Multiple fish predators: effects of identity, density, and nutrients on lower trophic levels
The effects of declining fish diversity on marine food webs are difficult to analyze, although theory suggests that the trophic effects of multiple fish predators are not additive. Reiss and colleagues demonstrate that predatory fishes reduce the biomass of key invertebrate herbivores, but the species-specific consumer effects are attenuated in mixed predator assemblages. Indirect cascading effects strongly increased algal biomass and did not depend on the predator species, but were instead mediated by nutrient enrichment and predator density. This study demonstrates that interference among predators determines diversity in food webs, but predator density may be more important for lower trophic levels.
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