Mucilages in Italian seas: the Adriatic and Tyrrhenian Seas, 1988–1991

Mucilage events, i.e. the accumulation of a gelatinous material at and below the water surface during summer months, have been known to occur at irregular intervals in the Northern Adriatic Sea for over 200 years, but events of the severity of those of 1872 and 1905 were less noted later in this century. The phenomenon reappeared in 1988 and in the years that followed. In 1991 it was also noted in the Tyrrhenian Sea. Our studies cover the events of 1988–1991 in the Northwest Adriatic and some aspects of the Tyrrhenian Sea. The results presented in this paper provide additional insight into the problem. In general, it can be stated that while we have a fair understanding of the phenomenological and dynamic aspects, and of the environmental consequences of the events, we know little about the causal factors which trigger and maintain the process.