A benthic mucilage event in North‐Western Mediterranean Sea and its possible relationships with the summer 2003 European heatwave: short term effects on littoral rocky assemblages

Abstract

In this contribution we document an anomalous mucilage growth which occurred in June 2003 along the rocky cliffs of the Portofino Promontory (Ligurian Sea, NW Mediterranean Sea), and we describe its dynamics and its negative effects on many benthic taxa. The zooxanthellate scleractinian Cladocora caespitosa underwent ‘bleaching’ and about 40% of biomass of the erect algae was detached by mucilage ‘lianas’ created and strengthened by bottom currents. The 2003 event differed from any other previously occurred in the northern Tyrrhenian Sea, in that the mucilage aggregates were formed by the free‐living form of the Phaeophyceae Acinetospora crinita (Harvey) Kornmann, a not usually dominant species in mucilage aggregates from the north Tyrrhenian Sea. The damage suffered by the benthic organisms living in this area was curtailed by a severe storm, occurred in July, which removed the mucilage to deeper depths, preventing irreversible damages. Only slow growing, perennant organisms, such as corallinales or scleractinians, were seriously affected, but a survey carried out 1 year later, in June 2004, allowed to appreciate a complete recovery of those organisms. This anomalous mucilage event occurred in coincidence of the 2003 European heatwave, and the anomalous temperature increase of seawater has to be regarded as the major contributing event that led to the mucilage outbreak.

Long‐term comparison of structure and dynamics of the red coral metapopulation of the Portofino Promontory (Ligurian Sea): a case‐study for a Marine Protected Area in the Mediterranean Sea

“…The Ligurian Sea has suffered in recent decades major changes in the structure of benthic communities and fish stocks due to anthropization of the coastline, pollution, fisheries and phenomena linked to global warming (Schiaparelli et al . ; Puce et al . ; Parravicini et al .…”

The other side of rarity: recent habitat expansion and increased abundance of the horny spongeIrcinia retidermata(Demospongiae: Dictyoceratida) in the southeast Aegean

“…Ilan et al (1994) reported it dubiously from a depth of 830 m off the Israeli Mediterranean coast. On the contrary, Bianchi and Morri (1983) and Schiaparelli et al (2007) reported it as shallow as 3 m, in the Aegean, and 12 m, in the Ligurian Sea, respectively. In all these records, the species came from rocks dispersed amidst sand or mud, or from rocky reefs.…”

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.…”