Eugenia A. Sar

The diatom genus Thalassiosira: species from the northern San Matias Gulf (Rio Negro, Argentina)

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 Matias Gulf, Argentina. Net samples were collected from the surface layer of the water column at Punta Orengo, Las Garzas, Banco Reparo, Los Alamos, 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.

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

El genero Chaetoceros es un componente importante del plancton marino, de amplia distribucion mundial en terminos de diversidad y biomasa. El presente trabajo esta abocado a la morfologia, taxonomia y distribucion de las especies pertenecientes al genero Chaetoceros encontradas en aguas costeras marinas de la Provincia de Buenos Aires, Argentina. Las muestras fitoplanctonicas fueron recolectadas desde noviembre de 1994 hasta septiembre de 2000 en siete estaciones ubicadas a lo largo de la costa bonaerense entre los paralelos 36o20� y 37°20� S. El material fue estudiado con microscopia optica y electronica de barrido. Veinte taxa fueron encontrados, identificados, descriptos, ilustrados y comparados con los taxa mas allegados. Tres de esos taxa pertenecen al subgenero Chaetoceros (= Phaeoceros) y los restantes diecisiete pertenecen al subgenero Hyalochaete. Chaetoceros filiferus y C. compressus var. hirtisetus son reportados por primera vez para el Oceano Atlantico sudoccidental. C. danicus, C. debilis, C. lorenzianus y C. socialis, mencionadas como especies nocivas en otras areas geograficas, no fueron asociados a eventos nocivos en el area de estudio durante este periodo.

Cocconeis Ehrenberg and Psammococconeis García (Bacillariophyta) from the Gulf of San Matías, Patagonia, Argentina

The morphology and taxonomy of species of the genera Cocconeis Ehrenberg and Psammococconeis Garcia from the Gulf of San Matías (Patagonia, Argentina) is documented in the present study. A total of 16 taxa of Cocconeis and one species of Psammococconeis were found in surface net hauls taken in shallow coastal waters of the Gulf. Cocconeis fluminensis var. fluminensis, C. fluminensis var. subimpleta, C. guttata, C. peltoides and C. neothumensis var. marina are new records for the southwestern Atlantic Ocean.

REVIEW OF MATERIALS REPORTED AS CONTAINING AMPHORA COFFEAEFORMIS (AGARDH) KÜTZING IN ARGENTINA

Amphora coffeaeformis (Agardh) Kutzing has been reported in Argentina from marine and inland environments. Since this species has frequently been misidentified, we carried out a review of materials corresponding to the records of A. coffeaeformis and compared them with photographs of the type material. All analyzed materials are similar as regards valve outline and dimensions; however, they differ in valve morphology, mainly in the type of striae and areolae. The presence of A. coffeaeformis was corroborated in materials from Buenos Aires (Arroyo Tapalque), Jujuy, San Luis and La Pampa. The materials from Mar del Plata correspond to Amphora hybrida Grunow, a new record for South America, and those found in samples from Lago Nahuel Huapi correspond to A. veneta var. capitata Haworth. Six other taxa purported to be A. coffeaeformis could not be determined and will be the subject of further research. Considering that A. coffeaeformis has been reported as a potential domoic acid producer, we compared our mate...

Dinophysis spp. asociadas a detección de toxinas diarreicas (DSTs) en moluscos y a intoxicación diarreica en humanos (Provincia de Buenos Aires, Argentina)

During January and February 2010 lipophilic shellfish toxins were detected in two bivalve species from Villa Gesell and Mar Azul (Argentina) by the mouse bio...

Marine diatoms from Buenos Aires coastal waters (Argentina). II. Thalassionemataceae and Rhaphoneidaceae

Este estudio describe la diversidad de especies de diatomeas pertenecientes a las familias Thalassionemataceae Round and Rhaphoneidaceae Forti encontradas frecuentemente en aguas costeras marinas de la Provincia de Buenos Aires, Argentina, entre octubre de 1994 y septiembre de 2000. En el se lleva a cabo el estudio morfologico, taxonomico y distribucional de las especies halladas en muestras planctonicas colectadas en San Clemente del Tuyu, Santa Teresita, La Lucila del Mar, Mar de Ajo, Nueva Atlantis, Pinamar y Villa Gesell. Material sin tratar y tratado fue analizado con microscopio optico y microscopio electronico de barrido. Cuatro taxa de Thalassionema Grunow ex Mereschkowsky amend. Hallegraeff, uno de Lioloma Hasle, dos de Delphineis Andrews y uno de Rhaphoneis Ehrenberg, fueron identificados. Thalassionema pseudonitzschioides (Schuette & Schrader) Hasle, Thalassionema synedriforme (Greville) Hasle y Lioloma pacificum (Cupp) Hasle in Hasle & Syvertsen son reportadas por primera vez para aguas costeras de Argentina

