Number of time series available showing increasing, decreasing or no trends in dissolved inorganic nitrogen and orthophosphate concentrations for each regional sea during the period 1980-2021

. North-East Atlantic Ocean and Macaronesia are not presented since data were not available for this indicator.
. Trends in concentrations of the nutrients, nitrogen (dissolved inorganic nitrogen-DIN) and phosphorus (orthophosphate), in the upper 10m of the water column in European seas during the season of low phytoplankton growth (SLPG) are shown for the period 1980-2021.
- Green bars indicate stations with significant (p<0.05) decreasing trends; orange bars show stations with significant (p<0.05) increasing trends; and grey bars show stations with no significant trends.
- The temporal range specified is the maximum range of dates for raw observations but this range varies upon the availability of observations at each location.
- DIN refers to the sum of ammonium, nitrite and nitrate concentrations, although in many samples not all three forms of nitrogen were measured.
- Data were aggregated into squares with sides of squares with sides of 1,375km for coastal stations within 20km from the coastline (m=80) and 5.5km for open water station more than 20km away from the coastline (m=20). A masking of 5km inwards from the coast was also applied.
- SLPG was considered for the winter months: January–March for stations within Baltic Sea and east of 15 E and January–February was used for all other stations.
- Temporal trends were estimated with the non-parametric Mann-Kendall test. Only stations having data of at least 5 years and having at least data in the last 5-year period (2017-2021) were considered. A p-value < 0.05 was used to consider a statistically significant trend.