Jean-Michel Cottalorda

The Introduced Green Alga Caulerpa Taxifolia Continues to Spread in the Mediterranean

The tropical green alga Caulerpa taxifolia in the Mediterranean has spread steadily since its introduction in 1984. At the end of 2000, approximately 131 km2 of benthos had been colonized in 103 independent areas along 191 km of coastline in six countries (Spain, France, Monaco, Italy, Croatia and Tunisia). Large regions neighboring the invaded areas appear favorable to further colonization, and there is thus no reason to believe that spreading will slow down in the years to come.

Occurrence of the toxic dinoflagellate Ostreopsis cf. ovata in relation with environmental factors in Monaco (NW Mediterranean)

To study environment characteristics favoring the toxic benthic dinoflagellate Ostreopsis cf. ovata, a survey was conducted in Monaco (NW Mediterranean Sea), in summers 2007 and 2008. Epiphytic and planktonic blooms occurred almost simultaneously and a high variation of abundances at low spatial scales was observed. An early and very marked bloom occurred in 2007, compared to a later and less abundant development in 2008. These distinct patterns in bloom timing corresponded with very different hydroclimatic scenarios in 2007 (hot spring and relatively cold summer) and 2008 (standard year compared to the median year profile estimated with data from 1995 to 2008). No clear impacts of summer seawater temperature, rainfall or nutrient concentrations were evident. Strong wind may favor the dispersal of benthic and planktonic cells. Our study suggests that further investigations are needed to examine the potential role of Ostreopsis nutritional mode (i.e. autotrophy vs. mixotrophy).

Standardization proposal for the mapping of Caulerpa taxifolia expansion in the Mediterranean sea

Fourteen years after the first observation of Caulerpa taxifolia (Valh) C. Agardh in the northwestern Mediterranean Sea, this green alga of tropical origin is now present in five countries (Spain, France, Monaco, Italy and Croatia). By the end of 1997, more than 46 km2, at depths of between 0 and 50 m, were found to be affected by this expansion. A standardization of the cartographic procedure is proposed here. Such a standardization is necessary to compare maps produced by various organizations from different countries. For a given independent station, it is based on the definition of three levels of colonization: • - Level I refers to a station where one or several colonies less than 100 m apart cover a total surface area inferior to 1000 m2; • - Level II refers to a station where several colonies less than 250 m apart totally cover more than 1000 m2 with fragments and small colonies dispersed over a surface area inferior to 10 ha; • - Level III is attained when several large colonies are dispersed over a surface area superior to 10 ha, with a total covered surface of more than 1000 m2, impossible to map with precision due to its size. For each of these colonization levels, descriptive parameters can be used to precisely describe the situation: covered surface area, dispersion surface (i.e. “affected” zone), estimation of very large affected zones (i.e. “concerned” zones) and the portions of the coastline along which an affected or concerned zone can be found.

Unexpected Temporal Stability of Cystoseira and Sargassum Forests in Port-Cros, one of the Oldest Mediterranean Marine National Parks

Abstract Fucales (Phaeophyceae, kingdom Stramenopiles) are ecosystem engineers and canopy forming seaweeds that are dramatically declining worldwide. In the Mediterranean Sea, Cystoseira spp. and Sargassum spp. have been shown to be locally extinct or locally functionally extinct, i.e. no longer forest forming, even in some Marine Protected Areas (MPAs). The patterns of change in the diversity and abundance of Fucales taxa within the Port-Cros Archipelago (Port-Cros National Park; PCNP) was studied by comparison of recent data (2005 to 2007) with previous data in order to measure the effects of protection since the creation of the park in 1963. Three taxa were reported before 1963, 10 between 1963 and 2005 and 17 between 2005 and 2007. Considering the biology of the species listed and the distance from the coast of the Port-Cros Archipelago, it is unlikely that this increase in species richness has resulted from colonisation events through the implementation and enforcement of effective protection of the area but is rather due to an increase in sampling effort. In contrast to other Mediterranean areas, the populations of Fucales are still highly diversified and stable. Only one species, C. brachycarpa var. brachycarpa, has declined in the 1-10-m depth zone in relation to the proliferation of herbivorous species, possibly enhanced by the PNPC conservation strategy. The overall good conservation of Fucales populations of the PCNP is probably the result of the absence of habitat destruction, high seawater quality and the regulation of human activities (fishing, tourism, diving).

Recent occurrences of opah, Lampris guttatus (Actinopterygii, Lampriformes, Lampridae), in the western Mediterranean Sea

The first records of Lampris guttatus in the Mediterranean Sea date back to 1807. Yet, until now it has been considered as a rare species (less than 25 specimens recorded in the literature). Since 2008, at least 23 spec- imens have been fished or observed along the French Mediterranean coast. In this paper, we present an updated review of records in the Mediterranean and discuss the possible link with the present sea water warming. We hypothesise that the recent Mediterranean specimens could come from the Atlantic, throughout the Gibraltar Strait, following a northward migration along the Northeast Atlantic coast due to present global warming. K eywords: new records, first record, Algeria, Mediterranean, rare species, SST, w arming