Biodiversity loss and degradation of natural habitats is increasing at an unprecedented rate. Of all marine habitats, biogenic reefs created by once-widespread shellfish, are now one of the most imperilled, and globally scarce. Conservation managers seek to protect and restore these habitats, but suitable baselines and indicators are required, and detailed scientific accounts are rare and inconsistent. In the present study the biodiversity of a model subtidal habitat, formed by the keystone horse mussel Modiolus modiolus (L.), was analysed across its Northeast Atlantic biogeographical range. Consistent samples of 'clumped' mussels were collected at 16 locations, covering a wide range of environmental conditions. Analysis of the associated macroscopic biota showed high biodiversity across all sites, cumulatively hosting 924 marine macroinvertebrate and algal taxa. There was a rapid increase in macroinvertebrate biodiversity (H') and community evenness (J) between 2 and 10 mussels per clump, reaching an asymptote at mussel densities of 10 per clump. Diversity declined at more northern latitudes, with depth and in coarser substrata with the fastest tidal flows. Diversity metrics corrected for species abundance were generally high across the habitats sampled, with significant latitudinal variability caused by current, depth and substrate type. Faunal community composition varied significantly between most sites and was difficult to assign to a 'typical' M. modiolus assemblage, being significantly influenced by regional environmental conditions, including the presence of algal turfs. Within the context of the rapid global increase in protection and restoration of bivalve shellfish habitats, site and density-specific values of diversity are probably the best targets for conservation management and upon which to base monitoring programmes.

Habitat restoration is an international priority. With this demand there is a need for ecological knowledge to underpin restoration projects to ensure their success and cost-effective delivery. This study is the first temperate marine restoration project to examine the role seasonality and location may have on restoration projects. The study found that the settlement of Serpula vermicularis, a rare biogenic reef forming species of conservation importance, was up to three times higher on materials deployed during July than other months. The results also found similar differences in settlement between restoration sites. These results suggest that the timing and location of a restoration effort could affect its overall success in the medium to long term. For the restoration of marine biogenic species of conservation importance, targeted spatial and temporal pre-restoration experiments can greatly increase a project's chance of success as well as making large-scale restoration programs more cost efficient.

Anthropogenic pressures on the marine environment have escalated and shellfish habitats have declined substantially around the world. Recently, Marine Protected Areas (MPAs) have rapidly increased in number, but management baselines rarely account for historical conditions. Marine examples of habitat restoration are therefore unusual. An interdisciplinary review of management baselines was undertaken for the Dornoch Firth protected area (NE Scotland) as well as three adjacent inlets and 50 km of open coastline. The protected area has low levels of industrial development, is sparsely populated, and previously achieved management objectives. Here we systematically searched for historical evidence of native oyster (Ostrea edulis) beds, a habitat now rare and of conservation importance throughout Atlantic Europe. Archaeological records, navigational charts, historical maps, museum collections, land-use records, fisheries records, public online databases and naturalists' records were searched. We conducted intertidal and subtidal surveys and sample oyster shells were radiocarbon dated. The combined interdisciplinary sources showed that O. edulis occurred in the inlets and open coast areas of NE Scotland, and specifically in the protected area: Probably since the end of the last glaciation to the late 1800s when they were likely over-fished. Present environmental conditions are also suitable for oyster restoration. Habitat restoration in protected areas is an emerging global theme. However, European oyster restoration effort is currently confined to remnant populations with a clear history of exploitation or dwindling associated fisheries. An interdisciplinary review of baselines will probably show scope for the restoration of O. edulis, for nature conservation, in many other European MPAs.

Limaria hiansfunctions as a keystone species in construction of a highly diverse biogenic habitat. An investigation to quantify the biodiversity of twoL. hiansbeds was carried out during the winter and summer seasons at two sites on the west coast of Scotland. Cores were taken semi-randomly through 100%L. hiansnest material, organisms removed, identified and enumerated. Univariate and multivariate analyses of the data were used to establish temporal and locational differences. A total of 7275 individuals were found representing 282 species from 16 phyla. Univariate analysis revealed significant differences between the species richness of the two populations, whilst multivariate analysis illustrated differences in the assemblage compositions between sites and times. This study showed that in terms of richness and diversity these beds are among the most important biogenic habitats in the UK.

