Eutrophication and gastrotrich diversity in the Northern Adriatic Sea

Marine Gastrotricha of littoral and sublittoral sands at nine locations along the northern Adriatic coast were sampled during July, 1991. Three locations on barrier islands near the Laguna Veneta (Alberoni, San Nicolò, and Punta Sabbioni) supported a higher number of species in the littoral and shallow sublittoral zones (six each) than were reported by Hummon et al. (1990), who found no species at the saure sites in 1989. The increased number of species may be related to colder temperatures during the winter previous to our study, which delayed formation of alga] mais in the littoral zone, preventing the depletion of oxygen in the littoral sediments that can lead to gastrotrich mortality. Locations in the northeastern Adriatic, Bibione (13 species) and Foce Isonzo (15 species), evidenced a more diverse gastrotrich fauna than the more northwestern locations, and may serve as a source for colonizing species, moved with longshore currents, to westward populations subject to extinction due to loca( anoxic events.