Red List of European Habitats
Habitat code & name
AA.H3L Baltic photic muddy sediment characterized by infaunal bivalves
Author and Date
HELCOM RED LIST Biotope Expert Team, November 2013.
Relationship to EUNIS
The biotope does not correspond directly to any EUNIS (2004) level 4 habitats due to
structural differences in the classification systems. The closest correspondence in EUNIS is
found in the level 4 habitat A5.31 ‘Sublittoral mud in low or reduced salinity’.
Habitat description
Baltic photic bottoms with at least 90% coverage of muddy sediment. The sediment must
contain at least 20% of mud, silt or clay (grain size less than 63 µm). No macrovegetation
or epibenthic macrofauna. Biomass of infaunal bivalves dominates in the group infaunal
bivalves/polychaetes/crustaceans/echinoderms/insect larvae. Appears in low to
moderate energy exposure classes.
The biotope is common throughout the Baltic Sea mainly represented by the subbiotope
AA.H3L1 ‘Baltic photic muddy sediment dominated by Baltic tellin (Macoma baltica). In
total four sub-biotopes with different dominant bivalve species have been identified;
‘Baltic photic muddy sediment dominated by Baltic tellin (Macoma baltica) (AA.H3L1),
‘Baltic photic muddy sediment dominated by ocean quahog (Arctica islandica)
(AA.H3L3), ‘Baltic photic muddy sediment dominated by Unionidae’ (AA.H3L6) and
‘Baltic photic muddy sediment dominated by Abra spp.’ (AA.H3L8).
The subbiotopes AA.H3L8 ‘Baltic photic muddy sediment dominated by Abra spp.’ and
AA.H3L3 ‘Baltic photic muddy sediment dominated by ocean quahog (Arctica
islandica)’ are only present in the Belt Sea. The latter sub-biotope is defined to have a
coverage of muddy sediments >90% and of the macroinfauna the biomass of the ocean
quahog (Arctica islandica) constitutes at least 50%. The biotope is limited to areas in the
Baltic Sea where the salinity is above 15 psu. Ocean quahog (Arctica islandica) is a
bivalve mollusk found buried in sandy and muddy sediments. Arctica islandica is a longlived species with a very slow growth rate. Populations of 40–80 year old specimens with
a substantial proportion over 100 years old have been observed. A. islandica is among
the longest-lived and slowest growing marine bivalves (OSPAR 2009). It is a large species
that can grow up to 20 cm length (Moen & Svensen 2004).
The subbiotope AA.H3L6 ‘Baltic photic muddy sediment dominated by Unionidae’ is
restricted to oligohaline lagoons, bays and estuaries and the northern most part of the
Bothnian Sea. The bivalve mollusk species in the Unionidae family are filter feeding
freshwater mussels and make up ≥ 50 % of the macroinfaunal biomass. The bivalves are
relatively large, approximately 10 cm in length, and can slowly move along in the muddy
substrate. They live in soft sediment, solitary or in groups. Unionids have slow growth, low
fecundity and are long lived (Karatayev et al. 1997).
Characteristic species
Characteristic species are the name-giving bivalve-species of the relevant sub-biotopes
which are mainly Arctica islandica, Macoma balthica, Abra alba and freshwaterbivalves of the family Unionidae: Unio tumidus, U.crassus, Anodonta cygnaea,
Pseudanodonta complanata.
Indicators of quality
Diversity, abundance and biomass of fauna.
Relationships with other schemes
Annex 1 relationships
The relationship between HUB biotopes and Annex 1 habitats has not yet been mapped
by HELCOM.
MAES relationships
Marine - Marine inlets and transitional waters
Marine - Coastal
MSFD relationships
Shallow sublittoral mud
EUSeaMap relationships
Shallow muds
IUCN ecosystem relationships
9.6. subtidal muddy
Other relationships
EUNIS (2004): A5.311 Baltic brackish water sublittoral muddy biocenoses influenced by
varying salinity.
Level 5 of the HELCOM HUB classification (2013). This habitat has four sub-habitats on HUB
level 6;
‘Baltic photic muddy sediment dominated by Baltic tellin (Macoma baltica) (AA.H3L1)
‘Baltic photic muddy sediment dominated by Abra spp.’ (AA.H3L8)
‘Baltic photic muddy sediment dominated by ocean quahog (Arctica islandica)
(AA.H3L3)
‘Baltic photic muddy sediment dominated by Unionidae’ (AA.H3L6)
Photograph
No photograph currently available for this habitat.
Countries list
To be inserted when data sheets completed.
Regional Sea
Baltic Sea
Baltic Proper
Belt Sea
Gulf of Bothnia
Gulf of Finland
Gulf of Riga
The Sound
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Map
This will be inserted by NatureBureau based on the Regional Sea information above.
References
Burlakova, L. E., Karatayev, A. Y., Padilla, D. K. (2000). The Impact of Dreissena
polymorpha (PALLAS) Invasion on Unionid Bivalves. International Review of Hydrobiology
85: 529-541.
Gogina, M., Zettler, M.L. 2010. Diversity and distribution of benthic macrofauna in the
Baltic Sea: Data inventory and its use for species distribution modelling and prediction.
Journal of Sea Research 64(3): 313–321.
Karatayev, A. Y., Burlakova, L. E., Padilla, D. K. (1997). The effect of Dreissena polymorpha
(Pallas) invasion on aquatic communities in Eastern Europe. Journal of Shellfish Research
16: 187–203.
Leppäkoski, E., Gollasch, S., Gruzka, P., Ojaveer, H., Olenin, S., Panov, V. (2002). The
Baltic—a sea of invaders. Canadian Journal of Fisheries and Aquatic Sciences 59: 11751188.
Moen, F. E., Svensen, E. (2004). Marine fish & invertebrates of Northern Europe. KOM,
Kristiansund. 608pp.
Orlova, M.I., Panov, V. E. (2004). Establishment of the zebra mussel, Dreissena polymorpha
(Pallas), in the Neva Estuary (Gulf of Finland, Baltic Sea): distribution, population structure
and possible impact on local unionid bivalves. Hydrobiologia 514: 207-217.
OSPAR 2009. OSPAR Background for Ocean quahog Arctica islandica. Biodiversity Series.
http://qsr2010.ospar.org/media/assessments/Species/P00407_Ocean_quahog.pdf
Ricciardi, A., Never, R. J., Rasmussen, J. B. (1998). Impending extinctions of North
American freshwater mussels (Unionoida) following the zebra mussel (Dreissena
polymorpha) invasion. Journal of animal ecology 67: 613-619.
Schloesser, D. W., Nalepa, T. F. (1996). Zebra Mussel Infestation of Unionid Bivalves
(Unionidae) in North America. American Zoologist 36: 300-310.
Zettler, M. L., Bönsch, R., Gosselck, F. 2001. Distribution, abundance and some population
characteristics of the ocean quahog, Arctica islandica (Linnaeus, 1767), in the
Mecklenburg Bight (Baltic Sea). Journal of Shellfish Research 20: 161–169