added 3 research items
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. undatum catches 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 rare M. modiolus reefs. 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. Edited By Alexander van Oudenhoven Edited By Alexander van Oudenhoven
Surveys by digital side-scan sonar, RoxAnnTM acoustic ground discrimination systems, multibeam echosounder and a sub-bottom profiling system showed that a Modiolus modiolus reef, in the Irish Sea off Pen Llŷn, north-west Wales, had a distinctive morphology and acoustic characteristics. The extent of the reef could therefore be determined and the benthic structure reliably mapped. The biogenic reef is in an area with moderately strong tidal currents and overlays lag gravel and cobbles with patchy sand veneers. The mussels form an undulating surface, orientated perpendicular to the current, with an average wavelength of 11.7 m and amplitude of 0.24 m that is significantly different from the surrounding seabed. Reef deposits reach a thickness of 1 m on top of the underlying lag gravels. The characteristic reef surface morphology helps distinguish the reef from the surrounding seabed on side-scan sonar and multibeam echosounder records and the undulations create the spatial complexity that influences the small-scale distribution of the associated epifauna, and infauna, reported in papers II and III of this series. The M. modiolus reef was recorded in the same location 40 y ago and has probably persisted there for over 150 y. Monitoring implications are discussed.
• Bivalve habitat restoration is growing in geographic extent and scale globally. While addressing the wide‐scale loss of these biogenic habitats is still a key motivation behind restoration efforts, stakeholders and funders are increasingly drawn to shellfish restoration for the many ecosystem services these habitats provide. • There is clear evidence for the provision of ecosystem services from species targeted for restoration in the USA, in particular Crassostrea virginica. Ecosystem services, however, remain largely unquantified or even undescribed for the majority of other species targeted for restoration. • A structured review of the literature was undertaken and supplemented by expert knowledge to identify which ecosystem services are documented in the following other bivalve species targeted for restoration: Ostrea edulis, Ostrea angasi, Crassostrea rhizophorae, Perna canaliculus, Modiolus modiolus, Mytilus edulis, Mytilus platensis, Crassostrea gigas, Ostrea denselamellosa, Crassostrea ariakensis, and Crassostrea sikamea. • Key knowledge gaps in quantifying ecosystem services and the ecosystem engineering properties of habitat‐building bivalves contributing to the provision of ecosystem services were identified. Ecosystem services with the potential to be widely applicable across bivalve habitat‐building species were identified. • Though there is evidence that many of the ecosystem engineering properties that underpin the provision of ecosystem services are universal, the degree to which services are provided will vary between locations and species. Species‐specific, in situ, studies are needed in order to avoid the inappropriate transfer of the ecosystem service delivery between locations, and to further build support and understanding for these emerging targets of restoration.
Globally, momentum to restore damaged habitats has been increasing. For example, the number of European shellfish restoration projects has quadrupled in the past 3 years. In line with the increasing focus on both restoration and climate change mitigation efforts, this study highlights how these two practices can complement each other. 2. This experimental study quantifies the active and passive sediment deposition associated with the European flat oyster (Ostrea edulis) and the organic and inorganic carbon fractions of the deposits. Treatments included ‘dead’, ‘live’, and control to account for (i) passive deposition, (ii) biodeposition and passive deposition, and (iii) background deposition respectively. By utilizing these data, the expected carbon deposition associated with a restored flat oyster bed was investigated. 3. The experiment was conducted ex situ, with natural seawater input. Covariate data on temperature, suspended particulate influx, salinity, and oxygen availability were recorded. Enhanced sedimentation (2.9 times) and organic carbon deposition (three times) were observed in the presence of living oysters, compared with the control. The shell structure of the oysters had no influence on passive sedimentation in this study. 4. By developing a full understanding of the ecosystem services (functioning, supporting, regulating, and cultural) provided by a habitat, it becomes possible to quantify overall ecosystem function. This evidence is key in advising policymakers, restoration funders, and marine spatial planners on the connection between keystone species restoration, ecosystem service restoration, and conservation management. 5. The enhancement of benthopelagic coupling by the European flat oyster, evidenced here for the first time, is contextualized from the perspective of quantification of ecosystem service provision for both restoration practices and blue carbon store management. The data produced in this study are discussed comparatively with work that has focused on other species from both Europe and the USA.
