Long-term changes of basic biological and chemical parameters at two stations in the middle Adriatic

Since the early 1960s regular monthly observations of basic hydrographic, chemical and biological parameters have been carried out at two stations in the middle Adriatic which are influenced to a varying degree by the coastal and open Adriatic waters. Based on the analysis of the relationship between diatom/dinoflagellate and primary production, it was established that the proportion of dinoflagellates in the phytoplankton community increased with an increase in primary production. All these changes were accompanied by a steady increase in percent oxygen saturation in the surface layers and a decrease in the bottom layers. The increase in primary production and changes in percent oxygen saturation in the open Adriatic occurred ten years after those in Kaštela Bay. Even though all the relevant data indicate that the changes in Kaštela Bay are closely related to an increase of anthropogenic nutrient loading, similar changes in the open sea suggest that primary production increase in the Bay might, at least partly, be due to global climatic changes.