Tidal effects on shortterm mesozooplankton distribution in small channels of a temperateturbid estuary, South West Atlantic

CHAZARRETA, C.J.; HOFFMEYER M.S.; CUADRADO D.G; BERASATEGUI A. A.

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Lugar: São Paulo; Año: 2015 vol. 63 p. 83 - 92

1679-8759

The shortterm variability of mesozooplankton distribution in terms of geomorphology, dynamics and anthropogenic influence was examined in two differents channels of the Bahia Blanca Estuary (BBE) along two tidal cycles. All the physicochemical measurements and mesozooplankton sampling were performed at a fixed site during approximately 22-23h at 3h 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, Echinodermata and Chordata) 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 was found in the two selected channels. Vertical mesozooplankton distribution was also found to vary along the tidal cycle in both channels in accordance with the channel´s geomorphology and dynamic characteristics. The variation of the abundace 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.