Intercomparison of six Mediterranean zooplankton time series

Abstract

We analyzed and compared Mediterranean mesozooplankton time series spanning 1957–2006 from six
\ncoastal stations in the Balearic, Ligurian, Tyrrhenian, North and Middle Adriatic and Aegean Sea. Our analysis
\nfocused on fluctuations of major zooplankton taxonomic groups and their relation with environmental
\nand climatic variability. Average seasonal cycles and interannual trends were derived. Stations
\nspanned a large range of trophic status from oligotrophic to moderately eutrophic. Intra-station analyses
\nshowed (1) coherent multi-taxa trends off Villefranche sur mer that diverge from the previous results
\nfound at species level, (2) in Baleares, covariation of zooplankton and water masses as a consequence
\nof the boundary hydrographic regime in the middle Western Mediterranean, (3) decrease in trophic status
\nand abundance of some taxonomic groups off Naples, and (4) off Athens, an increase of zooplankton
\nabundance and decrease in chlorophyll possibly caused by reduction of anthropogenic nutrient input,
\nincrease of microbial components, and more efficient grazing control on phytoplankton. (5) At basin
\nscale, the analysis of temperature revealed significant positive correlations between Villefranche, Trieste
\nand Naples for annual and/or winter average, and synchronous abrupt cooling and warming events centered
\nin 1987 at the same three sites. After correction for multiple comparisons, we found no significant
\ncorrelations between climate indices and local temperature or zooplankton abundance, nor between stations
\nfor zooplankton abundance, therefore we suggest that for these coastal stations local drivers (climatic,
\nanthropogenic) are dominant and that the link between local and larger scale of climate should
\nbe investigated further if we are to understand zooplankton fluctuations.