Ichthyoplankton community structure on the shelf break off northeastern Brazil.

Oceanographic features influence the early stages of fish to a high degree. We investigated the influence of continental shelf-slope gradient on the ichthyoplankton composition and distribution off Northeastern Brazil. Two oceanographic campaigns were performed during July-August 2010 and 2012. The samplings were performed along three transects composed by three stations, covering the continental shelf and slope areas. Abiotic data were obtained by an ADCP and a CTD. The ichthyoplankton was sampled through diurnal and nocturnal hauls using a 500-µm bongo net from 200 m to the surface. A total of 1634 larvae and 4023 eggs, representing 91 genera and 76 species, were collected. Higher concentrations of fish eggs were found on the continental shelf, probably because of the North Brazil Undercurrent flux. Higher concentrations of larvae were found at night and could be associated with net avoidance or natural variation. Neritic, oceanic and transition groups of species association were determined. Larvae of neritic, demersal and pelagic fishes prevailed on the continental shelf, while larvae of oceanic, mesopelagic and bathypelagic fishes on the continental slope. Melanostomiidae, Scorpaena sp., Lestidium atlanticum, Lampadena sp. and Diaphus sp. were identified as indicators of the continental slope.

Phytoplankton response to water quality seasonality in a Brazilian neotropical river.

Tropical wet-dry climate seasonality is widely recognized as an important condition to phytoplankton communities' structure in freshwater ecosystems; however, there are few studies in that field in northeast Brazilian rivers. This study aimed to evaluate the influence of water quality seasonal variability over the phytoplankton dynamics and identify seasonality in eutrophication phenomena in a poorly studied neotropical river. Water quality variables and phytoplankton were examined within the Jequitinhonha River lower course, Bahia (Brazil) from 2010 to 2012. A 3-year time series was analyzed for both rainy and dry seasons. Descriptive, inferential, and multivariate analyses (CCA) were performed. Results indicated that chemical oxygen demand, dissolved aluminum, and turbidity were the main factors which influenced phytoplankton community structure and composition. Dry season was favorable for diatoms and Chlorophyceae (chlorophylls) while rainy season was favorable for cyanobacteria. Still, it was revealed that, in dry season, lower values for turbidity, chemical oxygen demand, dissolved aluminum, and dissolved iron were related with an eutrophication phenomenon.

Large-Scale Spatial and Temporal Variability of Larval Fish Assemblages in the Tropical Atlantic Ocean.

This study investigated the large-scale spatial and temporal variability of larval fish assemblages in the west tropical Atlantic Ocean. The sampling was performed during four expeditions. Identification resulted in 100 taxa (64 families, 19 orders and 17 suborders). During the four periods, 80% of the total larvae taken represented eight characteristics families (Scombridae, Carangidae, Paralepididae, Bothidae, Gonostomatidae, Scaridae, Gobiidae and Myctophidae). Fish larvae showed a rather heterogeneous distribution with density at each station ranging from 0.5 to 2000 larvae per 100m3. A general trend was observed, lower densities at oceanic area and higher densities in the seamounts and islands. A gradient in temperature, salinity, phytoplankton biomass, zooplankton biomass and station depth was strongly correlated with changes in ichthyoplankton structure. Myctophidae, and Paralepididae presented increased abundance at high salinities and temperatures. Bothidae and Gobiidae were more abundant at higher phytoplankton biomass and zooplankton biomass. Scaridae, Scombridae and Gonostomatidae had higher abundances at deep offshore stations. Different events might be responsible for the formation, maintenance and breakdown of fish larvae assemblage in the tropical oceanic area of Brazil. The results suggested that the oceanographic variables (temperature, salinity, phytoplankton biomass, zooplankton biomass and station depth) played an important role on the distribution patterns of ichthyoplankton.

