Regionalisation of the Mediterranean basin (new MERMEX publication)

With the support of the MERMEX / MISTRALS program, an international team has just reviewed and synthesized the different regionalizations proposed so far for the Mediterranean Sea. This synthesis constitutes a reference step for management actions and spatial planning, such as the application of the European Marine Strategy Framework Directive, and for future biogeochemical and ecological studies in the Mediterranean Sea.

Marine ecosystems and associated ecosystem services are subject to severe climatic and anthropogenic pressures. This is especially true for the Mediterranean Sea, due to its semi-enclosed configuration and the concentration of human activities. Several regionalizations have been proposed in recent years for the Mediterranean Sea, each based on different and sometimes complementary criteria, such as the physico-chemical conditions, the transport constraints imposed by the ocean circulation, the concentration of the estimated surface chlorophyll by satellite, or the modeled distribution of a large number of pelagic species. However, the lack of a consensual geographical reference frame complicated the description, management and conservation of marine ecosystems within the Mediterranean. Such a frame of reference should be based on the objective definition of spatial entities (or « ecoregions ») characterized by relatively homogeneous physical, chemical and biological conditions.

The work by Ayata et al. (2017) reviews and compares the different regionalizations of the Mediterranean Sea and proposes a synthesis that can be used to inform management decisions as well as for future biogeochemical and ecological studies. By quantifying the congruence between the different regionalisations, the authors identified consensus zones and variable zones. They identified nine « consensus frontier zones », 11 « consensus regions » and 4 « heterogeneous and dynamic regions ». The identified boundaries and consensus regions are consistent with the main hydrodynamic structures known in the Mediterranean and constraining the hydrological and ecological variables. On the other hand, the heterogeneous regions are rather defined by a strong mesoscale hydrodynamic activity.

The article, the results of which are accessible via a dedicated web platform, is an essential first step for the establishment of future actions for the management and protection of Mediterranean marine ecosystems, and in particular for the implementation of the Marine Strategy Framework Directive. It also proposes a spatial reference system that will guide future ecological and biogeochemical studies in the Mediterranean Sea.

CItation: Ayata S.-D., Irisson J.-O., Aubert A., Berline L., Dutay J.-C., Mayot N., Nieblas A.-E., D’Ortenzio F., Palmiéri J., Reygondeau G., Rossi V., Guieu C., Regionalisation of the Mediterranean basin, a MERMEX synthesis. Progress in Oceanography, online 13 October 2017, ISSN 0079-6611


Sakina-Dorothée Ayata, LOV/OOV

E-mail: sakina.ayata@obs-vlfr.fr