Species diversity of dinophysoid dinoflagellates in the Clarion-Clipperton Fracture Zone, eastern Pacific

Species diversity of dinophysoid dinoflagellates is especially high in subtropical and tropical oceans. Only a few studies about the diversity of these dinoflagellates exist from the eastern Pacific. The offshore, subtropical Clarion-Clipperton Fracture Zone (CCZ), in the eastern part of the Pacific between Mexico and Hawaii, is an area of interest for deep sea manganese nodule mining. Therefore, geological research is ongoing, but also biodiversity research from the deep sea up to the surface is of importance. This study adds to the biodiversity knowledge by describing dinophysoid dinoflagellates in the area for the first time. Phytoplankton samples were collected during two cruises to the CCZ, MANGAN 2013 (April and May 2013) and ABYSSLINE AB01 (October 2013), and investigated morphologically. Sixty-six species of dinophysoid dinoflagellates were found and documented by light and scanning electron microscopy. These species belonged to 11 genera: Amphisolenia F.Stein (9), Citharistes F.Stein (1), Dinophysis Ehrenb. (15), Histioneis F.Stein (8), Latifascia sp. (1), Metaphalacroma L.S.Tai (1), Parahistioneis Kof. & Skogsb. (3), Phalacroma F.Stein (16), Pseudophalacroma Jorg. (2), Ornithocercus F.Stein (9) and Triposolenia Kof. (1). Seven of the taxa, Amphisolenia sp. 1 and 2, Phalacroma sp. 1, Dinophysis sp. 1, Pseudophalacroma sp. 1, Histioneis spec. and cf. Latifascia spec., could be identified only to the genus level and may represent new species. This diversity was unexpected compared to the available open ocean records for the eastern Pacific (14 species, four genera). Almost half the number of species recorded before in the eastern Pacific (including coastal samples) was observed, corresponding to about one-fifth of the known dinophysoid diversity.