Courtney E. Stuart

Ecosystem restoration is expected to enhance ecosystem resilience to climate change, but few empirical and mechanistic demonstrations of such assertions exist. Here, we explore this topic for tropical atoll systems, combining science on nutrient subsidies and geo-ecological functions through a unifying ecological energetics lens. We show that native forest cover and seabird nutrient inputs increase primary productivity and secondary metabolism on islands and adjacent coral reefs, scaling with key ecosystem processes. We then demonstrate that seabird and native forest restoration could contribute to reducing island climate change vulnerability by (i) increasing reef accretion rates such that they keep pace with sea-level rise under a 2.0°C warming scenario, (ii) enhancing the production rate of sediment, which could contribute to island maintenance, and (iii) increasing vegetation fine root length, aiding island sediment stabilization. Collectively, our findings provide an integrated energetics and geo-ecological perspective that suggests rewilding of atolls can contribute to climate resilience.

Resolving how environmental conditions, phylogenetic history, functional traits, and random spatio-temporal effects influence coral reef fish assemblage structure is important for predicting and managing reef resilience in a changing ocean. Here, we used nearly 20 years of survey data from Moorea, French Polynesia, to quantify the relative contributions of these variables to occurrence patterns for 142 reef fish species. Applying a multivariate hierarchical joint species distribution model, we partitioned community-level variation in occurrence and identified residual species associations. Environmental covariates accounted for 88% of the explained variation in species’ occurrence at the community level, while random spatio-temporal effects accounted for the remaining 12%. Reef geomorphic zone (40%) and depth (18%) contributed most strongly, followed by seafloor curvature and distance to land (12% each). Conversely, pulse disturbances, including a tropical cyclone, marine heatwaves, and corallivorous starfish outbreaks, had limited community-wide effects (<5% each), with impacts largely restricted to territorial taxa and species dependent on live coral. Species’ responses to environmental conditions exhibited an intermediate phylogenetic signal, indicating partial niche conservatism among closely related taxa. Traits associated with foraging, locomotion, habitat use, and reproductive behaviour explained only 1% of variation in species’ occurrence and 8% of variation in species-specific environmental responses, suggesting generally weak trait-based structuring at the community level. Nevertheless, several trait-environment interactions were supported with ≥95% posterior probability, particularly for pulse disturbances and benthic substratum composition. Positive and negative residual co-occurrence was detected among 444 and 193 species pairs, respectively, suggesting potential interspecific interactions such as cooperative foraging and competition. Together, these results indicate that Moorea's reef fish community is structured primarily by persistent environmental conditions and phylogenetically conserved niche relationships, while functional trait variation and acute disturbances play more limited roles — findings with direct implications for conservation and restoration initiatives seeking to strengthen long-term reef resilience.

Pelagic‐feeding seabirds deliver nutrient subsidies that enhance the productivity, biodiversity, and resilience of terrestrial and marine ecosystems, particularly in nutrient‐poor tropical environments. However, the biogeophysical variables governing the fluxes of these nutrients within and among interconnected ecosystems remain poorly understood. To address this, we examined the spatial distribution of seabird‐vectored nutrients in the seascape of Tetiaroa, a semi‐enclosed coral atoll in French Polynesia, where seabird populations and associated nutrient cycles are recovering after recent rat eradication. We focus on the nitrogen isotope (δ¹⁵N) signatures of a dominant marine alga as evidence of seabird‐vectored nutrient uptake. Integrating stable isotope analysis within a seascape ecology framework, we show that breeding seabird biomass, depth, distance to land, geographic location within the atoll, and seafloor curvature drive spatial patterns of nutrient enrichment. Specifically, our models account for up to 88% of the variation in algal δ¹⁵N signatures and reveal peak enrichment in shallow, nearshore areas where water flow slows and converges due to localised seafloor curvature. These results extend previous research by highlighting seafloor geomorphology, notably curvature, as a modulator of fine‐scale nutrient delivery patterns. Although a complex model incorporating 11 high‐resolution biogeophysical variables enhanced spatial predictions by revealing fine‐scale variations, a simpler model using only five of these variables was comparably effective in capturing overall spatial trends. This study identifies the key seascape configuration and complexity characteristics likely to affect the spatial patterns of recovery potential following the restoration of seabird‐driven nutrient cycles, offering valuable guidance for ongoing restoration efforts in this coupled island‐reef system. Future investigations could assess how the effects of biogeophysical variables on nutrient delivery vary in magnitude and direction across different geographic, geological, and anthropogenic contexts.

