A number of marine alien species have been described as invasive or locally invasive in the Mediterranean because of their proliferation, and/or their geographical spread and/or impact on native populations. Based on that information and on the documented impact they have on the biodiversity and socioeconomics of the basin, a preliminary list of the 100 ‘worst’ Invasive Alien Species (IAS) in the Mediterranean has been produced and presented in this work along with details on their impact. Emphasis is given to their impact on socioeconomics (fi sheries/aquaculture, health & sanitation, infrastructure & building), documented for 43 species. Such selection of the ‘worst’ IAS was diffi cult and controversial and is expected to attract much attention and scientifi c criticism since not only can the documentation of the impact of IAS be controversial, but also their inventory can be biased towards the effort and resources devoted to the study of the impact of certain species/taxonomic groups. Thus, while marine plants (phytobenthos and phytoplankton) are fairly well studied, less attention has been paid to the impact of vertebrates and even less to invertebrates. Nevertheless, the list highlights the need for continued research on the issue (monitoring aliens and their impact for an integrated ecosystem based management approach over the entire area). The preliminary list can provide the basis for selecting indicator species within the Mediterranean and thus be the common ground to build cooperation about IAS within countries in the region.

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Alien Marine Species in the Mediterranean - the 100 'Worst Invasives' and their Impact

Although ballast water has received much attention as a source of aquatic invasive species, aquariums and trade in aquarium and ornamental species are emerging as another important source for species likely to invade aquatic habitats. These species are spread throughout the world in a generally unregulated industry. The recent focus on the aquarium trade as a possible mechanism for environmentally sustainable development poses an especially dangerous threat, although this has so far escaped the attention of most environmentalists, conservationists, ecologists, and policy makers.

Beyond ballast water: aquarium and ornamental trades as sources of invasive species in aquatic ecosystems

https://www.int-res.com/articles/meps/207/m207p225.pdf

Marine chemical ecology

http://faculty.jsd.claremont.edu/emorhardt/159/pdfs/2007/3_29_07.pdf

Global change and marine communities: Alien species and climate change

Present-day Mediterranean marine biodiversity is undergoing rapid alteration. Because of the increased occurrence of warm-water biota, it has been said that the Mediterranean is under a process of ‘tropicalization’. This paper analyses the main patterns of the Mediterranean Sea tropicalization and considers briefly its extent and consequences. As happened during previous interglacial phases of the Quaternary, Atlantic water, entering via the Straits of Gibraltar, carries into the Mediterranean species that are prevalently of (sub)tropical affinity. On the other side of the basin, Red Sea species penetrate through the Suez Canal, a phenomenon called lessepsian migration from the name of F. de Lesseps, the French engineer who promoted the cutting of the Canal. Also the many exotic species introduced by humans voluntarily or involuntarily are nearly always typical of warm waters. Climate change combines with Atlantic influx, lessepsian migration and the introduction of exotic species by humans to the establishment of tropical marine biota in the Mediterranean Sea. Present-day warming ultimately favours the spread of warm-water species through direct and indirect effects, and especially by changing water circulation. It is impossible at present to foresee to what extent the exuberance of warm-water species will affect the trophic web and the functioning of marine ecosystems in the Mediterranean Sea of tomorrow. While Mediterranean Sea communities are modifying their pattern of species composition, they do not seem to be acquiring a more marked tropical physiognomy: Mediterranean coastal marine ecosystems are still dominated by fron-dose algae (even if the species that are gaining ascendancy are of tropical origin) and not by corals as is normal in tropical seas.

Biodiversity issues for the forthcoming tropical Mediterranean Sea

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.

Charles-Francçois Boudouresque

Papers

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