Seston biomass in plankton assemblages in the Southwestern Atlantic Ocean: spatial, vertical, and temporal variations.

Bioseston is a heterogeneous assemblage of bacterioplankton, phytoplankton, zooplankton, and planktonic debris. A detailed knowledge of biosestons is essential for understanding the dynamics of trophic flows in marine ecosystems. The distributional features of seston biomass in plankton (micro- and mesoplankton) in the Southwest Atlantic Ocean (Rio de Janeiro State, Brazil) were analyzed using stratified samples gathered to a depth of 2,400 m during night time. The horizontal pattern of biomass distribution was analyzed vis-a-vis station depth during both wet and dry periods, with higher values recorded in the continental shelf than in the slope, confirming the terrestrial contribution of nutrient sources to the marine environment. This horizontal variation reinforces the occurrence of seasonal vortices in Cabo Frio and Cabo de São Tomé on the central coast of Brazil. Environmental variables reflect the hydrological signatures of the water masses along the Brazilian coast. The largest seston biomass was related to high temperatures, salinities, and low inorganic nutrient concentrations in tropical and South Atlantic central waters. The observed distribution patterns suggest that seston biomass in plankton in the region may be structured based on partitioned horizontal and vertical habitats and food resources.

Variação da composição e abundância das espécies da Classe Appendicularia e seu uso como potenciais bioindicadoras de regiões e massas de água superficiais na área da Bacia de Campos, Rio de Janeiro, Brasil / Variation of species abundance of Class Appendicularia and their use as potential bioindicators of the regions and surface water mass in the area of the Campos Basin, Rio de Janeiro, Brazil

Studies about the relationship of the species of appendicularians with spatial gradients and water masses are rare, especially in the South Atlantic. The present study aims to fill the knowledge gap about the abundance of the community of appendicularians and on their bioindicator function in different regions (continental shelf and slope), with influence of different water masses in the South Atlantic. Sampling was conducted in the rainy season (February-April 2009) and the dry season (August-September 2009) in the subsurface layer. The water masses found on the continental shelf of the study area were the Tropical Water (AT), which was prevalent during the rainy season, and the Coastal Water (AC), which was prevalent in the dry season. In both sampling periods has not registered the presence of SACW on the surface over continental shelf. The appendicularians were more abundant in the region of the continental shelf influenced by the CW. A total of 18 species of appendicularian was registered. Oikopleura longicauda Vogt, 1854 and O. fusiformis Fol, 1872 were the most abundant appendicularian. Oikopleura dioica Fol, 1872 was found exclusively in the continental shelf on the CW. In despite of the SACW water had not registered on the surface, the presence of, high values of density of appendicularians in front of Cabo Frio region suggest the influence of an upwelling event in a anterior period in the region. In relation to the appendicularians abundance, high values were also observed in front of the Paraíba do Sul river with the CW influence. This fact suggests a high nutritional contribution of this river in the coastal marine area adjacent. The spatial variation and different water masses influenced the abundance and the composition of appendicularians. Among the species identified, only O. longicauda was considered as a bioindicator of the CW.

Estudos sobre a variação espacial das espécies de apendiculárias e sua relação com as massas de água são raros, principalmente no Atlântico Sul. O atual estudo pretende preencher a lacuna de conhecimento sobre a abundância, composição específica e a função de bioindicadora das apendiculárias, em diferentes regiões (plataforma continental e talude) e massas de água, no Atlântico Sul Ocidental. As coletas foram realizadas no período chuvoso (de fevereiro a abril de 2009) e no período seco (de agosto a setembro de 2009) na camada subsuperficial. As massas de água encontradas na superfície na plataforma continental da área de estudo foram a Água Tropical (AT), que predominou no período chuvoso, e a Água Costeira (AC), que predominou no período seco. Em ambos os períodos de coleta não foram registradas a presença da Água Central do Atlântico Sul (ACAS) na superfície na plataforma continental. As apendiculárias foram mais abundantes na região de plataforma continental influenciada pela AC. Foi identificado um total de 12 espécies da Classe Appendicularia. Oikopleura longicauda Vogt, 1854 e O. fusiformis Fol, 1872 foram as espécies mais abundantes. Oikopleura dioica Fol, 1872 foi encontrada exclusivamente na plataforma continental na AC. Apesar não ser observado a presença de ACAS na superfície, altos valores da densidade de apendiculária em frente a Cabo Frio sugerem a influência de uma pós-ressurgência no local. Também foram observados valores elevados na abundância das apendiculárias em frente ao rio Paraíba do Sul, com influência da AC. Este fato sugere a alta capacidade de incremento de nutrientes desse aporte fluvial. A variação espacial e as diferentes massas de água influenciaram a abundância e a composição das apendiculárias. Dentre as espécies identificadas, somente O. longicauda foi considerada como bioindicadora da AC.

