The diatom Chaetoceros in ships' ballast waters - survivorship of stowaways

摘要

Ship ballast water discharged by vessels into the receiving port is recognised today as all important vector for the spread of non-indigenous species and facilitates the introduction of potential invasive species. Here, we report on 18 species (of about 30 identified), both vegetative cells and spores, of the diatom genus Chaetoceros Ehrenberg found in ballast water collected from ships arriving at Canadian ports on the West Coast (WC), East Coast (EC) and the Great Lakes (GL). We found live, vegetative Chaetoceros cells (one of the most abundant taxa) in 49% of the 57 ballast water samples. The highest density of viable spores enumerated in our counts was 414 cells L-1. In 62% of 52 samples examined Using scanning electron microscopy (SEM), Chaetoceros spores were found, though fewer live, identifiable spores were found Using light microscopy. Three reportedly harmful species, C. convolutus, C. danicus, C. debilis were encountered in WC samples, and additionally, C. cf. hispidus, a species not yet reported from Canada. C. ceratosporus and C. cf. subsecundus, to date reported only from the EC of the USA, now have been transported to the port of Vancouver, British Columbia. Our findings contribute to the assessment of the effectiveness of ballast water treatment via water exchange, and serve to evaluate the diversity of diatom vegetative cells and spores transported in ballast water tanks.