Mass mortality in Northwestern Mediterranean rocky benthic communities: effects of the 2003 heat wave

Abstract

Late in summer 2003, extensive mass mortality of at least 25 rocky benthic macro-invertebrate species (mainly gorgonians and sponges) was observed in the entire Northwestern (NW) Mediterranean region, affecting several thousand kilometers of coastline. We were able to characterize the mortality event by studying six areas covering the main regions of the NW Mediterranean basin. The degree of impact on each study area was quantified at 49 sites by estimating the proportion of colonies affected in populations of several gorgonian species compared with reference data obtained in years without mortality signs. According to these data, the western areas (Catalan coast and Balearic Islands) were the least affected, while the central areas (Provence coast and Corsica-Sardinia) showed a moderate impact. The northernmost and eastern areas (Gulf of Genoa and Gulf of Naples) displayed the highest impact, with almost 80% of gorgonian colonies affected. The heat wave of 2003 in Europe caused an anomalous warming of seawater, which reached the highest temperatures ever recorded in the studied regions, between 1 and 3 degrees C above the climatic values (mean and maximum). Because this exceptional warming was observed in the depth ranges most affected by the mortality, it seems likely that the 2003 anomalous temperature played a key role in the observed mortality event. A correlation analysis between temperature conditions and degree of impact seems to support this hypothesis. Under the present climate warming trend, new mass mortality events may occur in the near future, possibly driving a major biodiversity crisis in the Mediterranean Sea

Coralligenous and maërl habitats: predictive modelling to identify their spatial distributions across the Mediterranean Sea

“…Climate change is also known to affect several key species that are part of coralligenous habitats, by increasing the incidence of thermal anomalies (e.g. [28][29][30] ) and storms 31 . Some invasive algal species (Womersleyella setacea, Acrothamnion preissii, Caulerpa racemosa v. cylindracea and C. taxifolia) can also pose a severe threat to these communities, either by forming dense carpets (i.e.…”

The red coral populations of the gulfs of Naples and Salerno: human impact and deep mass mortalities

“…In the western Mediterranean Sea, besides two large-scale episodes in September 1999 (Cerrano et al 2000;Perez et al 2000) and July 2003 (Schiaparelli et al 2007), mass mortalities occurred also in 2002, 2006(Garrabou et al 2009), always impacting shallow-water communities (above 40 m depth) where the seasonal temperature oscillations are wider.…”

Regional genetic differentiation among populations of Cladocora caespitosa in the Western Mediterranean

“…Global climate change, in synergy with other disturbances such as water pollution, coastal development, massive algal blooms, pathogenic organisms, and invasive species, among others, is expected to have significant effects on Mediterranean biodiversity in the near future Templado 2014). For over a decade, mass mortality events have recurrently impacted Mediterranean benthic communities owing to prolonged heat waves that affect some emblematic sessile invertebrates (Cerrano et al 2000;Perez et al 2000;Garrabou et al 2009;Lejeusne et al 2009). The scleractinian coral Cladocora caespitosa (Linnaeus, 1767) is among these affected species and mortalities of its reefs have been recorded, including those in the Adriatic Sea (Kružić et al 2012), Gulf of La Spezia (Rodolfo-Metalpa et al 2005), and Columbretes Islands where over 50 % of the coral cover has been affected by necrosis during the last decade (Kersting et al 2013a).…”