Variations of mesozooplankton composition in an eutrophicated semi-enclosed system (Encerrada Bay, Tierra del Fuego, Argentina).

BIANCALANA F.; TORRES A. I.

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Lugar: San Pablo.; Año: 2011 vol. 59 p. 195 - 199

1679-8759

Encerrada Bay (EB) is located off the coast of Ushuaia city, Argentina (54º49S ­ 68º19W) and receives the discharge of three sewage effluents (Onas, Guaraní and Beban) and Buena Esperanza stream (BES) (Fig. 1). The latter transports thaw water from Martial glacier, which is enriched with wastewater from Ushuaia city. Buena Esperanza stream has a flow range between 0.3 and 3.0 m3seg-1 depending on rain and thaw periods and the flow of the other effluents does not reach 0.01 m3 seg-1 (Torres et al., 2009). Encerrada Bay covers a total area of ~0.3 km2 and has a medium depth of 0.8 m. It is communicated with Ushuaia Bay (UB) through two 4.5 m long pathway vents (P1 and P2). Water exchange between EB and UB occurs through these vents at a rate of ~1 m3 seg-1 during semidiurnal tidal cycles. Water with low nutrient concentration enters EB during flood tide and water with high nutrient concentration flows out of UB during ebb tide (Torres et al., 2009). The aim of the present study was to analyze EB mesozooplankton composition taking into account the physicochemical parameters of the water column. Particular attention was paid to the presence of opportunistic species which favourably adapt to EB environmental conditions.