Meeting Abstract

P3.63  Sunday, Jan. 6  Feeding strategies and resource partitioning among mysids in oligotrophic marine caves. RASTORGUEFF, P.-A.*; HARMELIN-VIVIEN, M.; RICHARD, P.; CHEVALDONNé, P.; Aix-Marseille Université – UMR CNRS 7263 IMBE; Aix-Marseille Université – UMR CNRS 7294 MIO; Université de La Rochelle – UMR CNRS 7266 LIENSs; Aix-Marseille Université – UMR CNRS 7263 IMBE pierre-alexandre.rastorgueff@imbe.fr

The understanding of how large populations of several mysid (Crustacea) species coexist and share resources in oligotrophic underwater marine caves from the northwestern Mediterranean Sea was investigated using carbon and nitrogen stable isotopes. The isotopic signatures indicated food partitioning among the five species of cave-dwelling mysids. Hemimysis speluncola feeds mainly on phytoplankton and zooplankton from outside the caves, Siriella gracilipes on sedimentary organic matter and zooplankton from the outside, Harmelinella mariannae on small cave-dwelling crustaceans and Hemimysis margalefi and Hemimysis lamornae mediterranea on sedimentary particulate organic matter. Different diets seem to promote mysid coexistence in caves as resource partitioning reduces interspecific competition. However, the analysis of both seston and cave sediments indicates that the quantity and quality of organic matter are strongly reduced in caves compared to the outside. Therefore some mysid species have adapted to finding their food in another environment. Some species are indeed documented to migrate outside of caves at night, where phytoplankton and zooplankton are available. These outside-inside movements make cave-dwelling mysids important drivers in the organic matter transfer from the open sea to different locations inside caves. The organic matter from the open sea accumulated by mysids is then made available to other cave-dwellers by fecal pellet production and predation by cave-dwelling teleost fishes, decapod crustaceans or even carnivorous sponges.