences such as fishing may be more important in coastal marine ecosystems, particularly in kelp forest systems, than is commonly thought.

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