Relationships between the Hydrodynamics and Changes in Copepod Structure on the Algerian Coast

Aziz Hafferssas and Rabia Seridji (2010) Relationships between the hydrodynamics and changes in copepod structure on the Algerian coast. Zoological Studies 49(3): 353-366. We investigated the role of the Algerian Current on the structure of the copepod community during June 1990 that covered an area between 1°E and 5°E. In this area, 2 oligotrophic systems of different origins (one related to the Atlantic flow, and the other related to typical Mediterranean waters) and a frontal system were identified. Environmental differences among the 3 zones were related to changes in sea surface salinity, density, and phytoplankton biomass (chlorophyll (Chl)-a concentrations). Three main copepod assemblages were revealed to be distributed along well-defined environmental gradients characterized by the distribution of physical variables and Chl-a. The 1st group was located in the frontal zone where the highest Chl-a concentration was observed at the subsurface (> 1.5 mg/m3). This assemblage showed an important increase of herbivorous species (Paracalanus parvus, Clausocalanus arcuicornis, C. furcatus, Mesocalanus tenuicornis, and Eucalanus elongatus) which were numerically 4 times more abundant (> 90%) than in modified Atlantic water (MAW) and offshore surface Mediterranean water (SMW) systems (< 30 % and 35%, respectively). The 2nd group occupied the inshore MAW system, and was characterized by a typical neritic fauna (Acartia clausi, Euterpina acutifrons, Oithona nana, and Temora stylifera). The 3rd group was composed of several species (Scolecithricella dentata, S. vittata, Oncaea media