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Marine Ecology Progress Series

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MEPS 440:115-125 (2011)  -  DOI:

Marine reserve designation, trophic cascades and altered community dynamics

David O’Sullivan1, Mark Emmerson1,2,3,*

1School of Biological, Earth and Environmental Sciences, University College Cork, The Cooperage, Distillery Fields, North Mall, Cork, Ireland
2Environmental Research Institute, University College Cork, Lee Road, Cork, Ireland
3School of Biological Sciences, Medical and Biological Centre, Queen’s University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK

ABSTRACT: Marine ecosystems and their associated populations are increasingly at risk from the cumulative impacts of many anthropogenic threats that increase the likelihood of species extinction and altered community dynamics. In response, marine reserves can be used to protect exploited species and conserve biodiversity. The increased abundance of predatory species in marine reserves may cause indirect effects along chains of multi-trophic interactions. These trophic cascades can arise through direct predation, density-mediated indirect interactions (DMIIs), or indirect behavioural effects, termed trait-mediated indirect interactions (TMIIs). The extent of algal cover and the abundance of 4 primary consumers were determined in Lough Hyne, which was designated Europe’s first marine nature reserve in 1981. The primary consumers were the sea urchin Paracentrotus lividus, the topshell Gibbula cineraria, the oyster Anomia ephippium, and the scallop Chlamys varia. The abundances of 3 starfish species (Marthasterias glacialis, Asterias rubens, and Asterina gibbosa) were also determined, as were 2 potential crustacean predators, Necora puber and Carcinus maenas. These data were compared with historical data from a 1962 (prey) and a 1963 (predator) survey to determine the nature of community interactions over adjacent trophic levels. The present study reveals a breakdown in population structure of the 4 surveyed prey species. Marine reserve designation has led to an increase in predatory crabs and M. glacialis, a subsequent decrease in primary consumers, ­especially the herbivore P. lividus, and an increase in macroalgal cover which is indicative of a trophic cascade. The study shows that establishing a Marine Reserve does not guarantee that ­conservation benefits will be distributed equally.

KEY WORDS: Trophic cascades · Trait mediated indirect interactions · Marine reserves · Paracentrotus lividus

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Cite this article as: O’Sullivan D, Emmerson M (2011) Marine reserve designation, trophic cascades and altered community dynamics. Mar Ecol Prog Ser 440:115-125.

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