Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea

Abstract

In this paper the results from a workshop of the OSPAR Intersessional Correspondence Group on Eutrophication Modelling (ICG-EMO) held in Lowestoft in 2007 are presented. The aim of the workshop was to compare the results of a number of North Sea ecosystem models under different reduction scenarios. In order to achieve comparability of model results the participants were requested to use a minimum spin-up time, common boundary conditions which were derived from a widerdomain model, and a set of common forcing data, with special emphasis on a complete coverage of river nutrient loads. Based on the OSPAR requirements river loads were derived, taking into account the reductions already achieved between 1985 and 2002 for each country. First, for the year 2002, for which the Comprehensive Procedure was applied, the different horizontal distributions of net primary production are compared. Furthermore, the differences in the net primary production between the hindcast run and the 50% nutrient reduction runs are displayed. In order to compare local results, the hindcast and reduction runs are presented for selected target areas and scored against the Comprehensive Procedure assessment levels for the parameters DIN, DIP and chlorophyll. Finally, the temporal development of the assessment parameter bottom oxygen concentration from several models is compared with data from the Dutch monitoring station Terschelling 135. The conclusion from the workshop was that models are useful to support the application of the OSPAR Comprehensive Procedure. The comparative exercise formulated specifically for the

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

“…However, these studies rely on statistical analyses and the qualitative description of the interactions controlling the evolution of O 2 deficiency. Other studies investigated the effect of river nutrients on the North Sea biochemistry based on nutrient reduction scenarios (e.g., Skogen et al, 2004;Lenhart et al, 2010). Though, only Lenhart et al (2010) considered implications for the O 2 conditions in the North Sea based on a model comparison.…”

“…comm.) and constitute an updated dataset of that used by Lenhart et al (2010) , which are all available in the original data. Dissolved organic N is considered to be zero.…”

“…Thus, quantitative analyses of the influence of different nutrient sources on the O 2 dynamics required additional model scenarios within which individual nutrient sources were removed (e.g., Troost et al, 2013) or nutrient loads were reduced (e.g., Lenhart et al, 2010). This implies an individual scenario was required for each individual nutrient source in order to assess its impact on the O 2 conditions which is time-consuming and causes high computational costs.…”

Oceanic controls on the primary production of the northwest European continental shelf: model experiments under recent past conditions and a potential future scenario

“…For freshwater fluxes, daily discharge data for 250 rivers are used from the Global River Discharge Data Base (Vörösmarty et al, 2000) and from data prepared by the Centre for Ecology and Hydrology as used by Young and Holt (2007). River nutrient loading matches that used by Lenhart et al (2010), with raw data for the UK, Northern Ireland, Ireland, France, Norway, Denmark and the Baltic processed by van Leeuwen (CEFAS, UK) and raw data for Germany and the Netherlands was processed by Pätsch and Lenhart (2004). The Baltic exchange at the Belts is treated crudely as an inflow source using a mean annual cycle of depth averaged transport, salinity and nutrients.…”

“…The Baltic exchange at the Belts is treated crudely as an inflow source using a mean annual cycle of depth averaged transport, salinity and nutrients. A constant spatial field of atmospheric nitrogen deposition (oxidized and reduced) is provided by EMEP (Cooperative Programme for Monitoring and Evolution of the Longrange transmission of Air Pollutants in Europe; as is also used in some models considered by Lenhart, 2010). Aspects of this simulation have previously been reported by and a subset of data from this simulation is freely available 2 .…”