ROLE OF MICROORGANISMS AND MACROFAUNA IN BENTHIC PHOSPHORUS DYNAMICS IN THE PO RIVER-ADRIATIC SEA FRONTAL SYSTEM: AN EXPERIMENTAL APPROACH

Sediment biotic and abiotic attributes were determined during the PRISMA II oceanographic campaigns in the northern and central Adriatic Sea. The radiotracer orthophosphate P-32 was used under laboratory conditions to analyse the role of micro- and macrofauna in phosphorus dynamics at the water-sediment interface. Effects of infaunal suspensivores on microfungal growth were also investigated. Our findings emphasised: 1) significant differences in sediment P-32 uptake as related to the sampling area, occurrence of the pelagic frontal system, sediment grain size, microbial activity, and anoxia; 2) the crucial role played in P-32 dynamics by different tropho-functional groups-i.e., infaunal filter-feeders and epifaunal detritivore characterising the benthic community of the northern Adriatic basin. The significant changes in ergosterol concentration (adopted as an index of microfungal growth) observed in sediments subjected to infaunal activity, eventually provided a comprehensive insight into macrofauna-microorganism interactions. The potential impact of macrofaunal activity in phosphorus dynamics in the Adriatic benthic system is discussed.