Algal introductions to european shores

A novel suite of primers that provide potentially valuable tools for both population and phylogenetic studies in red and green algae has been developed. As the existing repertoire of markers is extremely limited, the effort of optimising universal primers in individual studies is greatly outweighed by the benefits of having new markers, particularly where existing ones were unsuitable.

A list of 15 invasive and 9 potentially invasive seaweed species, according to ecological and socioeconomic criteria, is available in the form of a publishable report. The list can be used in conservation and management of the coastal zone in Europe.

Changes in the structure of a low intertidal macroalgal assemblage after the arrival of Sargassum muticum have been studied on the North coast of Spain. Those localities invaded at the end of the 80s by Sargassum muticum showed changes in the abundance of dominant species as well as an increase in species richness and diversity. Localities not invaded remain unaltered. The results suggest that the arrival of Sargassum muticum has had a negative effect on the native red alga Gelidium spinosum. Indirect benefitial effect on many other species such as Bifurcaria bifurcata and turf species have been observed.

The present contribution revealed that macroalgae can be successfully transported inside ballast tanks. Since no thallus fragments were found, algal growth has to be related to the presence of microscopic forms able to survive and germinate. It is remarkable that in 90 litres of water analysed it was possible to identify 15 taxa, especially in respect to the water on board (thousands of tons). Almost all individuals grew from Mediterranean water samples and belong to the ubiquitous genus Ulva, common throughout the world in marine and estuarine habitats. The allochtonous species was found in Port Said ballast water samples. As the high number of entries passing through Port Said, this area can be regarded as hot spot for the dispersion of non indigenous species.

A database of reported locations of introduced seaweed species and of traits associated with these species is available. Overall, 128 introduced species have been characterised for biological and biogeographical traits. The most significant donor regions for Europe are Japan and California. The presence of a free floating stage significantly affects the probability that an introduced species will become common across a broad range or invasive.

This protocol is designed for sampling the hulls of large commercial ships while in commercial harbour in order to identify the biofouling macroalgae with particular attention to species likely to be introduced to the local area. Information about shipping traffic should be obtained on a daily basis by consultation with the harbour authorities. On the arrival of a suitable ship (with a particular focus on non-EU origin), an informal meeting with the captain is organized on board in the presence of the shipping agent, in order to explain the sampling programme and request authorization to sample the hull.

Our study shows that of the many demographic characteristics that theoretically can be beneficial for a species to invade new territory Sargassum muticum at our study locations mostly relies on persistence of non-reproductive adults. Since adult individuals have a high longevity the species only needs an occasionally year with effective recruitment. This however also implies that when the species enters an area with a lot of available substrate and survival conditions population growth rates can be high. Our model only worked on a local scale and was closed for net input or output of migrants therefore, dispersal events were not accounted for. This was done on purpose since no data is yet available on the connectivity of 'populations' on any spatial scale. However this also means we were not able to evaluate the importance of short and long distance dispersal for local population growth.

Oyster transfer is an important vector for marine macrophytes introductions.- Duration of transfer (emersion) has no effect on the survival of macrophyte propagules. - Immersion in hot-seawater or in brine are effective methods to avoid such introduction or/and dispersal of marine macrophytes.

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