Atlantic lower circalittoral mud
Quick facts
Red List habitat type | code NEAA5.37 |
---|---|
Threat status | |
Europe | Endangered |
EU | Endangered |
Relation to |
|
Source | European Red List habitat factsheet |
European Red List of habitats reports | |
European Red List of habitats (Excel table) |
Summary
In mud and cohesive sandy mud in the offshore circalittoral zone, typically below 50-70m, a variety of faunal communities may develop, depending upon the level of silt/clay and organic matter in the sediment. The relatively stable conditions associated with deep mud habitats often lead to the establishment of communities of burrowing megafaunal species where bathyal species may occur together with coastal species. The burrowing megafaunal species include burrowing crustaceans such as Nephrops norvegicus and Callianassa subterranea. The mud habitats in deep water can also support seapen populations and communities with Amphiura spp. The bioturbating activities of the infauna present in these biotopes are particularly important in controlling chemical, physical and biological processes, especially when the influences of physical disturbances such as wave action or strong currents are minimised (owing to their depth). The presence of burrowing fauna such as polychaetes significantly influence nutrient fluxes of nitrogen and phosphorus at the sediment-water interface, as their burrowing activity promotes oxygenation of the substrata. The organisms in these biotopes, particularly polychaetes and foraminiferans, are an important food source for higher trophic levels, particularly demersal fish and other benthic macrofauna. As such, the species characteristic of this habitat represent an important bentho-pelagic link increasing the overall biodiversity and ecological value of the habitat.
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. Examples of indicators of damage and naturalness have been proposed for offshore deep sea muds include; the presence of typical benthic invertebrate communities and other large burrowing megafauna, the sediment composition or sedimentation rates/disturbance, the presence of the climax community including crustacean and polychaetes populations, and an absence of Beggiatoa mats. A reduction in the abundance of less sessile and fragile species and an increase in more carnivorous and scavenging species are potential indicators of disturbance.
Threat status
Synthesis of Red List assessment
Most sedimentary benthic systems of the continental shelf of Europe have been modified by fishing activity in the last 100 years, particularly by mobile demersal gears, and this remains a significant pressure. Disturbance of the substratum due to intensive fishing activities using bottom trawls or dredges can damage or modify infaunal communities, with burrowing echinoderms and bivalves being particularly vulnerable.research suggests that some gears may also be modifying the biogeochemistry of the sediments by affecting organic matter remineralization and nutrient cycling through sediment resuspension and burial of organic matter to depth. Analysis by ICES (for the period 2009-2012) shows considerable overlap of this habitat with fishing intensity by gears which are known to have damaging effects on the epifauna and shallow infauna. More recent data for a single year (2013/2014) have revealed that more than 95% of modelled area of deep circalittoral mud across in the North Sea and Celtic Sea is considered to have been subject to fishing pressure by EU trawlers (bottom otter, beam and mid-water trawls) and that more than 80% of the deep circalittoral mud habitat across the North East Atlantic shelf area has been subject to abrasion disturbance. There are also regional studies, such as in the Kattegat, which show a similar pattern of overlap of this habitat type with the use of bottom gears that are known to alter the quality and take place at a frequency which maintains a disturbed condition. Much the same footprint of activity is likely each year and as this type of fishing pressure has been ongoing for many decades, there has most likely been a cumulative impact on habitat quality. Signficant effects have been observed in response to long-term chronic disturbance from otter trawling, for example, with negative effects on benthic infauna abundance, biomass and species richness with clear changes in community composition that may have far-reaching implications for the integrity of marine food webs.
Expert opinion is that there has been a very substantial reduction in quality of this habitat, most likely an intermediate decline affecting more than 80% of its extent although it is clear that in some locations there has also been a severe decline. The severity will depend on factors such as the intensity and frequency of disturbance. This habitat has therefore been assessed as Endangered for both the EU 28 and EU 28+ because of both past and likely continuing declines in quality.
EU | |
Red List Category | Red List Criteria |
Endangered | C/D1 |
Europe | |
Red List Category | Red List Criteria |
Endangered | C/D1 |
Confidence in the assessment
Pressures and threats
- Urbanisation, residential and commercial development
- Discharges
- Biological resource use other than agriculture & forestry
- Fishing and harvesting aquatic resources
- Professional active fishing
- Benthic or demersal trawling
- Demersal seining
- Benthic dredging
- Pollution
- Nutrient enrichment (N, P, organic matter)
- Natural System modifications
- Human induced changes in hydraulic conditions
- Modification of hydrographic functioning, general
Habitat restoration potential
Differences in the recoverability of different species groups following fishing may result in changes in community composition and ecosystem functioning over the long term.
Trends in extent |
|
Average current trend in quantity |
|
Unknown ![]() |
Unknown ![]() |
EU28 | EU28+ |
Trends in quality |
|
Average current trend in quality |
|
Decreasing ![]() |
Decreasing ![]() |
EU28 | EU28+ |
Conservation and management needs
List of conservation and management needs
- Measures related to spatial planning
- Other marine-related measures
- Establish protected areas/sites
- Measures related to hunting, taking and fishing and species management
- Regulation/Management of fishery in marine and brackish systems
- Measures related to special resouce use
- Regulating/Managing exploitation of natural resources on sea
Distribution
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) |
---|---|---|---|---|
Bay of Biscay and the Iberian Coast | Present | 64,816 | Decreasing | Unknown |
Celtic Seas | ||||
Kattegat | ||||
Greater North Sea | ||||
Macaronesia |
Extent of Occurrence, Area of Occupancy and habitat area
Extent of Occurrence (EOO) (Km2) | Area of Occupancy (AOO) | Current estimated Total Area | Comment | |
---|---|---|---|---|
EU28 | 2,576,337 | 1,868 | >64,816 | The area estimate for this habitat has been derived from a synthesis of EUNIS seabed habitat geospatial information for the European Seas but is recognised as being an underestimate. |
EU28+ | >1,868 | >64,816 | EOO and AOO have been calculated on the available data. Although this data set is known to be incomplete the figures exceed the thresholds for threatened status. |
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).
Characteristic species
Species scientific name | English common name | Species group |
---|---|---|
Amphiura chiajei | Invertebrates | |
Brissopsis lyrifera | Invertebrates | |
Callianassa subterranea | Invertebrates | |
Myriochele heeri | Invertebrates | |
Nephrops norvegicus | Invertebrates | |
Spiophanes kroyeri | Invertebrates | |
Styela gelatinosa | Invertebrates |