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The article offers information on a study regarding impaired recovery of the Great Barrier Reef (GBR) under cumulative stress. It mentions that that loss of recovery capacity was partly explained by the cumulative effects of chronic pressures including water quality and sublethal effects of disturbances. It states that recovery of digitate acroporids and pocilloporids is sensitive to physical damage, while branching and tabular acroporids are sensitive to chronic effects of thermal stress.

Abstract: Australia's Great Barrier Reef (GBR) is under pressure from a suite of stressors including cyclones, crown‐of‐thorns starfish (COTS), nutrients from river run‐off and warming events that drive mass coral bleaching. Two key questions are: how vulnerable will the GBR be to future environmental scenarios, and to what extent can local management actions lower vulnerability in the face of climate change? To address these questions, we use a simple empirical and mechanistic coral model to explore six scenarios that represent plausible combinations of climate change projections (from four Representative Concentration Pathways, RCPs), cyclones and local stressors. Projections (2017–2050) indicate significant potential for coral recovery in the near‐term, relative to current state, followed by climate‐driven decline. Under a scenario of unmitigated emissions (RCP8.5) and business‐as‐usual management of local stressors, mean coral cover on the GBR is predicted to recover over the next decade and then rapidly decline to only 3% by year 2050. In contrast, a scenario of strong carbon mitigation (RCP2.6) and improved water quality, predicts significant coral recovery over the next two decades, followed by a relatively modest climate‐driven decline that sustained coral cover above 26% by 2050. In an analysis of the impacts of cumulative stressors on coral cover relative to potential coral cover in the absence of such impacts, we found that GBR‐wide reef performance will decline 27%–74% depending on the scenario. Up to 66% of performance loss is attributable to local stressors. The potential for management to reduce vulnerability, measured here as the mean number of years coral cover can be kept above 30%, is spatially variable. Management strategies that alleviate cumulative impacts have the potential to reduce the vulnerability of some midshelf reefs in the central GBR by 83%, but only if combined with strong mitigation of carbon emissions. [ABSTRACT FROM AUTHOR]

Australia’s iconic Great Barrier Reef (GBR) continues to suffer from repeated impacts of cyclones, coral bleaching, and outbreaks of the coral-eating crown-of-thorns starfish (COTS), losing much of its coral cover in the process. This raises the question of the ecosystem’s systemic resilience and its ability to rebound after large-scale population loss. Here, we reveal that around 100 reefs of the GBR, or around 3%, have the ideal properties to facilitate recovery of disturbed areas, thereby imparting a level of systemic resilience and aiding its continued recovery. These reefs (1) are highly connected by ocean currents to the wider reef network, (2) have a relatively low risk of exposure to disturbances so that they are likely to provide replenishment when other reefs are depleted, and (3) have an ability to promote recovery of desirable species but are unlikely to either experience or spread COTS outbreaks. The great replenishment potential of these ‘robust source reefs’, which may supply 47% of the ecosystem in a single dispersal event, emerges from the interaction between oceanographic conditions and geographic location, a process that is likely to be repeated in other reef systems. Such natural resilience of reef systems will become increasingly important as the frequency of disturbances accelerates under climate change. [ABSTRACT FROM AUTHOR]

Controlling the spread of invasive species, pests, and pathogens is often logistically limited to interventions that target specific locations at specific periods. However, in complex, highly connected systems, such as marine environments connected by ocean currents, populations spread dynamically in both space and time via transient connectivity links. This results in nondeterministic future distributions of species in which local populations emerge dynamically and concurrently over a large area. The challenge, therefore, is to choose intervention locations that will maximize the effectiveness of the control efforts. We propose a novel method to manage dynamic species invasions and outbreaks that identifies the intervention locations most likely to curtail population expansion by selectively targeting local populations most likely to expand their future range. Critically, at any point during the development of the invasion or outbreak, the method identifies the local intervention that maximizes the long-term benefit across the ecosystem by restricting species' potential to spread. In so doing, the method adaptively selects the intervention targets under dynamically changing circumstances. To illustrate the effectiveness of the method we applied it to controlling the spread of crown-of-thorns starfish ( Acanthaster sp.) outbreaks across Australia's Great Barrier Reef. Application of our method resulted in an 18-fold relative improvement in management outcomes compared with a random targeting of reefs in putative starfish control scenarios. Although we focused on applying the method to reducing the spread of an unwanted species, it can also be used to facilitate the spread of desirable species through connectivity networks. For example, the method could be used to select those fragments of habitat most likely to rebuild a population if they were sufficiently well protected. [ABSTRACT FROM AUTHOR]

