Plankton ecosystem response to the decadal variation of winter intensity in the Mediterranean Sea : a long-term study (1979-2014)
2015
Goffart, Anne | Collignon, Amandine | Hecq, Jean-Henri | Binard, Marc | Lejeune, Pierre | MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
In the Mediterranean Sea, several studies with distinct data sets indicate that the pelagic ecosystem underwent periods of change in the late 1980s and in the early 2000s. Here we used a unique long-term time series of data collected in the well-preserved Bay of Calvi (Corsica island, Ligurian Sea, NW Mediterranean) from 1979 and 2014 to explore the synchrony between changes in environmental conditions and phyto- and zooplankton dynamics. We identified an almost decadal, long-term variability in winter intensity, with three distinct periods: the 1980s (1979-1988), the 1990s (1989-1998) and the 2000s (1999-2014), which were characterized by moderate, mild and highly variable winters, respectively. We pointed out how the decadal changes in winter intensity affected (i) the duration and intensity of phyto- and zooplankton blooms, (ii) the mean yearly biomasses, and (iii) the nature of the assemblages. High phyto- and zooplankton biomasses were observed in years characterized by moderate and severe winters, and low phyto- and zooplankton abundances were recorded in years with mild winters. Moderate/severe and mild winters were favorable for diatoms and gelatinous zooplankton, respectively. Focusing on meroplanktonic species, we explored ecological consequences of decadal variations observed in the Bay of Calvi for resource management. We highlighted parallelisms with other European seas.
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