Reduced epibenthic predation on intertidal bivalves after a severe winter in the European Wadden Sea


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mstrasser [ at ] awi-bremerhaven.de

Abstract

One hypothesis to explain the phenomenon of high bivalve recruitment after severe winters in the coastal North Sea sediments is reduced epibenthic predation. Using predator exclusion experiments I tested the hypothesis that epibenthic predation on the juvenile bivalves Cerastoderma edule, Macoma balthica and Mya arenaria was lower after a severe winter (1995/96) than after a moderate (1996/97) and a mild (1997/98) winter. In C. edule and M. arenaria there was two-fold evidence for reduced epibenthic predation after the severe winter: (i) significant predation effects occurred only in exclusion experiments after the two milder winters but not after the severe winter, (ii) recruits attained larger sizes in August and October after the severe winter suggesting continuous growth rather than truncation of the size spectrum by predators. In M. balthica predation effects also were significant only after the milder winters but with no effect on size. In all three bivalve species recruitment at the experimental sites in the fall was higher after the severe than after the two milder winters. These results suggest that high bivalve recruitment after severe winters is primarily caused by the post-settlement factor of reduced epibenthic predation on the tidal flats. The strategy to conduct several predator exclusion experiments in sand and in mud in three consecutive years with differential winter conditions, and while considering migration activity and size development in juvenile bivalves proved useful to distinguish between cage artefacts and predation effects.



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ISI/Scopus peer-reviewed
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Eprint ID
5591
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Strasser, M. (2002): Reduced epibenthic predation on intertidal bivalves after a severe winter in the European Wadden Sea , Marine Ecology-Progress Series, 241 , pp. 113-123 .


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