Coral seeding may help sustain coral populations in a warming ocean; however, key knowledge gaps currently temper the successful application of this method across varied reef environments. This study investigated the survival and growth of three common coral species seeded on two device designs and deployed across a broad range of benthic communities in the Keppel Islands, southern inshore Great Barrier Reef. We examined the influence of algal cover and biomass, sedimentation, water flow, and temperature on seeding success after one year. Benthic communities at deployment sites ranged from coral to macroalgal dominated, yet site-level differences in survival were only detected for Acropora millepora on one device type. Coral survival and size were related to macroalgal biomass and/or cover (particularly Sargassum), sedimentation, water temperature, and water flow, and the patterns were species specific. Overall, Montipora aequituberculata demonstrated higher survival than A. millepora and A. muricata, consistent with a previous deployment in the region. Higher survival was also observed in a side compared to an upward-facing orientation. Survival increased with the number of A. millepora spat on fixed devices and A. muricata spat on tethered devices, suggesting positive density-dependent effects. This study highlights the complex, taxa-dependent ways in which seeded coral survival is influenced by device design, pre-deployment spat number, and deployment environment.

The 2023 Fourth Global Bleaching Event impacted coral reef ecosystems worldwide. At the Veracruz Reef System National Park (VRSNP), the mean monthly sea surface temperature in August reached 30.3 ºC, and the Degree Heating Weeks values were 15 ºC-weeks. Mass coral bleaching was seen soon after in early September. The aim of this study was to quantify the bleaching prevalence of the hermatypic coral community at the onset of the first mass coral bleaching event in the VRSNP. Bleaching prevalence was determined through the visual analysis of videotransects of the reef bottom at the Anegada de Adentro, Blanquilla, and Isla Verde reefs, at different depths. The bleaching prevalence of the coral community ranged from 31.3% at 12 m in the Anegada de Adentro reef to 73.7% at 12 m in Isla Verde reef, with an overall prevalence of 55.3% for the VRSNP. Bleaching affected 24 coral species. Those with the higher prevalences, like Siderastrea siderea (73.2%), Acropora cervicornis (66.5%), Orbicella faveolata (62.7%), and Montastraea cavernosa (62.5%), are also the dominant species in the VRSNP. Considering the available SST data gathered by the Coral Reef Watch program for the Veracruz virtual station, VRSNP’s corals bleached when the sea surface temperature reached 30.3 ºC, that is 0.5 ºC above the calculated bleaching threshold temperature (29.8 ºC).

Carbon (C) and nitrogen (N) are essential nutrients for coral–Symbiodiniaceae associations, yet global change can disrupt C and N acquisition by corals, affecting their resilience under stress. We investigated how two octocorals (Sarcophyton glaucum, Lobophytum sp.) and two hexacorals (Stylophora pistillata, Turbinaria reniformis) assimilate nitrogen from three 15N-labelled sources—dissolved free amino acids (DFAAs), Synechococcus (picoplankton), and Artemia salina nauplii (microplankton)—supplied at 1 µM N, under control (26 °C) and heat stress (30 °C) conditions. Corals were also incubated with natural pico-nanoplankton assemblages, with concentrations measured via flow cytometry. In addition, we measured the rates of photosynthesis and respiration, to estimate the relative contribution of autotrophy to the corals’ respiratory needs. Across all species, Synechococcus was the most efficiently assimilated N source, with uptake increasing under heat stress. Estimates of heterotrophic carbon assimilation (using C:N ratio) coupled with respiratory measurements showed that Synechococcus can provide 30–70% of the corals’ daily respiratory carbon demand, especially in the most heterotrophic species. Octocorals exhibited lower C and N assimilation rates than hexacorals, likely due to lower N needs and consistent with their overall lower metabolic requirements. Notably, S. glaucum displayed great flexibility in compensating reduced autotrophy through heterotrophy under heat stress. Incubations with natural plankton assemblages revealed increases in pico-nanoplankton concentrations in the presence of corals, likely stimulated by coral mucus release. These results demonstrate that picoplankton contributes significantly to both carbon and nitrogen budgets during heat stress and highlight species-specific nutritional strategies that may shape coral resilience under future climate conditions.

Abstract Despite extensive research on the western Pacific crown-of-thorns starfish (CoTS; Acanthaster cf. solaris ), especially from Australia’s Great Barrier Reef (GBR), there are persistent knowledge gaps that constrain understanding and management. Given renewed population irruptions of CoTS on the GBR, alongside escalating climate impacts and direct anthropogenic pressures, a quantitative assessment of knowledge gaps was undertaken to identify research priorities and guide future efforts. In this study, 27 experts independently scored 206 research questions across seven Themes and 39 topics, based on four different criteria ( Knowledge gap , Feasibility , Urgency , and Applicability ). These questions were ultimately rationalized into 170 distinct questions, with scores aggregated across merged questions. Management was the highest scoring Theme for Urgency , Applicability , and overall. All but six of the 20 top-ranked questions were from the Management Theme and mainly related to Culling and/ or Monitoring. Most questions (158 out of 170) also scored highly for Feasibility , suggesting that there are existing methods and technical capability available to advance the extensive and diverse range of research questions that were posed, if resources were made available. This quantitative assessment provides guidance on the prioritization of potential research that could improve management of CoTS populations to improve coral protection outcomes on the GBR. This study also suggests that there are limited constraints to undertaking necessary research to address many of the persistent knowledge gaps relating to CoTS.

Abstract In an era of increasing disturbances, understanding the capacity for coral reefs to recover and the drivers that underpin resilience is critical for predicting the health of future coral reefs. Traditional resilience paradigms for Western Atlantic reefs suggest that high herbivore biomass and low macroalgal cover are tenets of resilient systems. Yet, it is clear that some locations, such as Florida’s reefs, and potentially other locations, are not well explained by this paradigm. Here, we suggest that the proliferation and increased dominance of long-sediment-laden algal turfs (LSATs) create an additional negative feedback process that helps explain the compromised resilience of Florida’s reefs and further extends the existing Western Atlantic model. Collectively, coral mortality, reef flattening, and intense grazing appear to have created a series of negative feedback processes that reinforce a flat, sediment-laden benthos that impedes the recovery of already diminished coral populations. Importantly, feedbacks associated with LSATs could be strengthened in the presence of high herbivore biomass, thereby undermining foundational expectations of resilience based on grazing pressure alone. Here, we outline this destructive cycle and provide support for the mechanisms that drive these feedbacks. Although we focus on the ecological context of Florida’s reefs, our expansion of the conceptual framework will likely apply to other reef systems in the Caribbean with similar ecological attributes. Mounting evidence suggests that LSAT dominance represents a novel ecosystem state for Western Atlantic reefs.