A survey of epiphytic dinoflagellates from the coastal waters of the island of Hawai‘i

Three hundred and sixty-nine macroalgal and non-algal samples were collected from six coastal sites around the island of Hawai‘i on a biweekly basis over a 1-year period to ascertain (1) the presence of potentially toxigenic benthic dinoflagellates, and (2) substrate and environmental preferences of the dinoflagellates. Twenty-six genera/species of dinoflagellates were encountered including the (potentially) toxigenic species Amphidinium sp., Coolia monotis, Gambierdiscus sp., Ostreopsis ovata, Prorocentrum concavum, Prorocentrum hoffmannianum, Prorocentrum lima, and Prorocentrum mexicanum. Twenty of the species are being reported for the first time as present in Hawaiian coastal waters. There was some evidence of macroalgal host preference (e.g., C. monotis on Tolypiocladia glomerulata), although host morphology preferences was greater (e.g., Gambierdiscus sp., and P. lima on filamentous turfs; O. sp. 1 on sheet-like macroblades). While some dinoflagellate groups were significantly correlated with nutrient concentrations (e.g., total dinoflagellates with nitrate + nitrite and phosphate concentrations), others were not (e.g., Gambierdiscus sp., Prorocentrum emarginatum, P. lima, and Sinophysis microcephalus). The presence of several potentially toxigenic dinoflagellate species in Hawai‘i merits future study on possible impacts of these dinoflagellates on coastal food webs and human health.