The Greater North Sea is a semi enclosed basin, situated on the continental shelf of north-west Europe. Its Southern part is very prone to eutrophication, as it receives most of the run-offs and is relatively isolated from the direct influence of the Atlantic waters. We aim here to assess the impact of a reduction in nitrogen and phosphorus loads originating from coastal discharges by performing numerical modelling experiments. The configuration used is the 5km ocean model GETM (General Estuarine Transport Model) coupled with ERSEM (European Regional Seas Ecosystem Model). The GREEN (Geospatial Regression Equation for European Nutrient losses) hydrological model provided nutrients loads. After a 30 years spinup, 16 sensitivity experiments have been integrated from 2010 to 2015. The nitrogen and phosphorus discharges have been independently set to 20, 50, 80 and 100 % of the original nutrient load. We analysed the mean levels of several criteria of the descriptor D5 related to Eutrophication. In particular we focus on D5C1 (nutrients), D5C2 (chlorophyll), D5C5 (bottom oxygen), and determined Good Environmental Status (GES) based on Threshold Values (TVs). Dissolved inorganic phosphate (DIP) presents a smaller sensitivity to a load decrease than Dissolved Inorganic Nitrogen (DIN). DIN and DIP reduction have to be performed simultaneously to maintain the DIN:DIP ratio to a constant value, which is important for an healthy ecosystem functioning

DUTEIL Olaf;  MACIAS MOY Diego;  STIPS Adolf; 

2023-06-16

Publications Office of the European Union

JRC132207

978-92-68-03120-9 (online),   

1831-9424 (online),   

EUR 31495 EN,    OP KJ-NA-31-495-EN-N (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC132207,   

10.2760/039666 (online),