Study of the present state and of recent temporal changes in the benthic macrofauna composition of Gulf of Lions soft-bottoms macrobenthic communities, NW Mediterranean

The main objectives of my thesis were:

1. to assess the present state and recent (1998 vs. 2010) changes in benthic macrofauna composition of the Gulf of Lions soft-bottom communities through the long term comparison of 91 stations;
2. to test the current paradigm regarding the control of those communities by climatic parameters through a 10-year monitoring of 4 stations located in the Bay of Banyuls-sur-Mer;
3. to assess the influence of Rhône River inputs on the composition of benthic macrofauna through the sampling, of 5 stations, under 4 hydrological regimes; and
4. to update the ecological quality status of Gulf of Lions benthic habitats.

My results have shown the persistence of the same 3 communities between 1998 and 2010, the strong influence of both the NAO and the Rhône River on benthic macrofauna composition in the whole Gulf. They also showed a control of benthic macrofauna by climatic oscillations with the WeMO contributing most especially during wintertime. Moreover, the stations most impacted by Rhône River inputs were located close to its mouth. They are negatively affected during floods and positively affected during dry periods. Lastly, I have updated the sensitivity/tolerance levels of Mediterranean species and confirmed the existence of major discrepancies in the results derived from different biotic indices used, although all tested indices indicated an overall stability in the ecological quality status of benthic habitats between 1998 and 2010.