Seasonal changes in the distribution and abundance of marine cladocerans of the Northwest Alboran Sea (Western Mediterranean), Spain

The annual cycle of marine cladocerans was studied over six years from 1994 to 1999 within the frame of the monitoring Project ECOMALAGA at a nine stations in the NW of the Alboran Sea, with the aim of assessing seasonal patterns and interannual trends in distribution and abundance of marine cladocerans. Seven species (Penilia avirostris, Evadne nordmanni, Evadne spinifera, Pseudoevadne tergestina, Pleopis polyphemoides, Podon leuckarti and Podon intermedius) were detected in the northwest Alboran Sea. Total cladoceran relative abundance varied from 0 to 89 percent of the total cladocerans. The abundance of cladocerans was higher in summer-autumn than in winter-spring (7012 - 4711.100 and 743 - 217.100m-3 , respectively). The species composition was very different in terms of seasonality. P. polyphemoides, P. leuckarti and P. intermedius appeared mostly during the spring. P. tergestina, E. spinifera and E. nordmanni predominantly occurred during the winter. P. avirostris occurred mostly during the summer and autumn.

Registro de branqueamento sazonal em siderastrea spp. Em poças intermareais do recife de guarajuba, Bahia, Brasil / Record of seasonal bleaching in siderastrea spp. From tidal pools of the guarajuba reef, Bahia, Brazil / Registro de la decoloración estacional en siderastrea spp. De pozas de marea del arrecife de guarajuba, Bahía, Brasil

O fenômeno do branqueamento em corais é caracterizado pela despigmentação da colônia em conseqüência da desestabilização da relação simbiótica entre o coral e as zooxantelas, resultando em perda desses simbiontes e/ou dos seus pigmentos fotossintetizantes. O presente trabalho teve como objetivo avaliar se o branqueamento das colônias do coral Siderastrea spp., observado nas poças intermareais do topo do recife de Guarajuba, ocorreu em função das variações sazonais da temperatura, salinidade e pH. A avaliação foi efetuada mediante análise da densidade das zooxantelas em amostras do coral coletadas no período de março de 2005 a março de 2006. Dentre os parâmetros analisados, a temperatura da água das poças foi o que variou mais significativamente. A densidade das zooxantelas foi maior nas colônias coletadas no mês mais frio (junho/05). Nos meses em que a temperatura da água das poças foi mais alta as contagens celulares foram baixas, evidenciando, assim, perda de zooxantelas.

Coral bleaching is a phenomenon characterized by the lack of pigmentation in the coral tissue due to the loss of the existing relationship between corals and their symbiotic zooxanthellae, resulting in loss of zooxanthellae and/or of its photosynthetic pigments. The purpose of the present work was to evaluate if bleaching of Siderastrea spp. colonies from the tidal pools of the Guarajuba Reef top, occurred as a result of seasonal variations of sea water parameters such as temperature, salinity and pH. The evaluation was based upon measurement of the density of zooxanthellae in the coral samples, which were collected in the tidal pools during low spring tides, from March 2005 to March 2006. Amongst the analyzed parameters, sea water temperature varied more significantly. Considering the density of the symbiotic zooxanthellae, the results indicated that it was higher in the colonies collected in the coldest month (June/05) of the studied period than in the other months, when water temperature in the tidal pools was warmer, thus characterizing a seasonal influence in the bleaching of coral colonies.

El fenómeno de blanqueamiento en corales se caracteriza por la despigmentación de la colonia debido a la desestabilización de la relación simbiótica entre los corales y zooxantelas, lo cual resulta en la pérdida de simbiontes y/o de sus pigmentos fotosintetizantes. El estudio tuvo como objetivo evaluar si la pérdida de color en las colonias del coral Siderastrea spp. presentes en las pozas de marea en la parte superior del arrecife de Guarajuba, se produjo en función de los cambios estacionales de temperatura, salinidad y pH. La evaluación se realizó mediante el análisis de la densidad de zooxantelas en muestras de corales recogidas de marzo de 2005 a marzo de 2006. Entre los parámetros analizados, la temperatura del agua de mar fue el que varió más significativamente. La densidad de zooxantelas fue mayor en las colonias recogidas en el mes más frío (junio/05). En los meses en que la temperatura del agua de las piscinas de marea fue mayor se evidenció la pérdida de zooxantelas.

