Closing the gap between existing large-area imaging research and marine conservation needs.

Emerging technology has immense potential to increase the scale and efficiency of marine conservation. One such technology is large-area imaging (LAI), which relies on structure-from-motion photogrammetry to create composite products, including 3-dimensional (3-D) environmental models, that are larger in spatial extent than the individual images used to create them. Use of LAI has become widespread in certain fields of marine science, primarily to measure the 3D structure of benthic ecosystems and track change over time. However, the use of LAI in the field of marine conservation appears limited. We conducted a review of the coral reef literature on the use of LAI to identify research themes and regional trends in applications of this technology. We also surveyed 135 coral reef scientists and conservation practitioners to determine community familiarity with LAI, evaluate barriers practitioners face in using LAI, and identify applications of LAI believed to be most exciting or relevant to coral conservation. Adoption of LAI was limited primarily to researchers at institutions based in advanced economies and was applied infrequently to conservation, although conservation practitioners and survey respondents from emerging economies indicated they expect to use LAI in the future. Our results revealed disconnect between current LAI research topics and conservation priorities identified by practitioners, highlighting the need for more diverse, conservation-relevant research using LAI. We provide recommendations for how early adopters of LAI (typically Global North scientists from well-resourced institutions) can facilitate access to this conservation technology. These recommendations include developing training resources, creating partnerships for data storage and analysis, publishing standard operating procedures for LAI workflows, standardizing methods, developing tools for efficient data extraction from LAI products, and conducting conservation-relevant research using LAI.

Reducción de la brecha entre la investigación actual de imágenes de gran superficie y las necesidades de la conservación marina Resumen Las nuevas tecnologías tienen un enorme potencial para aumentar la escala y la eficiencia de la conservación marina. Una de ellas son las imágenes de gran superficie (IGS), que se basan en la fotogrametría de estructura a partir del movimiento para crear productos compuestos, incluidos modelos ambientales tridimensionales (3D), cuya extensión espacial es mayor que la de las imágenes individuales utilizadas para crearlos. El uso de las IGS se ha generalizado en determinados campos de las ciencias marinas, principalmente para medir la estructura tridimensional de los ecosistemas bentónicos y realizar un seguimiento de los cambios a lo largo del tiempo. Sin embargo, el uso de las IGS en el campo de la conservación marina parece limitado. Realizamos una revisión de la bibliografía sobre el uso de las IGS en los arrecifes de coral para identificar temas de investigación y tendencias regionales en las aplicaciones de esta tecnología. También encuestamos a 135 científicos de arrecifes de coral y profesionales de la conservación para determinar la familiaridad de la comunidad con las IGS, evaluar las barreras a las que se enfrentan los profesionales en el uso de las IGS e identificar sus aplicaciones consideradas como las más interesantes o relevantes para la conservación del coral. La adopción de las IGS se limitó principalmente a los investigadores de las instituciones con sede en las economías avanzadas y se aplicó con poca frecuencia a la conservación, aunque los profesionales de la conservación y los encuestados de las economías emergentes indicaron que esperan utilizar las IGS en el futuro. Nuestros resultados revelaron una desconexión entre los actuales temas de investigación de las IGS y las prioridades de conservación identificadas por los profesionales, lo que subraya la necesidad de una investigación más diversa y relevante para la conservación mediante el uso de las IGS.

Harnessing island-ocean connections to maximize marine benefits of island conservation.

