Transoceanic ships as vectors for nonindigenous freshwater bryozoans

• Published in: Diversity & distributions 2010, Vol.16 (1), p.77-83
• Main Authors: Kipp, R., Bailey, S. A., MacIsaac, H. J., Ricciardi, A.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Ballast tanks; Ballast water; Biodiversity Research; Biological and medical sciences; Biological taxonomies; Bryozoa; Ecological invasion; Ecology; Fredericella sultana; Fresh water; Fundamental and applied biological sciences. Psychology; General aspects; Great Lakes; Introduced species; invasive species; Invertebrates; Lakes; Less representative or incertae sedis groups: acanthocephala, chaetognatha, gnathostomulida, lophophoria, merostomata, mesozoa, myxozoa, nematorhyncha, pararthropoda, placozoa, priapuloidea, prochordata, pycnogonida, rotifera; Lophopodella carteri; Lophopus crystallinus; Nonnative species; Plumatella casmiana; propagule pressure; Sediments; ship ballast tanks; Ships; Species diversity; statoblasts
• ISSN: 1366-9516; 1472-4642
• DOI: 10.1111/j.1472-4642.2009.00629.x

The transport of organisms in ships' ballast tanks is a dominant vector for aquatic invasions worldwide. Until recently, efforts to manage this vector have overlooked the potential transport of invertebrate resting stages in the residual waters and sediments within emptied ballast tanks, i.e. NOBOB ('No Ballast On Board') tanks. The resting stages (statoblasts) of freshwater bryozoans are often buoyant and locally abundant and thus can be taken up easily during ballasting operations. They are also resistant to extreme environmental conditions and can generate new colonies after being dormant for decades; as such, they would likely remain viable propagules after lengthy transport in ship ballast tanks. This study quantified the occurrence of freshwater bryozoan statoblasts in ballast tank sediments of transoceanic ships. North American Great Lakes. We quantified the frequency of occurrence, abundance and diversity of bryozoans (as statoblasts) in residual sediment samples taken from 51 NOBOB tanks of 33 transoceanic ships visiting the Great Lakes from 2000 to 2002. Our study identified 11 species, comprising nearly 12% of the total number of freshwater bryozoans known worldwide. These include two exotic species unrecorded in the Great Lakes (Fredericella sultana and Lophopus crystallinus), an exotic species already established in the region (Lophopodella carteri) and three cosmopolitan species (Plumatella casmiana, P. fungosa and P. repens). Our estimates suggest that a ship with NOBOB tanks may carry up to 10⁶ statoblasts. The discovery of species unrecorded in the Great Lakes and the potentially large numbers of statoblasts being transported in ship ballast tanks indicate a significant risk of new species introductions. Furthermore, the presence of cosmopolitan species and an exotic species already established in the Great Lakes suggests the strong possibility of cryptic invasions via the introduction of exotic genotypes.