Published online by Cambridge University Press: 20 December 2013
Benthic dinoflagellates collected in spring–summer 2010 and 2011 from intertidal sandy sediments of the shore of Wimereux (north-east English Channel, France) were examined by light microscopy, and some of them by scanning electron microscopy. High dinoflagellate species richness, 70 species, was evidenced when compared to the plankton observed in the coastal waters of the north-east English Channel. The greatest difficulty in performing accurate species identification mainly concerned the heterotrophic species of Amphidinium sensu lato, the laterally flattened species of Amphidiniopsis, as well as some heterotrophic species of Thecadinium. Several undescribed species are here illustrated, mainly within these genera. The differences in size between species of Herdmania and Sabulodinium suggest the occurrence of at least a second species for these monotypic genera. The species Amphidiniopsis hexagona, A. rotundata, A. uroensis and Sinophysis minima are reported for the first time in the Atlantic Ocean and on European coasts. Although these species were only previously known from the Pacific Ocean, they should not necessarily be considered as newcomers or invasive species due to the scarce coverage of the previous studies on sand-dwelling dinoflagellates.