Islands support unique plants, animals, and human societies found nowhere else on the Earth. Local and global stressors threaten the persistence of island ecosystems, with invasive species being among the most damaging, yet solvable, stressors. While the threat of invasive terrestrial mammals on island flora and fauna is well recognized, recent studies have begun to illustrate their extended and destructive impacts on adjacent marine environments. Eradication of invasive mammals and restoration of native biota are promising tools to address both island and ocean management goals. The magnitude of the marine benefits of island restoration, however, is unlikely to be consistent across the globe. We propose a list of six environmental characteristics most likely to affect the strength of land-sea linkages: precipitation, elevation, vegetation cover, soil hydrology, oceanographic productivity, and wave energy. Global databases allow for the calculation of comparable metrics describing each environmental character across islands. Such metrics can be used today to evaluate relative potential for coupled land-sea conservation efforts and, with sustained investment in monitoring on land and sea, can be used in the future to refine science-based planning tools for integrated land-sea management. As conservation practitioners work to address the effects of climate change, ocean stressors, and biodiversity crises, it is essential that we maximize returns from our management investments. Linking efforts on land, including eradication of island invasive mammals, with marine restoration and protection should offer multiplied benefits to achieve concurrent global conservation goals.

Evidence of Biological Self-Organization in Spatial Patterns of a Common Tropical Alga.

AbstractTropical reef communities contain spatial patterns at multiple scales, observable from microscope and satellite alike. Many of the smaller-scale patterns are generated physiologically (e.g., skeletal structures of corals at <1-m scale), while some of the larger patterns have been attributed to scale-dependent feedbacks (e.g., spur and groove reefs at 10-100-m scales). In describing the spatial patterning of reef benthic communities at landscape levels, we uncovered unique spatial patterning among living marine algae. Populations of the calcifying green alga Halimeda were observed to form a consistent polygonal pattern at a characteristic scale of 3-4 m. The pattern showed no clear evidence of having been formed through biologically created shifts in hydrodynamical conditions or related mechanisms. In considering the specifics of Halimeda growth patterns, a model of self-organization involving separation and patterned extension is proposed, a mechanism revealed in some geological pattern formation. This observation reinforces the diversity of pathways by which striking spatial patterns can occur in ecosystems.

Post-settlement demographics of reef building corals suggest prolonged recruitment bottlenecks.

For many organisms, early life stages experience significantly higher rates of mortality relative to adults. However, tracking early life stage individuals through time in natural settings is difficult, limiting our understanding of the duration of these 'mortality bottlenecks', and the time required for survivorship to match that of adults. Here, we track a cohort of juvenile corals (1-5 cm maximum diameter) from 12 taxa at a remote atoll in the Central Pacific from 2013 to 2017 and describe patterns of annual survivorship. Of the 537 juveniles initially detected, 219 (41%) were alive 4 years later, 163 (30%) died via complete loss of live tissue from the skeleton, and the remaining 155 (29%) died via dislodgement. The differing mortality patterns suggest that habitat characteristics, as well as species-specific features, may influence early life stage survival. Across most taxa, survival fit a logistic model, reaching > 90% annual survival within 4 years. These data suggest that mortality bottlenecks characteristic of 'recruitment' extend up to 5 years after individuals can be visually detected. Ultimately, replenishment of adult coral populations via sexual reproduction is needed to maintain both coral cover and genetic diversity. This study provides key insights into the dynamics and time scales that characterize these critical early life stages.

Automated 2D, 2.5D, and 3D Segmentation of Coral Reef Pointclouds and Orthoprojections.

Enabled by advancing technology, coral reef researchers increasingly prefer use of image-based surveys over approaches depending solely upon in situ observations, interpretations, and recordings of divers. The images collected, and derivative products such as orthographic projections and 3D models, allow researchers to study a comprehensive digital twin of their field sites. Spatio-temporally located twins can be compared and annotated, enabling researchers to virtually return to sites long after they have left them. While these new data expand the variety and specificity of biological investigation that can be pursued, they have introduced the much-discussed Big Data Problem: research labs lack the human and computational resources required to process and analyze imagery at the rate it can be collected. The rapid development of unmanned underwater vehicles suggests researchers will soon have access to an even greater volume of imagery and other sensor measurements than can be collected by diver-piloted platforms, further exacerbating data handling limitations. Thoroughly segmenting (tracing the extent of and taxonomically identifying) organisms enables researchers to extract the information image products contain, but is very time-consuming. Analytic techniques driven by neural networks offer the possibility that the segmentation process can be greatly accelerated through automation. In this study, we examine the efficacy of automated segmentation on three different image-derived data products: 3D models, and 2D and 2.5D orthographic projections thereof; we also contrast their relative accessibility and utility to different avenues of biological inquiry. The variety of network architectures and parameters tested performed similarly, ∼80% IoU for the genus Porites, suggesting that the primary limitations to an automated workflow are 1) the current capabilities of neural network technology, and 2) consistency and quality control in image product collection and human training/testing dataset generation.

