Trophic ecology of the rocky shore community associated with the Ascophyllum nodosum zone (Roscoff, France): A delta C-13 vs delta N-15 investigation
Résumé
This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the rocky shore of Roscoff by using delta C-13 and delta N-15. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high delta N-15 range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on delta N-15 values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat. (C) 2008 Elsevier Ltd. All rights reserved.