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Marine Ecology Progress Series

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MEPS 610:51-63 (2019)  -  DOI:

Density-dependent growth of bivalves dominating the intertidal zone of Banc d’Arguin, Mauritania: importance of feeding mode, habitat and season

Matthijs van der Geest1,2,*, Jorge A. C. van der Lely1, Jan A. van Gils1, Theunis Piersma1,3, Tamar Lok1

1NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems, and Utrecht University, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
2MARBEC Centre for Marine Biodiversity, Exploitation and Conservation, UMR 9190, IRD-IFREMER-CNRS-UM, Université de Montpellier, 34095 Montpellier cedex 5, France
3Conservation Ecology Group, Groningen Institute for Evolutionary Life Sciences (GELIFES), University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands
*Corresponding author:

ABSTRACT: Accurate predictions of population dynamics require an understanding of the ways by which environmental conditions and species-specific traits affect the magnitude of density dependence. Here, we evaluated the potential impact of season and habitat (characterized by sediment grain size and seagrass biomass) on the magnitude of density dependence in shell growth of 3 infaunal bivalve species dominating the tropical intertidal benthic communities of Banc d’Arguin, Mauritania. Two of our focal species were filter feeders (Senilia senilis and Pelecyora isocardia) and one was a facultative mixotroph (Loripes orbiculatus), mainly relying on organic carbon provided by sulphide-oxidizing endosymbiotic gill-bacteria (i.e. chemosymbiotic). Distinguishing 2 seasons, winter and summer, we manipulated local bivalve densities across habitats (from bare sandy sediments to seagrass-covered mud). In situ growth of individually tagged and relocated clams was measured and compared with those of tagged clams that were allocated to adjacent sites where local bivalve densities were doubled. Growth was negatively density-dependent in both winter and summer in P. isocardia and L. orbiculatus, the 2 species that mainly inhabit seagrass sediments, but not in S. senilis, usually found in bare sediments. As reproduction and survival rates are generally size-dependent in bivalves, our results suggest that in our tropical study system, the bivalve community of seagrass-covered sediments is more strongly regulated than that of adjacent bare sediments, regardless of species-specific feeding mode or season. We suggest that ecosystem engineering by seagrasses enhances environmental stability, which allows bivalve populations within tropical seagrass beds to stay close to carrying capacity.

KEY WORDS: Carrying capacity · Chemosymbiosis · Density dependence · Environmental heterogeneity · Feeding guild · Seagrass · Soft-sediment habitat

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Cite this article as: van der Geest M, van der Lely JAC, van Gils JA, Piersma T, Lok T (2019) Density-dependent growth of bivalves dominating the intertidal zone of Banc d’Arguin, Mauritania: importance of feeding mode, habitat and season. Mar Ecol Prog Ser 610:51-63.

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