A summary of the ‘Burrowed Mud’ mpa search feature What is burrowed mud?

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A summary of the ‘Burrowed Mud’ MPA search feature

  1. What is burrowed mud?

The ‘burrowed mud’ search feature refers to soft sediments ranging from fine mud to muddy sand which tend to occur in areas with low energy conditions (where the effects of current and wave action are low). Burrowed mud is a surprisingly important marine habitat which supports a rich community of animals that can, broadly, be split into two components. Firstly, there are the burrow-making animals that live within the mud itself, including fish, worms, brittlestars, crabs and shrimps. Secondly, there are those animals found living on or at the surface of the mud and these include tube worms, groves of seapens, the fireworks anemone and a wide variety of fish.

  1. Why is burrowed mud considered to be of conservation importance in Scotland?

Burrowed mud is considered to be of conservation importance in Scotland for the following reasons:

  • Ecological significance - burrowed mud plays an important role in the marine ecosystem. The activities of the burrowing animals have a dramatic churning effect on the muddy seabed, allowing exchange and cycling of oxygen, nutrients and minerals between the water and the sediment. The burrowing animals can occur in abundance and highly modify the surface topography of the mud with mounds and many dozens of burrow entrances peppering each metre of seabed. Below the surface, the burrows of some species form intricate lattice-like networks and may penetrate a metre or more downwards. This means that the burrowed mud is a surprisingly productive habitat, providing food and shelter for a wide range of mud-dwellers and other animals that forage in and over the mud.

  • Proportional importance of Scottish waters - burrowed mud is widely distributed across the North-East Atlantic from the Mediterranean to Biscay, around the UK and Scandinavia. However, Scotland has some of the largest areas of burrowed mud in Europe and the majority of that found in the UK’s waters.

  • Degree of threat and/or decline - across the North-East Atlantic the burrowed mud search feature is subject to impacts arising from physical disturbance and pollution and as a result is included on the OSPAR Threatened and/or Declining (T&D) list1.

  1. What is the economic importance of burrowed mud in Scotland?

  • Commercial fisheries - the high productivity of the burrowed mud habitat is underlined by its importance for commercial fishing. Indeed, the langoustine (Nephrops norvegicus) is the target of the most important shellfish fishery in Scotland. Burrowed mud habitat also provides rich feeding grounds for a variety of commercial fish species, including cod, haddock and whiting. It is likely that quite a large proportion of the burrowed mud habitats in Scottish waters are exposed to fishing activity in some form, although the nature and intensity of fishing will vary considerably. Some areas are trawled regularly while at other sites trawling will be less frequent, and there are areas where only static gear is used and areas where there is little or no fishing.

  1. Where is burrowed mud found around Scotland?

Burrowed mud occurs in sheltered basins along Scotland’s west coast (including sea lochs), throughout the Minch, in the Moray Firth and Firth of Forth, and in the northern North Sea. Patches of burrowed mud are also present in deep water off the west coast, such as around the St. Kilda Basin, along the edge of the Continental Shelf and south of Rockall (Fig.  1).

  1. How are MPA search locations being identified for burrowed mud?

Burrowed mud habitats are not uniform. There is variation as a result of prevailing physical conditions and the composition of associated species. The Scottish MPA search feature also reflects the following component habitats and species that are considered to be of particular relevance in a Scottish context:

  • Tall sea pen Funiculina quadrangularis

  • Fireworks anemone Pachycerianthus multiplicatus

  • Mud burrowing amphipod Maera loveni

The characterising species coexist spatially to some degree but do not fully overlap (some also overlap with Nephrops). The mud volcano worm habitat, the tall sea pen and the fireworks anemone are restricted mainly to the west coast (illustrated in Figures 2a - 2c). The seapens and burrowing megafauna habitat and the mud burrowing amphipod are more widely distributed (see Figures 3a and 3b). The network of MPAs across Scottish waters should provide for sufficient representation and replication of the range of distinct burrowed mud features. In practice, this means:

  • Representing the component habitats and species of the burrowed mud search feature across the main physical settings (i.e. in sea lochs, in open water away from the coast and further offshore) and geographically, within each OSPAR region in which they occur (Greater North Sea, Celtic Seas, and wider Atlantic); and,

  • Replicating coverage of these different types of burrowed mud to ensure resilience within the network.

  1. What are the aims of protecting burrowed mud through an MPA?

This will be set out in the conservation objectives developed for each future MPA. Broadly the aims would be:

  • To protect the extent, distribution, structure and function of the habitat and the broad composition of the associated community of animals. The structure of burrowed mud (i.e. the burrows and tunnels made by the communities living within the mud) is key to the way in which it functions and this in turn supports its conservation interest and its productivity.

  • To maintain or enhance the populations of the component species, e.g. sea pens, fireworks anemone, echiuran worm Maxmuelleria lankesteri, and mud burrowing amphipod Maera loveni.

  1. What would be identified as a protected feature of an MPA?

We are trying to identify and protect the specific burrowed mud habitats or species listed at 5. above. While Nephrops is clearly an important species in the community of animals in burrowed mud, their abundance is not being used as a search characteristic and neither is the MPA process being used as a mechanism to protect Nephrops in its own right or manage the fishery. The management of a sustainable Nephrops fishery, whether inside or outside of MPAs, is crucial for maintaining both productive Nephrops populations and the overall quality of burrowed mud habitat (in line with the three pillar approach to the conservation of Scotland’s marine environment).

  1. Further information

For more information on burrowed mud and the selection of MPA search features see:


Figure 1 Putative distribution of the burrowed mud MPA search feature in Scottish waters. Inset map presents wider OSPAR T&D habitat distribution. Records categorised as ‘potential burrowed mud’ have yet to be assigned to specific habitat categories, this work is ongoing and on the basis of initial results it is anticipated that~95%+ of these records will be formally confirmed as the MPA search feature

Figures 2a - 2c The distribution of fireworks anemones, burrowed mud with the mud volcano worm and the tall seapen on the west coast. Whilst this is the main centre of their distribution there are important if sparse records of fireworks anemones and tall seapens on the east coast

Figures 3a - 3b The distribution of the seapens and burrowing megafauna habitat and the mud amphipod Maera loveni

1The OSPAR T&D habitat is entitled ‘Seapens and burrowing megafauna communities’ which broadly equates to the burrowed mud MPA search feature, encompassing the 2 component habitats and 3 component species considered of particular relevance in Scottish waters

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