2024 Red List II of Macrophytes
The Baltic Sea hosts a distinctive and diverse community of macrophytes that are essential to maintaining the regions ecological balance. These plants provide critical ecosystem services, including habitat for a wide range of aquatic organisms, nutrient cycling, and water quality regulation. The macrophytes of the Baltic Sea are characterized by a unique blend of marine and freshwater species, each species adapted to the brackish water and fluctuating environmental conditions.
Macrophytes in the Baltic Sea include both submerged and emergent species, such as seagrasses, macroalgae, and freshwater plants, all of which have adapted to the sea’s variable salinity. These plants are vital components of the food web, supporting numerous invertebrates, fish, and waterfowl. They also play a key role in coastal protection by stabilizing sediments and reducing erosion. However, macrophyte communities are highly sensitive to environmental stressors such as nutrient pollution, climate change, and invasive species, which can impact their distribution and abundance. Understanding the dynamics of these plant communities is crucial for effective management and conservation of the Baltic Sea ecosystem.
Overview of the assessment results for macrophytes
There were 3 macrophyte species assessed as threatened (CR, EN, VU) of the total 350 species that were evaluated in the HELCOM Red List II assessment. One species, Lamprothamnium papulosum, remained Endangered (EN) as in 2013 and two species, Hippuris tetraphylla and Zostera (Zosterella) noltei, were categorized as Vulnerable (VU). The total list of the assessed macrophyte species and the categories assigned to them are available in Annex 1 of the Red List II species report. Altogether, 19 species were red-listed (RE-DD) in 2024, compared to 14 species in 2013.
Evaluated, Not Evaluated (NE) or Not Applicable (NA) species
Out of the total list of 558 macrophyte species of the HELCOM Checklist 2.0 (HELCOM 2020), a total of 352 species entered the Red List II assessment process, out of which 350 species were evaluated, one species (0.3%) was left unevaluated (Not Evaluated) and the category Not Applicable (NA) was given only to one species. In 2013 Red List 526 macrophyte species entered the assessment process, out of which 317 of them were evaluated. A total of 187 species were categorized as Not Evaluated (NE) and 22 species were categorized as Not Applicable (NA).
Red List categories within the assessed macrophyte species
The proportion of the category Least Concern (LC) was very high: 331 species (94%) in 2024 and high also in 2013, being 300 species (57%). The proportion of the assignment of the Not Evaluated (NE) category (187 species, 35.6%) was high in 2013 compared to one Not Evaluated species (Alisma gramineum) in 2024. The Not Evaluated category was chosen in 2013 when there were identification difficulties or taxonomical uncertainties, or the species was very poorly known. One species (Chara connivens) was categorized as Not Applicable (NA) in 2024 as the species is listed on the non-indigenous species (NIS) lists of the Baltic Sea (e.g. AquaNIS), in 2013 22 species were categorized as NA (4.2%) since introduced after 1800 and regarded as neophytes.
Red List categories and Species Information Sheets (SIS)
The Species Information Sheets (SIS) were updated for those species that were categorized as threatened during the Red List II project, meaning those assessed as Critically Endangered, Endangered, Vulnerable and those categorised as Regionally Extinct. For those species that were categorized as threatened for the first time, a SIS was produced with only a summary table and distribution map.
| Red List II / SIS 2024 | Criteria 2024 | Scientific name | Common name | Red List / SIS 2013 | Criteria 2013 |
|---|---|---|---|---|---|
 | B2b(i,ii,iii,iv,v) c(iv) | Lamprothamnium papulosum | | B2ab(ii,iii,iv,v) | |
 | B2ab(ii,iii,v); D2 | Hippuris tetraphylla | Fourleaf mare’s tail | | B2ab(i,ii,iii,iv,v) |
| A2b; B2ab(ii,iii,v) | Zostera (Zosterella) noltei | Dwarf eelgrass | | B2ab (iii, iv) |
 | B2ab(ii,iii) | Persicaria foliosa | | B2ab(ii,iii,iv,v) | |
| B2ab(ii,iii,iv,v) | Alisma wahlenbergii | | B2ab(ii,iii,iv,v) | |
| B2ab(ii,iii,iv,v) | Chara braunii | Braun’s stonewort | | B2ab(iii) |
| B1a | Nitella hyalina | Many-branched stonewort | | B2ab(iii) |
| Potamogeton friesii |  | B2a | ||
| Nitellopsis obtusa | Starry stonewort | | B2a | |
 | Chara horrida | | B2b(ii,iii,iv,v) | ||
| Botrytella reinboldii |  | |||
| Myriocladia lovenii | | |||
| Helminthora divaricata | | |||
| Delamarea attenuata | | |||
 | Crassula aquatica | | B2ab(ii,iii,iv,v) c(iv) | ||
| Chara tomentosa | Coral stonewort; mossy stonewort |  | ||
| Fucus serratus | Serrated wrack; toothed wrack | | ||
| Fucus vesiculosus | Bladder wrack; popweed; rockweed | | ||
| Furcellaria lumbricalis | Red seaweed | | ||
 | Chara connivens | Convergent stonewort | | ||
| Rosenvingiella constricta | | ||||
| Stypocaulon scoparium | |