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Biodiversitat i estructura de la comunitat íctica litoral del substrat rocós del Parc Natural de serra Gelada (sud-oest del mar Mediterrani) Aquest estudi analitza la comunitat íctica litoral sobre substrat rocós del Parc Natural de serra Gelada (Alacant) i s’aporten dades de base que permetran avaluar a llarg termini els canvis deguts a diverses mesures de gestió. Es van fer censos visuals en transsectes lineals sobre fons rocosos entre 1 i 32 m de profunditat. A les set localitats estudiades es van comptar 44 espècies. El nombre d’espècies, l’abundància, la biomassa i l’estructura de talles van ser similars entre les zones amb alta i baixa protecció. La composició d’espècies observada va ser similar a les d’altres àrees marines protegides del Mediterrani occidental. Les diferències entre localitats podrien ser causades per l’alta heterogeneïtat i complexitat de l’hàbitat a petita escala.

Irregular sea urchins such as the spatangoid Spatangus purpureus are important bioturbators that contribute to natural biogenic disturbance and the functioning of biogeochemical cycles in soft sediments. In the coastal waters of the Balearic Islands S. purpureus occurs in soft red algal beds, and can reach high densities. The diet of S. purpureus is unknown and it is particularly difficult to analyze the stomach contents of this group; therefore, we analyzed the fatty acid (FA) composition of the gonads and potential food resources in order to assess the trophic relationships of this species. The FA profiles of the gonads of S. purpureus agree well with the FA composition of the potential trophic resources (algae and sediment) and reveals changes between localities with different available resources. Three polyunsaturated FAs mainly contributes in the composition in the S. purpureus gonads: eicosapentaenoic acid (C20:5n-3) and arachidonic acid (C20:4n-6), both abundant in the macroalgal material, and palmitoleic acid (C16:1n-7), which is characteristic of sediment samples. Trophic markers of bacterial input and carnivorous feeding were significantly more abundant in sea urchins caught on bottoms with less vegetation. The current study demonstrates that the FA content of S. purpureus gonads is a useful marker of diet, as differences in the profiles reflected the variations in detritus composition. The results of this study show that this species has omnivorous feeding behavior; however, viewed in conjunction with available abundance data the results suggest that phytodetritus found within algal beds is an important carbon source for this species., (Copyright © 2011 Elsevier Ltd. All rights reserved.)