Marine diatoms from Buenos Aires coastal waters (Argentina). IV. Rhizosolenia s. str., Neocalyptrella, Pseudosolenia, Proboscia

I. Sunesen & E.A. Sar 2007. Marine diatoms from Buenos Aires coastal waters (Argentina). IV. Rhizosolenia s. str., Neocalyptrella, Pseudosolenia, Proboscia. Phycologia 46: 628–643. DOI: 10.2216/07-13.1 The present paper describes the morphology, taxonomy, and distribution of species belonging to the diatom genera Rhizosolenia s. str., Neocalyptrella, Pseudosolenia and Proboscia, found in the marine coastal waters of Buenos Aires Province, Argentina. The phytoplankton samples were collected from October 1994 to September 2000 at seven locations and were analyzed by light and scanning electron microscopy. Rhizosolenia antennata f. antennata, R. bergonii, R. hyalina, R. imbricata, R. setigera f. setigera, R. setigera f. pungens, Neocalyptrella robusta, Pseudosolenia calcar-avis, Proboscia alata and P. indica were studied and compared with allied taxa. Morphology of the frustule and of the resting spore of R. setigera, which is considered by some authors incerta sedis, shows that this species might be included into the genus Rhizosolenia s. str. Rhizosolenia hyalina is reported for the first time from Argentinean coastal waters. R. setigera f. setigera, R. setigera f. pungens, P. alata, and P. calcar-avis, cited as harmful non-toxigenic taxa in other geographical areas, were never associated with harmful events in the study area.

Chaetoceros resting spores in the Gerlache Strait, Antarctic Peninsula

The formation of resting spores in diatoms is a common phenomenon in neritic environments. Here we report on resting spores of the genus Chaetoceros associated with a layer of increased chlorophyll fluorescence, at a depth of more than 200 m, north of Brabant Island and in Wilhelmina Bay, southeast coast of the Gerlache Strait (64°41.0′S, 62°0.5′W). Six species of Chaetoceros were identified by the morphology and size of the resting spores. Given that Chaetoceros spp., both in vegetative cells and as resting spores, are commonly found in Antarctic coastal surface waters, their location at depth could represent the pelagic “waiting” or “seeding” populations mentioned for other environments.

Thalassiosira fryxelliae nov. spec. (Bacillariophyceae) from Argentinian coastal waters

Abstract The new marine nanoplanktonic diatom, Thalassiosira fryxelliae, is described with light and scanning electron microscopy from material collected in Argentinian coastal waters. T. fryxelliae is a morphologically distinctive species with: 1) cells embedded in irregular gelatinous masses, 2) absence of central, sub-central and scattered strutted processes on the valve surface, 3) one marginal ring of strutted processes with external tubes, 4) one marginal labiate process included in the ring of the strutted processes, 5) areolation pattern variable linear, sublinear, eccentric or irregular. Externally, the marginal strutted processes have double tubes, at least in the distal part, cut distally and with the half-cylinder bent vertically with crenulated distal edges and the labiate process has a simple tube. Internally, the strutted processes are short with four operculate satellite pores and the labiate process is sessile and radially located. Thalassiosira fryxelliae is similar to T. angulata and T. nanolineata in morphology and distribution pattern of the marginal strutted processes and in the location of the labiate process and to T. leptopus and some specimens of T. guillardii and T. pseudonana in lacking one central strutted process.

A MORPHOLOGICAL STUDY OF CHAETOCEROS TENUISSIMUS MEUNIER, A LITTLE-KNOWN PLANKTONIC DIATOM, WITH A DISCUSSION OF THE SECTION SIMPLICIA, SUBGENUS HYALOCHAETE

The morphology of Chaetoceros tenuissimus Meunier, a little-known species, has been studied for the first time with electron microscopy. C. tenuissimus has been placed as a synomyn of C. simplex Ostenfeld since approximately 1930, and has been misidentified or neglected in routine phytoplankton counts. The cells are very small and solitary, square to rectangular in girdle view. The setae are narrow and straight, arising from the two poles of the valve at an angle of 45° to its apical axis. The valve face possesses an annulus, delimited by a hyaline rim. Costae and small areolae radiate from the annulus. A single rimoportula occurs within the annulus. The rimoportula opens externally in a flatened tube and internally by a simple slit. The setae exhibit spirals of minute pores and an intricate pattern of spiral and perpendicular costae; spines are regularly present. Similarities with closely related species in Section Simplicia are discussed.