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The success of oyster reef restoration can be enhanced by data on the distribution of remnant populations to inform the selection of suitable restoration locations. A quantitative polymerase chain reaction‐based environmental DNA (eDNA) assay was designed to provide distribution data for the oyster, Ostrea angasi, whose reefs are functionally extinct in Port Phillip Bay, Australia.Ostrea angasi eDNA accumulation and decay was measured in aquaria containing oysters in low and high densities, prior to testing the efficacy of the eDNA approach for detection of oysters at 15 field sites. Ostrea angasi eDNA accumulated significantly faster in aquaria where more individuals were present, while eDNA became undetectable 2–6 days after oysters were removed in low‐density treatments.The eDNA samples were successful at detecting O. angasi in the field when taken in close proximity of an oyster population. Increasing the sample number and volume could maximize oyster detection, demonstrating the potential of eDNA to identify suitable sites for the restoration of functionally extinct marine ecosystems. [ABSTRACT FROM AUTHOR]

Kelp beds are a defining feature of temperate reefs worldwide, playing a fundamental role as ecosystem engineers and primary producers. Overgrazing by the native sea urchin Heliocidaris erythrogramma has driven a phase shift from kelp beds of Ecklonia radiata to barrens across much of Port Phillip Bay, Victoria. Here, we present the results of a transplant experiment, which took juvenile E. radiata sporophytes from a source reef and attached them with silicon tubing to basalt tiles. Following an initial localized cull, we monitored the development and survival of individual E. radiata to investigate the drivers of loss during transplantation, including disturbance (control vs. procedural control), receiving environment (kelp canopy vs. no canopy), and translocation site (within vs. between reefs). We also investigated the role of holdfast reattachment and developmental stage on kelp survival. Sixty‐nine percent of the kelp transplants survived over the 17 weeks, with no increased loss resulting from transplantation to a reef 41 km away. We observed high survival of transplants in the absence of ongoing urchin exclusion. Furthermore, the provision of a canopy is not necessary and may result in adverse impacts on survival and development of juvenile sporophyte transplants presumably through competition for light. Individuals at the collection location (controls) were unlikely to survive to maturity suggesting their removal for transplanting is likely to have minimal impact on the kelp population of the donor reef. The methods used could be feasibly upscaled for rehabilitating or restoring kelp beds both in Port Phillip Bay and elsewhere. [ABSTRACT FROM AUTHOR]

Background and Aims Coastal protection from erosion and flooding is a significant ecosystem service provided by vegetated marine systems. Kelp beds are a dominant habitat-forming species on temperate reefs worldwide. While they are valued as hotspots of biodiversity, there is a paucity of information that supports their use in nature-based coastal defence. This includes the effectiveness of kelp beds in attenuating waves approaching the shore and how this influences sediment transport. Methods Wave loggers were deployed at paired kelp bed and control (urchin barren) treatments at four sites in Port Phillip Bay, Australia. The significant wave height offshore (exposed side) to onshore (sheltered side) of the treatment were compared to determine wave attenuation. Key Results At three sites, the wave attenuation of kelp beds was significantly less than that of the control. This result was consistent across the environmental conditions recorded in this study. At the fourth site, on average there was no significant difference in wave transmission between kelp and control. However, wave attenuation at kelp beds was 10 % greater than the control during periods of northerly winds. We highlight the importance of disentangling the effects of the reef substratum and kelp when evaluating the efficacy of kelp at providing coastal protection. Conclusions We have highlighted a significant gap in the research on ecosystem services provided by kelp beds. A greater understanding is needed on which kelp species are able to provide coastal protection, and under what conditions. Such future research is essential for providing managers and policy makers with actionable information on sustainable and cost-effective solutions for coastal defence when faced with a changing climate. [ABSTRACT FROM AUTHOR]