The species diversity of phytoplankton exhibits large year-on-year fluctuations, but no trend over time. However, the number of species varies relatively little when calculated on the North Sea scale, and no temporal trends are still seen here. Overall, the species diversity of phytoplankton cannot be stated as being in good environmental condition, as the data base is currently too flimsy to be able to assess this.

The total marine mammal biomass is stable or increased from 1994 to 2016. The biomass in 2005 was lower than in 1994 (Figure 23.6). Porpoises make up 82-89% of the biomass all year, and the total figures for marine mammals are therefore mainly controlled by the biomass of harbour porpoises. The spotted seal has increased in number from 1994 to 2005 and from 2005 to 2016 in both areas. Gray seal was virtually absent in 1994 and 2005, but in 2016 the number has increased significantly in the MRU. Furthermore, according to the GES decision, good environmental status for seals and porpoises is considered to correspond to favorable conservation status under the Habitats Directive. Here, the condition of marine mammals in the Danish marine areas was assessed in 2013 under Article 17. It was considered that the condition of the spotted seal and porpoises in the North Sea and the Kattegat was favorable, while the condition of gray seal was unfavorable. On this basis, it is not possible to make an overall assessment of the state of the trophic level.

The biomass of small pelagic fish around Denmark has increased slightly in the period from 2010 to 2016, as both North Sea herring and North Sea sprat have increased. The food supply for predators on these species has thus been the site in recent years. Especially sprat is eaten by many birds and fish species.

The overall plankton biomass has been steadily declining in the North Sea and the Kattegat from 1978 to 2016. A slight increase is seen after 2012.

Data from the North Sea show that the proportion of zooplankton biomass exceeding 2000 μm in 2017 was below average for 2012-2015 and significantly below the highest value from 2014. Thus, the feeding conditions for both filtering (eg. herring) and particulate (e.g. sand eel) eating fish somewhat below average during the summer period in 2017. The time series is too short for trends to be described for longer periods.

The biomass of large fish-eating fish (piscivore) around Denmark increased slightly in the period from 2010 to 2016 in the North Sea. The biomass of medium-sized pelagic fish around Denmark was at a high level in the period from 2010 to 2016, as the mackerel population has again increased after a period of low biomasses. This probably involves increased food competition with other planktivorous fish and increased mortality of herring, sand eel, sprat and cod.

For birds, good environmental status corresponds to the assessment under Article 12 of the Birds Protection Directive. Data from the recent report (2013) of breeding birds shows that, in general, certain species groups are stable or progressive, such as herbivores and birds foraging in the water column. For groups such as waders and birds foraging in the surface, less than 75% of the species are stable or in progress. For wintering birds, most of the species groups are stable, progressive or fluctuating, but not birds that seek food on the seabed.