Life history mediates the association between parasite abundance and geographic features.

Although parasites are ubiquitous in marine ecosystems, predicting the abundance of parasites present within marine ecosystems has proven challenging due to the unknown effects of multiple interacting environmental gradients and stressors. Furthermore, parasites often are considered as a uniform group within ecosystems despite their significant diversity. We aim to determine the potential importance of multiple predictors of parasite abundance in coral reef ecosystems, including reef area, island area, human population density, chlorophyll-a, host diversity, coral cover, host abundance and island isolation. Using a model selection approach within a database of more than 1,200 individual fish hosts and their parasites from 11 islands within the Pacific Line Islands archipelago, we reveal that geographic gradients, including island area and island isolation, emerged as the best predictors of parasite abundance. Life history moderated the relationship; parasites with complex life cycles increased in abundance with increasing island isolation, while parasites with direct life cycles decreased with increasing isolation. Direct life cycle parasites increased in abundance with increasing island area, although complex life cycle parasite abundance was not associated with island area. This novel analysis of a unique dataset indicates that parasite abundance in marine systems cannot be predicted precisely without accounting for the independent and interactive effects of each parasite's life history and environmental conditions.

Emerging insights on effects of sharks and other top predators on coral reefs.

Predation is ubiquitous on coral reefs. Among the most charismatic group of reef predators are the top predatory fishes, including sharks and large-bodied bony fishes. Despite the threat presented by top predators, data describing their realized effects on reef community structure and functioning are challenging to produce. Many innovative studies have capitalized on natural experimental conditions to explore predator effects on reefs. Gradients in predator density have been created by spatial patterning of fisheries management. Evidence of prey release has been observed across some reefs, namely that potential prey increase in density when predator density is reduced. While such studies search for evidence of prey release among broad groups or guilds of potential prey, a subset of studies have sought evidence of release at finer population levels. We find that some groups of fishes are particularly vulnerable to the effects of predators and more able to capitalize demographically when predator density is reduced. For example, territorial damselfish appear to realize reliable population expansion with the reduction in predator density, likely because their aggressive, defensive behavior makes them distinctly vulnerable to predation. Relatedly, individual fishes that suffer from debilitating conditions, such as heavy parasite loads, appear to realize relatively stronger levels of prey release with reduced predator density. Studying the effects of predators on coral reefs remains a timely pursuit, and we argue that efforts to focus on the specifics of vulnerability to predation among potential prey and other context-specific dimensions of mortality hold promise to expand our knowledge.

Brilliantia kiribatiensis, a new genus and species of Cladophorales (Chlorophyta) from the remote coral reefs of the Southern Line Islands, Pacific Ocean.

The marine green alga Brilliantia kiribatiensis gen. et sp. nov. is described from samples collected from the coral reefs of the Southern Line Islands, Republic of Kiribati, Pacific Ocean. Phylogenetic analysis of sequences of the large- and small-subunit rDNA and the rDNA internal transcribed spacer region revealed that Brilliantia is a member of the Boodleaceae (Cladophorales), containing the genera Apjohnia, Boodlea, Cladophoropsis, Chamaedoris, Phyllodictyon, and Struvea. Within this clade it formed a distinct lineage, sister to Struvea elegans, but more distantly related to the bona fide Struvea species (including the type S. plumosa). Brilliantia differs from the other genera by having a very simple architecture forming upright, unbranched, single-celled filaments attached to the substratum by a rhizoidal mat. Cell division occurs by segregative cell division only at the onset of reproduction. Based on current sample collection, B. kiribatiensis seems to be largely restricted to the Southern Line Islands, although it was also observed on neighboring islands, including Orona Atoll in the Phoenix Islands of Kiribati, and the Rangiroa and Takapoto Atolls in the Tuamotus of French Polynesia. This discovery highlights the likeliness that there is still much biodiversity yet to be discovered from these remote and pristine reefs of the central Pacific.

