Influencia de El Niño de 1997-98 en las comunidades planctónicas del Mar de Alboran (Mediterraneo Occidental)

Abstract

The Alboran Sea is the westernmost basin of the Mediterranean Sea. Its particular location, as entrance of the Atlantic Surface Water (ASW) into the Mediterranean, has led to an intense paleoceanographic and paleoclimatic research. Nevertheless, only a limited number of studies provide information related to the dynamics and ecological characteristics of the downward particle flux. In order to determine the influence of seasonal oceanographic changes on the export of particles in the Alboran Sea, one mooring line, ALB-5-F, was deployed from July 1997 to May 1998 at 35º55.47’N/01º30.77’W. The mooring location was under the influence of the Almeria-Oran Front (AOF), which is formed by the interaction between the Atlantic jet and the denser and more saline Mediterranean waters. Information based on SeaWIFS images of chlorophyll-a concentration, current-meter, and meteorological data on wind direction and intensity were used. The annual oceanographic pattern of the AOF during the studied period was directly related to the evolution of the Western Anticyclonic Gyre (WAG) and to the 1997-98’ El Niño Event. Detailed analyses of the planktonic foraminifera, diatom and phytolith fluxes reflect seasonal changes in the main hydrographic and meteorological features in the eastern Alboran Sea. El Niño Event caused a sea surface temperature (SST) increase during fall that forced the proliferation of Globigerinoides ruber and the reduction of the diatoms. Benthic tests were also collected in the sediment trap; highest fluxes of the group were probably related to high bottom water activity. Wind-driven particles were collected along the year, but their fluxes follow the local wind regime