Clarisse Odebrecht

Dinophysiales (Dinophyceae) no extremo Sul do Brasil (inverno de 2005, verão de 2007)

The dinoflagellates of the Dinophysiales order are a morphologically diverse and ecologically heterogeneous group that includes autotrophic, mixotrophic and heterotrophic species and others containing endosymbionts or phycotoxin producers. In this research Dinophysis, Ornithocercus, Histioneis and Amphisolenia species have been identified in both coastal and oceanic waters of the Southern region of Brazil next to Santa Marta Grande Cape, SC and Albardao-Chui, RS. Vertical hauls were performed with plankton nets (20 µm) on board of the R. V. Atlântico Sul at 33 oceanographic stations sampled in August/September 2005 (Winter) and February 2007 (Summer). The plankton was fixed with formaldehyde (4%) and analyzed with the help of an inverted microscope. A total of 43 Dinophysiales species were identified, most of them widely distributed in the coastal, continental and oceanic areas such as Dinophysis acuminata, D. exigua, D. ovata and Histioneis hyalina in the Summer of 2007 and D. acuminata, D. caudata, D. fortii e D. schroederi in the Winter of 2005. The distribution of some species was restricted to the oceanic region under the influence of the Brazil Current as it was observed for Dinophysis dubia, D. exigua, D. schuetti, Histioneis para, Ornithocercus thumii and O. splendidus in the Winter of 2005 and D. similis, D. rapa, H. megalocopa, H. milneri, O. heteroporus and O. splendidus in the Summer of 2007. Six potentially toxic species were registered, Dinophysis acuminata, D. caudata, D. fortii, D. mitra, D. tripos and D. rotundata.

Morphology and ecology of Thalassiosira Cleve (Bacillariophyta) species rarely recorded in Brazilian coastal waters

The detailed description of rarely recorded Thalassiosira species in Brazil is presented with light microscope (LM) and scanning electron microscope (SEM) illustrations. A total of 78 phytoplankton net samples (20 microm) collected between the years 2000 and 2006 in coastal waters of southern Brazilian, Cassino Beach and the estuary of Lagoa dos Patos, were studied in cleaned material using the Axiovert Zeiss LM and Jeol 6060 SEM. Water temperature and salinity of samples and six species are presented: Thalassiosira endoseriata, T. hendeyi, T. lundiana, T. minuscula, T. oceanica and T. wongii. Two species, Thalassiosira hendeyi and T. endoseriata were the most common being observed in all seasons at Cassino Beach in a wide temperature range (10-26 masculineC), while only sporadically in the estuary of Lagoa dos Patos. Thalassiosira endoseriata, T. lundiana, T. oceanica and T. wongii are for the first time reported in Brazilian coastal waters. The latter two species, rarely recorded in the world, are fully illustrated based on Brazilian material.

Loricate Choanoflagellates from the South Atlantic coastal zone (~32 °S) including the description of Diplotheca tricyclica sp. nov.

The biodiversity of marine heterotrophic protists is poorly known in the South Atlantic coastal zone (~32 °S) especially regarding the nanoflagellates. The presence of loricate choanoflagellates was reported for the first time in the Patos Lagoon estuary and the adjacent coastal zone. Seventeen species of eleven genera of loricate choanoflagellates were observed between October 1998 and May 2000 in fixed water samples (lugols solution + glutaraldehyde) in a JEM 100-SX transmission electron microscope. Most species were recorded in euhaline and mixopolyhaline waters during the spring and summer, none in autumn and a few (four) in winter. The absence of choanoflagellates at the more sheltered inshore stations is due freshwater influence, and at the beach station, probably due the strong wave action. The probably cosmopolitan species Pleurasiga minima, Cosmoeca norvegica, C. ventricosa and Parvicorbicula circularis were present in spring or summer in the estuary channel and coastal area while Stephanoeca diplocostata which apparently prefers lower temperature, was recorded in winter. Calotheca alata and Campyloacantha spinifera are mainly temperate species and were present in spring. The new species Diplotheca tricyclica was recorded at the estuary channel in the summer 1999, in high salinity water.

