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RESEARCH PRODUCT

Sedimentary and particulate organic matter: mixed sources for cockleCerastoderma glaucumin a shallow pond, Western Mediterranean

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Seasonal changes in feeding habits and diet of the cockle Cerastoderma glaucum (Mollusca, Bivalvia) were analysed using carbon (δ 13 C) and nitrogen (δ 15 N) stable isotopes. I aimed to investigate the role of benthic and pelagic sources in the diet of this dominant infaunal bivalve on a western Mediterranean sandy bottomed pond. Adult C. glaucum and all potential organic sources (particulate and sedimentary organic matter, seagrass, macroalgae, het- erotrophic detritus) were collected and analysed for δ 13 Ca ndδ 15 N. In total 5 dominant organic sources were found, ranging between -21.0 and -8.0%� for δ 13 C and from 3.0 to about 7.0%� for δ 15 N. C. glaucum assimilated fraction ranged between -14.0/-15.0%� and 6.0/9.0%� respectively, for carbon and nitrogen, while its estimated fractionation seasonally varied between 1 and 1.5 for carbon and was about 3 for nitrogen. C. glaucum reflected the isotopic com- position of its food while maintaining, throughout the year, a fairly constant isotopic composition in its assimilated fraction, despite the high variability in isotopic composition of available sources.