For many ecosystem services, it remains uncertain whether the impacts of climate change will be mostly negative or positive and how these changes will be geographically distributed. These unknowns hamper the identification of regional winners and losers, which can influence debate over climate policy. Here, we use coral reefs to explore the spatial variability of climate stress by modelling the ecological impacts of rising sea temperatures and ocean acidification, two important coral stressors associated with increasing greenhouse gas ( GHG) emissions. We then combine these results with national per capita emissions to quantify inequities arising from the distribution of cause ( CO2 emissions) and effect (stress upon reefs) among coral reef countries. We find pollution and coral stress are spatially decoupled, creating substantial inequity of impacts as a function of emissions. We then consider the implications of such inequity for international climate policy. Targets for GHG reductions are likely to be tied to a country's emissions. Yet within a given level of GHG emissions, our analysis reveals that some countries experience relatively high levels of impact and will likely experience greater financial cost in terms of lost ecosystem productivity and more extensive adaptation measures. We suggest countries so disadvantaged be given access to international adaptation funds proportionate with impacts to their ecosystem. We raise the idea that funds could be more equitably allocated by formally including a metric of equity within a vulnerability framework. [ABSTRACT FROM AUTHOR]

Many ecosystems suffer systemwide outbreaks of damaging species propagating from primary outbreak sites. Connectivity patterns can identify parts of the ecosystem that help turn local outbreaks into a systemwide contagion through a series of transmission events. Here, we show that patterns of larval connectivity among reefs can help explain periodic crown-of-thorns starfish ( COTS) epidemics across the Great Barrier Reef ( GBR)., We simulated potential dispersal of COTS larvae to obtain a connectivity network of coral reefs across the entire GBR. Network analysis revealed areas of high local connectivity where any outbreaks could be amplified locally, as well as those areas with potential to cause large-scale epidemics with ecosystem-wide impacts., We find that the regions where COTS epidemics are known to originate are predictable from their high local and systemwide connectivity. Extensive larval exchanges among reef clusters in these regions can start a chain reaction of COTS population build-up. The same regions also have high potential to reach and affect other parts of the GBR, thereby maximizing the likelihood that any outbreaks would eventually propagate throughout the ecosystem., Hydrodynamic properties and geography of the GBR make it vulnerable to COTS epidemics. Using network analysis to identify regions with high-risk high-impact sources could help control these devastating events in future., Synthesis and applications. The observed centre of origin for COTS epidemics (the Cooktown-Cairns region) can be predicted from its elevated short- and long-range levels of larval connectivity. Connectivity analysis of per-reef risks provides spatially explicit targets to guide surveillance and control measures that might help curtail COTS epidemics through prioritization of highly connected reefs. The analytical approach developed here for COTS connectivity can also be applied to identify well-connected patches and regions in other interconnected ecological systems. [ABSTRACT FROM AUTHOR]

