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Coral bleaching is occurring more frequently as the climate changes, with multiple mass mortality events recently recorded on the Great Barrier Reef. Thermal stress coupled with high irradiance have previously been shown to be primary causes for coral bleaching. Therefore, a reduction in either of these pressures could reduce coral stress and eventual bleaching. Herein, we report the early development of a novel technology capable of reducing the amount of light entering a water body by ~20% in open ocean conditions. This mono-particle "sun shield" consists of an ultra-thin monolayer material and reflective calcium carbonate particles. The monolayer enables spreading of the particles into a thin film across the water surface, with only small amounts of material needed: 7.1 g/m2. A numerical modelling case study of residence times and the build-up of reactive oxygen stress in corals showed that the successful application of a stable film over the Lizard Island reef flat could reduce the reactive oxygen stress to below bleaching levels across approximately 1.5 km2 of reef area. With further development, mono-particle films such as this have the potential to be deployed over at-risk coral reefs at relatively small scales during predicted heatwave conditions, potentially reducing the severity of bleaching on coral reefs. [ABSTRACT FROM AUTHOR]

A range of new statistical approaches is being developed and/or adopted in ecotoxicology that, when combined, can greatly improve the estimation of no‐effect toxicity values from concentration–response (CR) experimental data. In particular, we compare the existing no‐effect‐concentration (NEC) threshold‐based toxicity metric with an alternative no‐significant‐effect‐concentration (NSEC) metric suitable for when CR data do not show evidence of a threshold effect. Using a model‐averaging approach, these metrics can be combined to yield estimates of N(S)EC and of their uncertainty within a single analysis framework. The outcome is a framework for CR analysis that is robust to uncertainty in the model formulation, and for which resulting estimates can be confidently integrated into risk assessment frameworks, such as the species sensitivity distribution (SSD). Integr Environ Assess Manag 2024;20:279–293. © 2023 Commonwealth of Australia and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key Points: Estimating concentrations of "no‐effect" of contaminants is critical to effective environmental risk assessment and management.Concentration–response (CR) data can take many forms and do not always exhibit the clear threshold responses required for no‐effect‐concentration (NEC) threshold‐based toxicity models to be validly applied.We compare the existing NEC threshold‐based toxicity metric with an alternative no‐significant‐effect‐concentration (NSEC) metric suitable for when CR data do not show evidence of a threshold effect.We demonstrate how, embedded in a model‐averaging approach, the NEC and NSEC can be combined in a single analysis to yield estimates of N(S)ECs and of their uncertainty. [ABSTRACT FROM AUTHOR]

Coral seeding is a promising intervention being tested and applied in global reef‐restoration efforts. However, high mortality of newly settled corals, particularly in degraded environments, is one of several hurdles to overcome to up‐scale this technique. Incorporating design features that mitigate drivers of mortality could increase coral‐seeding effectiveness. Here we tested five ceramic seeding‐device designs that incorporated various features intended to act as coral microrefugia. Devices seeded with Acropora tenuis spat were deployed to three sites on a shallow mid‐shelf reef on the central Great Barrier Reef (GBR), and survival was assessed after 219 days. Average yield (device‐level survival) was moderate across the device designs (22%) and all devices performed comparably. However, there was a nearly threefold increase in survival at one site compared with the other, similar sites less than 100 m away. Assessment of the benthic community around each device suggested that the sites hosted similar communities, although multivariate analyses identified a weak but significant positive relationship between survival and the first principal component (only 17% of variance), characterized by higher cover of sponges and epilithic algal communities. These results suggest that within‐reef scale variations (10s of meters) in environmental conditions, or variations in community constituents not investigated here (e.g. grazing fishes, mobile invertebrates), may impact the success of coral seeding. Further investigations into the drivers of coral survival at fine spatial scales, particularly abiotic conditions, are required to guide the placement of coral‐seeding devices and to predict their effectiveness. [ABSTRACT FROM AUTHOR]

Microorganisms are known to induce settlement or metamorphosis in a wide range of invertebrate species. The community structure of developing coral reef biofilms and the role they play in triggering metamorphosis of scleratin coral are studied.