Correction: Quantifying Climatological Ranges and Anomalies for Pacific Coral Reef Ecosystems.

[This corrects the article DOI: 10.1371/journal.pone.0061974.].

Considering the rates of growth in two taxa of coral across Pacific islands.

Reef-building coral taxa demonstrate considerable flexibility and diversity in reproduction and growth mechanisms. Corals take advantage of this flexibility to increase or decrease size through clonal expansion and loss of live tissue area (i.e. via reproduction and mortality of constituent polyps). The biological lability of reef-building corals may be expected to map onto varying patterns of demography across environmental contexts which can contribute to geographic variation in population dynamics. Here we explore the patterns of growth of two common coral taxa, corymbose Pocillopora and massive Porites, across seven islands in the central and south Pacific. The islands span a natural gradient of environmental conditions, including a range of pelagic primary production, a metric linked to the relative availability of inorganic nutrients and heterotrophic resources for mixotrophic corals, and sea surface temperature and thermal histories. Over a multi-year sampling interval, most coral colonies experienced positive growth (greater planar area of live tissue in second relative to first time point), though the distributions of growth varied across islands. Island-level median growth did not relate simply to estimated pelagic primary productivity or temperature. However, at locations that experienced an extreme warm-water event during the sampling interval, most Porites colonies experienced net losses of live tissue and nearly all Pocillopora colonies experienced complete mortality. While descriptive statistics of demographics offer valuable insights into trends and variability in colony change through time, simplified models predicting growth patterns based on summarized oceanographic metrics appear inadequate for robust demographic prediction. We propose that the complexity of life history strategies among colonial reef-building corals introduces unique demographic flexibility for colonies to respond to a wide breadth of environmental conditions.

Modelling the linkage between coral assemblage structure and pattern of environmental forcing.

Geographical comparisons suggest that coral reef communities can vary as a function of their environmental context, differing not just in terms of total coral cover but also in terms of relative abundance (or coverage) of coral taxa. While much work has considered how shifts in benthic reef dynamics can shift dominance of stony corals relative to algal and other benthic competitors, the relative performance of coral types under differing patterns of environmental disturbance has received less attention. We construct an empirically-grounded numerical model to simulate coral assemblage dynamics under a spectrum of disturbance regimes, contrasting hydrodynamic disturbances (which cause morphology-specific, whole-colony mortality) with disturbances that cause mortality independently of colony morphology. We demonstrate that the relative representation of morphological types within a coral assemblage shows limited connection to the intensity, and essentially no connection to the frequency, of hydrodynamic disturbances. Morphological types of corals that are more vulnerable to mortality owing to hydrodynamic disturbance tend to grow faster, with rates sufficiently high to recover benthic coverage during inter-disturbance intervals. By contrast, we show that factors causing mortality without linkage to morphology, including those that cause only partial colony loss, more dramatically shift coral assemblage structure, disproportionately favouring fast-growing tabular morphologies. Furthermore, when intensity and likelihood of such disturbances increases, assemblages do not adapt smoothly and instead reveal a heightened level of temporal variance, beyond which reefs demonstrate drastically reduced coral coverage. Our findings highlight that adaptation of coral reef benthic assemblages depends on the nature of disturbances, with hydrodynamic disturbances having little to no effect on the capacity of reef coral communities to resist and recover with sustained coral dominance.

Meeting fisheries, ecosystem function, and biodiversity goals in a human-dominated world.

