[OANNES Foro] Food web structure within kelp holdfasts (Laminaria): a stable isotope study

[Mario Cabrejos]

Marine Ecology
Article first published online: 13 SEP 2011
DOI: 10.1111/j.1439-0485.2011.00487.x

Food web structure within kelp holdfasts (Laminaria): a stable isotope study
Gauthier Schaal1,2,3, Pascal Riera2,3, Cédric Leroux2,4
1Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa2 UPMC Univ Paris 06, Station Biologique de Roscoff, Roscoff, France3 CNRS, UMR 7144 AD2M, Roscoff, France4 CNRS, FR 2424, Roscoff, France. Correspondence: Gauthier Schaal, E-mail: G.Schaal en ru.ac.za
Abstract
Kelp holdfasts are highly reticulated structures which host a large diversity of small fauna. These microhabitats have been reported to play a crucial role in the biodiversity associated to kelp forest ecosystems. This study aimed at identifying trophic links and the main food sources sustaining food webs within communities associated with kelp holdfasts, through a stable isotope (?13C and ?15N) approach. Sampling of the main invertebrates inhabiting Laminaria digitata holdfasts, and of their potential food sources, took place in February and May 2007. Stable isotope results reveal that most of the primary consumers, including filter-feeders and deposit-feeders, rely on the particulate organic matter sedimented within kelp holdfasts. Only three grazers departed from this general pattern. The correspondence between the stable isotope ratios of predators and sediment consumers indicated that this source is at the base of the main pathway through which energy and matter transit in the food web. ?15N ranges found for consumers revealed that the food web associated with kelp holdfasts is composed of 3.5 levels. In spite of the low diversity of food sources at the base of the food web, these microhabitats can therefore be considered micro-scale ecosystems, from a functional perspective.



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