Trends in dissolved inorganic nitrogen and orthophosphate concentrations in transitional, coastal and marine waters in Europe, 1980-2021

Figure Created 17 Jan 2024 Published 25 Jan 2024 Last modified 21 May 2024
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Trends in concentrations of 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 circles indicate stations with significant (p<0.05) decreasing trends; orange circles show stations with significant (p<0.05) increasing trends; and grey circles show stations with no significant trends. In these cases, p is a statistical term describing the probability that the trend is significant.

European data


Additional information

- 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.

- 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.

- SLPG was considered for the winter months: January-March for stations within Baltic Sea and east of 15 E longitude. Period from January–February was used for all other stations.


Geographic coverage

Temporal coverage


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