engleski

Hemispheric climate oscillations and the Mediterranean Sea – identifying relationships between plankton, hydrological patterns and climate

The Mediterranean basin plays a key role as a heat reservoir and source of moisture for surrounding land areas, but it also encompasses a high marine biodiversity. Global changes noticed in the Northern Hemisphere during the last decades suggest therefore the possibility of causal links between climate change and modifications in hydrological features of the Mediterranean, as well as in the marine populations inhabiting the basin. In this study, we used synoptic climatology to investigate the link between regional atmospheric weather and hemispheric-wide climate oscillations over the second half of the twentieth century (1950 – 2005). Afterwards, we investigate their potential relationship with a variety of hydrological and plankton decadal records taken in different areas of the Western Mediterranean (e.g. Balearic, Ligurian and Adriatic Seas). We show close connections between climate variability, regional weather, hydrographic patterns and plankton functional groups ranging from primary producers to pelagic fish. Northern Hemispheric climate forcing on Western Mediterranean have changed since the 1980s and affected in an opposite way regional weather patterns. Whilst a positively link was found between Hemispheric-wide climate changes and the weather patterns in the westernmost areas, the Balearic and Ligurian Seas, a tightly negative relationship was revealed between weather patterns in the Adriatic Sea and the same climatic oscillations. The interrelationships between regional and Hemispheric-wide oscillations have subsequently lead outbreaks/collapses in plankton communities, but also phenological changes in different groups of plankton were noticed, suggesting therefore alterations in the functioning of the pelagic ecosystems. Although, there is not excluded a causal link between pelagic changes and the anthropogenic forcing, the approach used allows identifying some mechanisms translating hemispheric wide ocean-atmospheric circulation into the long-term changes of Mediterranean plankton populations. Overall, these results may be useful to map possible scenarios of large scale climate forcing and potential ecological responses, but also to improve models of the dynamics of the pelagic ecosystem and biogeochemical fluxes in the Western Mediterranean.

global changes; hydrology; Mediterranean Sea; synoptic meteorology

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