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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]

One of the paramount goals of oyster reef living shorelines is to achieve sustained and adaptive coastal protection, which requires meeting ecological (i.e., develop a self‐sustaining oyster population) and engineering (i.e., provide coastal defense) targets. In a large‐scale comparison along the Atlantic and Gulf coasts of the United States, the efficacy of various designs of oyster reef living shorelines at providing wave attenuation was evaluated accounting for the ecological limitations of oysters with regard to inundation duration. A critical threshold for intertidal oyster reef establishment is 50% inundation duration. Living shorelines that spent less than one‐half of the time (<50%) inundated were not considered suitable habitat for oysters, however, were effective at wave attenuation (68% reduction in wave height). Reefs that experienced >50% inundation were considered suitable habitat for oysters, but wave attenuation was similar to controls (no reef; ~5% reduction in wave height). Many of the oyster reef living shoreline approaches therefore failed to optimize the ecological and engineering goals. In both inundation regimes, wave transmission decreased with an increasing freeboard (difference between reef crest elevation and water level), supporting its importance in the wave attenuation capacity of oyster reef living shorelines. However, given that the reef crest elevation (and thus freeboard) should be determined by the inundation duration requirements of oysters, research needs to be refocused on understanding the implications of other reef parameters (e.g., width) for optimizing wave attenuation. A broader understanding of the reef characteristics and seascape contexts that result in effective coastal defense by oyster reefs is needed to inform appropriate design and implementation of oyster‐based living shorelines globally. [ABSTRACT FROM AUTHOR]

Oyster reef living shorelines have been proposed as an effective alternative to traditional coastal defence structures (e.g. bulkheads, breakwaters), with the benefit that they may keep pace with sea‐level rise and provide co‐benefits, such as habitat provision. However, there remains uncertainty about the effectiveness of shoreline protection provided by oyster reefs, which limits their broader application.We draw evidence from studies along the east and gulf coasts of the United States, where much research and implementation of oyster reef restoration has occurred, to better define the existing gaps in our understanding of the use of restored oyster reefs for shoreline protection.We find potential disconnects between ecological and engineering functions of reefs. In response, we outline how engineering and ecological principles are used in the design of oyster reef living shorelines and highlight knowledge gaps where an integration of these disciplines will lead to their more effective application.Synthesis and applications. This work highlights the necessary steps to advance the application of oyster reef living shorelines. Importantly, future research should focus on appropriate designs and conditions needed for these structures to effectively protect our coasts from erosion, while supporting a sustainable oyster population, thereby providing actionable nature‐based alternatives for coastal defence to diverse end‐users. This work highlights the necessary steps to advance the application of oyster reef living shorelines. Importantly, future research should focus on appropriate designs and conditions needed for these structures to effectively protect our coasts from erosion, while supporting a sustainable oyster population, thereby providing actionable nature‐based alternatives for coastal defence to diverse end‐users. [ABSTRACT FROM AUTHOR]

An innovative pervious concrete containing recycled oyster shells for artificial reef structures has been developed. The new artificial reef concrete incorporating oyster shells contained higher amounts of supplementary cementitious material and sea sand instead of river sand. Investigations on homogeneity, strength characteristics, pH levels and mussel larvae (Mytilus galloprovincialis) settlement were performed to verify the effectiveness of different constituents. The proposed concrete mixes have the potential for use in artificial reef construction representing improved characteristics with regards to weight, cost, environmental sustainability, carbon footprint and attachment of shellfish larvae to the reef, enabling nature-based coastal protection solutions, or 'living shorelines. • A pervious concrete containing recycled oyster shells for artificial reef structures developed. • The effect of using a high slag blend as well as sand type (river sand/sea sand) investigated. • Compressive strength, surface pH, carbonation and mussel larvae preferential tests performed. • Oyster shell waste can be used to create a biologically conductive substrate for artificial reefs. [ABSTRACT FROM AUTHOR]

Coastal areas are especially vulnerable to habitat loss, sea-level rise, and other climate change effects. Oyster-dominated eco-engineered reefs have been promoted as integral components of engineered habitats enhancing coastal resilience through provision of numerous ecological, morphological, and socio-economic services. However, the assessed 'success' of these eco-engineered oyster reefs remains variable across projects and locations, with their general efficacy in promoting coastal resilience, along with related services, often mixed at best. Understanding factors influencing the success of these eco-engineered habitats as valuable coastal management tools could greatly inform related future efforts. Here, we review past studies incorporating reef-building oysters for coastal resilience and enhanced ecosystem services. Our aims are to better understand their utility and limitations, along with critical knowledge gaps to better advance future applicability. Success depends largely on site selection, informed by physical, chemical and biological factors, and adjacent habitats and bottom types. Better understanding of oyster metapopulation dynamics, tolerance and adaptation to changing conditions, and interactions with adjacent habitats will help to better identify suitable locations, and design more effective eco-engineered reefs. These eco-engineered reefs provide a useful tool to assist in developing coastal resilience in the face of climate change and sea level rise. • Oyster-dominated reefs have been promoted as integral components of engineered habitats for reducing coastal vulnerability. • Oyster reefs can be a useful tool in our toolkit for achieving ecological, morphological and socio-economic benefits. • Understanding the factors influencing the success of these eco-engineered habitats could greatly inform related future efforts. • Oyster reefs can support coastal resilience in the face of climate change and related rising sea-levels [ABSTRACT FROM AUTHOR]