In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature (T) time series obtained during 1999-2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Reserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11-13 degrees C, and summer T mainly around 22-24 degrees C near surface to 18-20 degrees C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999,2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1-2 degrees C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is extremely likely. In such context, the acquisition of dedicated high resolution T series proves to be crucial for increasing our detection, understanding and forecasting abilities. (C) 2010 Elsevier Ltd. All rights reserved.
- effects of climate change
- coastal oceanography
- thermal structure
- thermal regime
- mortality outbreak
- positive temperature anomalies
- Gulf of Lions
- SUMMER 1999
[Bensoussan, Nathaniel; Harmelin, Jean-Georges; Garrabou, Joaquim] Univ Aix Marseille 2, UMR DIMAR 6540, CNRS, Ctr Oceanol Marseille,Stn Marine Endoume, F-13007 Marseille, France; [Romano, Jean-Claude] Univ Corse, CNRS, UMR 6134, Lab Syst Phys Environm, F-20000 Ajaccio, France; [Garrabou, Joaquim] CSIC, Inst Ciencias Mar, E-08003 Barcelona, Spain
Bensoussan, N (reprint author), Inst Phys Globe, 35 Rue Helene Brion,Case 7052, F-75205 Paris 13, France.
- Diversité, évolution et écologie fonctionnelle marine, UMR6540
- Institut de Physique du Globe de Paris (IPGP), UMR7154
- Sciences Pour l'Environnement (S P E), UMR6134