Jamison M. Gove

Ecosystem‐based fisheries management (EBFM) is increasingly recognized as an effective management strategy, especially in systems with dynamic components that have integrated responses to interacting drivers. Management targets therefore need to incorporate these complex dynamics, which may be accomplished by establishing targets based on the indicators. Here, we leverage existing data to evaluate the use of indicators in EBFM for nearshore ecosystems in Hawai‘i. We screened for potential nonlinearities in the spatial relationships between ecosystem indicators and environmental drivers over a 10‐year period, and assessed commonalities in identified indicator–driver thresholds. To understand how the ecosystem indicators relate to commonly used metrics in single‐species assessments, we also tested whether these relationships were consistent across species, species complexes, and functional groups. Gradient forests and generalized additive mixed models revealed detectable threshold relationships across five environmental drivers and six ecosystem indicators. Several indicators showed considerable overlap in threshold locations with common drivers, especially for rugosity (habitat complexity) and wave forcing. While some indicators comprising nested species, species complexes, and functional groups had comparable thresholds with a common driver, this was not always the case, highlighting the need for careful consideration when selecting indicators for management applications. We demonstrate the use of these thresholds in environmental drivers by evaluating them along a gradient of fish biomass. The use of multi‐model inference to incorporate multiple statistical methods to define the relationship between an ecosystem indicator and driver offers a quantitative basis for ecosystem management. Our results here provide a rubric by which to test for the existence of thresholds in indicator–driver relationships across spatial gradients and additionally identify clear thresholds for which to consider when managing fisheries.

The influence of depth and associated gradients in light, nutrients and plankton on the ecological organization of tropical reef communities was first described over six decades ago but remains untested across broad geographies. During this time humans have become the dominant driver of planetary change, requiring that we revisit historic ecological paradigms to ensure they capture the dynamics of contemporary ecological systems. Analysing >5,500 in-water reef fish surveys between 0 and 30 m depth on reef slopes of 35 islands across the Pacific, we assess whether a depth gradient consistently predicts variation in reef fish biomass. We reveal predictable ecological organization at unpopulated locations, with increased biomass of planktivores and piscivores and decreased primary consumer biomass with increasing depth. Bathymetric steepness also had a striking influence on biomass patterns, primarily for planktivores, emphasizing potential links between local hydrodynamics and the upslope propagation of pelagic subsidies to the shallows. However, signals of resource-driven change in fish biomass with depth were altered or lost for populated islands, probably due to depleted fish biomass baselines. While principles of depth zonation broadly held, our findings expose limitations of the paradigm for predicting ecological dynamics where human impacts confound connections between ecological communities and their surrounding environment.

Coral reef ecosystems are being fundamentally restructured by local human impacts and climate-driven marine heatwaves that trigger mass coral bleaching and mortality¹. Reducing local impacts can increase reef resistance to and recovery from bleaching². However, resource managers lack clear advice on targeted actions that best support coral reefs under climate change³ and sector-based governance means most land- and sea-based management efforts remain siloed⁴. Here we combine surveys of reef change with a unique 20-year time series of land–sea human impacts that encompassed an unprecedented marine heatwave in Hawai‘i. Reefs with increased herbivorous fish populations and reduced land-based impacts, such as wastewater pollution and urban runoff, had positive coral cover trajectories predisturbance. These reefs also experienced a modest reduction in coral mortality following severe heat stress compared to reefs with reduced fish populations and enhanced land-based impacts. Scenario modelling indicated that simultaneously reducing land–sea human impacts results in a three- to sixfold greater probability of a reef having high reef-builder cover four years postdisturbance than if either occurred in isolation. International efforts to protect 30% of Earth’s land and ocean ecosystems by 2030 are underway⁵. Our results reveal that integrated land–sea management could help achieve coastal ocean conservation goals and provide coral reefs with the best opportunity to persist in our changing climate.

Marine heatwaves are triggering coral bleaching events and devastating coral populations globally, highlighting the need to identify processes promoting coral survival. Here, we show that acceleration of a major ocean current and shallowing of the surface mixed layer enhanced localized upwelling on a central Pacific coral reef during the three strongest El Niño–associated marine heatwaves of the past half century. These conditions mitigated regional declines in primary production and bolstered local supply of nutritional resources to corals during a bleaching event. The reefs subsequently suffered limited post-bleaching coral mortality. Our results reveal how large-scale ocean-climate interactions affect reef ecosystems thousands of kilometers away and provide a valuable framework for identifying reefs that may benefit from such biophysical linkages during future bleaching events.

The influence of depth and associated gradients in light, nutrients, and plankton on the ecological organisation of tropical reef communities was first described over six decades ago but remains untested across broad geographies. Humans have also become the dominant driver of planetary change, requiring we re-visit historic ecological paradigms to ensure they capture the dynamics of contemporary ecological systems. Analysing >5,500 in-water reef fish surveys between 0–30 m depth across reef slopes at 35 islands in the Pacific, we assess whether a depth gradient consistently predicts variation in reef fish biomass. We reveal predictable ecological organisation in the absence of local human populations, with increased biomass of planktivores and piscivores, and decreased biomass of primary consumers with increasing depth. Bathymetric steepness also had a striking influence on biomass patterns, primarily for planktivores, emphasising potential links between local hydrodynamics and the upslope propagation of pelagic subsidies to the shallows. However, signals of resource-driven depth zonation were altered or lost at populated islands, likely due to depleted fish biomass baselines. While principles of depth zonation broadly held, our findings expose limitations of the paradigm for predicting ecological dynamics where human-mediated impacts confound the connections between ecological communities and their surrounding environment.

