engleski

Influence of climate changes on marine ecosystem and fish stock in the Adriatic Sea

The warming that occurred in the last few decades influenced various aspects of variability of biotic parameters in the sea, from benthos and plankton to fish populations. These influences can be noted at interannual, decadal and secular scales in connection with climate oscillations important for the Adriatic like North Atlantic Oscillation (NAO) and Mediterranean Oscillation (MO). Since changeable atmospheric forcing shows interannual variability connected to hemispheric processes, it is expected that marine ecosystem and fish stock variations are influenced by atmospheric processes on spatial scales larger that the Adriatic. The evidence for this are observed through variations in sea surface temperature, advection, mixing, upwelling and some other parameters that control productivity, growth and migration of marine organisms. In this paper, the influence of climate changes on regional atmospheric forcing, important for the marine ecosystem in the coastal zone of the eastern Adriatic Sea, has been recognized as a key factor which controls variations in primary production and fish stock from decadal to long-term scales. To analyze interannual and decadal variations of fish population under the regional atmospheric influence, various atmospheric parameters (wind speed, air pressure, air temperature) and fish landings data (9 fish species from demersal to pelagic ones) were used. Both steady and abrupt regional atmospheric variations were recognized in the air pressure and the air temperature series. The wind speed was used as an indicator of mixing and upwelling, since upwelled waters enrich the surface coastal waters with nutrients, supporting primary productions and consequetly the abundace of fish. The data were analysed using principal component analysis and correlation tehniques. It is obvious that synhronicity exists between the variability of wind speed and fish stock. The major features obtained through the analysis point that: 1) regional atmosferic forcing was significantly correlated with hemispheric climate variability in such way that support steady and abrupt changes ; 2) regional space and time variations of wind speed and the sea surface temperature were highly correlated to fish abundance along the estern Adriatic coast, which all pointed to the conclusion that climate changes through regional atmospheric variations have significantly impacted the marine ecosystem.

climate change; Adriatic; ecosystem; fish

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