Predator diversity enhances secondary production and decreases the likelihood of trophic cascades |
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Authors: | Eoin J O’Gorman Ruth A Enright Mark C Emmerson |
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Institution: | (1) Environmental Research Institute, University College Cork, Lee Road, Cork, Ireland;(2) Department of Zoology, Ecology and Plant Sciences, University College Cork, Distillery Fields, North Mall, Cork, Ireland |
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Abstract: | We manipulated the diversity of top predators in a three trophic level marine food web. The food web included four top benthic
marine fish predators (black goby, rock goby, sea scorpion and shore rockling), an intermediate trophic level of small fish,
and a lower trophic level of benthic invertebrates. We kept predator density constant and monitored the response of the lower
trophic levels. As top predator diversity increased, secondary production increased. We also observed that in the presence
of the manipulated fish predators, the density of small gobiid fish (intermediate consumers) was suppressed, releasing certain
groups of benthic invertebrates (caprellid amphipods, copepods, nematodes and spirorbid worms) from heavy intermediate predation
pressure. We attribute the mechanism responsible for this trophic cascade to a trait-mediated indirect interaction, with the
small gobiid fish changing their use of space in response to altered predator diversity. In the absence of top fish predators,
a full-blown trophic cascade occurs. Therefore the diversity of predators reduces the likelihood of trophic cascades occurring
and hence provides insurance against the loss of an important ecosystem function (i.e. secondary production). |
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Keywords: | BEF Trait-mediated indirect interaction Multiple predator effects Species richness Risk reduction |
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