Sandbanks which are slightly covered by sea water all the time

Compiled by Dalia Gudaitiene Holiman, Lithuania

1. European Unions Natural Marine Habitat types definitions

1110 Sandbanks which are slightly covered by sea water all the time

 PAL.CLASS.: 11.125, 11.22, 11.31

Fehmarn Belt in the Baltic Sea, top of a subaquatic dune (sandbank subtype megaripple) with sea star (photo BfN © Krause & Hübner).

1.1. Definition:

Sandbanks are elevated, elongated, rounded or irregular topographic features, permanently submerged and predominantly surrounded by deeper water. They consist mainly of sandy sediments, but larger grain sizes, including boulders and cobbles, or smaller grain sizes including mud may also be present on a sandbank. Banks where sandy sediments occur in a layer over hard substrata are classed as sandbanks if the associated biota are dependent on the sand rather than on the underlying hard substrata.

“Slightly covered by sea water all the time” means that above a sandbank the water depth is seldom more than 20 m below chart datum. Sandbanks can, however, extend beneath 20 m below chart datum. It can, therefore, be appropriate to include in designations such areas where they are part of the feature and host its biological assemblages.

1.2. Characteristic animal and plant species

Vegetation:Zostera sp., Potamogeton spp., Ruppia spp., Tolypella nidifica, Zannichellia spp., carophytes. On many sandbanks macrophytes do not occur.

Animals: Invertebrate and demersal fish communities of sandy sublittoral (fine and medium grained sands, coarse sands, gravely sands), e.g. polychaetes: Scoloplus armiger, Pygospio elegans, Nereis diversicolor, Travisia sp., e.g. bivalves: Macoma balthica, Mya arenaria, Cerastoderma sp., e.g. crustaceans: Crangon crangon, Saduria entomon, e.g. fish species: Platichthys flesus, Nerophis ophidion, Pomatoschistus spp., Ammodytes tobianus.

1.3. Corresponding categories

German classification: “Sandbank der Ostsee (ständig wasserbedeckt) (040202a)"

Nordic classifications: Vegetationstyper i Norden, Påhlsson (ed.) 1994: “Zostera marina-typ (4.4.1.1)”, “Ruppia maritima-typ (4.4.1.2)”, “Chara-typ (6.3.3.1)”, “Potamogeton pectinatus (6.3.2.2)”. -typ (4.4.1.1)”, “Ruppia maritima-typ (4.4.1.2)”, “Chara-typ (6.3.3.1)”,“Potamogeton pectinatus (6.3.2.2)”.

Kustbiotoper i Norden, Nordiska Ministerrådet 2001: “Sandbottnar (7.7.1.2; 7.8.1.2; 7.8.4.2; 7.8.5.2; 7.8.6.7; 7.8.6.8; 7.8.6.9; 7.8.7.9; 7.8.7.10; 7.8.7.11; 7.9.1.1.; 7.9.2.1; 7.9.3.1; 7.9.4.1).”

HELCOM classification: “Sublittoral gravel bottoms. Banks with or without macrophyte vegetation (2.4.2.3)”, “Sublittoral sandy bottoms. Banks with or without macrophyte vegetation (2.5.2.4)”.

EUNIS classification: Relevant types within “A4.4, A4.55, A4.1, A4.2, A4.51, A4.5, A4.53, A4.1, A4.2, A4.51, A4.5, A4.53, A4.4, A4.55, A7.32, A4.51, A4.53, A4.552, 4.521, A4.521, A4.513, A6.22, A4.51, A4.141, A4.13, A8.13”.

1.4. Associated habitats

Sandbanks can be found in association with mudflats and sandflats not covered by seawater at low tide (1140) and reefs (1170). Sandbanks may also be a component part of habitat 1130 Estuaries and habitat 1160 Large shallow inlets and bays.

1.5. References

Dyer KR & Huntley DA (1999). The origin, classification and modelling of sand banks and ridges. Continental Shelf Research 19 1285-1330.

Ericson, L. & Wallentinus, H.-G. (1979). Sea-shore vegetation around the Gulf of Bothnia. Guide for the International Society for Vegetation Science, July-August 1977. Wahlenbergia 5:1 – 142.

European Environment Agency (2002). EUNIS habitat classification. Version 2.3. Copenhagen, EEA (Internet publication: http://eunis.eea.europa.eu/habitats.jsp ).

HELCOM (1998). Red List of Biotopes and Biotope Complexes of the Baltic Sea, the Belt Sea and the Kattegat. Baltic Sea Environment Proceedings No. 75.: 126pp.

