An ecosystem-based approach to evaluate the ecological quality of Mediterranean undersea caves

Pierre-Alexandre Rastorgueff (1) , Denise Bellan-Santini (1) , Carlo Nike Bianchi , Simona Bussotti , Pierre Chevaldonne (1) , Paolo Guidetti , Jean-Georges Harmelin (2) , Monica Montefalcone , Carla Morri , Thierry Perez (1) , S. Ruitton (2) , Jean Vacelet (1) , Sebastien Personnic (2)

1 IMBE - Institut méditerranéen de biodiversité et d'écologie marine et continentale
2 MIO - Institut méditerranéen d'océanologie

tA theoretical model of structure and functioning was constructed for the Mediterranean undersea caveecosystem. This model integrates almost all representative components of the cave ecosystem and givesan idea of their faunal compositions, characteristics and related interactions.This model constitutes the basis of the Ecosystem-Based Quality Index (EBQI) of the European Union’sMarine Strategy Framework Directive, which aims at evaluating the ecological quality of an ecosystem. Itis based on four crucial complementary elements: (i) each component was weighted in accordance withits importance in determining the structure and functioning of the cave ecosystem; (ii) a suite of relevantparameters were defined to assess the ecological state of each component of the cave ecosystem; (iii)these parameters were aggregated into one relevant index, the Cave EBQI (CavEBQI), to summarize thequality evaluation for each cave site; (iv) each value of ecological state is accompanied by a ConfidenceIndex as a measure of its reliability.The CavEBQI was used on 22 Mediterranean undersea caves of France and Italy. Disparities of ecologicalquality were found among caves but most of them ranged from moderate to high ecological quality. Forsome caves, no conclusion can be drawn when our method predicts a poor reliability of the evaluationof their ecological quality.This ecosystem-based evaluation of the quality of undersea caves seems to be a powerful tool, withthe advantage of being based on almost all its components, rather than just on a few species. It is accom-panied by a measure of its reliability, hence it provides a reliable idea of the ecological state of the entireecosystem at each cave site. Monitoring the ecological state of caves and the effects of disturbancesover large geographic and temporal scales is made possible with CavEBQI. Applying the same method toother ecosystems, can provide an integrated view of a marine region, which is essential when addressingquestions about protection, conservation and restoration.

Mots clés: Ecosystem-based quality index; Ecological quality; Marine Strategy Framework Directive; Undersea caves; Underwater marine caves; Mediterranean Sea

Domaines: Biodiversité et Ecologie

Pierre-Alexandre Rastorgueff, Denise Bellan-Santini, Carlo Nike Bianchi, Simona Bussotti, Pierre Chevaldonne, et al.. An ecosystem-based approach to evaluate the ecological quality of Mediterranean undersea caves. Ecological Indicators, 2015, 54, pp.137-152. ⟨10.1016/j.ecolind.2015.02.014⟩. ⟨hal-01433601⟩