Experimental assessment of oyster transfers as a vector for macroalgal introductions

Abstract

Introduction of non-indigenous species can alter marine communities and ecosystems. In shellfish farming, transfer of livestock, especially oysters, is a common practice and potentially constitutes a pathway for non-indigenous introductions. Many species of seaweeds are believed to have been accidentally introduced in association with these transfers, but there is little direct evidence. We experimentally simulated the transfer of oysters from the Thau Lagoon (France). These transfers involved increasing periods of aerial emersion and additional brine and hot water treatments. The brine and hot water treatments were evaluated as a means of reducing the probability of algal introductions with oyster transfers. Shells were cultured for 40 days in experimental tanks to identify the macroalgae likely to be introduced with any oyster transfer. A total of 57 macroalgal taxa, including 16 taxa not indigenous to the Thau Lagoon, were recorded across all treatments and experiments. The abundance of some species increased in several cases following aerial emersion. Elimination treatments (immersion in brine or hot water) significantly reduced algal diversity, with hot water treatments resulting in no species or only tubular Ulva spp. present. The results support the hypothesis that oyster transfers are effective as primary and secondary vectors of macroalgal introductions. Relatively simple changes to the transfer practice (particularly hot water treatments) are suggested as a means of reducing the risk of non-indigenous algal introductions.

Updated records and range expansion of alien marine macrophytes in Greece (2009)

“…In the Mediterranean Sea, more than 110 taxa of alien marine macrophytes have been hitherto recorded, most of which originate from the Indo-Pacific Ocean, and are introduced into the Mediterranean Sea through aquaculture, shipping, and via the Suez Canal (BOUDOURESQUE & VERLAQUE, 2002;CORMACI et al, 2004;MINEUR et al, 2007;VERLAQUE et al, 2007, in press;ZENETOS et al, 2008). Several alien marine macrophytes, such as Caulerpa taxifolia (M. Vahl) C. Agardh (THIBAUT & MEINESZ, 2004) and Caulerpa racemosa var.…”

Predicting invasion patterns in coastal ecosystems: relationship between vector strength and vector tempo

“…This can be explained by the fact that the Thau Lagoon is richer in macroalgal species (Stegenga et al 1997, Verlaque 2001, and harbors an exceptionally high number of introduced macroalgae, particularly from the Northwest Pacific Ocean (Verlaque 2001). This said, the epifloral communities are similar relative to taxonomic groups and species composition: on the Thau Lagoon oysters the Rhodophyceae were also the dominant group and 17 species recorded on oysters from the Oosterschelde were also found on Thau Lagoon oysters (Mineur et al 2007). …”

“…More recently, Mineur et al (2007) investigated the epiflora on cleaned valves of Pacific oysters from the Thau Lagoon on the Mediterranean coast of France. The number of macroalgal species recorded from our oysters (37 identified species, see Table S2 in the supplement) is lower than the number of species found on Thau lagoon oysters (46 species).…”

The Japanese alga Polysiphonia morrowii (Rhodomelaceae, Rhodophyta) on the South Atlantic Ocean: first report of an invasive macroalga inhabiting oyster reefs

“…Several Polysiphonia species have been frequently recorded in oyster reefs or associated with oyster ponds and mainly to the pacific oyster C. gigas (Connor 1980;Hoagland 1982;Kamara 1982;Maggs and Stegenga 1999;Mineur et al 2007). Exotic Polysiphonia species, such as P. setacea (currently regarded as a taxonomic synonym of Womersleyella setacea) have been also recorded in monospecific stands (Rindi et al 1999).…”

“…As noticed by several authors, the possible vectors of their introductions include ballast water, vessel fouling and transport of oysters, especially of Crassostrea gigas (Thunberg, 1793) (Kapraun and Searles 1990;Curiel et al 2002;Kim et al 2004;Geoffroy et al 2012). Oyster transfer for commercial purposes is considered the most important vector of macroalgae introductions (Gruet 1976;Verlaque 1981;Stegenga et al 1997;Mineur et al 2007).…”