Biodiversity, Conservation Importance and Sensitivity of the Biotope
Feasibility of management
The criteria for assessing the importance of a species or
community from a conservation-related perspective have been the subject of much debate.
They are perhaps especially difficult to establish in the marine environment, where basic
knowledge of distributions, life cycles and ecological functioning is still at a low level
compared with the terrestrial situation. A number of criteria (not necessarily exhaustive)
for assessing conservation importance are listed below, with details of their relevance to
the Sea pens and burrowing megafauna biotope complex. Criteria include those
listed by Hiscock (submitted).
Habitats, communities or species may be considered
important from a conservation - related perspective if they are:
Rare or very restricted in distribution
Of the MNCR-defined biotopes included within this complex, the most
restricted are CMU.SpMeg.Fun and IMU.PhiVir, both of which are confined to a small number
of Scottish sea lochs (IMU.PhiVir has one isolated example in Portland Harbour). The sea
loch representatives are distributed along a large stretch of the western Scottish
coastline, but their collective spatial extent must be fairly small.
Species falling within this category are the sea pen Funiculina
quadrangularis, the anemones Pachycerianthus multiplicatus and Scolanthus
callimorphus, and the brittlestar Asteronyx loveni. All of these species do
occur outside British waters, so that their conservation importance must be defined in a
British context. Some megafaunal burrowers (eg. Axius stirhynchus) are known from
only a small number of records, but these animals are too easily overlooked to be classed
with any confidence as truly rare.
In decline or have been
None of the biotopes or species considered here are known to be
currently declining. Existing records are inadequate to determine whether any declines
have occurred in the recent past.
A high proportion of the regional or world population or extent
Biotopes with sea pens and megafauna have certainly been
best-characterized and studied in British waters, but as discussed in Chapter II, similar
biological communities are known from sedimentary habitats in many parts of the world. The
anemone Pachycerianthus multiplicatus is known only from Scotland, Ireland and
Scandinavia, so that British waters might conceivably hold a significant proportion of its
Particularly good or extensive examples of their type
British and Irish waters do support good examples of the biotopes in
question, with a high diversity of burrowing megafauna and several sea pen species. Their
perceived importance may change as information is gained from other regions, but at
present the British representatives are probably the best-known examples of their type.
Keystone species providing a habitat for other species
The various small invertebrates found as commensals in megafaunal
burrows are also found as members of the general sediment fauna rather than being
specialized burrow associates. The one example known in this category is the brittlestar Asteronyx
loveni, which appears to be an obligate commensal of large anthozoans such as Funiculina
Biotopes with a particularly high species richness
Marine sediments do support a large number of invertebrate species,
especially if the entire size range of animals is considered. Biotopes characterized by
sea pens and burrowing megafauna are not known to be unusually species-rich, but have not
been compared systematically with sediments lacking this component of the fauna. It is
possible that the patchwork of disturbance created by megafaunal burrowers may promote a
higher local species diversity (of macro- and meiofauna) than would otherwise exist.
Biotopes important for the efficient functioning of regional ecosystems
Marine sediments are certainly important in the geochemical cycling of
carbon, nutrients and metals in coastal environments. Bioturbation is known to affect
geochemical processes but no studies have yet been able to assess its importance at the
ecosystem level (ie. comparing the efficiency of cycling through bioturbated and
Of high aesthetic, symbolic or recreational importance
The biotope complex does not possess any features within this category.
This assessment leads to the overall conclusion that the conservation
importance of the Sea pens and burrowing megafauna biotope complex lies in:
- The restricted distribution and spatial extent of the biotopes and species listed under
- The fact that the British representatives are particularly good examples of their type.
As discussed in Chapters V and VI, the biotopes within this complex
(including CMU.SpMeg.Fun and IMU.PhiVir, defined above as being of conservation
importance) are sensitive to disturbance by trawling and organic pollution, and probably
by chemical contamination of various kinds. The ability of these biotopes to recover after
disturbance (ie. return to their original state) is not well-understood. Sediment
macrofaunal communities can recover following the cessation of organic enrichment,
although the time required for this to occur is strongly dependent on local conditions
(Pereira, 1997). The life cycles of some animal species may act as a barrier to
recolonization following local disappearance. This will be true especially of species with
low reproductive rates, and short-lived larvae with low dispersal abilities (Hiscock,
submitted). Species with a sessile or sedentary lifestyle as adults will clearly also be
unable to recolonize an area other than by larval dispersal.
The life cycles of most of the characteristic species of this biotope
complex are poorly-known, but the studies reviewed in Chapter IV suggest that taxa with
poor colonization ability will include the three sea pens, Pachycerianthus
multiplicatus, Calocaris macandreae and possibly Maxmuelleria lankesteri.
Local extinction might not be easily (or ever) reversed in these species, a feature of
particular importance to those with fragmented distributions (eg. Funiculina,
Feasibility of management
The biotopes and species defined above as being of conservation
importance are limited in their distribution within the UK to semi-enclosed water bodies
of relatively small spatial extent (sea lochs, Portland Harbour). In these circumstances,
effective habitat management to promote their survival is a feasible proposition. This
would involve monitoring of, and possibly regulation of, those human activities likely to
damage the species and communities of interest, namely the use of mobile fishing gear and
the discharge of organic material into the sea.
Examples of the Sea pens and burrowing megafauna biotope
complex existing in open sea areas (Clyde, Irish Sea, Minches, North Sea) may also be
subject to management, but any measures taken (eg. closure of areas to trawling) will come
within the context of fishery regulation, these areas being the major commercial Nephrops