Graham J. Edgar’s research while affiliated with University of Tasmania and other places

Diel partitioning of animals within ecological communities is widely acknowledged, yet rarely quantified. Investigation of most ecological patterns and processes involves convenient daylight sampling, with little consideration of the contributions of nocturnal taxa, particularly in marine environments. Here we assess diel partitioning of reef faunal assemblages at a continental scale utilizing paired day and night visual census across 54 shallow tropical and temperate reefs around Australia. Day–night differences were most pronounced in the tropics, with fishes and invertebrates displaying distinct and opposing diel occupancy on coral reefs. Tropical reefs in daytime were occupied primarily by fishes not observed at night (64% of all species sighted across day and night, and 71% of all individuals). By night, substantial emergence of invertebrates not otherwise detected during sunlit hours occurred (56% of all species, and 45% of individuals). Nocturnal emergence of tropical invertebrates corresponded with significant declines in the richness and biomass of predatory and herbivorous diurnal fishes. In contrast, relatively small diel changes in fishes active on temperate reefs corresponded to limited nocturnal emergence of temperate invertebrates. This reduced partitioning may, at least in part, be a result of strong top‐down pressures from fishes on invertebrate communities, either by predation or competitive interference. For shallow reefs, the diel cycle triggers distinct emergence and retreat of faunal assemblages and associated trophic patterns and processes, which otherwise go unnoticed during hours of regular scientific monitoring. Improved understanding of reef ecology, and management of reef ecosystems, requires greater consideration of nocturnal interactions. Without explicit sampling of nocturnal patterns and processes, we may be missing up to half of the story when assessing ecological interactions.

The abundance of herbivorous fishes is known to vary strongly with latitude. However, our understanding of this pattern is largely based on the examination of nominally herbivorous fishes (i.e. both herbivores and detritivores) as a single group. Therefore, we do not know how this collective classification may have confounded our understanding of distribution patterns, nor how different trophic pathways function across latitudes and associated temperature gradients. This constrains our ability to predict how tropicalising reefs may function as oceans warm, especially following range extensions of tropical taxa. Here, we explored the productivity of seven groups of roving nominally herbivorous fishes across eastern (34° of latitude; ~3800 km) and western (23°; ~2600 km) Australia, with specific consideration of the herbivore versus detritivore dichotomy across key spatial and environmental gradients. In terms of the total nominally herbivorous fish community, we found near-continuous declines in species richness with increasing distance from the equator, while total biomass and productivity were maintained across nearly 30° of latitude in eastern Australia. However, when we separated herbivores and detritivores, we found detritivore productivity dominated the tropics but declined abruptly in temperate regions, with this decline closely correlated with decreasing temperature in a synchronous manner along both coastlines. No such synchronous relationship was observed between herbivore productivity and temperature. These results highlight the importance of the herbivore versus detritivore division in understanding reef trophodynamics across latitudes, and the importance of understanding fish-based detritivory when predicting how the trophodynamic functioning of reefs may change along warming coastlines.

The services provided by the world’s coral reefs are threatened by increasingly frequent and severe marine heatwaves. Heatwave-induced degradation of reefs has often been inferred from the extent of the decline in total coral cover, which overlooks extreme variation among coral taxa in their susceptibility and responses to thermal stress. Here, we provide a continental-scale assessment of coral cover changes at 262 shallow tropical reef sites around Australia, using ecological survey data on 404 coral taxa before and after the 2016 mass bleaching event. A strong spatial structure in coral community composition along large-scale environmental gradients largely dictated how coral communities responded to heat stress. While heat stress variables were the best predictors of change in total coral cover, the pre-heatwave community composition best predicted the temporal beta-diversity index (an indicator of change in community composition over time). Indicator taxa in each coral community differed before and after the heatwave, highlighting potential winners and losers of climate-driven coral bleaching. Our results demonstrate how assessment of change in total cover alone may conceal very different responses in community structure, some of which showed strong regional consistency, and may provide a telling outlook of how coral reefs may reorganize in a warmer future.

Warming seas are expected to drive marine life poleward. However, few systematic observations confirm movement among entire communities at both warm and cool range edges. We analysed two continent-scale reef monitoring datasets to quantify changes in latitudinal range edges of 662 Australian shallow-water reef fishes and invertebrates over a decade punctuated by climate extremes. Temperate and tropical species both showed little net movement overall, with retreat often balancing expansion across the continent. Within regions, however, range edges shifted ~100 km per decade, on average, in the poleward or equatorward directions expected from warming or cooling. Although some species responded rapidly to temperature change, we found little evidence for mass poleward migration over the decade. Previous studies based on extreme species observations, rather than tracking all species through time, may have overestimated the prevalence, magnitude and longevity of range shifts amongst marine taxa.

Effective fisheries management requires accurate estimates of stock biomass and trends; yet, assumptions in stock assessment models generate high levels of uncertainty and error. For 230 fisheries worldwide, we contrasted stock biomass estimates at the time of assessment with updated hindcast estimates modeled for the same year in later assessments to evaluate systematic over- or underestimation. For stocks that were overfished, low value, or located in regions with rising temperatures, historical biomass estimates were generally overstated compared with updated assessments. Moreover, rising trends reported for overfished stocks were often inaccurate. With consideration of bias identified retrospectively, 85% more stocks than currently recognized have likely collapsed below 10% of maximum historical biomass. The high uncertainty and bias in modeled stock estimates warrants much greater precaution by managers.