This study describes the impact of the first passage of two types of bottom-towed fishing gear on rare protected shellfish-reefs formed by the horse mussel Modiolus modiolus (L.). One of the study sites was trawled and the other was scallop-dredged. Divers collected HD video imagery of epifauna from quadrats at the two study sites and directed infaunal samples from one site. The total number of epifaunal organisms was significantly reduced following a single pass of a trawl (90%) or scallop dredge (59%), as was the diversity of the associated community and the total number of M. modiolus at the trawled site. At both sites declines in anthozoans, hydrozoans, bivalves, echinoderms and ascidians accounted for most of the change. A year later, no recovery was evident at the trawled site and significantly fewer infaunal taxa (polychaetes, malacostracans, bivalves and ophuroids) were recorded in the trawl track. The severity of the two types of impact reflected the undisturbed status of the habitats compared to previous studies. As a ‘priority habitat’ the nature of the impacts described on M. modiolus communities are important to the development of conservation management policy and indicators of condition in Marine Protected Areas (EU Habitats Directive) as well as indicators of ‘Good Environmental Status’ under the European Union Marine Strategy Framework Directive. Conservation managers are under pressure to support decisions with good quality evidence. Elsewhere, indirect studies have shown declines of M. modiolus biogenic communities in fishing grounds. However, given the protected status of the rare habitat, premeditated demonstration of direct impact is unethical or illegal in Marine Protected Areas. This study therefore provides a unique opportunity to investigate the impact from fishing gear whilst at the same time reflecting on the dilemma of evidence-based conservation management.
The spatial heterogeneity of epifauna on a Modiolus modiolus reef off north-west Wales was investigated using divers. The community associated with these horse mussels was similar to that described previously from Loch Creran and the north basin of Strangford Lough. Some differences in epifauna may be attributable to the less sheltered nature of the site. Modiolus modiolus numbers and the associated epifaunal community were significantly different between ridge and trough sub-habitats. Troughs can be considered ‘reduced’ ridge communities whereas ridges have high densities of horse mussels and certain sessile taxa were correlated with their abundance. Modiolus modiolus aggregation as a competitive response to the feeding environment, enhanced food availability on ridges and sediment deposition amongst mussel clumps may start to explain the undulating bed-form. Patchiness in community composition and periodic cover by ophuroids has implications when considering the monitoring of the horse mussel community. Stratified, in situ recording of the highly populated ridges could improve the statistical sensitivity of monitoring horse mussel reefs whilst simultaneously focusing on the more sensitive indicators of fishing threats.
Beds of Modiolus modiolus, in areas of moderate to strong tidal currents, develop into reefs with a relief of wave like undulations 0.09 – 0.45 m in amplitude and length scales of 6 – 18 m. Cores taken by diver operated suction sampler were targeted at positions on the ridges and troughs of a reef, in the Irish Sea off north-west Wales, allowing the fauna to be compared between adjoining ridges and troughs. Sessile epifauna was mostly attached to the larger mussels clumped together on the ridges. The crevice fauna and infauna were also nearly three times more abundant on the ridges, but the lists of species were similar from the two sub-habitats. Species richness was higher on the ridges, however, diversity and evenness measures were similar for ridges and trough samples. The Modiolus sub-habitats were found to be distinct from other macrofaunal assemblages in the wider southern Irish Sea. Deposition of faecal pellets in the spatially complex habitat amongst the mussels provided conditions suitable for an infauna more typical of inshore muddy sands enriched by organic matter. The scale of the ridge and trough morphology may increase variability between replicates when grabs are used remotely to sample this type of biogenic feature.