Remarks on the morphology and distribution of some rare centric diatoms in southern Brazilian continental shelf and slope waters

This paper provides information on the morphology and occurrence of extant diatoms of the family Asterolampraceae and Azpeitia species of the southernmost Brazilian continental shelf and slope waters in the Southwestern Atlantic Ocean (28 -34oS), under the influence of Tropical, Subtropical, Subantarctic Waters, terrestrial discharges from La Plata River and Lagoa dos Patos lagoon. Plankton was sampled (20 µm net; vertical hauls) at the same 27 stations in winter 2005 and summer 2007. Among Asterolampraceae, Asteromphalus flabellatus was the most frequent species (57% of samples) observed mainly in winter samples (92%) in Subtropical Shelf Water but also under the influence of La Plata River plume (salinity <35). Lower frequencies were observed for Asterolampra marylandica, Asteromphalus elegans, Asteromphalus heptactis and Spatangidium arachne. Four species of Azpeitia were observed: A. barronii and A. neocrenulata for the first time in the South Atlantic Ocean while A. africana and A. nodulifer had already been registered in equatorial and southern areas of Brazil. All Azpeitia species were rare (19%) in offshore samples (100-200 m depth. Remarks on the morphology based on light and scanning electron microcopy observations are provided along with their distribution in the study area.

Chave dicotômica ilustrada para a identificação de espécies de Thalassiosira Cleve (diatomácea) no estuário da Lagoa dos Patos e área costeira adjacente (Rio Grande do Sul, Brasil)

The paper presents a dichotomous key and a comparative table summarizing dimension data and diagnostic characteristics of seventeen Thalassiosira species (diatoms) commonly found in Lagoa dos Patos estuary and the coastal adjacent area (~32° S and 52° W). For all studied species, optic microscope illustrations and comments on significant morphological features are provided, together with scanning electron microscopy images.

Flagellates Versus Diatoms: Phytoplankton Trends in Tropical and Subtropical Estuarine-Coastal Ecosystems

Attempts to provide general patterns of phytoplankton and their regulating factors benefit from ecosystem comparisons, but these are strongly biased toward high-latitude environments of the northern hemisphere (> 20°N). In the present study, we compare the phytoplankton biomass and composition variability in two coastal environments in the southern hemisphere, the tropical Guanabara Bay, GB (23°S), and the subtropical Patos Lagoon Estuary, PLE (32°S), located on the South American southeast coast at the state of Rio de Janeiro and Rio Grande do Sul, respectively. These environments present contrasting features regarding the magnitude of anthropic impacts, the watershed size, geomorphology, and hydrology. Our goal was to identify the main factors that regulate the phytoplankton biomass and composition comparing data obtained at monthly intervals between the years 2011 and 2012 at a single station located in an area of significant water exchange in each environment. Surface water temperature, salinity, inorganic dissolved nutrients, chlorophyll a, phytoplankton biomass (carbon) and composition were analyzed. Phytoplankton biomass in the GB and PLE was dominated, respectively, by flagellates and diatoms, whereas cyanobacteria were more important in the former. Salinity was about twofold higher in the GB (mean 32.6 ± 1.5) than PLE (mean 15.4 ± 9.1) and, together with nutrient concentrations and their proportions, largely explained the observed different communities and much higher biomass in GB. GB presented strong eutrophication signals, with high ammonium and phosphate and lower, closer to limitation, silicate concentration. In contrast, high silicate concentration favored the predominance of diatoms in the PLE. Despite large environmental differences between both environments, the chlorophyll a presented a rather similar seasonal pattern, with maxima in austral summer/autumn and spring in both ecosystems. We suggest the seasonal pattern was associated to the incident light variation, but this hypothesis should be further explored.