This record provides an overview of the scope and research output of NESP Marine Biodiversity Hub Project B4 - "Underpinning the repair and conservation of Australia’s threatened coastal-marine habitats". For specific data outputs from this project, please see child records associated with this metadata. -------------------- The primary objective of this project is to provide essential research to underpin restoration efforts to increase the success and efficiency of shellfish and saltmarsh repair. The secondary objective is to quantify clear easily understood benefits of repair to further increase groundswell, Indigenous and interest group support for repair efforts. For Phase 2 this involves: Shellfish reefs 1. Providing critical research to underpin the success of companion works investments into Sydney rock oyster (Saccostrea glomerata) restoration in Qld and NSW 2. Ongoing engagement with Indigenous groups, focused around especially SEQ and NSW to match the emphasis on Sydney rock oyster; 3. Through the Nature Conservancy, linking to shellfish restoration works in Port Phillip Bay (Vic), St Vincent’s Gulf (SA) and Oyster Harbour (WA) so that a National Business Case complete with examples of successes to date can be developed; 4. Underpinning this succinct business case with an information base for any follow-on activities such as assessment of shellfish reefs as an endangered community. Salt marshes 1. Estimating the benefits of salt marsh repair for an easily publicly understood indicator - prawn species. 2. Undertaking this work in NSW and Qld in parallel with proposed repair works so that very concrete case studies are available to demonstrate the benefits of repair. Planned Outputs Shellfish reef project outputs: • A scientific paper published in an eminent, peer-reviewed journal describing the ecology and biodiversity of shellfish reefs and biodiversity comparison against other marine habitats; • A scientific paper published in an eminent, peer-reviewed journal which identifies trajectories of change from past baselines to current condition and develops achievable targets for repair; • News stories, web articles, social media, brochures and oral presentations at national/international conferences, which communicate the key research findings to coastal stakeholders such as fishers, divers, NRM groups and government agencies; • News stories, web articles and social media which communicate the importance of shellfish reefs and shellfish food sources to Indigenous Australians; • Summary of community benefit and business propositions for coastal wetland repair expanding on the vision of a rejuvenated coastal ecology and written at the level required for input to various investors, agencies and public policy; • Updates at the end of 2016 as part of stakeholder engagement and continued communication. Salt marsh prawn productivity outputs: • A scientific paper published in an eminent, peer-reviewed journal quantifying and contrasting prawn productivity in healthy and degraded salt marsh communities in tropical and temperate environments; • Publicly accessible communication resources (brochures, social media, media releases and webpages) which articulate simply the prawn productivity values of salt marshes and links this to the need for the protection, conservation and restoration of degraded salt marsh communities.

Estimates of the value of habitats can provide an objective basis for the prioritisation of conservation and restoration actions. Bivalve habitats, three-dimensional structures made of high-densities of bivales (most often oysters or mussels), their shells and other organisms, used to be a dominant habitat found in temperate and subtropical coastal waters. These habitats, provide a suite of ecosystem services such as habitat provision and food supply for many species, substrate stabilisation and shoreline protection, and water quaility improvements through their filter feeding. Bivalve habitat restoration is increasingly seen as an opportunity to return lost ecosystem services. In Australia, there is growing interest in bivalve habitat restoration, but there is a knowledge gap in regards to the services they provide. Here, we determined the habitat value of a historically dominant oyster species in Australia, Saccostrea glomerata. At remnant soft-sediment oyster reefs at four locations we estimated density, biomass, productivity and composition of mobile macroinvertebrate communities and compared these with adjacent ‘bare’ soft sediments, which typically replace ecologically extinct oyster reefs. The oyster reefs had a distinct assemblage of macroinvertebrates, with 30% higher densities, 5 times the biomass and almost 5 times the productivity of adjacent bare sediments. Infauna macroinvertebrate productivity was more than twice as high below oyster reefs, suggesting these reefs facilitate infaunal productivity. Crustaceans, an important food source for small fishes, were 13 times more productive on oyster reefs compared to adjacent bare sediments. These results demonstrate that oyster reefs provide an important habitat for macroinvertebrates and that restoration efforts are likely to provide significant returns in enhanced productivity.

Policy and decision makers often seek guidance as to the benefits of conservation and repair of coastal seascapes, to justify and underpin any potential investments. Much is already known about the broad habitat and nursery values of seascapes among the science community, but there is also a need for estimation of clear and unambiguous market-based benefits that may arise from investment in repair. Recognising that this economic knowledge is imperfect for Australian seascapes, three case studies spanning tropical, subtropical and temperate environments explored the benefits in question. The case studies focus on saltmarsh habitats in particular, which have received very little investment in repair despite subtropical and temperate coastal saltmarsh listed as vulnerable ecological community under Australian Federal legislation. A subset of economically important species and conservative judgments were used to characterise the minimum potential economic benefit. For each of the case studies the conclusion was that while the biological information will remain imperfect, the business case for investment in the repair and conservation of coastal seascapes is compelling. We outline priorities for further research to make the business case more tangible to policy makers, stakeholders and the general public.

The threatened status of shellfish reefs has been well established globally (e.g Beck et al 2011) however the ecological consequences of these losses is still largely unknown. In Australia, shellfish reefs are one of the most imperilled marine habitat types (Gillies et al 2018), due to historical overharvest and widespread eutrophication of coastal waters through the use of fertilizers, livestock and human waste. Marine bivalves are important ecosystem engineers providing habitat, shelter and a food source for other species in benthic soft-sediment environments. In addition, filter-feeding bivalves link benthic and pelagic components of ecosystems through filtration and excretion. Through their filter feeding, they produce large amounts of faeces (digested seston) and pseudofaeces (rejected particles bound up in mucus) which are deposited on the benthos. This process brings energy and nutrients from the pelagic system to the benthic system (bentho-pelagic coupling). The removal of large quantities of seston can serve an important ecosystem function by improving water quality and clarity. The filtration of water performed by bivalves has been demonstrated to reduce water turbidity, improving light penetration and thereby enhancing growing conditions for seagrasses (Wall et al 2008). In systems where healthy populations of bivalves remain, they can filter a volume equivalent or larger than the entire estuary volume within the residence time of the water (zu Ermgassen et al 2013). While such densities of oysters are rare today, this highlights the critical ecosystem services that are lost when oyster reefs decline. Furthermore, it demonstrates the potential functions that can be regained through oyster reef restoration. Given the increasing awareness of the decline of these ecosystems, interest in restoration efforts to restore critical ecosystem functions has been growing. However, conservation and restoration decision making is underpinned by reliable quantification of relevant ecosystem services (zu Ermgassen et al 2016). For example, there are plans to restore some of the natural oyster reefs of Sydney Rock Oyster (Saccostrea glomerata) in Port Stephens, New South Wales. One of the main drivers motivating this restoration project is restoring lost ecosystem services. The filtration rates of Australian oysters has been demonstrated in aquarium studies using filtered water augmented with algae, yet little is known about filtration and biodeposition rates of oysters using raw seawater. In this study, we provide the first evaluation of the filtration and biodeposition rate of four species of bivalves using raw seawater, providing a proxy for natural biodeposition rates. As such, this study provides a first indication of the filtration/nutrient cycling function that may be restored following oyster restoration efforts.