The study aims to provide the first detailed account of the diversity and composition of the community associated with biogenic reefs formed by serpulid worms. Ten reefs (aggregations of calcareous Serpula vermicularis tubes), spanning a broad size-range, were collected from Loch Creran, Scotland, a Special Area of Conservation designated principally for the protection of its biogenic reefs. Total faunal abundance was strongly linearly related to reef weight, whilst taxon richness exhibited a hyperbolic relationship with reef size. 278 taxa were recorded from the ten reefs, with a reef of 0.1 m2 area supporting 163 taxa and 12756 individuals, which appears to represent considerable augmentation of diversity and abundance for sedimentary areas of the loch where the reefs occur. The reef assemblage was dominated by polychaetes (94 taxa), molluscs (70 taxa) and crustaceans (45 taxa). Species composition varied with reef size, although reefs greater than 25 cm width exhibited relatively little variation. In comparison with other biogenic polychaete habitats, S. vermicularis reefs appear to support a highly diverse community, which exhibits a high degree of similarity with that found in association with aggregations of the horse mussel, Modiolus modiolus. The presence of the Connemara clingfish, Lepadogaster candollei, rarely recorded at such a northerly latitude, on several reefs, indicates that the reef habitat may provide a stronghold for this species at the edge of its biogeographical range.

1. This study describes investigations into mapping of the biogenic reefs produced by the polychaete worm, Serpula vermicularis, for the purposes of conservation management.2. Reef distribution throughout Loch Creran, Scotland. was mapped using a diver transect technique and was found to be restricted to a peripheral band, with a mean upper limit of distribution of 2.7 m. The mean lower limit was found to decrease with distance from the mouth of the loch, with a lower limit of 9.3 in the lower basin rising to 6.6 m in the upper basing the likely influence of a corresponding decrease in the upper depth distribution of muds is discussed.3. Through determination of the mean width of the reef band and coastline length, the areal extent of the reef band was estimated as 108ha, revealing Loch Creran to harbour the most extensive known development of S. vermicularis reef habitat in the world.4. The utility of sidescan sonar in mapping serpulid reefs was examined in four of the major embayments. Reef material appeared as characteristic patterning on the sonargrams, with the morphology of individual larger reefs being discernible.5. Sidescan sonar was found to be particularly valuable for the identification and monitoring of threats to the conservation of serpulid reefs. Sidescan sonar surveying was found to facilitate identification of loss of habitat extent resulting from anthropogenic activities such as moorings, aquaculture installations and dredging and can also be used to monitor the potentially damaging activity of otter trawling. Further improvements in the mode of deployment of sidescan sonar are discussed. Copyright (C) 2008 John Wiley & Sons, Ltd.

This study aimed to contribute to conservation management of reefs of Serpula vermicularis by increasing understanding of the factors influencing larval settlement. The study was carried out in Loch Creran, which supports the most extensive known development of S. vermicularis reefs in the world. Settlement plates were deployed to examine the influence of season, depth, reef density, substrate type and orientation. Monthly deployment of plates revealed settlement of S. vermicularis to occur predominantly from mid-June to mid-October, peaking in late August to early September. Settlement of Pomatoceros spp. peaked much earlier, in late May to early June. Deployment of plates at different depths revealed a marked reduction in S. vermicularis settlement intensity between 6 and 12m. As this corresponds with the deeper limit of the peripheral fringe of serpulid reefs in the loch, it is suggested that this limit is imposed by a depth-correlated settlement response, rather than reduction in available substrata. Comparisons of various substrata showed a preference by S. vermicularis larvae for a slate over a scallop substrate and no evidence of enhanced recruitment to occupied or unoccupied tubes of S. vermicularis, suggesting that gregarious attraction is unlikely to be a factor causing reef formation. Settlement onto the upper side of a horizontal scallop substrate was found to be insignificant in comparison with the underside or a vertically orientated scallop. Evidence for the role of light in controlling the depth and substrate-orientation preferences of S. vermicularis larvae is discussed. Based on the results of this study, recommendations are made regarding remediation of areas suffering reef damage.

1. The large size, patchiness and fragility of serpulid reefs present difficulties for the measurement of reef coverage for mapping and monitoring studies. Video transect measures of cover are assessed in terms of accuracy and sensitivity of the method for the identification of spatial or temporal changes.2. By comparison with direct in situ measurement of reef cover, it was found that still photography was capable of providing an accurate means for the measurement of the seabed coverage by individual reefs.3. By comparison of video and still photographic measurement of reef cover, it was found that video transects were capable of providing cover estimates of sufficient accuracy for conservation purposes, differing from still photographic estimates by 0.3% cover.4. Power analysis was employed on replicate video estimates of reef cover in order to determine the degree of replication required to identify different levels of spatial or temporal change in cover using video transects of different lengths. The modest level of replication required to identify changes in coverage as small as 25% of the initial value suggests that the use of video transects offers great potential in monitoring and mapping studies. Copyright (C) 2002 John Wiley Sons, Ltd.