Marchini Agnese

This paper provides an updated account of the occurrence and abundance of non-indigenous species (NIS) in an area of high risk of introduction: the Lagoon of Venice (Italy). This site is a known hotspot of NIS introductions within the Mediterranean Sea, hosting all the most important vectors of intro- duction of marine NIS—shipping, recreational boat- ing, shellfish culture and live seafood trade. The recent literature demonstrates that the number of NIS in Venice is continuously changing, because new species are being introduced or identified, and new evidence shows either an exotic origin of species previously believed to be native, or a native origin of formerly believed ‘‘aliens’’, or demonstrates the cryptogenic nature of others. The number of NIS introduced in the Venetian lagoon currently totals 71, out of which 55 are established. This number exceeds those displayed by some nations like Finland, Portugal or Libya. Macroalgae are the taxonomic group with the highest number of introduced species (41 % of NIS): the most likely vector for their introduction is shellfish culture. The source region of NIS introduced to Venice is mainly represented by other Mediterranean or Euro- pean sites (76 %). The Lagoon of Venice represents a sink but also a source of NIS in the Mediterranean Sea, as it is the site of first record of several NIS, which have since further spread elsewhere.

The results of a survey on bryozoans and entoprocts in the Ria de Aveiro (NW Portugal) are presented. The Ria de Aveiro is a coastal lagoon hosting large port facilities and several tourist marinas, thus presenting a wide variety of submerged structures and consequently a rich fouling community. In June and July 2004, 10 stations were selected and biological samples were collected from hard substrates such as wooden piles and floating pontoons. The identification to species level revealed the presence of 2 entoprocts and 16 bryozoans (5 ctenostomes and 11 cheilostomes). The most common species are Bowerbankia gracilis (found in all stations), Cryptosula pallasiana and Bugula neritina (found in 8 and 9 out of 10 stations, respectively). Noteworthy is the occurrence of Tricellaria inopinata; it is well established in several sites of the two investigated channels and even becomes dominant in the Canal de Ovar. This cheilostome bryozoan is an alien species of Pacific origin, first introduced to Europe in the lagoon of Venice (Italy); this record in the Ria de Aveiro is the first one for Portuguese coasts. The case of T. inopinata has been studied in the lagoon of Venice as a meaningful example of bryozoan biodiversity loss related to the spread of alien species due to aquaculture activity and/or shipping (commercial vessels). The Ria de Aveiro, with its important port and tourist marinas, constitutes an ideal site for the development of alien species’ propagules and a source for secondary dispersal; thus, improved monitoring of its fouling community could be useful to control and prevent the dispersal of non-native biota.