Diatoms from marine coastal environments of Argentina. Species of the genus Pleurosigma (Pleurosigmataceae)

This study focuses on the analysis of the morphology, taxonomy and distribution of species belonging to the diatom genus Pleurosigma W. Smith found in marine coastal waters of Argentina. Net samples were collected from the surface layer of the water column at several coastal stations in Buenos Aires and Rio Negro Provinces. Unprocessed and cleaned materials were examined by light and scanning electron microscopy. Species identified were Pleurosigma decorum W. Smith, P. distinguendum Hustedt, P. inflatum Shadbolt, P inscriptura M. A. Harper, P normanii Ralfs and P. simonsenii Has le. Two new taxa are described. Pleurosigma patagonicum var. paucistriatum nov. var. is compared with type material of Pleurosigma patagonicum (Ferrario & Sar) Sterrenburg & Sar var. patagonicum and P. perlucidum nov. spec. is compared with P elongatum W. Smith, P. delicatulum W. Smith, P. amara Stidolph and P. brunii H. Peragallo based on type materials and/or protologues. New observations on Pleurosigma decorum, P. distinguendum, P inflatum, P inscriptura and P. normanii are included and differences from related species are discussed. P. inflatum is recorded for the first time from Argentina and Pleurosigma distinguendum and P inscriptura are recorded for first time from the South Atlantic Ocean.