Mudflats and sandflats not covered by seawater at low tide 

Compiled by Anda Ikauniece, Latvia

1. European Unions Natural Marine Habitat types definitions:
1140 Mudflats and sandflats not covered by seawater at low tide

PAL.CLASS.: 14

Sands and muds of the coasts of the oceans, their connected seas and associated lagoons, not covered by sea water at low tide, devoid of vascular plants, usually coated by blue-green algae and diatoms. They are of particular importance as feeding grounds for wildfowl and waders. The diverse intertidal communities of invertebrates and algae that occupy them can be used to define subdivisions of 11.27, eelgrass communities that may be exposed for a few hours in the course of every tide have been listed under 11.3, brackish water vegetation of permanent pools by use of those of 11.4.

Note: Eelgrass communities (11.3) are included in this habitat type.

2. Additional HELCOM information

2.1 Description of the habitat

In the Baltic Sea this habitat type is part of the hydrolittoral which means that these sands and muds are episodically dry falling. Thus, they belong to the relatively small wind induced littoral zone below the mean water line. Depending on the exposition such Baltic Mudflats and Sandflats occur with and without macrophyte vegetation. 

2.2. Distribution (past and present)

Mudflats and sandflats not covered by sea water at low tide occur in all parts of the Baltic Sea area, but patterns and descriptions of their distribution are mostly missing. In the Lahemaa area (Southern Gulf of Finland) for example, they are representing 3% of all habitats and also in the German Baltic Sea region form a very narrow strip along the coast. No information is available on their historical distribution.

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

The habitat is of particular importance as feeding ground for waterfowl and waders. Diverse species of invertebrates and algae occupy it and also macrophyte beds that may be exposed for a few hours are included in this habitat type. Mudflats and sandflats not covered by sea water at low tide are a widespread habitat type on coasts of Atlantic Europe, but in the Baltic Sea almost exclusively induced by wind. Therefore this habitat type is considered to be of global importance in the Baltic Sea area.

2.4. Status of threat/decline

The habitat type is threatened in almost every sub-region of the Baltic Sea area. According to the HELCOM Red List of Biotopes and Biotope Complexes (HELCOM, 1998) the Baltic wide threat category is "Endangered", but the actual status of threat and/or decline is not exactly known.

2.5. Threat/decline factors

Human activities have caused various pressures. According to the HELCOM Red List of Biotopes and Biotope Complexes (HELCOM, 1998) they are caused by: constructions, dredging, dumping of dredged material, eutrophication (fertilization, sewage, combustion), pollution, coastal defence (e.g., dyking, stabilization of sand), traffic and tourism.

2.6. Options for improvement

Particularly natural and unaffected shorelines need to become strictly protected by law. Additionally, programs and measures are needed to restore natural conditions where the habitat type is degraded (BSAP). Further protective measures could be: restriction of new constructions (HELCOM Rec. 15/1), prevention of an unregulated growth of tourism and harmful recreational activities. Furthermore, according to the HELCOM Rec. 16/3, natural processes along the coast have to be preserved. 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 also 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. Appendix I: Marine Habitat types definitions. Update of “Interpretation Manual of European Union Habitats” (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.

Kotta, J., Martin, G. & Torn, K. (2003). Benthic communities of four selected habitat types in the sea area of Lahemaa National Park, southern Gulf of Finland. Proceedings of the Estonian Academy of Sciences, Vol.52, No.3, 236–253.