Scientific working groups bring together experts from different disciplines and perspectives to tackle the "wicked problems" facing natural systems and society. Yet participants can feel overwhelmed or inadequate in groups within academic environments, which tends to be most acute at early career stages and in people from systematically marginalized backgrounds. Such feelings can block innovation that would otherwise arise from gaining the full spectrum of unique perspectives, knowledge and skills from a group. Drawing on personal experiences and relevant literature, we identify ten contribution strategies, ranging from generating ideas, analyzing data, and producing visuals to supporting facilitation. Next, we share approaches for an inclusive and supportive process, considering the roles of both participants and leads. Generating the most productive and relevant outcomes from working groups requires engaging the full team in a constructive and supportive environment. We advocate that adopting inclusive approaches that respect the diversity of personality types and perspectives will lead to more innovative solutions to achieve conservation and sustainability goals.

Marine protected areas (MPAs) are the most widely applied tool for marine biodiversity conservation, yet many gaps remain in our understanding of their species‐specific effects, partly because the socio‐environmental context and spatial autocorrelation may blur and bias perceived conservation outcomes. Based on a large data set of nearly 3000 marine fish surveys spanning all tropical regions of the world, we build spatially explicit models for 658 fish species to estimate species‐specific responses to protection while controlling for the environmental, habitat and socio‐economic contexts experienced across their geographic ranges. We show that the species responses are highly variable, with ~40% of fishes not benefitting from protection. When investigating how traits influence species' responses, we find that rare top‐predators and small herbivores benefit the most from MPAs while mid‐trophic level species benefit to a lesser extent, and rare large herbivores experience adverse effects, indicating potential trophic cascades.

Protection from direct human impacts can safeguard marine life, yet ocean warming crosses marine protected area boundaries. Here, we test whether protection offers resilience to marine heatwaves from local to network scales. We examine 71,269 timeseries of population abundances for 2269 reef fish species surveyed in 357 protected versus 747 open sites worldwide. We quantify the stability of reef fish abundance from populations to metacommunities, considering responses of species and functional diversity including thermal affinity of different trophic groups. Overall, protection mitigates adverse effects of marine heatwaves on fish abundance, community stability, asynchronous fluctuations and functional richness. We find that local stability is positively related to distance from centers of high human density only in protected areas. We provide evidence that networks of protected areas have persistent reef fish communities in warming oceans by maintaining large populations and promoting stability at different levels of biological organization.

Marine protected areas (MPAs) are widely used for ocean conservation, yet the relative impacts of various types of MPAs are poorly understood. We estimated impacts on fish biomass from no-take and multiple-use (fished) MPAs, employing a rigorous matched counterfactual design with a global dataset of >14,000 surveys in and around 216 MPAs. Both no-take and multiple-use MPAs generated positive conservation outcomes relative to no protection (58.2% and 12.6% fish biomass increases, respectively), with smaller estimated differences between the two MPA types when controlling for additional confounding factors (8.3% increase). Relative performance depended on context and management: no-take MPAs performed better in areas of high human pressure but similar to multiple-use in remote locations. Multiple-use MPA performance was low in high-pressure areas but improved significantly with better management, producing similar outcomes to no-take MPAs when adequately staffed and appropriate use regulations were applied. For priority conservation areas where no-take restrictions are not possible or ethical, our findings show that a portfolio of well-designed and well-managed multiple-use MPAs represents a viable and potentially equitable pathway to advance local and global conservation.

Aim The aim of this study was to define reef benthic habitat states and explore their spatial and temporal variability at a global scale using an innovative clustering pipeline. Location The study uses data on the transects surveyed on shallow (< 20m) reef ecosystems across the globe. Time period: Transects sampled between 2008 and 2021. Major taxa studied: Macroalgae, sessile invertebrates, hydrozoans, seagrass, corals. Methods Percentage cover was estimated for 24 functional groups of sessile biota and substratum from annotated underwater photoquadrats taken along 6,554 transects by scuba divers contributing to the Reef Life Survey dataset. A clustering pipeline combining a non-linear dimension-reduction technique ( UMAP ), with a density-based clustering approach ( HDBSCAN ), was used to identify benthic habitat states. Spatial and temporal variation in habitat distribution was then explored across ecoregions. Results The UMAP-HDBSCAN pipeline identified 17 distinct clusters representing different benthic habitats and gradients of ecological state. Certain habitat states displayed clear biogeographic patterns, predominantly occurring in temperate regions or tropical waters. Notably, some reefs dominated by turf algae were ubiquitous across latitudinal zones. Transition zones between temperate and tropical waters emerged as spatial hotspots of habitat state diversity. Temporal analyses revealed changes in the proportion of certain states over time, notably an increase in turf algae occurrence. Main Conclusions The UMAP-HDBSCAN clustering pipeline effectively characterised fine-scale benthic habitat states at a global scale, confirming known broader biogeographic patterns, including the importance of temperate-tropical transition zones as hotspots of habitat state diversity. This fine-scale, yet broadly-scalable habitat classification could be applied as a standardised template for tracking benthic habitat change across space and time at a global scale. The UMAP-HDBSCAN pipeline has proven to be a powerful and versatile approach for analysing complex biological datasets and can be applied in various ecological domains.