Distribution and abundance of carangidae (Teleostei, Perciformes) associated with oceanographic factors along the northeast brazilian exclusive economic zone

This work had as objective to study the distribution and abundance of the Carangidae larvae and to analyze the influence of the hydrological (temperature and salinity) and biological factors (phytoplanktonic biomass and zooplanktonic biomass), on the space and temporal distribution of the larvae. Ichthyoplankton was collected during four expeditions from the Northeast Exclusive Economic Zone. Six species (Trachurus lathami, Decapterus punctatus, Chloroscombrus chrysurus, Selene setapinnis, Selene vomer and Elagatis bipinnulata) and Caranx- Carangoides complex were identified. D. punctatus was the species most abundant (52 percent of the total), with higher abundance during the Period 3, while the Period 2 was the period of low abundance. C. chrysurus was the second species in abundance representing 30 percent of the total of carangid. This species had higher abundance during the Period 2 and the Period 1. However, in Period 3 abundance were lesser. The third species in abundance was T. lathami that corresponded 8 percent of the total of carangid larvae. S. setapinnis, S. vomer and E. bipinnulata were the species less abundant, representing together 2 percent of the total identified larvae. The larvae of Caranx- Carangoides complex represented 9 percent of the carangid total.

Este trabalho teve como objetivo estudar a distribuição e abundância das larvas de Carangidae, foi analisada também a influência de fatores hidrológicos (temperatura e salinidade) e biológicos (biomassa fitoplanctônica e biomassa zooplanctônica), sobre a distribuição espacial e temporal dessas larvas. O ictioplâncton foi coletado durante quatro expedições: Período 1 (Agosto Outubro 1995), Período 2 (Janeiro Abril 1997), Período 3 (Abril Julho 1998) e Período 4 (Setembro Dezembro 2000)), realizadas na Zona Econômica Exclusiva do nordeste. Em um total de 313 larvas foram identificadas 6 espécies (Trachurus lathami, Decapterus punctatus, Chloroscombrus chrysurus, Selene setapinnis, Selene vomer e Elagatis bipinnulata) e o Complexo Caranx Carangoides pertencentes à família Carangidae. D. punctatus foi a espécie mais abundante neste estudo (52 por cento do total). Sua maior abundância foi observada no Período 3 e a menor no Período 2. C. chrysurus foi a segunda espécie em abundância representando 30 por cento do total de carangídeos. Esta espécie teve maior abundância durante o Período 2, enquanto que os Períodos 1 e 3 foram ás épocas de menor abundância. A terceira espécie em abundância foi T. lathami que correspondeu 8 por cento do total de larvas de carangídeos, sendo o Período 4 o mais abundante. S. setapinnis, S. vomer e E. bipinnulata foram bem menos abundantes que as outras espécies analisadas, representando juntas 2 por cento do total de larvas identificadas. Larvas do Complexo Caranx - Carangoides representaram 9 por cento do total de carangídeos.

Interannual variation of larval fish assemblages in the Gulf of Cádiz ( SW Iberian Peninsula ) in relation to summer oceanographic conditions

Duas amostragens de ictioplâncton foram realizadas durante Julho de 1994 e Julho de 1995, no Golfo de Cádiz, com o objetivo de descrever a composição, abundância, padrões de distribuição e variações interanuais das associações de larvas de peixes. Diferenças interanuais foram encontradas neste estudo. Em 1994 salinidades mais elevadas foram observadas nas estações da plataforma externa, enquanto que, em 1995 os valores mais elevados foram encontrados nas estações da plataforma interna. A coluna de água foi mais quente em 1994 e apresentou menor densidade de larvas de peixes. Durante 1994 Sardinella aurita e Engraulis encrasicolus foram abundantes, porém com localização espacial oposta. Em 1995, a abundância de ambas as espécies foi muito diferente, mas com padrão espacial semelhante. A análise de cluster revelou grupos bem definidos de estações e associações de larvas, primariamente relacionadas com a batimetria. A "associação costeira" ocupou as zonas menos profundas; suas espécies características, vinculadas a sistemas estuarinos, compreenderam principalmente Engraulis encrassicolus e Gobiidae. A "associação de plataforma" esteve formada por larvas cujos adultos habitam a plataforma continental e desovam nesta mesma zona, tais como: Sardinella aurita e Trachurus spp. Variações interanuais na composição e extensão dos subgrupos podem ser atribuídas aos principais padrões de circulação, vazão de águas continentais e as estratégias de desova dos peixes.