Benthic fluxes and nutrient budgets for sediments in the Northern Adriatic Sea: burial and recycling efficiencies

The distribution of sterols and organic-walled dinoflagellate cysts in surface sediments of the North-western Adriatic Sea (Italy)

“…The three sites along the Chioggia transect exhibit organic carbon content around 1% similar to the values reported for surface sediments influenced by the Po river deposits (Giordani et al, 1992;Fabbri et al, 2001), whereas lower values are observed in the Ancona transect. The C/N atomic ratios range between 8.8 and 10.0 and values slightly decrease with increasing distance from the coast for both transects.…”

“…Therefore the occurrence of heterotrophic cysts in sediments can be affected by oxygen availability in waters. In the North Adriatic Sea about a half of the productivity in surface waters reaches the sea floor (Giordani et al, 1992) and anoxic or near anoxic events frequently occur in bottom waters, especially in late summer and autumn as a consequence of high downward organic fluxes, microbial decay and thermal stratification (Justic et al, 1987;Degobbis, 1989;Zavatarelli et al, 1998). In order to avoid interpretations biased by possible different oxygen concentrations of the overlying waters and/or sediments, a group of oxygen resistant cysts (including Nematosphaeropsis labyrinthus, O. centrocarpum and Pentapharsodinium dalei, according to Versteegh and Zonneveld, 2002) is also taken into consideration for discussion.…”

Reconstructing 150 years of eutrophication in the north-western Adriatic Sea (Italy) using dinoflagellate cysts, pollen and spores

“…Water circulation is dominated by a counter-clockwise flow, induced by thermohaline factors and Coriolis acceleration, which confines the nutrient-enriched freshwaters to the western coastal regions (Franco et al, 1982;Franco and Michelato, 1992;Zavatarelli et al, 1998). Benthic flux measurements indicate that recycled nutrients from the sea bottom may be comparable to the input of nutrients from the Po River (Giordani et al, 1992). The Po River represents a primary source of nutrients to the Adriatic Sea (e.g., Bortoluzzi et al, 1984;Degobbis and Gilmartin, 1990;Provini et al, 1992).…”

“…Anthropogenic nutrient loading of rivers entering the north-western Adriatic Sea has considerably increased nutrient input to the system during the late 20th century, especially between 1968 and 1980 (Marchetti et al, 1989). A major fraction of the productivity in surface waters reaches the sea floor (Giordani et al, 1992) and anoxic or near anoxic events frequently occur in bottom waters, especially in late summer and autumn as a consequence of high downward organic fluxes, microbial decay and thermal stratification (Justic, 1987;Justic et al, 1987;Degobbis, 1989;Zavatarelli et al, 1998).…”

The dynamics of the Adriatic Sea ecosystem.

“…The shallow depth of the whole northern region also enhances the role of benthic}pelagic interactions, in particular the nutrient recycling due to mineralization of organic matter in the sediment and redistribution into the water column. This is estimated to be a signi"cant source of nutrients in the water column (Giordani et al, 1992).…”