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Tidal influence on zonation and occurrence of resident and temporary zooplankton in a shallow system (Estuary of Mundaka, Bay of Biscay)
F. Villate

Tide-induced variability in the zooplankton community was analysed during 2 tidal series of 14 h during spring tides and neap tides in the shallow estuary of Mundaka by relating short-term changes in composition and spatial distribution of populations to tide-associated parameters (water level, current velocity and direction, mixing and stratification, and salinity). A strong tidal influence was found in the zooplankton composition and distribution on a day-week time scale (spring-neap tidal cycles) and at hour time scale (high-low tidal cycle). During spring tides, suspended meiofauna shows high densities at flood and ebb tides; the neritic zooplankton can reach the inner estuary at high water, and the autochthonous zooplankton move from the inner zone, at high water, to the outer zone, at low water, over distances of more than one third of the estuary length. During neap tides, autochthonous populations remain around the low middle estuary, the penetration of neritic zooplankton is feeble, and the occurrence of benthic forms in the water column is negligible. The observed effects on the abundance and zonation of resident and temporary zooplankton indicate that tides are a key factor in the estuary of Mundaka by regulating the stock of neritic and autochthonous zooplankton within the estuary, the reproductive success of benthic populations which have planktonic larval development, and meiofauna dispersion and availability as food in the water column.

Contents of this volume Sci. Mar. 61(2) : 173-188 Back PDF
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