The Mediterranean climate as a template for Mediterranean marine ecosystems: the example of the northeast Spanish littoral

The Mediterranean climate exerts a major influence on the basic properties of the Mediterranean Sea, which constrains the structure and dynamics of th e ecosystem. Seasonal variations in the marine climate follow the expected unimodal seasonality only for temperature, while most other forcing factors show a complex variance structure, with dominant time scales of 50-100 day s (e.g. wave action), and with some of the factors acting as random factors ('white noise') at the annual scale (e.g. rainfall), thereby limiting the predictability of the system. The resulting ecosystem seasonality is unconv entional and poorly linked to temperature. The prolonged period of high atm ospheric pressure and associated high irradiance and calm waters in late wi nter is the main seasonal trigger in the NW Mediterranean Sea, setting the development of a phytoplankton bloom, as well as the recruitment of the ben thos, Decadal changes in the Mediterranean marine climate are characterized by the dominance of oscillations with a 22-year period, suggesting an impo rtant solar forcing on the climate. This forcing masks the monotonous trend s, such as the warming and increased sea level in the Mediterranean, expect ed from anthropogenic forcing. Records of decadal changes in the ecosystem often display a monotonous trend in the deterioration of water quality, ind icative of human effects as the main forcing agent, while climatic forcing, which displays oscillatory variation, is of secondary importance. The pauc ity of long-term records precludes a robust analysis of ecosystem response to decadal climatic forcing. This absence can be partially remediated by th e ability to interrogate the long-lived organisms that represent an importa nt. albeit endangered component of Mediterranean biodiversity, to extract r ecords (e.g. growth, temperature, changes in the nature of the dissolved in organic carbon pool) of the changes they have witnessed. (C) 1999 Elsevier Science Ltd. All rights reserved.