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Brazilian Journal of Oceanography

versão impressa ISSN 1679-8759versão On-line ISSN 1982-436X

Resumo

CHAZARRETA, Javier; HOFFMEYER, Monica Susana; CUADRADO, Diana G.  e  BERASATEGUI, Anabela Anahí. Tidal effects on short-term mesozooplankton distribution in small channels of a temperate-turbid estuary, Southwestern Atlantic. Braz. j. oceanogr. [online]. 2015, vol.63, n.2, pp.83-92. ISSN 1679-8759.  http://dx.doi.org/10.1590/S1679-87592015076806302.

The short-term variability of mesozooplankton distribution and physicochemical variables was examined in two different channels of the Bahía Blanca Estuary, Argentina, during two tidal cycles. All the physicochemical measurements and mesozooplankton sampling were performed at a fixed site during approximately 22-23 h at 3-h intervals. Pumps were used to obtain surface and bottom mesozooplankton samples and the water speed of each stratum was measured with an Acoustic Doppler Current Profiler (ADCP). In all, 23 mesozooplanktonic taxa belonging to four phyla (Arthropoda, Annelida, Echinodermata and Chordata) were identified. The most abundant taxa during the two tidal cycles were Balanus glandula larvae, Eurytemora americana and Acartia tonsa. A discernible variability in the water conditions and vertical mesozooplankton distribution (VMD) different from that known for the estuary's main channel, was found in the other two selected channels. VMD varied during the tidal cycle in both channels in accordance with the channel's geomorphology and water dynamic characteristics of each of them. The variation of the abundance of the different taxa during ebb and flood currents might indicate the existence of a tidal vertical migration of the mesozooplankton as a response to particular dynamic water conditions.

Palavras-chave : Zooplankton; Estuary; Tidal Currents; Vertical Distribution; ADCP; Tidal Vertical Migration.

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