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 the 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 days (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 unconventional and poorly linked to temperature. The prolonged period of high atmospheric pressure and associated high irradiance and calm waters in late winter is the main seasonal trigger in the NW Mediterranean Sea, setting the development of a phytoplankton bloom, as well as the recruitment of the benthos. Decadal changes in the Mediterranean marine climate are characterized by the dominance of oscillations with a 22-year period, suggesting an important solar forcing on the climate. This forcing masks the monotonous trends, such as the warming and increased sea level in the Mediterranean, expected from anthropogenic forcing. Records of decadal changes in the ecosystem often display a monotonous trend in the deterioration of water quality, indicative of human effects as the main forcing agent, while climatic forcing, which displays oscillatory variation, is of secondary importance. The paucity of long-term records precludes a robust analysis of ecosystem response to decadal climatic forcing. This absence can be partially remediated by the ability to interrogate the long-lived organisms that represent an important, albeit endangered component of Mediterranean biodiversity, to extract records (e.g. growth, temperature, changes in the nature of the dissolved inorganic carbon pool) of the changes they have witnessed.