Biodiversity loss in a Mediterranean ecosystem due to an extreme warming event unveils the role of an engineering gorgonian species

Abstract

Este artículo contiene 11 páginas, 7 figuras, 2 tablas. ; Stochastic perturbations can trigger major ecosystem shifts. Marine systems have been severely affected in recent years by mass mortality events related to positive thermal anomalies. Although the immediate effects in the species demography affected by mortality events are well known, information on the mid- to long-term effects at the community level is much less documented. Here, we show how an extreme warming event replaces a structurally complex habitat, dominated by long-lived species, by a simplified habitat (lower species diversity and richness) dominated by turf-forming species. On the basis of a study involving the experimental manipulation of the presence of the gorgonian Paramuricea clavata, we observed that its presence mitigated the effects of warming by maintaining the original assemblage dominated by macroinvertebrates and delaying the proliferation and spread of the invasive alga Caulerpa cylindracea. However, due to the increase of sediment and turf-forming species after the mortality event we hypothesize a further degradation of the whole assemblage as both factors decrease the recruitment of P.clavata, decrease the survival of encrusting coralligenous-dwelling macroinvertebrates and facilitate the spreading of C. cylindracea. ; Financial support has been provided by a Spanish Ministry Project ANIMA (CGL2016-76341-R), OAPN project (CORCLIM 759S/2012 and 766S/2012) and European Union's Horizon 2020 (grant agreement No. 689518) MERCES Project. This output reflects only the authors' view and the European Union cannot be held responsible for any use that may be made of the information contained therein. J.V. has been funded by a IFUdG2016 grant. Managers of ACNP are acknowledged for sampling permissions. We also thank to David Díaz, Eneko Aspillaga, Pol Capdevila, Bernat Hereu and Fiona Tomas for their collaboration in fieldwork. J.V., C.L. and E.C. are members of the Marine Conservation Research Group (www.medrecover.org; 2017 SGR 1521) and R.C. is part of the Marine Biogeochemistry and Global Change Research Group (2017SGR1011) from the Generalitat de Catalunya. ; Peer reviewed