Revue d’Ecologie (Terre et Vie), Vol. 73 (3), 2018 : 211-226

211 BIODIVERSITY AND ABUNDANCE OF GELATINOUS ZOOPLANKTON ALONG THE ALGERIAN COAST Ghollame Ellah Yacine KHAMES1* & Aziz HAFFERSSAS1

_ Gelatinous zooplankton forms a taxonomically diverse group of macroplankton with varied and significant roles in pelagic communities (Madin & Harbiso, 2001; Robison, 2004). There has been limited exploration of its diversity, and the density of the species is frequently over-or underestimated due to their fragility (Raskoff et al., 2003; Bouillon et al., 2006). Although often similar in their morphology (typically being fragile, and transparent, or with a translucent body) and ecology (planktonic lifestyle), these species are taxonomically and phylogenetically distant (Olenycz, 2015). In recent years, strong and sustained blooms of gelatinous populations have been recorded in different geographic marine areas (Mills, 2001; Brodeur et al., 2002). These blooms have often been related to global warming, which can be particularly important in temperate zones. Combined with eutrophication, it can generate a rapid increase in the abundance of phytoplankton, which in turn can lead to an increase of mesozooplankton abundance (Mills, 2001; Lynam et al., 2004; Attrill et al., 2007). Some gelatinous species can bloom in very high densities and seriously affect prey populations, and fish eggs production (Purcell, 1997; Richardson et al., 2009). Previous studies of zooplankton communities in the Algerian basin and Alboran Sea have tended to focus on copepods, the major zooplankton component, providing considerable qualitative and quantitative data (Seridji & Hafferssas, 2000; Youssara & Gaudy, 2001; Andersen