Marine diatoms from Buenos Aires coastal waters (Argentina). V. Species of the genusChaetoceros

The genusChaetoceros is an important component of the marine plankton all over the world in terms of diversity and biomass. The present work is devoted to the morphology, taxonomy, and distribution of the diatom species belonging to the genus Chaetoceros found in the marine coastal waters of Buenos Aires Province, Argentina. Phytoplanktonic samples were collected from November 1994 to September 2000 at seven sampling stations along the coast between parallels 36º20’ and 37°20’S. Material was studied by light and scanning electron microscopy. Twenty taxa were found, identified, described, illustrated and compared with allied taxa. Three of these taxa belong to the subgenus Chaetoceros (= Phaeoceros) and the other seventeen taxa to the subgenus Hyalochaete. Chaetoceros filiferus and C. compressus var. hirtisetus are reported for the first time from south western Atlantic Ocean.C. danicus, C. debilis, C. lorenzianus and C. socialis, mentioned as harmful in other geographical areas, were not associated with harmful events in the study area.