Coastal ecosystems are disproportionally inhabited by global human population. Consequently, human impacts originating from land and sea combine with climate-driven disturbances to fundamentally restructure nearshore marine ecosystems. These coincident human stressors are especially acute in the tropics where population centres concentrate along shorelines and marine heatwaves increasingly trigger mass coral bleaching and mortality. However, despite decades of research, we lack consensus as to whether local management supports coral reef resilience under climate change. Here we combined recurring reef surveys with a unique time series of land-sea human impacts over a 20-year period that encompassed an unprecedented marine heatwave in Hawaiʻi. Reefs with high fish biomass and reduced land-based impacts such as wastewater pollution had positive coral trajectories pre-disturbance and experienced minimal coral loss following severe heat stress. Concurrent land-sea management resulted in a 3- to 7-fold increase in the probability of a reef having high reef-builder cover four years post-disturbance. International efforts to conserve 30% of Earth’s ecosystems are gaining momentum, but do not intrinsically link land and ocean conservation targets. Our findings suggest coupled land-sea policy measures are required to realise global conservation goals and provide coral reefs with the best opportunity for persistence in our changing climate.

Corals are a major habitat-building life-form on tropical reefs that support a quarter of all species in the ocean and provide ecosystem services to millions of people. Marine heat waves continue to threaten and shape reef ecosystems by killing individual coral colonies and reducing their diversity. However, marine heat waves are spatially and temporally heterogeneous, and so too are the environmental and biological factors mediating coral resilience during and following thermal events. This combination results in highly variable outcomes at both the coral bleaching and mortality stages of every event. This, in turn, impedes the assessment of changing reef-scale patterns of thermal tolerance or places of resistance known as reef refugia. We developed a large-scale, high-resolution coral mortality monitoring capability based on airborne imaging spectroscopy and applied it to a major marine heat wave in the Hawaiian Islands. While water depth and thermal stress strongly mediated coral mortality, relative coral loss was also inversely correlated with preheat-wave coral cover, suggesting the existence of coral refugia. Subsequent mapping analyses indicated that potential reef refugia underwent up to 40% lower coral mortality compared with neighboring reefs, despite similar thermal stress. A combination of human and environmental factors, particularly coastal development and sedimentation levels, differentiated resilient reefs from other more vulnerable reefs. Our findings highlight the role that coral mortality mapping, rather than bleaching monitoring, can play for targeted conservation that protects more surviving corals in our changing climate.

Coral is the life-form that underpins the habitat of most tropical reef ecosystems, thereby supporting biological diversity throughout the marine realm. Coral reefs are undergoing rapid change from ocean warming and nearshore human activities, compromising a myriad of services provided to societies including coastal protection, fishing, and cultural practices. In the face of these challenges, large-scale operational mapping of live coral cover within and across reef ecosystems could provide more opportunities to address reef protection, resilience, and restoration at broad management- and policy-relevant scales. We developed an airborne mapping approach combining laser-guided imaging spectroscopy and deep learning models to quantify, at a large archipelago scale, the geographic distribution of live corals to 16-m water depth throughout the main Hawaiian islands. Airborne estimates of live coral cover were highly correlated with field-based estimates of live coral cover (R² = 0.94). Our maps were used to assess the relative condition of reefs based on live coral, and to identify potential coral refugia in the face of human-driven stressors, including marine heat waves. Geospatial modeling revealed that water depth, wave power, and nearshore development accounted for the majority (>60%) of live coral cover variation, but other human-driven factors were also important. Mapped interisland and intraisland variation in live coral location improves our understanding of reef geography and its human impacts, thereby guiding environmental management for reef resiliency. Significance Coral reefs are changing at unprecedented rates, and the majority of reefs are undergoing widespread losses in live coral cover. Management and policy development efforts focused on conserving and restoring coral reefs are hampered by a lack of geographically consistent and actionable high-resolution information on the specific location and extent of live coral. Based on an operational airborne technique, we developed and applied a live coral mapping capability across the main Hawaiian islands to identify potential coral refugia as well as reefs for potential coral restoration. Our findings inform current management actions across the archipelago and demonstrate the tactical role that live coral mapping can play to support decision-making at large ecological scales.

Life for many of the world’s marine fish begins at the ocean surface. Ocean conditions dictate food availability and govern survivorship, yet little is known about the habitat preferences of larval fish during this highly vulnerable life-history stage. Here we show that surface slicks, a ubiquitous coastal ocean convergence feature, are important nurseries for larval fish from many ocean habitats at ecosystem scales. Slicks had higher densities of marine phytoplankton (1.7-fold), zooplankton (larval fish prey; 3.7-fold), and larval fish (8.1-fold) than nearby ambient waters across our study region in Hawai‘i. Slicks contained larger, more well-developed individuals with competent swimming abilities compared to ambient waters, suggesting a physiological benefit to increased prey resources. Slicks also disproportionately accumulated prey-size plastics, resulting in a 60-fold higher ratio of plastics to larval fish prey than nearby waters. Dissections of hundreds of larval fish found that 8.6% of individuals in slicks had ingested plastics, a 2.3-fold higher occurrence than larval fish from ambient waters. Plastics were found in 7 of 8 families dissected, including swordfish (Xiphiidae), a commercially targeted species, and flying fish (Exocoetidae), a principal prey item for tuna and seabirds. Scaling up across an ∼1,000 km ² coastal ecosystem in Hawai‘i revealed slicks occupied only 8.3% of ocean surface habitat but contained 42.3% of all neustonic larval fish and 91.8% of all floating plastics. The ingestion of plastics by larval fish could reduce survivorship, compounding threats to fisheries productivity posed by overfishing, climate change, and habitat loss.