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A mass mortality event of the red coral Corallium rubrum (L.) occurred in the NW Mediterranean region in summer 1999. The main objectives of the present study were to document the mortality suffered by the red coral populations in the Provence region and assess ecological correlates of the mortality which could help to identify the putative agent or agents of the event. The mortality outbreak resulted in partial to complete loss of the coenenchyme. The first observations of red coral mortality in the study area were in early October 1999 and continued until November 1999. To determine the extent of mortality on red coral populations, the incidence (= % colonies suffering mortality) and the virulence (= % coenenchyme loss) were quantified. Twelve surveys were carried out from November 1999 to January 2000. A total of 874 colonies of the 2375 observed showed some mortality. Incidence and virulence differed significantly among surveys. In some cases about 80% of the colonies were affected, while in others only 5% of colonies showed some mortality. Depth had a strong influence on the incidence of mortality. Shallower populations had the greatest incidence, while populations deeper than 30 m depth showed no mortality. However, virulence was similar in the 10 to 30 m depth range. With regard to habitat, the entrances of caves displayed a significantly higher incidence but not virulence than the interiors. Given the life history traits of red coral (mainly slow growth and low recruitment), it seems that recovery from the outbreak will be a long-term process. However, further studies are urgently required to provide basic information regarding red coral population dynamics as a basis for hypotheses on the actual recovery capability of affected populations. The cause of the mass mortality is unknown. However, during late summer 1999, the NW Mediterranean area affected by the mass mortality event experienced high temperatures and hydrographic stability over a period of several weeks. This temperature anomaly could have caused physiological stress or/and triggered the development of pathogenic agents that otherwise would have remained non-virulent. This hypothesis is reinforced by the absence of signs of mass mortality below 30 m depth in red coral populations. Since the NW Mediterranean seems to be affected by the global warming trend, if the temperature hypothesis is confirmed, the long-term consequences of a repetition of this kind of event could severely endanger the persistence of shallow-water red coral populations.

Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015-2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning.

ABSTRACT1. We present in this review a general description of marine protected areas (MPAs) in the northwestern Mediterranean and some general principles for the establishment of protected areas, including their size, location, biotope composition, regulation, and management.2. Many Mediterranean MPAs are located around or adjacent to islands, but the placement of a marine reserve close to a large urban area is not necessarily a handicap, as has been demonstrated by some examples. It is not, therefore, necessary to restrict future MPAs solely to regions of low human density.3. The conceptual question of MPA size (single large or several small SLOSS debate) has never been explicitly considered in the selection of Mediterranenan MPAs. However, studies of fish recruitment in MPAs, and the development of a network of small MPAs between Spain and France have highlighted the importance and value of small sized MPAs (200 -2000 ha).4. Whatever the location of a future MPA, its success as measured in terms of stock restoration will depend on whether (i) sufficient suitable habitat is available, (ii) the variety and abundance of prey species are adequate and (iii) the possibilities for recruitment of the biota are reasonable.5. The initial choices of zonation and legislation regulating the management of any future MPA are of primary importance. The zonation plan should be as simple as possible (gradation of 2 or 3 levels) and it should be acknowledged that the significance of management conflicts within a MPA will be inversely proportional to the extent of preliminary consultations with all of the users, both professional and amateur.6. The examples of semi-protected areas where professional fishing is still allowed demonstrate without ambiguity the negative impact of spear-fishing, and the limited impacts from regulated professional activities on fish assemblages. The means of regulating consist essentially of (i) a prohibition of certain type of fishing methods (trawling); and (ii) a limitation of the numbers of fishermen by a system of restriction or authorization.7. In the MPAs examined, there is a great diversity of situations in relation to the size of and distribution of duties between staff assigned to their management. However, the single most

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