Pelagic-feeding seabirds deliver nutrient subsidies that enhance the productivity, biodiversity, and resilience of terrestrial and marine ecosystems, particularly in nutrient-poor tropical environments. However, the biogeophysical variables governing the fluxes of these nutrients within and among interconnected ecosystems remain poorly understood. To address this, we examined the spatial distribution of seabird-vectored nutrients in the seascape of Tetiaroa, a semi-enclosed coral atoll in French Polynesia, where seabird populations and associated nutrient cycles are recovering after recent rat eradication. We focus on the nitrogen isotope (δ ¹⁵ N) signatures of a dominant marine alga as evidence of seabird-vectored nutrient uptake. Integrating stable isotope analysis within a seascape ecology framework, we show that breeding seabird biomass, depth, distance to land, geographic location within the atoll, and seafloor curvature drive spatial patterns of nutrient enrichment. Specifically, our models account for up to 88% of the variation in algal δ ¹⁵ N signatures and reveal peak enrichment in shallow, nearshore areas where water flow slows and converges due to localised seafloor curvature. These results extend previous research by highlighting seafloor geomorphology, notably curvature, as a modulator of fine-scale nutrient delivery patterns. Although a complex model incorporating 11 high-resolution biogeophysical variables enhanced spatial predictions by revealing fine-scale variations, a simpler model using only 5 of these variables was comparably effective in capturing overall spatial trends. This study identifies the key seascape configuration and complexity characteristics likely to affect the spatial patterns of recovery potential following the restoration of seabird-driven nutrient cycles, offering valuable guidance for ongoing restoration efforts in this coupled island-reef system. Future investigations could assess how the effects of biogeophysical variables on nutrient delivery vary in magnitude and direction across different geographic, geological, and anthropogenic contexts.

Context: Seascape connectivity refers to how the spatial configuration of marine habitats facilitates or hinders the movement of organisms, nutrients, materials or energy. Predicting and ranking potential connectivity among habitat patches for coral reef fishes helps to understand how reef fishes could utilize and connect multiple habitat types through the flow of nutrients, energy and biomass across the wider seascape during foraging movements. Objectives: To advance a spatially explicit understanding of connectivity linkages within a tropical atoll system by modeling, mapping and quantifying potential seascape connectivity for two locally abundant herbivorous reef fish species, the parrotfish, Chlorurus spilurus (pahoro hohoni or pa’ati pa’apa’a auahi), and the surgeonfish, Acanthurus triostegus (manini). Methods: We applied a two-step modeling approach by first mapping habitat suitability for the focal species. A graph-theoretic modeling technique was then applied to model and measure the contribution of benthic habitat patches to species-specific potential connectivity within the seascape. Results: Habitat suitability was higher and less fragmented for C. spilurus than for A. triostegus. Potential ecological connectivity estimates for C. spilurus were higher across the entire seascape, with differences between species likely driven by local-scale benthic habitat patch configuration and species home ranges. Hotspots of ecological connectivity across the atoll were mapped for both species. Conclusions: Despite advances in the application of graph-theoretic techniques in the coastal environment, few marine conservation and restoration measures currently integrate spatial information on ecological connectivity. This two-step spatial modeling approach holds great potential for rapid application of connectivity modeling at multiple spatial scales, which may predict ecological responses to conservation actions including active habitat restoration.

Coastal habitats have experienced significant degradation and fragmentation in recent decades under the strain of interacting ecosystem stressors. To maintain biodiversity and ecosystem functioning, coastal managers and restoration practitioners face the urgent tasks of identifying priority areas for protection and developing innovative, scalable approaches to habitat restoration. Facilitating these efforts are models of seascape connectivity, which represent ecological linkages across heterogeneous marine environments by predicting species-specific dispersal between suitable habitat patches. However, defining the suitable habitat patches and migratory pathways required to construct ecologically realistic connectivity models remains challenging. Focusing on two reef-associated fish species of the Florida Keys, United States of America (USA), we compared two methods for constructing species- and life stage-specific spatial models of habitat suitability—penalized logistic regression and maximum entropy (MaxEnt). The goal of the model comparison was to identify the modeling algorithm that produced the most realistic and detailed products for use in subsequent connectivity assessments. Regardless of species, MaxEnt’s ability to distinguish between suitable and unsuitable locations exceeded that of the penalized regressions. Furthermore, MaxEnt’s habitat suitability predictions more closely aligned with the known ecology of the study species, revealing the environmental conditions and spatial patterns that best support each species across the seascape, with implications for predicting connectivity pathways and the distribution of key ecological processes. Our research demonstrates MaxEnt’s promise as a scalable, species-specific, and spatially explicit tool for informing models of seascape connectivity and guiding coastal conservation efforts.

We explored patterns, rates, and unexpected socio‐ecological consequences of tooth replacement in serrasalmids and characids of the Peruvian Amazon using microCT. Of 24 specimens collected in February 2019—representing a mix of red‐bellied piranha Pygocentrus nattereri, redeye piranha Serrasalmus rhombeus, silver dollar fish Ctenobrycon hauxwellianus, and mojara Astyanax abramis—six individuals possessed edentulous jaw quadrants. On average, 22.9% of fish collected per day from these species featured incomplete dentition, a value three to five times higher than anticipated based on replacement rates estimated from captive fish—differences that may be driven by ontogeny, seasonality, or environmental quality.