Variação da composição e abundância das espécies da Classe Appendicularia e seu uso como potenciais bioindicadoras de regiões e massas de água superficiais na área da Bacia de Campos, Rio de Janeiro, Brasil

ABSTRACT Studies about the relationship of the species of appendicularians with spatial gradients and water masses are rare, especially in the South Atlantic. The present study aims to fill the knowledge gap about the abundance of the community of appendicularians and on their bioindicator function in different regions (continental shelf and slope), with influence of different water masses in the South Atlantic. Sampling was conducted in the rainy season (February-April 2009) and the dry season (August-September 2009) in the subsurface layer. The water masses found on the continental shelf of the study area were the Tropical Water (AT), which was prevalent during the rainy season, and the Coastal Water (AC), which was prevalent in the dry season. In both sampling periods has not registered the presence of SACW on the surface over continental shelf. The appendicularians were more abundant in the region of the continental shelf influenced by the CW. A total of 18 species of appendicularian was registered. Oikopleura longicauda Vogt, 1854 and O. fusiformis Fol, 1872 were the most abundant appendicularian. Oikopleura dioica Fol, 1872 was found exclusively in the continental shelf on the CW. In despite of the SACW water had not registered on the surface, the presence of, high values of density of appendicularians in front of Cabo Frio region suggest the influence of an upwelling event in a anterior period in the region. In relation to the appendicularians abundance, high values were also observed in front of the Paraíba do Sul river with the CW influence. This fact suggests a high nutritional contribution of this river in the coastal marine area adjacent. The spatial variation and different water masses influenced the abundance and the composition of appendicularians. Among the species identified, only O. longicauda was considered as a bioindicator of the CW.

RESUMO Estudos sobre a variação espacial das espécies de apendiculárias e sua relação com as massas de água são raros, principalmente no Atlântico Sul. O atual estudo pretende preencher a lacuna de conhecimento sobre a abundância, composição específica e a função de bioindicadora das apendiculárias, em diferentes regiões (plataforma continental e talude) e massas de água, no Atlântico Sul Ocidental. As coletas foram realizadas no período chuvoso (de fevereiro a abril de 2009) e no período seco (de agosto a setembro de 2009) na camada subsuperficial. As massas de água encontradas na superfície na plataforma continental da área de estudo foram a Água Tropical (AT), que predominou no período chuvoso, e a Água Costeira (AC), que predominou no período seco. Em ambos os períodos de coleta não foram registradas a presença da Água Central do Atlântico Sul (ACAS) na superfície na plataforma continental. As apendiculárias foram mais abundantes na região de plataforma continental influenciada pela AC. Foi identificado um total de 12 espécies da Classe Appendicularia. Oikopleura longicauda Vogt, 1854 e O. fusiformis Fol, 1872 foram as espécies mais abundantes. Oikopleura dioica Fol, 1872 foi encontrada exclusivamente na plataforma continental na AC. Apesar não ser observado a presença de ACAS na superfície, altos valores da densidade de apendiculária em frente a Cabo Frio sugerem a influência de uma pós-ressurgência no local. Também foram observados valores elevados na abundância das apendiculárias em frente ao rio Paraíba do Sul, com influência da AC. Este fato sugere a alta capacidade de incremento de nutrientes desse aporte fluvial. A variação espacial e as diferentes massas de água influenciaram a abundância e a composição das apendiculárias. Dentre as espécies identificadas, somente O. longicauda foi considerada como bioindicadora da AC.

Variação da composição e abundância das espécies da Classe Appendicularia e seu uso como potenciais bioindicadoras de regiões e massas de água superficiais na área da Bacia de Campos, Rio de Janeiro, Brasil / Variation of species abundance of Class Appendicularia and their use as potential bioindicators of the regions and surface water mass in the area of the Campos Basin, Rio de Janeiro, Brazil

Studies about the relationship of the species of appendicularians with spatial gradients and water masses are rare, especially in the South Atlantic. The present study aims to fill the knowledge gap about the abundance of the community of appendicularians and on their bioindicator function in different regions (continental shelf and slope), with influence of different water masses in the South Atlantic. Sampling was conducted in the rainy season (February-April 2009) and the dry season (August-September 2009) in the subsurface layer. The water masses found on the continental shelf of the study area were the Tropical Water (AT), which was prevalent during the rainy season, and the Coastal Water (AC), which was prevalent in the dry season. In both sampling periods has not registered the presence of SACW on the surface over continental shelf. The appendicularians were more abundant in the region of the continental shelf influenced by the CW. A total of 18 species of appendicularian was registered. Oikopleura longicauda Vogt, 1854 and O. fusiformis Fol, 1872 were the most abundant appendicularian. Oikopleura dioica Fol, 1872 was found exclusively in the continental shelf on the CW. In despite of the SACW water had not registered on the surface, the presence of, high values of density of appendicularians in front of Cabo Frio region suggest the influence of an upwelling event in a anterior period in the region. In relation to the appendicularians abundance, high values were also observed in front of the Paraíba do Sul river with the CW influence. This fact suggests a high nutritional contribution of this river in the coastal marine area adjacent. The spatial variation and different water masses influenced the abundance and the composition of appendicularians. Among the species identified, only O. longicauda was considered as a bioindicator of the CW.(AU)