The worldwide decline of coral reefs necessitates targeting management solutions that can sustain reefs and the livelihoods of the people who depend on them. However, little is known about the context in which different reef management tools can help to achieve multiple social and ecological goals. Because of nonlinearities in the likelihood of achieving combined fisheries, ecological function, and biodiversity goals along a gradient of human pressure, relatively small changes in the context in which management is implemented could have substantial impacts on whether these goals are likely to be met. Critically, management can provide substantial conservation benefits to most reefs for fisheries and ecological function, but not biodiversity goals, given their degraded state and the levels of human pressure they face.

Decoding diversity in a coral reef fish species complex with restricted range using metagenomic sequencing of gut contents.

AIM: Identification of the processes that generate and maintain species diversity within the same region can provide insight into biogeographic patterns at broader spatiotemporal scales. Hawkfishes in the genus Paracirrhites are a unique taxon to explore with respect to niche differentiation, exhibiting diagnostic differences in coloration, and an apparent center of distribution outside of the Indo-Malay-Philippine (IMP) biodiversity hotspot for coral reef fishes. Our aim is to use next-generation sequencing methods to leverage samples of a taxon at their center of maximum diversity to explore phylogenetic relationships and a possible mechanism of coexistence. LOCATION: Flint Island, Southern Line Islands, Republic of Kiribati. METHODS: A comprehensive review of museum records, the primary literature, and unpublished field survey records was undertaken to determine ranges for four "arc-eye" hawkfish species in the Paracirrhites species complex and a potential hybrid. Fish from four Paracirrhites species were collected from Flint Island in the Southern Line Islands, Republic of Kiribati. Hindgut contents were sequenced, and subsequent metagenomic analyses were used to assess the phylogenetic relatedness of the host fish, the microbiome community structure, and prey remains for each species. RESULTS: Phylogenetic analyses conducted with recovered mitochondrial genomes revealed clustering of P. bicolor with P. arcatus and P. xanthus with P. nisus, which were unexpected on the basis of previous morphological work in this species complex. Differences in taxonomic composition of gut microbial communities and presumed prey remains indicate likely separation of foraging niches. MAIN CONCLUSIONS: Our findings point toward previously unidentified relationships in this cryptic species complex at its proposed center of distribution. The three species endemic to the Polynesian province (P. nisus, P. xanthus, and P. bicolor) cluster separately from the more broadly distributed P. arcatus on the basis of relative abundance of metazoan sequences in the gut (presumed prey remains). Discordance between gut microbial communities and phylogeny of the host fish further reinforce the hypothesis of niche separation.

Ecophysiology of coral reef primary producers across an upwelling gradient in the tropical central Pacific.

Upwelling is an important source of inorganic nutrients in marine systems, yet little is known about how gradients in upwelling affect primary producers on coral reefs. The Southern Line Islands span a natural gradient of inorganic nutrient concentrations across the equatorial upwelling region in the central Pacific. We used this gradient to test the hypothesis that benthic autotroph ecophysiology is enhanced on nutrient-enriched reefs. We measured metabolism and photophysiology of common benthic taxa, including the algae Porolithon, Avrainvillea, and Halimeda, and the corals Pocillopora and Montipora. We found that temperature (27.2-28.7°C) was inversely related to dissolved inorganic nitrogen (0.46-4.63 µM) and surface chlorophyll a concentrations (0.108-0.147 mg m-3), which increased near the equator. Contrary to our prediction, ecophysiology did not consistently track these patterns in all taxa. Though metabolic rates were generally variable, Porolithon and Avrainvillea photosynthesis was highest at the most productive and equatorial island (northernmost). Porolithon photosynthetic rates also generally increased with proximity to the equator. Photophysiology (maximum quantum yield) increased near the equator and was highest at northern islands in all taxa. Photosynthetic pigments also were variable, but chlorophyll a and carotenoids in Avrainvillea and Montipora were highest at the northern islands. Phycobilin pigments of Porolithon responded most consistently across the upwelling gradient, with higher phycoerythrin concentrations closer to the equator. Our findings demonstrate that the effects of in situ nutrient enrichment on benthic autotrophs may be more complex than laboratory experiments indicate. While upwelling is an important feature in some reef ecosystems, ancillary factors may regulate the associated consequences of nutrient enrichment on benthic reef organisms.

