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In the summer of 2011, the infralittoral fringe of Linosa Island (Sicilian Channel, Italy) was surveyed through visual census, by both scuba diving and snorkelling, with the aim of collecting updated data on marine alien species distribution and abundance on the island. Surveys revealed the presence ofPinctada imbricata radiata, an invasive alien bivalve of Indo-Pacific origin, first recorded in the Mediterranean Sea at the end of the 19th century in Egyptian waters. Since then, the species has successfully spread throughout the Mediterranean, systematically colonizing new habitats of the eastern basin and becoming very abundant in the Levantine Sea. Conversely, occurrences in the western basin have been reported only sporadically. Many studies have been carried out onP. imbricata radiatain its native range (Indian Ocean and Red Sea) while the Mediterranean populations have been investigated only in Tunisia. The finding ofP. imbricata radiataaround Linosa Island (Sicilian Channel, Italy) is discussed analysing the biometric features of the species and taking into consideration its ecological characteristics and possible pathways of introduction in the Marine Protected Area of Linosa Island. [ABSTRACT FROM PUBLISHER]

Biological invasions in marine environment are the lesser known aspect of global change. However, recent events which occurred in the Mediterranean Sea demonstrate that they represent a serious ecological and economical menace leading to biodiversity loss, ecosystem unbalancing, fishery and tourism impairment. In this paper we review marine bioinvasions using examples taken from the Mediterranean/Black Sea region. Particular attention is given to the environmental status of the receiving area as a fundamental pre-requisite for the colonisation success of alien species. The spread of the tropical algae belonging to the genus Caulerpa in the northwestern basin of the Mediterranean Sea has been facilitated by pre-existing conditions of instability of the Posidonia oceanica endemic ecosystem in relation to stress of both natural and anthropogenic origin. Human interventions caused long-term modification in the Black Sea environment, preparing a fertile ground for mass bioinvasion of aquatic nuisance species which, in some cases, altered the original equilibrium of the entire basin. Finally, the Venice lagoon is presented as the third example of an environment subjected to high propagule pressure and anthropogenic forcing and bearing the higher “diversity” of non-indigenous species compared to the other Mediterranean lagoons. Stressed environments are easily colonised by alien species; understanding the links between human and natural disturbance and massive development of non-indigenous species will help prevent marine bioinvasions, that are already favoured by global oceanic trade. [Copyright &y& Elsevier]

Soft bottom macrobenthos at a station located off Cesenatico (Emilia Romagna, Northern Adriatic Sea) was investigated seasonally for six years from July 1996 to July 2002. Species composition and abundance of the community have been studied in relation to fluctuation in the water environment parameters, sediment texture patterns and mucilage, that occurred mainly in the water column at the study site. Three major Po river flow peaks occurred in November 1996, October 2000 and May 2002; after these events the community was reduced to minimum abundance values (total density<2000 individuals m(-2)). In the period between the first two episodes the river discharge remained rather low and conditions of increased salinity, lower nutrients and chl a and good oxygen saturation were experienced. The fossorial Crustacean Ampelisca diadema became dominant in the community between the first two river flow events, reaching maximum density of 10,200 individuals m(-2) and substituting the bivalve Corbula gibba, indicator of sediment instability. Species richness increased in the same period. The role of Ampelisca as a facilitator in structuring the community is discussed. Corbula gibba never recovered to initial densities, apart from an abundance peak that occurred in the summer of 2000. Faunal composition seemed to evolve slowly towards a higher degree of structural complexity (positive trend in diversity and evenness index). In the study site near-bottom mucilage events occurred in the summers of 1997, 1998, 2002; they appeared uncorrelated with the observed changes in the community structure. Multivariate analysis of community structure (MDS, ANOSIM) illustrates that community changes in this station are driven mainly by hydrographical conditions influencing sediment texture patterns and trophic resources for the benthos.