Estudos sobre a variação espacial das espécies de apendiculárias e sua relação com as massas de água são raros, principalmente no Atlântico Sul. O atual estudo pretende preencher a lacuna de conhecimento sobre a abundância, composição específica e a função de bioindicadora das apendiculárias, em diferentes regiões (plataforma continental e talude) e massas de água, no Atlântico Sul Ocidental. As coletas foram realizadas no período chuvoso (de fevereiro a abril de 2009) e no período seco (de agosto a setembro de 2009) na camada subsuperficial. As massas de água encontradas na superfície na plataforma continental da área de estudo foram a Água Tropical (AT), que predominou no período chuvoso, e a Água Costeira (AC), que predominou no período seco. Em ambos os períodos de coleta não foram registradas a presença da Água Central do Atlântico Sul (ACAS) na superfície na plataforma continental. As apendiculárias foram mais abundantes na região de plataforma continental influenciada pela AC. Foi identificado um total de 12 espécies da Classe Appendicularia. Oikopleura longicauda Vogt, 1854 e O. fusiformis Fol, 1872 foram as espécies mais abundantes. Oikopleura dioica Fol, 1872 foi encontrada exclusivamente na plataforma continental na AC. Apesar não ser observado a presença de ACAS na superfície, altos valores da densidade de apendiculária em frente a Cabo Frio sugerem a influência de uma pós-ressurgência no local. Também foram observados valores elevados na abundância das apendiculárias em frente ao rio Paraíba do Sul, com influência da AC. Este fato sugere a alta capacidade de incremento de nutrientes desse aporte fluvial. A variação espacial e as diferentes massas de água influenciaram a abundância e a composição das apendiculárias. Dentre as espécies identificadas, somente O. longicauda foi considerada como bioindicadora da AC.(AU)

Horizontal and vertical distribution of mesozooplankton species richness and composition down to 2, 300 m in the southwest Atlantic Ocean

We describe the species richness, distribution and composition of mesozooplankton over the continental shelf and slope, and in the water masses in the Campos Basin, southwest Atlantic Ocean. We analyzed the mesozooplankton from two oceanographic cruises (rainy and dry seasons, 2009) with samples taken in five different water masses from the surface to 2,300 m depth. In the Subsurface Water (SS), in both sampling periods, more species were recorded over the slope (rainy: 100; dry: 128) than the continental shelf (rainy: 97; dry: 104). Over the slope, species richness decreased with increasing depth: the highest values were observed in the South Atlantic Central Water (SACW), and the lowest values in the North Atlantic Deep Water (NADW), in both sampling periods. We recorded 262 species in 10 groups (Hydrozoa, Siphonophora, Ctenophora, Branchiopoda, Copepoda, Euphausiacea, Decapoda, Chaetognatha, Appendicularia e Thaliacea), with 13 new occurrences for the southwest Atlantic. Copepoda was the group with the highest species richness, containing 138 species. In both periods, the samples from SS, SACW and Antarctic Intermediate Water (AAIW)/Upper Circumpolar Deep Water (UCDW) were clustered in different faunistic zones, based on species composition. This study confirmed that zooplankton richness in the southwest Atlantic Ocean is underestimated, and suggests that additional efforts must be directed toward a better understanding of this fairly unknown region.

Horizontal and vertical distribution of mesozooplankton species richness and composition down to 2, 300 m in the southwest Atlantic Ocean

We describe the species richness, distribution and composition of mesozooplankton over the continental shelf and slope, and in the water masses in the Campos Basin, southwest Atlantic Ocean. We analyzed the mesozooplankton from two oceanographic cruises (rainy and dry seasons, 2009) with samples taken in five different water masses from the surface to 2,300 m depth. In the Subsurface Water (SS), in both sampling periods, more species were recorded over the slope (rainy: 100; dry: 128) than the continental shelf (rainy: 97; dry: 104). Over the slope, species richness decreased with increasing depth: the highest values were observed in the South Atlantic Central Water (SACW), and the lowest values in the North Atlantic Deep Water (NADW), in both sampling periods. We recorded 262 species in 10 groups (Hydrozoa, Siphonophora, Ctenophora, Branchiopoda, Copepoda, Euphausiacea, Decapoda, Chaetognatha, Appendicularia e Thaliacea), with 13 new occurrences for the southwest Atlantic. Copepoda was the group with the highest species richness, containing 138 species. In both periods, the samples from SS, SACW and Antarctic Intermediate Water (AAIW)/Upper Circumpolar Deep Water (UCDW) were clustered in different faunistic zones, based on species composition. This study confirmed that zooplankton richness in the southwest Atlantic Ocean is underestimated, and suggests that additional efforts must be directed toward a better understanding of this fairly unknown region.(AU)