Foraging consistency of coral reef fishes across environmental gradients in the central Pacific.

We take advantage of a natural gradient of human exploitation and oceanic primary production across five central Pacific coral reefs to examine foraging patterns in common coral reef fishes. Using stomach content and stable isotope (δ15N and δ13C) analyses, we examined consistency across islands in estimated foraging patterns. Surprisingly, species within the piscivore-invertivore group exhibited the clearest pattern of foraging consistency across all five islands despite there being a considerable difference in mean body mass (14 g-1.4 kg) and prey size (0.03-3.8 g). In contrast, the diets and isotopic values of the grazer-detritivores varied considerably and exhibited no consistent patterns across islands. When examining foraging patterns across environmental contexts, we found that δ15N values of species of piscivore-invertivore and planktivore closely tracked gradients in oceanic primary production; again, no comparable patterns existed for the grazer-detritivores. The inter-island consistency in foraging patterns within the species of piscivore-invertivore and planktivore and the lack of consistency among species of grazer-detritivores suggests a linkage to different sources of primary production among reef fish functional groups. Our findings suggest that piscivore-invertivores and planktivores are likely linked to well-mixed and isotopically constrained allochthonous oceanic primary production, while grazer-detritivores are likely linked to sources of benthic primary production and autochthonous recycling. Further, our findings suggest that species of piscivore-invertivore, independent of body size, converge toward consuming low trophic level prey, with a hypothesized result of reducing the number of steps between trophic levels and increasing the trophic efficiency at a community level.

Diel population and functional synchrony of microbial communities on coral reefs.

On coral reefs, microorganisms are essential for recycling nutrients to primary producers through the remineralization of benthic-derived organic matter. Diel investigations of reef processes are required to holistically understand the functional roles of microbial players in these ecosystems. Here we report a metagenomic analysis characterizing microbial communities in the water column overlying 16 remote forereef sites over a diel cycle. Our results show that microbial community composition is more dissimilar between day and night samples collected from the same site than between day or night samples collected across geographically distant reefs. Diel community differentiation is largely driven by the flux of Psychrobacter sp., which is two-orders of magnitude more abundant during the day. Nighttime communities are enriched with species of Roseobacter, Halomonas, and Alteromonas encoding a greater variety of pathways for carbohydrate catabolism, further illustrating temporal patterns of energetic provisioning between different marine microbes. Dynamic diel fluctuations of microbial populations could also support the efficient trophic transfer of energy posited in coral reef food webs.

Insights into coral reef benthic dynamics from nonlinear spatial forecasting.

Nonlinear time-series forecasting, or empirical dynamic modelling, has been used extensively in the past two decades as a tool for distinguishing between random temporal behaviour and nonlinear deterministic dynamics. Previous authors have extended nonlinear time-series forecasting to continuous spatial data. Here, we adjust spatial forecasting to handle discrete data and apply the technique to explore the ubiquity of nonlinear determinism in irregular spatial configurations of coral and algal taxa from Palmyra Atoll, a relatively pristine reef in the central Pacific Ocean. We find that the spatial distributions of coral and algal taxa show signs of nonlinear determinism in some locations and that these signals can change through time. We introduce the hypothesis that nonlinear spatial determinism may be a signal of systems in intermediate developmental (i.e. successional) stages, with spatial randomness characterizing early (i.e. recruitment dominated) and late-successional (i.e. 'climax' or attractor) phases. Common state-based metrics that sum community response to environmental forcing lack resolution to detect dynamics of (potential) recovery phases; incorporating signal of spatial patterning among sessile taxa holds unique promise to elucidate dynamical characters of complex ecological systems, thereby enhancing study and response efforts.

