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We examined the risk of introduction associated with potentially toxic or otherwise harmful algae (HA) or nonindigenous species (NIS) of dinoflagellates in ballast water from 63 commercial ships visiting ports of eastern Canada in 2007-2009. Ship categories included transoceanics undergoing ballast water exchange (BWE) and coastal ships with or without BWE. Of 159 species of dinoflagellates observed in Lugol-preserved samples, 15 were potential HA (six Dinophysis spp.) and 46 were NIS (including three HA). We found at least one species of HA in 81% of all ships examined, and maximum cell concentrations reached nearly 4000 cells x [L.sup.-1]. Coastal nonexchanged tankers carried the greatest cell concentrations of HA. NIS dinoflagellates were found in 56% of ships, significantly more in ships with BWE. There was no evidence that ships with BWE contained significantly fewer taxa or lower concentrations of HA dinoflagellates, indicating that BWE is not efficient in controlling the introduction of these organisms. In fact, BWE promoted the transport of NIS dinoflagellates, possibly because of the wide distribution of several of these species. Coastal ship traffic is a significant introduction pathway for HA (ships with and without BWE) and NIS (ships with BWE) dinoflagellates in eastern Canada. Le risque d'introduction associe a la presence de dinoflagelles potentiellement nuisibles ou toxiques (algues nuisibles, HA) ou especes non-indigenes (NIS) dans l'eau de ballast est examine pour 63 navires commerciaux visitant des ports de l'est du Canada en 2007-2009. Ces navires se repartissent en trois categories : transoceaniques effectuant un echange d'eau de ballast (BWE), navires cotiers avec ou sans BWE. Des 159 differentes especes de dinoflagelles observees, 15 sont HA (dont six Dinophysis spp.) et 46 NIS (incluant trois HA). Au moins une espece de HA se retrouve dans 81 % des navires examines et les concentrations maximales atteignent pres de 4000 cellules x [L.sup.-1]. Les bateaux-citernes cotiers sans BWE montrent les plus fortes concentrations de HA. Les NIS se retrouvent dans 56 % des navires, significativement plus abondantes dans les navires avec BWE. Il n'y a pas d'evidence que les navires avec echange ont des concentrations ou des nombres d'especes HA plus faibles, indiquant l'inefficacite de cette strategie de mitigation. En fait, les echanges de ballast favorisent le transport de dinoflagelles NIS, possiblement a cause de leur large distribution geographique. Le trafic maritime cotier represente une voie significative d' introduction pour les dinoflagelles HA (navires avec et sans BWE) et NIS (navires avec BWE) dans l' est du Canada., Introduction Ship traffic has increased steadily over the last decades, in terms of both ship size and numbers, as well as the frequency of voyages (Bourgeois et al. 2001; Hulme [...]

Abstract: Models of ocean colour rely on information about phytoplankton absorption, which varies according to community composition and photoacclimation. Here we show that pigment packaging, which is strongly determined by [...]