Analysis of a 24-hour cycle of zooplankton sampling in a lagoon of the Po River Delta

Short-term zooplankton samples were collected in a lagoon ofthe Po River Delta (Sacca del Canarin) over a 24-h cycle inAugust 1981. The biocoenosis was mainly represented by taxa(especially copepods) coming into the lagoon from the sea and,to a lesser extent, by autochthonous zooplankton (gastropod,cirripede and decapod larvae). Density fluctuations of sometaxa were found to be greatly influenced by hydro dynamic factors,in particular by the tidal currents. A daily balance of inputand output through one of the two mouths connecting the lagoonto the sea was calculated for different taxa; quantitative estimatesof zooplankton exchanges between lagoon and sea due to tidaltransportation were obtained.