Tidal effects on short-term mesozooplankton distribution in small channels of a temperate-turbid estuary, South West Atlantic

CHAZARRETA CARLO J.; HOFFMEYER MÓNICA S.; CUADRADO DIANA G.; BERASATEGUI ANABELA

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Lugar: São Paulo; Año: 2015 vol. 63

1679-8759

The short-term variability of mesozooplankton distribution and physicochemical variables was examined in two different channels of the Bahía Blanca Estuary (BBE) along 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 total, 23 mesozooplanktonic taxa belonging to four phyla (Arthropoda, Annelida and Echinodermata were identified. The most abundant taxa along 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 to that known for the estuary main channel, was found in the two selected channels. VMD varied along the tidal cycle in both channels in accordance with the channel?s geomorphology and water dynamic characteristics. The variation of the abundance of the different taxa during ebb and flood currents might indicate the existence of a tidal vertical migration (TVM) of the mesozooplankton as a response to particular dynamic water conditions.