Spatial and temporal variation of the zooplankton community in the area of influence of the Itajaí-açu River, SC (BRAZIL)

Abstract

On the north coast of the State of Santa Catarina (Brazil), the Itajaí-Açu River mouth shows a lowsaline water plume on the internal shelf with strong density gradients. This oceanographic condition has a possible influence over the pelagic community, and it has been little investigated on the Brazilian coast. The present work seeks to evaluate the spatial and temporal variations of the zooplankton community in the area of influence of the Itajaí-açu River, and its relations with the abiotic forces of temperature (seasonal variation) and salinity of the river plume. For this purpose, 14 monthly oceanographic cruises were carried out during the years 2002 and 2003, to obtain physical and chemical parameters, and zooplankton hauls in 9 sampling points. The zooplankton analyses were carried out at the lowest taxon possible to characterize the resident community of the river mouth. It was observed that the zooplankton presented the highest densities in winter and spring. The species with higher densities and frequencies of occurrence were Paracalanus quasimodo, Parvocalanus crassirostris, Acartia lilijeborgi, Temora stylifera, T. turbinata, and Penilia avirostris, indicating a prevalence in this region, of Tropical Water from the Brazil Current and greater similarity with the coastal community of the Southeast region of Brazil. However, even for the species typical of Tropical Water, there were alterations in dominance of the species, due to the seasonality and level of flow rate of the river on the salinity of the internal shelf of the study area. RESUMONo norte do estado de Santa Catarina (Brasil) a desembocadura do Rio Itajaí-açu apresenta uma pluma de água de baixa salinidade e com forte gradiente de densidade sobre a plataforma interna. Essa condição oceanográfica pode influenciar a comunidade pelágica costeira local e este processo tem sido pobremente investigado na costa brasileira. O presente trabalho teve como objetivo estudar as variações espaço-temporais da comunidade zooplanctônica na região da pluma do Rio Itajaí-açu e determinar a existência de alguma influência sobre esta comunidade. Para isso, 14 campanhas oceanográficas foram realizadas mensalmente entre os anos de 2002 e 2003 com a obtenção de parâmetros físico-químicos e arrastos de zooplâncton em 9 pontos amostrais. Foi observado que o zooplâncton apresentou suas maiores densidades nos meses de inverno e primavera. As espécies com maiores densidades e freqüências de ocorrência foram Paracalanus quasimodo, Parvocalanus crassirostris, Acartia lilijeborgi, Temora stylifera, T. turbinata, e Penilia avirostris, indicando domínio da Água Tropical da Corrente do Brasil na região e maior similaridade com a comunidade da costa da região sudeste do Brasil. Entretanto, mesmo para as espécies típicas da Água Tropical, houve alterações na dominância de espécies em função da sazonalidade e do grau de influência da vazão do rio sobre a salinidade na plataforma interna da área de estudo.

Spatio-temporal variability in the Cladocera assemblage of a subtropical hypersaline lagoon

“…Their incidence has been described in waters from the South China Sea to the Northeast of Honshu (Japan) and there are sporadic records for Aqaba Bay (Red Sea) and Madagascar (Indian Ocean). In Brazilian waters, some records were made by: Rocha (1985) on the coast of São Paulo; Resgalla Júnior and Montú (1993) on the southern coast; Marazzo (2002); in the Guanabara Bay, Rio de Janeiro; Resgalla Júnior et al (2008;Resgalla Júnior, 2011) on the coast of Santa Catarina and in the southern coast among…”

Genotoxicity Evaluation of Tilapia (Oreochromis niloticus) Exposed to Waters From Two Sites of Itajaí-Açu River (SC, Brazil)

“…In the Blumenau, the results showed high rates of genotoxic effects since 48 h of exposure up to the last time analyzed 240 h (10 days). This can be attributed to the large population of the Blumenau city, the activity of several industries, and therefore to its considerable proportion of contaminants discharged on the river (Resgalla-Jr et al, 2008). The results suggest that this pollution load may be diluted along the way down, since it receives the input of several minor water streams, or it may be that much of the genotoxicants sediment at the river bed, so that when the waters reach Ilhota they are already alleviated from much of the genotoxicants input of Blumenau.…”