Physical control of the eutrophic response in the northern Adriatic Sea, illustrated by a nitrogen budget from ELNA data. Eutrophic Limits of the Northern Adriatic.
The northern Adriatic Sea would normally classify as an oligotrophic sea except for the eutrophic effect caused by its large runoff of nutrients. The coastal transports and the fresh-water distributions of the 1994 ELNA data suggests that, in the mean, a high percentage (approximately 84%) of the fresh water remains trapped in the nearshore and is exported from the northern Adriatic. The distributions of fresh water and primary production are well correlated: high values of fresh water and primary production (approximately 178 gC/m2/yr) in the nearshore, "dystrophic zone"; less fresh water and deeper production of approximately 85 gC/m2/yr in the interior, "eutrophic zone" compared to the background level of production of approximately 56 gC/m2/yr in the "oligotrophic zone". An inorganic nitrogen budget, revealed that only about 16% of the total nutrient input is directly exported; that 67% is utilized in the dystrophic zone; and that the production in the eutrophic zone was supported mostly by nutrients recycled from the organic matter produced in the dystrophic zone but subsequently sedimented out to the deeper interior. Thus, biological transport dominated over physical mixing as the more important mechanism of transferring nutrients to the interior.
Hopkins
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TS
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, USA.
D005068:Eutrophication; D005618:Fresh Water / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D009792:Oceans and Seas; D012623:Seawater / Q000032:analysis*
D009584:Nitrogen