The Gulf of Lions in the Western Mediterranean Sea is particularly interesting for the study of riverine material fluxes and their potential impacts in the marine system. The sedimentary system forms one of the largest platforms in the Mediterranean which receives great amounts of terrestrial inputs via rivers. As a consequence, also the biological systems are characterized by high productivity rates.
Regular monitoring of nutrients and other basic water quality parameters in rivers has been established in many bordering countries of the Mediterranean. Even if many of these data are still difficult to access for the scientific community, there is increasing effort on the political level to release these data into the public domain. But scientific knowledge and questions evolved since and a number of key elements are not monitored. Dissolved silica, for example, is generally considered as a natural compound and not analyzed, although this nutrient can be important for the marine ecosystems depending on the riverine nutrient loads. Time series on dissolved silica fluxes in Mediterranean rivers are therefore almost impossible to find. Also more and more organic and inorganic contaminants (trace metals, PCBs, pharmaceuticals, …) were identified as potentially harmful for the marine biota, but mostly ignored in the national monitoring programs as well. In the context of the contaminants in the Mediterranean Sea (see MERMEX project), it is important to better constrain the spatial distribution and the evolution of anthropogenic compounds in the marine ecosystems. The uncertainty on sources contribution and the transfer mode in between the marine reservoirs are important, especially for emergent substances. Chemical contaminants constitute as well pertinent tracers useful for improving comprehension of physical and biogeochemical mechanisms.
High frequency and regular monitoring of nutrients and contaminants in rivers are needed to better constrain the spatial distribution and the evolution of anthropogenic compounds in the marine ecosystems. The uncertainty on sources contribution and the transfer mode between the marine reservoirs are important, especially for emergent substances.
The Rhone is the largest Mediterranean river in terms of its freshwater discharge and its inclusion in the Moose network is mandatory. Knowledge about the nutrient fluxes in the Rhone can be reconstructed for about the last 30 years and following the trends in the future defines one of the fundamental forcing functions of the marine ecosystems in the future.
Small rivers are naturally less important in global material budgets, but they are very typical for the Mediterranean drainage basin. Adding their fluxes together is far from being negligible and may even surpass the material transport from the large rivers. Moreover, as the small Mediterranean river basins are highly reactive to local climatic features, they may be more vulnerable in the context of climate change and modifications in the frequency of extreme climatic events (floods, droughts) can have server consequences on the river fluxes.
In the framework of MOOSE two rivers are actually equipped with autonomous samplers: Têt and Rhône.