| Abstract: | Ka
tela Bay is a semi-enclosed coastal bay in the Middle Adriatic which behaves as a dilution basin, as the result of a freshwater inflow. The area near a river mouth is heavily polluted by a number of sewage outfalls. Red tide (RT) events have been observed there regularly every summer in the last decade. During summer 1988, the concentrations of the RT organisms and bacterioplankton, and some chemical and hydrographic parameters, were monitored. The purpose of this paper is to determine, on the basis of the RT monitoring results, whether there is an interaction between concentrations of RT organisms and state variables, i.e. pH, dissolved oxygen, temperature and salinity. Additionally, the relationship between the concentration of the RT organisms and bacterioplankton is examined. Attention is also focused on the dependence of the concentration of the RT organisms on the wind field variations. The empirical orthogonal function (EOF) analysis method is applied. The results of the study suggest that quiescent periods are characterized by the highest concentration of RT organisms. On the other hand, vertical mixing induced by strong wind events is associated with a decrease of concentration of RT organisms. Variations in the oxygen concentration in the surface layer are associated with the phytoplankton density. |
