Varying Patterns of water circulation in Canal de Cotegipe, Baía de Todos os Santos

Abstract

ABSTRACT. The Canal de Cotegipe is a 30 m deep, 4 km long tidal channel in northeastern Brazil connecting the small Baía de Aratu (24.5 km 2 ) to the much larger Baía de Todos os Santos (1223 km 2 ). Several industrial and port facilities surround the channel and Baía de Aratu, and polluted riverine discharge as well as a direct release of toxic residuals by harbor operations makes the area one of the four polluted hot-spots within Baía de Todos os Santos. An analysis of current measurements, tidal elevation records and water quality monitoring has allowed for a preliminary understanding of the driving forces that affect the channel. Tidal flows are modulated by the extent of intertidal inundation in the channel and the bay, with stronger ebb-dominant flow conditions associated with neap tides at the seaward end of the channel and with spring tides at the landward end of the channel. Subtidal flows are mainly driven by density gradients normally oriented towards Baía de Todos os Santos, leading to a vertically stratified, estuarine like flow. This structure is strengthen in the wet season and weakened in the dry season when unstratified or even and inverse estuarine stratification may develop as a result of higher evaporation rates.

Chronology of anthropogenic impacts reconstructed from sediment records of trace metals and Pb isotopes in Todos os Santos Bay (NE Brazil)

“…On the contrary, the northern region of the Bay is covered by a regressive mud facies that is composed of a mixture of fine-grained siliciclastic rocks from the Recôncavo Sedimentary Basin that surrounds BTS, and autochthonous biogenic materials (Lessa et al, 2000). Fine sediments entering the Bay in suspension are likely to be trapped by the gravitational circulation, which drives a mean flow of bottom water into the bay (Cirano and Lessa, 2007;Pereira and Lessa, 2009). The spatial distribution of the sedimentation rates suggested a highly skewed distribution of these processes towards the CI2 area, where sediments are accumulating up to almost 7 times faster than in other areas.…”

Comunidade Zooplanctônica Da Plataforma Continental De Salvador, Bahia

“…Além disso, a área estudada está sob influência da Corrente do Brasil, sendo esta responsável por transportar Água Tropical (AT) com salinidade entre 36-38 e temperatura entre 24-26ºC (Garfield, 1990). O clima da região é classificado como tropical e úmido e, além disso, comumente é registrado um período chuvoso entre março e julho sendo este, responsável por 60% da precipitação anual e um período seco entre agosto e fevereiro (Pereira & Lessa, 2009).…”

Influence of oceanographic seasonality and dredging activities on the fish larvae assemblage in the Port of Aratu, Todos os Santos Bay

“…This region is influenced by a tropical climate with well-defined dry (August to February) and wet (March to July) seasons, when it rains approximately 60% of the total annual precipitation (Pereira & Lessa, 2009).…”

“…1). Aratu Bay is shallow, with an average depth of 1.8 m and a maximum width and length of 214 m and 4.1 km, respectively (Pereira & Lessa, 2009). The fluvial discharge from a small catchment area reaches the bay via two perennial rivers, Santa Maria and Cotegipe Rivers, which together have an estimated average annual discharge of 1.65 m 3 s -1 (CRA, 2000).…”

“…Despite all the sampling campaigns were carried out during the considered dry period (Pereira & Lessa, 2009), the rain cycle differed from the expected during the study and the campaigns of dredging and post-dredging were performed in periods with high rainfall (INMET, 2012).…”