Atlantic upper circalittoral fine mud

This habitat has a large natural range in the North East Atlantic region being reported on the Atlantic coast of Portugal, in sealochs on the west coast of Ireland and around Scotland, as well as in the central North Sea. Some decline in habitat quantity (as a result of shifts to different sediment composition) have been recorded and there are many well documented examples of decline in quality.
Most sedimentary benthic systems on the continental shelf of Europe have been modified by fishing activities in the last 100 years, particularly by mobile demersal gears, and this habitat remains under fishing 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), has revealed that just over 50% of the estimated circalittoral fine mud habitat was subject to trawling fishing pressure in the North Sea and Celtic Sea and more than 80% of the circalittoral fine mud across the North East Atlantic shelf area was likely subject to abrasion disturbance. 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.

• Urbanisation, residential and commercial development
• Discharges
• Biological resource use other than agriculture & forestry
• Marine and Freshwater Aquaculture
• Fishing and harvesting aquatic resources
• Professional active fishing
• Pollution
• Nutrient enrichment (N, P, organic matter)
• Natural System modifications
• Human induced changes in hydraulic conditions
• Modification of hydrographic functioning, general

The frequency of incidents of damaging activity, the type of damaging activity and the predominant species, influences recovery. Studies have shown that recovery times following dredging were significantly shorter for short-lived species (<1 – 3 years), free-living and tube-dwelling species and for scavenging or opportunistic species, than for medium-lived species (3 – 10 years), burrow-dwelling species and suspension feeders. Free living species are also likely to recolonise areas more quicky that those that grow attached to the substratum and have an erect or stalked body form such as seapens. Differences in the recoverability of different species groups following fishing may result in changes in community composition and ecosystem functioning over the long term.