Zooplankton variability and climatic anomalies from 1994 to 2001 in the Balearic Sea (Western Mediterranean)

The long-term and seasonal changes in biomass and zooplankton abundance at a station off Mallorca Island (Balearic Sea) were studied in relation to the main physical and chemical conditions. The results are based on a total of 276 samples collected every 10 days during 8 years by means of oblique hauls from bottom to surface. At this neritic station (77-m depth) located in a hydrographic area between northern Mediterranean and Atlantic southern waters, salinity ranged from 37 to 38.4 psu and temperature from 13.4°C (February 1996) to 27.4°C (August 1998). With the exception of salinity, the other environmental parameters and the most abundant zooplankton groups showed irregular but seasonal cycles. Interannual variability was also observed, with higher zooplankton abundance during the cooler and more saline years when the influence of northern water was stronger. Zooplankton abundance decreased during a warm period in 1998. Copepods were the most abundant group (54%) and their abundance was significantly correlated with temperature (negatively) and salinity (positively). Here, we summarize the changes in the zooplankton community abundance and how hydrographic forcing and other climatic factors have changed during the period from 1994 to 2001 in the Balearic Sea (Western Mediterranean).