The diatom genus Thalassiosira: species from the northern San Matias Gulf (Rio Negro, Argentina)
Sar, Eugenia A.; Sunesen, Inés Lavigne
This study deals with the morphology, taxonomy and distribution of species belonging to the diatom genus Thalassiosira found in the marine waters along the northern coast of San Matías Gulf, Argentina. Net samples were collected from the surface layer of the water column at Punta Orengo, Las Garzas, Banco Reparo, Los álamos, Las Grutas, Piedras Coloradas, Bajo de Oliveira and El Fuerte from April 1998 to February 2000. Untreated and cleaned diatom samples were examined by light and scanning electron microscopy. Eighteen taxa were identified. T. frenguelliopsis is reported for the first time after its original description. T. mediterranea is a new record for the southwestern Atlantic Ocean, T. mala is a new record for Argentina, and T. angulata, T. endoseriata, T. hendeyi, T. nanolineata, T. pacifica and T. proschkinae are new records for Patagonia. Descriptions, illustrations, analysis of valve morphology and distribution are provided for the species not previously studied in detail from Argentinian coastal waters. New observations on T. frenguelliopsis and comparisons with related species known to have, or suspected of having, a similar ultrastructure are also included.