Search

Benthic marine invertebrates, such as oysters, rely on larval recruitment for their populations to persist. This can be by self‐recruitment to the natal population or recruitment from geographically distant populations.Marine invertebrate larvae are increasingly understood to influence their dispersal through vertical migrations, based on a combination of responses to external cues and the larvae's ontogenetic stage.This study examined the larval behaviour of the European oyster Ostrea edulis in laboratory experiments. The aim was to establish if larvae show systematic behaviour that could affect dispersal. Vertical distribution, swimming speeds, and behaviour of O. edulis larvae were quantified throughout their ontogenetic development, and under scenarios of light/dark, food/no food, and two temperatures.Most O. edulis larvae concentrated at the bottom of the aquarium, independent of developmental stage or treatment, and consistently over time. Larvae behaved actively in ~50% of all bottom observations, indicating a behavioural function other than resting. At the surface, larvae frequently formed aggregations. In the water column, larvae swam with high vertical directionality and their distribution was homogenous. Swimming speeds ranged from 0.001 to 9.07 mm s−1.Advection close to the seabed is slower than in any other part of the water column. The demersal preference of O. edulis may be targeted towards increasing the likelihood of self‐recruitment, which is consistent with the larvae's preference to settle in the presence of conspecifics. Stronger hydrodynamic environments are likely to override the larvae's demersal behaviour. It is recommended to restore European oyster beds at sufficient scale, density, and rugosity to promote retention of larvae within the natal population and minimize larval loss and mortality, as well as to account for the observed behaviours in networks of restoration sites. [ABSTRACT FROM AUTHOR]

Modiolus modiolus L. (horse mussel) reefs are a priority marine habitat of high conservation value that is currently listed as endangered and/or threatened across its European distribution. Population structure, density or shell morphology may influence the biodiversity of a reef, either directly or indirectly. Thus, such metrics are important considerations for successful conservation management of these biodiversity hotspots. Population structure, shell morphology and growth rates were examined in M. modiolus reefs across the UK range of the habitat to examine differences between key populations, including those near the Lleyn Peninsula in Wales (southern range), off Port Appin in Western Scotland (mid-range) and in Scapa Flow in the Orkney Isles, Scotland (northern range). Additionally, the influence of physical conditions (temperature and tidal flow) to growth rate and predicted maximum shell length for each population was examined. Growth rates were determined using acetate peels of sectioned shells. Lower juvenile abundance was observed in Scapa Flow. Small, narrow-shaped shells were found to be characteristic of North Lleyn mussels, and larger, globular-shaped shells were characteristic of mussels in Scapa Flow and off Port Appin. Mussels in Scapa Flow were slower growing, yet reached a longer asymptotic length (L ∞) than mussels of Port Appin and North Lleyn. Growth curves from sites within this study were analysed with other published data. A trend of higher L ∞ at higher latitudes and at lower flow rates was observed. Variations in growth and age are discussed in relation to flow regimes, connectivity to other reefs, density and latitude. [ABSTRACT FROM AUTHOR]

Demonstrating the benefits that marine ecosystems provide to society can support marine spatial planning and enhance the protection of fragile, biodiverse habitats. However, the importance of ecosystem services provided by such habitats is rarely accounted for in spatial management due to a lack of detailed information. The present study investigated the ‘habitat provision’ ecosystem service delivered by horse mussel (Modiolus modiolus(L.)) reefs, a ‘Priority Marine Habitat’ in the NE Atlantic. By working with local fishers, the abundance and demographics of commercially important whelks (Buccinum undatum) were examined.B. undatumcatches were three times higher on reef sites and a greater number of smaller individuals were caught on the reefs compared to off-reef habitats. We therefore show that these productive and physically complex mussel reefs are important feeding and nursery areas for whelks, demonstrating the ‘essential fish habitat’ value of the now rareM. modiolusreefs. The results are discussed in the context of marine spatial planning and the potential for historically more widespread shellfish habitats to have been capable of providing substantial ecosystem services. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Horse mussel ( Modiolus modiolus ) shellfish reefs are a threatened and declining habitat in the North East Atlantic and support high levels of biodiversity. Shellfish can influence the surrounding water column and modify the quality of material that reaches the seabed by filtering water, actively depositing particles and changing the benthic boundary layer due to surface roughness. In the present study M. modiolus biodeposition was measured in a field location for the first time. The results show that M. modiolus enhance sedimentation and contribute to the downward flux of material to the seabed. Approximately 30% of the total sediment deposition was attributed to active filter feeding and overall, the presence of horse mussels enhanced deposition two fold. The results are discussed in terms of the potential for horse mussel reefs to provide ecosystem services to society, through functions such as benthopelagic coupling and sediment stabilisation. Highlighting the societal benefits supplied by marine habitats can help prioritise conservation efforts and feed into the sustainable management of coastal water bodies. [ABSTRACT FROM AUTHOR]