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Marine Ecology Progress Series

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MEPS 596:49-60 (2018)  -  DOI:

Hitchhiking in the East Australian Current: rafting as a dispersal mechanism for harmful epibenthic dinoflagellates

Michaela E. Larsson1,*, Olivier F. Laczka1, Iain M. Suthers2, Penelope A. Ajani1, Martina A. Doblin1

1Climate Change Cluster, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW 2007, Australia
2Fisheries and Marine Environmental Research Facility, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia

ABSTRACT: Due to their small size, planktonic marine microorganisms have large dispersal capacity in the global ocean. However, it is not known how epibenthic microalgae disperse across long distances because they are generally associated with a substrate. In this study, we examined a long-term data series (~50 yr) of microalgal composition from a coastal station in southeast Australia for the presence of epibenthic dinoflagellates in the plankton. In addition, we collected drifting macrophytes (i.e. macroalgae and seagrass) and plastic debris from the East Australian Current, identified the associated microalgal assemblage, assessed their viability, and used phylogenetic analyses to taxonomically identify cryptic harmful epibenthic dinoflagellate species. We found no occurrences of epibenthic dinoflagellates from the genera Gambierdiscus, Fukuyoa, Ostreopsis, and Coolia at the long-term coastal station, concluding that entrainment of cells in ocean currents is an unlikely mechanism for transport of these taxa. The epibenthic microalgal communities associated with macrophyte rafts and plastic debris were primarily comprised of diatom taxa. However, intact cells of potentially harmful epibenthic dinoflagellates from the genera Coolia, Amphidinium, and Prorocentrum were also observed, and their viability was confirmed by division of isolated cells and establishment into clonal cultures. Phylogenetic analyses confirmed the presence of C. palmyrensis on a drifting Sargassum sp. raft, the first report of this potentially harmful epibenthic species in temperate Australian waters. This study shows that epibenthic dinoflagellates can attach to, and remain viable, when associated with macrophyte fragments that drift in the open ocean, therefore revealing rafting as a potential vector for dispersal of these organisms.

KEY WORDS: Coolia · Drifting algae · East Australian Current · EAC · Epibenthic · Macrophyte · Rafting · Seagrass

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Cite this article as: Larsson ME, Laczka OF, Suthers IM, Ajani PA, Doblin MA (2018) Hitchhiking in the East Australian Current: rafting as a dispersal mechanism for harmful epibenthic dinoflagellates. Mar Ecol Prog Ser 596:49-60.

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