Influence of aggregation on benthic coral reef spatio-temporal dynamics.

Spatial patterning of coral reef sessile benthic organisms can constrain competitive and demographic rates, with implications for dynamics over a range of time scales. However, techniques for quantifying and analysing reefscape behaviour, particularly at short to intermediate time scales (weeks to decades), are lacking. An analysis of the dynamics of coral reefscapes simulated with a lattice model shows consistent trends that can be categorized into four stages: a repelling stage that moves rapidly away from an unstable initial condition, a transient stage where spatial rearrangements bring key competitors into contact, an attracting stage where the reefscape decays to a steady-state attractor, and an attractor stage. The transient stage exhibits nonlinear dynamics, whereas the other stages are linear. The relative durations of the stages are affected by the initial spatial configuration as characterized by coral aggregation-a measure of spatial clumpiness, which together with coral and macroalgae fractional cover, more completely describe modelled reefscape dynamics. Incorporating diffusional processes results in aggregated patterns persisting in the attractor. Our quantitative characterization of reefscape dynamics has possible applications to other spatio-temporal systems and implications for reef restoration: high initial aggregation patterns slow losses in herbivore-limited systems and low initial aggregation configurations accelerate growth in herbivore-dominated systems.

Gradients in Primary Production Predict Trophic Strategies of Mixotrophic Corals across Spatial Scales.

Mixotrophy is among the most successful nutritional strategies in terrestrial and marine ecosystems. The ability of organisms to supplement primary nutritional modes along continua of autotrophy and heterotrophy fosters trophic flexibility that can sustain metabolic demands under variable or stressful conditions. Symbiotic, reef-building corals are among the most broadly distributed and ecologically important mixotrophs, yet we lack a basic understanding of how they modify their use of autotrophy and heterotrophy across gradients of food availability. Here, we evaluate how one coral species, Pocillopora meandrina, supplements autotrophic nutrition through heterotrophy within an archipelago and test whether this pattern holds across species globally. Using stable isotope analysis (δ13C) and satellite-derived estimates of nearshore primary production (chlorophyll-a, as a proxy for food availability), we show that P. meandrina incorporates a greater proportion of carbon via heterotrophy when more food is available across five central Pacific islands. We then show that this pattern is consistent globally using data from 15 coral species across 16 locations spanning the Caribbean Sea and the Indian and Pacific Oceans. Globally, surface chlorophyll-a explains 77% of the variation in coral heterotrophic nutrition, 86% for one genus across 10 islands, and 94% when controlling for coral taxonomy within archipelagos. These results demonstrate, for the first time, that satellite-derived estimates of nearshore primary production provide a globally relevant proxy for resource availability that can explain variation in coral trophic ecology. Thus, our model provides a pivotal step toward resolving the biophysical couplings between mixotrophic organisms and spatial patterns of resource availability in the coastal oceans.

Community-wide scan identifies fish species associated with coral reef services across the Indo-Pacific.

Determining whether many functionally complementary species or only a subset of key species are necessary to maintain ecosystem functioning and services is a critical question in community ecology and biodiversity conservation. Identifying such key species remains challenging, especially in the tropics where many species co-occur and can potentially support the same or different processes. Here, we developed a new community-wide scan (CWS) approach, analogous to the genome-wide scan, to identify fish species that significantly contribute, beyond the socio-environmental and species richness effects, to the biomass and coral cover on Indo-Pacific reefs. We found that only a limited set of species (51 out of approx. 400, approx. 13%), belonging to various functional groups and evolutionary lineages, are strongly and positively associated with fish biomass and live coral cover. Many of these species have not previously been identified as functionally important, and thus may be involved in unknown, yet important, biological mechanisms that help sustain healthy and productive coral reefs. CWS has the potential to reveal species that are key to ecosystem functioning and services and to guide management strategies as well as new experiments to decipher underlying causal ecological processes.