MUCILAGINOUS MASSES IN THE ADRIATIC SEA IN THE SUMMER OF 1989

This paper reports on one of the most recent episodes of mucilage form ation in the central northern part of the Adriatic coast in July-Augus t 1989. The stretch of coast examined goes from the estuary of the Riv er Po to the border of the Marche-Abruzzo coast (Italy). The possible events (nutrients, N/P ratio, particular climatic conditions) that cau se the formation of the mucilage masses were examined and are discusse d here. Furthermore, the oxygenation state of the water on the surface and on the bottom as well as the possible effects on molluscs were al so examined. The field results indicated that no anoxia phenomena were found in bottom waters caused by mucilages, and that mollusc death wa s probably due to mechanical reasons. Finally the places where the muc ilages formed and their subsequent movements are described.