S. Sei et al., ZOOPLANKTON VARIABILITY RELATED TO ENVIRONMENTAL-CHANGES IN A EUTROPHIC COASTAL LAGOON IN THE PO DELTA, Hydrobiologia, 329(1-3), 1996, pp. 45-55
Zooplankton variability in a lagoon of the Po Delta, the Sacca di Gore
, was studied in relation to changes in its hydrodynamic and hydrologi
cal features. From 1987 to 1992 the lagoon was affected each summer by
severe anoxia due to the decomposition of dense and widespread beds o
f Ulva rigida. In August 1992 a canal was opened through the sand bank
closing off the lagoon from the sea in order to improve the water cir
culation. This hydraulic intervention led to significant environmental
changes in the lagoon: during the two subsequent years the summer dys
trophic crises were brief and less severe, due to a sharp decrease in
the Ulva cover. At the same time a clear increase in phytoplankton bio
mass values was observed. Following the opening of the channel, the mo
st remarkable change in zooplankton was a significant density increase
of calanoids, particularly of Acartia tonsa.