Search

Abstract:Thalassiosiraspecies are an important component of phytoplankton populations, and most species are considered cosmopolitan. Many authors have investigated the diversity of Thalassiosiraspecies in order to understand their ecological roles in local areas. Our regional taxonomic study revealed the presence of 44 Thalassiosiraspecies at 124 sites in Korean coastal waters. Of these, 14 species are newly reported in Korean waters and are described in detail with external and internal valve illustrations. Some morphologically confused taxa, such as the Thalassiosira s.s. group, T. curviseriata/T. tealata, T. simonsenii/Planktoniella blandaand T. proschkinae/T. spinulata, are clearly distinguished using additional morphological criteria. In addition, the full biogeographical distribution of Thalassiosirais described and compared with the Korean species. Korean waters seem to be the ‘Maginot Line’ for the cold- and warm-water Thalassiosiraspecies. Knowledge of Thalassiosiraspecies diversity will increase with more intensive work in relatively little-studied regions, such as the Indo-Pacific and tropical Atlantic Oceans. more...

Abstract:To propose identification criteria for Chaetocerossubgenus Chaetocerosbased on setae ultrastructure, we sampled 38 Korean coastal water locations and 12 Chukchi Sea, Arctic Ocean sites and we studied 11 species using light microscopy and scanning electron microscopy. We selected seven criteria for species-specific identification: (1) spine form; (2) poroid arrangement; (3) number poroid rows between costae; (4) costae presence or absence; (5) angle of costa against the seta rim; (6) spine cross-sectional shape; and (7) seta wall silicification. On the basis of these criteria, we constructed a flowchart to enable species-specific identification. We showed that similar species within the subgenus Chaetoceroscan be distinguished solely on the basis of setae criteria. more...