Kautsky, N. (1974). Quantitative investigations of the red algae belt in the Askö area, Northern Baltic proper. Contrib. Askö Lab. Univ. Stockholm 3: 1-29.

Lappalainen, A., Hällfors, G. & Kangas, P. (1977). Littoral benthos of the northern Baltic Sea. IV. Pattern and dynamics of macrobenthos in a sandy bottom Zostera marina community in Tvärminne.

Nordiska Ministerrådet (2001). Kustbiotoper i Norden. Hotade och representativa biotoper. TemaNord 2001: 536. 345 pp.

Oulasvirta, P., Leinikki, J. & Reitalu, T. (2001). Underwater biotopes in Väinameri and Kõpu area, Western Estonia. The Finnish Environment 497.

Påhlsson, L. (ED.) (1994). Vegetationstyper i Norden. TemaNord 1994: 665. 627 pp.

Ravanko, O. (1968). Macroscopic green, brown and red algae in the southwestern achipelago o Finland. Acta Bot. Fennica 79: 1-50.

Riecken, U., Ries, U. & Ssymank, A. (1994). Rote Liste der gefährdeten Biotoptypen der Bundesrepublik Deutschland - Schriftenreihe für Landschaftspflege und Naturschutz. 41: 184 pp.

2. Additional HELCOM information

2.1. Description of the habitat

Sandbanks are sublittoral elevated features. They consist mainly of sandy sediments.

2.2. Distribution

Sandbanks are widely spread throughout the whole Baltic Sea area, and occur in all HELCOM sub-regions. Sandbanks of the Pomeranian Bay (southwest of the Baltic Sea) are highly representative for the Baltic Sea. The central morphological structure of the bay, north of the Oder estuary, is a 7-8 m shallow fine grained sandbank – the Oderbank. The Oderbank extends into the German and Polish EEZs and is a large sandbank of ideal characteristic and a representative habitat for the Baltic Sea as the whole.

2.3. Importance (sub-regional, Baltic-wide, global)

Submerged sandbanks are considered to be of Baltic-wide importance. They provide for example important wintering habitat to many bird species, in particular Melanitta nigra, but also Gavia stellata and Gavia arctica. They host rare, threatened and/or declining benthic species or communities. Furthermore, they provide spawning and nursery grounds for many fish species. Sandbanks are also important as regeneration and re-colonization reservoir after catastrophic oxygen depletion events with mass mortality in deeper areas. On shallow Baltic sandbanks, seagrass beds are common.

2.4. Status of threat/decline

Sandbanks are threatened and/or declining mainly in the southern Baltic Sea area. According to the HELCOM Red List of Biotopes and Biotope Complexes (HELCOM, 1998) the Baltic wide threat category is "Endangered".

2.5. Threat/decline factors

Eutrophication and pollution, fisheries (e.g. bottom trawling), mineral extraction, offshore constructions, dredging and dumping of dredged material are considered to be the most potential and/or actual threats. Eutrophication of the Baltic Sea has resulted in significant declines of seagrass and other sensible species on sandbanks, but contributed to an increased abundance and biomass of very few less sensible makrozoobenthic species.

2.6. Options for improvement

Eutrophication must be reduced significantly. This would probably result in a more favourable development of sandbanks. In some countries sandbanks are protected by law. Additional protective measures could be: introduction of ecologically sound fishing methods, restrictions for mineral extractions and dumping of dredged material. As for all natural habitat types an inventory and a monitoring and assessment programme (also for human activities) is obligatory for EU Member States. They are further obliged to take all appropriate steps to avoid further deterioration. This includes the obligation to protect this natural habitat type within the Natura 2000 network, and thus to designate as many SACs as necessary to guarantee its favourable conservation status. Member States have to follow Article 6 (3) of the Habitats Directive: Plans and projects which are not directly connected with or necessary to the management of a Natura 2000 site but likely to have a significant effect thereon, either individually or in combination with other plans or projects, shall be subject to appropriate assessment of its implications.

2.7. References

European Commission (2007). Guidelines for the establishment of the Natura 2000 network in the marine environment. Application of the Habitats and Birds Directives. (EU interpretation manual) 

HELCOM (1998). Red List of Marine and Coastal Biotopes and Biotope Complexes of the Baltic Sea, Belt Sea and Kattegat - Including a comprehensive description and classification system for all Baltic Marine and Coastal Biotopes. HELCOM-Baltic Sea Environment Proceedings 75, Helsinki Commission. 115 pp.