The past and present topology and structure of Mediterranean subtidal rocky-shore food webs

The understanding of the taxonomic composition of Mediterranean subtidal rocky-shore food webs is extraordinary; the information on trophic links and food-web structure is, however, still meager. An initial description of the rocky-bottom food web of the Medes Islands off the Catalan coast includes a minimum of 1350 species organized in five trophic levels. A minimum of 151 trophic links have been identified for 37 broad trophic/taxonomic categories (including humans), although estimates of the total number of links at the species level may be on the order of thousands for fishes alone. Mediterranean food webs are dynamic, their topology and structure varying along seasonal and environmental gradients. Fishing has been for thousands of years the single major factor provoking changes in the structure of these Mediterranean food webs. Ecologically extinct megafauna (monk seal, loggerhead turtle, sharks) accounted for 24% of the identified trophic interactions. The removal of these large consumers had undescribed ecological consequences. Improved understanding of present and past Mediterranean food webs will improve understanding of the effects of human activities and help us preserve and restore these food webs.