Trends in dissolved inorganic nitrogen and orthophosphate concentrations in transitional, coastal and marine waters in Europe, 1980-2019

Figure Created 05 Sep 2022 Published 12 Sep 2022 Last modified 07 Dec 2023
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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 1980-2019. 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.
- To improve the aggregation into time series, data were aggregated into squares of 0.01 degree × 0.01 degree for coastal stations (within 20km of the coastline) and 0.05 degree × 0.05 degree for open water stations.
- SLPG was considered: August-October in the Mediterranean and Black Seas, January-March in the Baltic Sea and January-February in the other regional seas.
- 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 (2015-2019) were considered. A p-value <0.05 was used to consider a statistically significant trend.


Geographic coverage

Temporal coverage


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