The DYFAMED series station: a reference to coastal studies in the Mediterranean Sea

In the Mediterranean, seasonal variations of the trophic environment (primary production, specific biomasses, particulate export) are extremely large, in response to physical constraints, specifically seawater temperature induced by seasonal exposure to the sun. Since 1991, systematic biogeochemical studies were conducted at the DYFAMED site (28 nautical miles off Nice) with monthly cruises and continuous observation from a permanent mooring, in the form of a Observation Scientific Service of the marine environment from INSU /CNRS. The time-series station is located in the central zone of the Ligurian Sea, and protected from lateral imputs by the presence of the liguro-provencal front, acting as a barrier to exchanges with the coastal zone. The anthropic imputs to the zone aera only though the atmosphere. Then, the observed system is independant from anthropogenic coastal imputs and constitute a reference area for the study of the "natural" variability ot Mediterranean sea is relatively homogeneous in term of atmospheric forcings, it can be considered that these "natural" variations of marine environment occur with a comparable intensity and ryhtmicity in the coastal and open sea areas. A coastal perturbation may then produce modifications of this background evolution. The data presented here aim to characterize the hydrological and trophic seasonnal variations at the DYFAMED observation site. Some results of studies undertaken since 1997 on the Nice-Calvi (Corsica) transect are also presented in order to explore the synchronism between the temporal succession of species from coast to open sea. With the aim to reach the scale of pertubation processes, it is clear that a continuous record of selected parameters is necessary. We present here some data obtained using optical sensors (absorption/transmission at 9 wavelenght, which allow to attain some biogeochemical characteristics of waters) on the transect. These sensors will eventually be placed on moorings in the future. A meterological buoy will be moored at the DYFAMED time series station in fall 1998 by Meteo-France, which will gave the local atmospheric forcings for monthly biogeochemical studies and possibly the support to oceanographic sensors.