ZOOPLANKTON BIOMASS, FEEDING AND METABOLISM IN A GEOSTROPHIC FRONTAL AREA (ALMERIA-ORAN FRONT, WESTERN MEDITERRANEAN) - SIGNIFICANCE TO PELAGIC FOOD WEBS

Mesozooplankton abundance and physiological rates in copepods were mea sured at selected sites in the Alboran Sea, in May 1991, on Cruise Alm ofront 1 (JGofs-France). Higher total zooplankton standing stocks, hig her copepod abundance, higher feeding activity by the latter and a hig her proportion of phytoplankton-derived carbohydrates in their diet we re found in the geostrophic jet of inflowing Atlantic water than in su rrounding areas, which offered a range of oligotrophic conditions. Rel ationships with data obtained in other disciplinary fields on the same cruise show that biological enrichment was due to locally enhanced pr oduction rather than advection of exogenous living matter. In the most productive context, sustained production effected by phytoplankton ce lls in the > 10 mum class size (diatoms) was being significantly trans ferred to higher trophic levels through herbivores with a relatively l ong generation time (copepods). The processes responsible for the fert ilization, and their relationship to the jet and its frontal boundary, are discussed.