Early warning and mitigation of the impact of invasive colonial ascidian tunicates

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Invasive species are among the most important anthropogenic components of global change. Shipping has led to a global homogenization of the distribution of species, resulting in catastrophic reduction in native species biodiversity with severe economic consequences. Invasive species have caused large reductions in native species biodiversity on the east and west coasts of Canada and have reduced the sustainability of aquaculture. We have discovered two species of invasive colonial ascidian tunicates in several harbours on the south coast of Newfoundland. They have not yet attained high densities however, providing the rare opportunity to conduct 'pre-invasion' research and increasing the probability of successful mitigation. Our first objective is to develop TaqMan gene probes and real-time PCR assays, permitting early detection of a single ascidian egg or larva in a plankton sample. These probes will be based upon the nucleotide sequence of the cytochrome oxidase I gene of mitochondrial DNA, a reliable indicator of species identity. The gene probes may be made commercially available in 3-5 years.