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Many communities around the world face a pressing need to increase coastal resilience due to widespread coastal erosion and rising sea levels. Natural habitats such as mangrove forests have been increasingly recognised for their ability to protect coastlines through wave attenuation and sediment deposition and stabilisation. However, attempts to rehabilitate mangroves for coastal protection have been met with difficulties due to smaller windows of opportunity for seedling survival at sites experiencing high wave energy and erosion. In this study, we planted the mangrove Avicennia alba in planting pods (n = 348) deployed on an eroding shoreline in Singapore and compared survival to those planted in control plots. Several ecological factors that might influence A. alba survival were manipulated, such as life stage during planting, reduction of wrack accumulation, elevation, and post-planting maintenance. We found that mangrove pods significantly increased mangrove seedling survival. Planting older A. alba seedlings, reducing wrack accumulation, and deploying the pods at a higher elevation further increased survival. Additionally, pressure gauges deployed showed that the pods were able to attenuate wave energy, thus providing hydrodynamic shelter to mangroves. Hybrid living shorelines have the potential to facilitate mangrove rehabilitation through the alleviation of adverse environmental conditions, but other ecological requirements for mangrove seedling survival will need to be met to optimise rehabilitation efforts. [Display omitted] [ABSTRACT FROM AUTHOR]

The growing number of artificial structures in estuarine, coastal and marine environments is causing “ocean sprawl”. Artificial structures do not only modify marine and coastal ecosystems at the sites of their placement, but may also produce larger-scale impacts through their alteration of ecological connectivity - the movement of organisms, materials and energy between habitat units within seascapes. Despite the growing awareness of the capacity of ocean sprawl to influence ecological connectivity, we lack a comprehensive understanding of how artificial structures modify ecological connectivity in near- and off-shore environments, and when and where their effects on connectivity are greatest. We review the mechanisms by which ocean sprawl may modify ecological connectivity, including trophic connectivity associated with the flow of nutrients and resources. We also review demonstrated, inferred and likely ecological impacts of such changes to connectivity, at scales from genes to ecosystems, and potential strategies of management for mitigating these effects. Ocean sprawl may alter connectivity by: (1) creating barriers to the movement of some organisms and resources - by adding physical barriers or by modifying and fragmenting habitats; (2) introducing new structural material that acts as a conduit for the movement of other organisms or resources across the landscape; and (3) altering trophic connectivity. Changes to connectivity may, in turn, influence the genetic structure and size of populations, the distribution of species, and community structure and ecological functioning. Two main approaches to the assessment of ecological connectivity have been taken: (1) measurement of structural connectivity - the configuration of the landscape and habitat patches and their dynamics; and (2) measurement of functional connectivity - the response of organisms or particles to the landscape. Our review reveals the paucity of studies directly addressing the effects of artificial structures on ecological connectivity in the marine environment, particularly at large spatial and temporal scales. With the ongoing development of estuarine and marine environments, there is a pressing need for additional studies that quantify the effects of ocean sprawl on ecological connectivity. Understanding the mechanisms by which structures modify connectivity is essential if marine spatial planning and eco-engineering are to be effectively utilised to minimise impacts. [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]