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h1. H1140 - Mudflats and sandflats not covered by seawater at low tide
h1. General
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|| General characteristics || ||
| Common name | Mudflats and sandflats not covered by seawater at low tide |
| Region | The Netherlands |
| Water systems | coastal waters|
| Nature parameter |Vegetation and habitat types  |
|HR nr|H1140 |
| Fact sheet by |K.E. van de Wolfshaar |{column}{column:width=20%}
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h1. Description habitat



h3. General occurrence


In the Netherland, mud flats and sand-flats can be found in the Wadden Sea. In the Delta region, this habitat type is called mudflats if it is connected to the main land or sandflats when completely surrounded by water [#1].


h3. Environmental boundary conditions
This habitat type includes mudflats and sandflats not covered by seawater at low tide, the so-called intertidal flats. Most intertidal flats are devoid of vascular plants, or sometimes coated by algae and cyanobacteria. Indigenous eelgrass communities are included in this habitat type (_Zostera marina_ and _Zostera noltii_) [#1]. A large density of invertebrates occur in this habitat type, including characteristic species such as the common cockle (_Cerastoderma edule_), Baltic clam (_Macoma balthica_), Soft-shell clams  (_Mya arenaria_), Lugworm  (_Arenicola marina_), Ragworm (_Nereis diversicolor_), Sand mason worm) (_Lanice conchilega_) and Lugworm (_Scoloplos armiger_). Large concentrations of mussels can be found locally in specific habitat mussel beds. They are in fact complex communities, including mussels (_Mytilus edulis_), a large number of worms, crustaceans and small fish. This habitat is of particular importance as feeding ground for waders, including the Common Spoonbill (_Platalea leucorhodia_), Common Shelduck (_Tadorna tadorna_), Eurasian Oystercatcher  (_Haematopus ostralegus_), Pied Avocet  (_Recurvirostra avosetta_), Grey Plover  (_Pluvialis squatarola_), Red Knot  (_Calidris canutus_), Dunlin  (_Calidris alpina_), Bar-tailed Godwit  (_Limosa lapponica_), Eurasian Curlew, (_Numenius arquata_), Common redshank (_Tringa totanus_) and various kinds of gulls. During high water, the intertidal flats are a feeding ground for fish, such as the Viviparous eelpout  (_Zoarces viviparus_), Shorthorn sculpin  (_Myoxocephalus scorpius_), Striped seasnail (_Liparis liparis_), Butterfish (_Pholis gunnellus_), Common English flounder (_Pleuronectes flesus_), Fivebeard rockling  (_Ciliata mustela_) and various goby species (_Pomatoschistus_). Tidal waters are also important breeding areas for fish such as Plaice (_Pleuronectus platessa_), Common Sole (_Solea solea_), Herring (_Clupea harengus_) and European sprat (_Sprattus sprattus_). Seals use the mud flats and sand flats as resting sites. Intertidal flats not covered by seawater at low tide occur in The Netherlands in the Wadden Sea area and the Voordelta near the islands of Zeeland and South Holland. For the Westerschelde and the Oosterschelde, these sand flats are part of the habitat types [H1130 - Estuaries| HBTDB: Estuaries] and [H1160 - Large shallow inlets and bays|HBTDB:H1160 - Large shallow inlets and bays] respectively [#1] respectively.


h3. Control and growth opportunities
This habitat type is mainly sensitive to changes in velocity and flooding frequency. Mechanical damage makes this habitat unsuitable for invertebrates and their predators [#1].



h1. Dose-effect relations
Sandflats and mudflats are landscape elements that are difficult to capture with habitat factors. However, the occurrence of Benthivorous birds can be predicted with the aid of habitat factors. Therefore, this group of birds is included as an additional dose-effect relation.
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h4. Flowchart
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h4. Dose-effect relations

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{chart:type=bar|title=Tidal influence|xlabel=tidal influence|yLabel=HAI |dataDisplay=true|dataOrientation=vertical|legend=false}
||tidal influence || HAI ||
|always dry|0|
|dry during low tide | 1 |
| always covered with water| 0 |

{chart}
Reference: [#1]
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h5. Occurrence of characteristic species

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The occurrence of characteristic species is beneficial for the quality of a habitat type. This applies to all above-mentioned characteristic species of, for example, invertebrates and eelgrass. Most Dutch sandflats are devoid of plants, but locally algal communities or eelgrass covering can be found.  This concerns mostly Dwarf eelgrass  (_Zostera noltii_), as Common eelgrass needs to be covered by water. Dose-effect relations for the occurrence of eelgrass is included under macrophytes (Dwarf eelgrass - Zostera noltii] and [Common eelgrass - Zostera marina]) (!) only available in Dutch. For a number of invertebrates, there are already dose-effect relations. These will be included in the database soon. 

Mudflats and sandflats are an important feeding ground for Benthivorous birds. Therefore, the habitat suitability of this group of birds has been included as an additional dose-effect relation. The dose-effect relations of Benthivorous birds are described on page [General - Benthivorous birds].

{column:width=50%}
{chart:type=XYline|title=Occurrence Benthivorous birds birds|xlabel= Benthivorous birds birds (HAI)|yLabel=HAI |dataDisplay=true|dataOrientation=vertical|legend=false}
|| Benthivorous birds (HAI) ||HAI ||
| 0| 0|
| 1.0|1.0|
{chart}
Reference: [#2]
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h1. Uncertainty and validation
(!) These dose-effect relations have not been validated. 


h1. Applicability
To describe a landscape element according to the habitat factors is very difficult. It is more informative to determine if an area that is defined as mudflats and sandflats not covered by seawater at low tide is suitable for, for instance, Benthivorous birds. This will give an indication of the quality of the area as main feeding ground. 



h1. Example project
At present, there is no example of a project available.  


h1. References
1 {anchor:1} [http://www.minlnv.nl/natura2000]
2 {anchor:2} Haasnoot, M. en K.E. van de Wolfshaar (ed). Habitat analyse in het kader van de Planstudie/MER voor Krammer, Volkerak en Zoommeer. WL report Q4015. 2006