Odense Pilot River Basin: implementation of the EU Water Framework Directive in a shallow eutrophic estuary (Odense Fjord, Denmark) and its upstream catchment

Abstract

Implementation of the EU Water Framework Directive (WFD) is a huge environmental management challenge for Europe, demanding an integrated sustainable approach to water management and a common objective of obtaining 'good status' for all water bodies before 2015. The main task is the preparation of a river basin management plan for each of the 96 European river basin districts before the end of 2009. In Odense River Basin (island of Fyn, Denmark), one of 14 appointed European Pilot River Basins, the implementation of the WFD has been developed and tested in practice. Reference conditions and ecological status classification for Odense Fjord, based on eelgrass (Zostera marina) depth limit and nutrient concentrations, have been drawn up through a combination of historical data and modelling tools. A subsequent quantitative linking of pressures and impact, in casu between land-based nitrogen (N) loading of the fjord and resulting nutrient concentrations and eelgrass appearance, provided an estimate of the needed nitrogen load reduction of the fjord. This amounted to approx. 1,200 tonnes N per year (an annual load reduction of ca. 11 kg N ha -1 of catchment area or ca. 19.5 g N m -2 of fjord surface)-a load reduction of ca. 60% from the present level-to obtain at least 'good' ecological status sensu WFD. It is presently not possible to quantify a target load for phosphorus (P) in relation to marine environmental objectives. An economically feasible programme of measures to obtain 'good' status in all surface water and groundwater bodies in Odense River Basin, using an integrated cost-effectiveness analysis, showed that re-establishment of wetlands, catchcrops, and reduced fertilisation norms are the most effective measures if large reductions in N loads to the aquatic environment are to be achieved. The total socioeconomic cost of implementing the WFD in the river basin amounts to about 13 million €/year, which will Electronic supplementary material The online version of this article (

Influence of benthic macrofauna community shifts on ecosystem functioning in shallow estuaries

“…Odense Fjord has a large catchment area (1046 km 2 ), resulting in substantial nutrient loading primarily due to agricultural runoff. The loading was ∼3000 t N year −1 and ∼300 t P year −1 prior to 1990, but after the implementation of several water action plans during the last 20 years nutrient loading has gradually been reduced to the present levels of <2000 t N year −1 and ∼50 t P year −1 (Petersen et al, 2009). As a consequence, the nutrient concentrations in the fjord diminished, now typically rendering dissolved inorganic phosphorus (DIP = PO 3− 4 ) and dissolved inorganic nitrogen (DIN = NH + 4 and NO − 3 ) limiting factors for (1985-1992); 7 (1993-1997); 12 (1998-2001); 26 (2002-2006); 10 (2007-2009)] (data kindly provided by The Danish Nature Agency).…”

Coastal eutrophication research: a new awareness

“…We now have a better appreciation of the scale of problem (e.g., Nixon, 2009), a better understanding of its processes and dynamics (e.g., Cloern, 2001;Boesch, 2002;Howarth & Marino, 2006;Conley et al, 2009;Duarte et al, 2009;Soetaert & Middelburg, 2009), improved diagnostic tools and indicators (e.g., Eyre & Ferguson, 2009;Jaanus et al, 2009), and have taken action to mitigate it (e.g., Nørring & Jørgensen, 2009, Petersen et al, 2009Savchuk & Wulff, 2009), as clearly exemplified by the papers compiled in this issue. Collectively, these papers portray a major development of the field over the past decade.…”

Short-term fate of seagrass and macroalgal detritus in Arenicola marina bioturbated sediments

“…Eelgrass Zostera marina (hereafter referred to as 'Zostera'), was collected at Enebaerodde in the outer part of Odense Fjord, Denmark (Petersen et al 2009). Green Zostera leaves were gathered from an eelgrass bed at approximately 1 m water depth and kept in seawater during transport back to the laboratory.…”

“…The well-studied estuary, Odense Fjord (Denmark), can provide evidence of the short-term impact of Arenicola bioturbation when extrapolated to the ecosystem scale (Petersen et al 2009). The average Zostera biomass in the 62 km 2 fjord estimated based on 3% coverage is about 400 kg C yr −1 (Fyns Amt 2001, Carstensen et al 2016.…”