Secondary production of Acartia tonsa Dana, 1849 and A. lilljeborgii Giesbrecht, 1889 in an Amazonian estuary (Brazil).

The dynamics of the copepods A. tonsa and A. lilljeborgii were described for the first time in the Taperaçu Estuary. The acartiids were collected using plankton nets (200 µm) in June 2012, March 2013 (rainy season) and September 2012 and 2013 (dry season). The oscillations in rainfall and the fluctuations in hydrological variables influenced the abundance, biomass, and production of both A. tonsa (17 ± 23 to 8501 ± 13,248 ind.m-3; 16,385.29 mg.C.m-3; 0.09 ± 0.21 to 355.17 ± 590.84 mg.C.m-3.d-1) and A. lilljeborgii (14 ± 11 to 1470 ± 1591 ind.m-3; 22,398.40 mg.C.m-3; 177.99 ± 263.13 mg.C.m-3.d-1) with clear monthly, seasonal, and spatial patterns. The high levels of production observed may be related to the presence of waters rich in particulate organic material derived from the adjacent mangrove forests. This material is consumed by a number of copepod species, in particular A. tonsa and A. lilljeborgii, favoring the development and reproduction of both species which are characterized by high rates of productivity in the study estuary. The present results indicate that the biomass and productivity in equatorial mangrove estuaries may be relatively high in comparison with the levels observed in other coastal systems around the world and that earlier stages of both species have a great relevance for biomass and production in Amazonian estuaries.

Seasonal variation in the copepod community structure from a tropical Amazon estuary, Northern Brazil.

The main purpose of this study was to investigate the seasonal variation of copepod community structure during the months of July, September and November 2003 (dry season) and January, March and May 2004 (rainy season) in the Curuçá estuary, northern Brazil. Samples were collected during neap tides via gentle 200microm mesh net tows from a small powerboat. Measurements of surface water conductivity were accomplished in situ using an electronic conductivimeter and salinity was later obtained through the transformation of the conductivity values. Salinity varied seasonally from 7.2 +/- 0.1 to 39.2 +/- 1.8 (mean +/- standard deviation) and was influenced mainly by differences in the amount of rainfall between the studied sampling seasons. In total, 30 Copepoda taxa were identified and Acartia tonsa comprised the most representative species throughout the entire studied period followed by Acartia lilljeborgii, Subeucalanus pileatus and Paracalanus quasimodo. In the present study, the density values, ecological indexes and copepod species dominance presented a clear seasonal pattern, showing that the studied area may be considered seasonally heterogeneous in relation to the investigated parameters.

Seasonal variation in the copepod community structure from a tropical Amazon estuary, Northern Brazil

The main purpose of this study was to investigate the seasonal variation of copepod community structure during the months of July, September and November 2003 (dry season) and January, March and May 2004 (rainy season) in the Curuçá estuary, northern Brazil. Samples were collected during neap tides via gentle 200µm mesh net tows from a small powerboat. Measurements of surface water conductivity were accomplished in situ using an electronic conductivimeter and salinity was later obtained through the transformation of the conductivity values. Salinity varied seasonally from 7.2 ± 0.1 to 39.2 ± 1.8 (mean ± standard deviation) and was influenced mainly by differences in the amount of rainfall between the studied sampling seasons. In total, 30 Copepoda taxa were identified and Acartia tonsa comprised the most representative species throughout the entire studied period followed by Acartia lilljeborgii, Subeucalanus pileatus and Paracalanus quasimodo. In the present study, the density values, ecological indexes and copepod species dominance presented a clear seasonal pattern, showing that the studied area may be considered seasonally heterogeneous in relation to the investigated parameters.

O presente estudo teve como objetivo principal avaliar a variação sazonal na estrutura da comunidade dos copépodos durante os meses de julho, setembro e novembro de 2003 (período seco) e janeiro, março e maio de 2004 (período chuvoso) no estuário do Curuçá, Norte do Brasil. As amostras foram coletadas nas marés de quadratura com auxílio de uma rede deplâncton com 200µm de abertura de malha, rebocada por meio de uma pequena embarcação a motor. As medidas de condutividade da água foram realizadas in situ utilizando-se um condutivímetro eletrônico e a salinidade foi posteriormente obtida através da transformação dos valores de condutividade. Os valores de salinidade variaram sazonalmente de 7, 2 ± 0, 1a 39, 2 ± 1, 8 (média ± desvio padrão), tendo sido principalmente influenciados pelas diferenças nas taxas de precipitação entre os períodos de amostragem estudados. Foram identificados no total 30 táxons, com Acartia tonsa constituindo a espécie mais representativa durante todo o período de estudo,seguida por Acartia lilljeborgii, Subeucalanus pileatus e Paracalanus quasimodo. Durante este trabalho, os valores de densidade, índices ecológicos e dominância das espécies de copépodos apresentaram um padrão sazonal claro, mostrando que a área estudada pode ser considerada sazonalmente heterogênea em relação a estes parâmetros investigados.