Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL15 Submerged rooted plant communities on Baltic infralittoral coarse sediment

Submerged rooted plant communities on Baltic infralittoral coarse sediment

Quick facts

Red List habitat type code BAL15
Threat status
Europe Near Threatened
EU Near Threatened
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This benthic habitat occurs  in the photic zone with at least 90% coverage of coarse sediment according to the HELCOM HUB classification. Coarse sediments covered by rooted plants  (which also includes plants with rhizoids,i.e. Charales) are mainly distributed in areas of moderate exposure to wave actioin. The habitat covers the full salinity range of the Baltic Sea and is distributed from the Belt Sea up to the northern part of Bothnian Bay. Depending on the salinity the dominant species (>50% of the biovolume), defining the associated biotope type, varies. They also occupy different depth zones. Five associated biotopes have been identified: ’Baltic photic coarse sediment dominated by pondweed (Potamogeton perfoliatus and/or Stuckenia pectinata)’ (AA.I1B1); ’Baltic photic coarse sediment dominated by Ranunculus spp.’ (AA.I1B6 );  ’Baltic photic coarse sediment dominated by Charales’ (AA.I1B4);  ’Baltic photic coarse sediment dominated by Zannichellia spp. and/or Ruppia spp. and/or Zostera noltei’ (AA.I1B2) and  ’Baltic photic coarse sediment dominated by common eelgrass (Zostera marina)’ (AA.I1B7).

The latter differs most strongly from the other biotopes in distribution, occurring mainly at moderate to high exposure and in salinities of 5 psu or higher. It is typically found in deeper waters than the other biotopes (1-6 m) and often marks the lower depth limit distribution of soft bottom vegetation. This biotope is absent from areas with low salinity in the inner part of the Gulf of Bothnia.

Indicators of quality: 

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change over time. There are no commonly agreed indicators of quality for this habitat, although particular parameters may have been set in certain situations e.g. protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis.

The vertical depth limit of submerged rooted plants is used in several countries as a Water Framework Directive parameter for assessing ecological status. The overall quality and continued occurrence of this habitat is, however, largely dependent on the presence of the rooted plant species, which create the biogenic structural complexity on which the characteristic associated communities depend. The density and the maintenance of a viable population of these species is a key indicator of habitat quality, together with the visual evidence of presence or absence of physical damage.

Characteristic species
For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

The presence of this habitat type in the Baltic is well established with different submerged rooted plant communities dominating depending on the salinity and exposure. The best studied associated biotopes are those dominated by seagrass, brackish water angiosperms and charophytes and for most of them there have been declines in extent.
There have been significant declines (>25%) in the extent of the seagrass and charophyte dominated communities in the last 50 years and in the quality of some of the associated biotopes. Zostera marina and several species of charophyts are also on the HELCOM Red List of threatened species in the Baltic. The overall assessment for this EUNIS level 4 habitat has been based on the HELCOM (2013) assessments for the associated HELCOM HUB biotopes. Draft assessments were derived using a weighted approach whereby the HELCOM assessment outcomes were assigned a score. This was averaged across the relevant biotopes. The outcomes were reviewed by Baltic experts to reach a final conclusion. HELCOM (2013) assessed AA.I1B1, AA.I1B2 and AA.I1B6 as Least Concern (A1) and AA.I1B4 and AA.I1B7 as Near Threatened (A1). With no additional information on changes in extent or quality of this habitat the overall assessment for this habitat type based on expert opinion is Near Threatened fro both the EU 28 and EU 28+.
Red List Category Red List Criteria
Near Threatened A1
Red List Category Red List Criteria
Near Threatened A1

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Biological resource use other than agriculture & forestry
    • Marine and Freshwater Aquaculture
    • Intensive fish farming, intensification
    • Professional active fishing
    • Benthic or demersal trawling
  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Nutrient enrichment (N, P, organic matter)
    • Input of contaminants (synthetic substances, non-synthetic substances, radionuclides) - diffuse sources, point sources, acute events
  • Natural System modifications
    • Removal of sediments (mud...)
    • Estuarine and coastal dredging
    • Dykes, embankments, artificial beaches, general
    • Sea defense or coast protection works, tidal barrages
  • Climate change
    • Changes in abiotic conditions
    • Temperature changes (e.g. rise of temperature & extremes)
    • Changes in biotic conditions
    • Habitat shifting and alteration

Habitat restoration potential

The associated biotope AA.I1B7 ’Baltic photic coarse sediment dominated by common eelgrass (Zostera marina)’ can be slow to recover after strong decline (>20 yrs) although intervention (planting) may speed up the recovery. Tansplantation experiments have had limited success to date. Regeneration from root systems is slow and recovery of entire beds, with characteristic structure and associated species will take long. For the other associated biotopes natural recovery can probably occur within 10 years.

Trends in extent

Average current trend in quantity

Decreasing Decreasing
EU28 EU28+

Trends in quality

Average current trend in quality

Unknown Unknown
EU28 EU28+

Conservation and management needs

All actions to reduce eutrophication of the Baltic Sea are important for the conservation of this habitat. Conservation measures such as area protection and restrictions on coastal construction and dredging would also benefit this habitat.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to marine habitats
    • Restoring marine habitats
  • Measures related to spatial planning
    • Establish protected areas/sites
  • Measures related to urban areas, industry, energy and transport
    • Other measures
    • Managing marine traffic


For each habitat a distribution map was produced from a wide variety of sources indicating known and potential occurrences of the habitat in 10x10 km grids within Europe. Occurrences in grid cells were given in two classes: actual distribution from relatively reliable sources (surveys, expert knowledge), and potential distribution based on models or less reliable indicators. Please download the fact sheet to see the map.

Geographic occurrence and trends

Seas Present or presence uncertain Current area of habitat (Km2) Recent trend in quantity (last 50 years) Recent trend in quality (last 50 years)
Baltic Proper Present Unknown Unknown Decreasing
Belt Sea
Gulf of Bothnia
Gulf of Finland
Gulf of Riga
The Sound

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 732,697 434 Unknown This habitat is present in all the Baltic sub-basins.
EU28+ >50 Unknown This habitat is present in all the Baltic sub-basins
AOO = the area occupied by a habitat measured in number of 10x10 km grid cells.
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).

Characteristic species

Not available

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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1050 Copenhagen K
Phone: +45 3336 7100