A recent review of marine invasive species confirms earlier assessments that international shipping, followed by aquaculture represent the major means of introduction.
The review, undertaken by Jennifer Molnar, Rebecca Gamboa, Carmen Revenga and Mark Spalding, is due to be published in the journal Frontiers in Ecology and the Environment.
The authors used data from more than 350 databases to synthesize information on 329 marine invasive species, including their distribution, impacts on biodiversity, and introduction pathways.
The authors identified 84% of the world s marine ecoregions to be suffering from invasions by non-native species, although they consider this figure to be lower than the actual situation because of under-reporting.
Among the most heavily invaded marine ecoregions in the world the authors have identified are: northern California (56 harmful species), the North Sea (47 harmful species), and the western Mediterranean (43 harmful species). One species that the authors highlight in their study is the Pacific oyster (Crassostrea gigas).
This native of northeastern Asia has been introduced in at least 45 ecoregions worldwide to be cultured for food. The oyster has negatively impacted native marine life wherever it has been introduced.
They have the potential to smother other marine life, such as scallops, destroying habitat and causing eutrophication that affects water quality. They also pose a direct threat to human safety because of their propensity to cut feet and shoes with their sharp shells.
The authors believe that the information they have compiled can be useful for formulating large-scale strategies necessary to prevent future introductions.
They write: This global perspective allows researchers and regulators to better consider where and how invasive species are likely to be introduced and invade in the future.
This can help to inform risk assessments and decisions about potential future introductions, as well as the development of species- and pathway-specific regulations and geographically targeted policies.
For a different perspective on the introduction of aquatic organisms, please see this blog post.
For more information, see the paper: Molnar, JL, RJ Gamboa, C Revenga and MD Spalding (2008) Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and the Environment doi: 10.1890/070064