title: Responses of biological and chemical components in North East Atlantic coastal water to experimental nitrogen and phosphorus addition--a full scale ecosystem study and its relevance for management.
abstract: The objective of this study was to quantify chemical and biological responses to an experimentally increased nutrient input to an open coastal planktonic ecosystem and to contribute to a scientific concept and credible indicators for managing nutrient supply to coastal waters. Data were derived in a 5 year fertilisation experiment of a tidal driven coastal lagoon at the outer coast off Central Norway (63°36' N, 9°33' E), with a surface area of 275.000 m(2), volume of 5.5 mill m(3), mean depth of 22 m and a water exchange rate of 0.19 day(-1). The lagoon was fertilised in the summer season 1998 and 1999, while summer seasons 1996-97 and 2000 and inflowing water were used as unfertilised references. Most measured chemical and biological variables showed linear responses with an increasing loading rate of inorganic N and P (LN and LP, respectively). PON, POP and POC (< 200 μm) responded significantly (P<0.05) as did chlorophyll a and phytoplankton C. DIN and DIP remained, however, constant and independent of LN and LP, respectively (P>0.05) as did heterotrophic biomass (P>0.05). We evaluate the response variables assuming a stepwise incorporation process of nutrients in the planktonic ecosystem and how that will interact with biological response times and water dilution rates. We suggest that PON is a credible indicator of both chemical and ecological states of the planktonic ecosystem and that natural background and upper critical concentrations are 46 and 88 mg PON m(-3), respectively. The study was supported by data from mesocosms. We discuss the scientific relevance of our suggestions, how results can be extrapolated to a broader geographical scale, and we propose a science-based concept for the management of nutrient emission to open coastal waters.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Electronic address: yngvar.olsen@ntnu.no.
authors.forename: Yngvar
authors.initials: Y
authors.lastname: Olsen
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
authors.forename: Helge
authors.initials: H
authors.lastname: Reinertsen
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, D-24148 Kiel, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sommer
authors.affiliation: Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
authors.forename: Olav
authors.initials: O
authors.lastname: Vadstein
mesh_terms: D002734:Chlorophyll; D000077194:Chlorophyll A; D017753:Ecosystem; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis*; D009664:Norway; D010758:Phosphorus / Q000032:analysis*; D010839:Phytoplankton; D012621:Seasons; D012623:Seawater; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D010758:Phosphorus; D009584:Nitrogen; D000077194:Chlorophyll A
keywords: Biological and chemical responses; Experimental eutrophication; Indicators; Management concept; North East Atlantic; PON and POP