Ecosystem management frequently aims to manage resilience yet measuring resilience has proven difficult. Here, we quantify the ecological resilience of the largest reef in the Caribbean and map potential benefits of marine reserves under two scenarios of greenhouse gas emissions. Resilience is calculated using spatial ecological models and defined as the probability of a reef remaining in its coral-dominated basin of attraction such that it does not flip into an alternate, algal-dominated attractor. In practice, resilience is the probability that coral populations will maintain the ability to exhibit a recovery trend after acute disturbances such as hurricanes. The inputs required to estimate resilience are a reef's initial state, physical environment, and disturbance regime. One major driver of reef resilience is herbivory by parrotfish and recent action to protect parrotfish in Belize was found to have increased resilience 6-fold. However, the expected benefits of parrotfish protection to future coral cover were relatively modest with only a 2- to 2.6-fold improvement over a business-as-usual scenario, demonstrating how resilience and ecosystem states are decoupled. Global action to reduce greenhouse gas emissions had little impact on average coral state unless it was accompanied by local controls of fishing. However, combined global and local action reduced the rate of reef degradation threefold. Operationalizing resilience explicitly integrates available biophysical data and accommodates the complex interactions among ecological processes and multiple types of disturbance. [ABSTRACT FROM AUTHOR]

Migrating species are common within seascapes, but the potential for these movements to alter the populations and functional roles of non-migrating species (e.g. by increasing predation) is rarely investigated. This study considers whether the presence of nursery habitats (mangroves and seagrass) simply enhances the abundance of nursery-using parrotfishes and piscivores on nearby coral reefs, or also affects other parrotfishes. Data from 131 reef sites and multiple seascape configurations across 13 degrees of latitude were used to model correlations between biophysical variables, including nursery habitat connectivity, and the abundance and grazing pressure of both nursery-using species and other parrotfishes and piscivore biomass. Connectivity to mangroves and dense seagrass was positively correlated with the biomass of nursery-using species, but was also negatively correlated with non-nursery parrotfish populations. This reduction may be caused indirectly by nursery habitats increasing confamilial competition and predation by nursery-using piscivores, particularly affecting small parrotfishes settling directly onto reefs. As key reef grazers, parrotfishes affect coral demographics. Consequently, a spatial simulation model predicted the impacts after five years of changes in grazing pressure because of nursery habitat connectivity. The model demonstrated that high nursery connectivity was correlated to changes in grazing pressure on nearby reefs that could potentially lead to differences in coral cover of ∼3-4% when compared to low connectivity reefs. However, the direction of this change depended on the seascapes' characteristics. Historically, large-bodied, nursery-using parrotfish would have increased grazing in all nursery-rich seascapes. Overfishing means that nursery availability may have spatially variable impacts on coral cover, influencing reserve design. This study suggests that nursery availability may directly and indirectly modify an ecological process, and alter an ecological cascade (migrating species increase predator and competitor abundances, affecting other grazers and consequently corals). Therefore, elucidating the multi-species impacts of animal movements is required to better understand ecosystem functioning. [ABSTRACT FROM AUTHOR]

Climate change has become the greatest threat to the world's ecosystems. Locating and managing areas that contribute to the survival of key species under climate change is critical for the persistence of ecosystems in the future. Here, we identify 'Climate Priority' sites as coral reefs exposed to relatively low levels of climate stress that will be more likely to persist in the future. We present the first analysis of uncertainty in climate change scenarios and models, along with multiple objectives, in a marine spatial planning exercise and offer a comprehensive approach to incorporating uncertainty and trade‐offs in any ecosystem. We first described each site using environmental characteristics that are associated with a higher chance of persistence (larval connectivity, hurricane influence, and acute and chronic temperature conditions in the past and the future). Future temperature increases were assessed using downscaled data under four different climate scenarios (SSP1 2.6, SSP2 4.5, SSP3 7.0 and SSP5 8.5) and 57 model runs. We then prioritized sites for intervention (conservation, improved management or restoration) using robust decision‐making approaches that select sites that will have a benign climate under most climate scenarios and models. The modelling work is novel because it solves two important issues. (1) It considers trade‐offs between multiple planning objectives explicitly through Pareto analyses and (2) It makes use of all the uncertainty around future climate change. Priority intervention sites identified by the model were verified and refined through local stakeholder engagement including assessments of local threats, ecological conditions and government priorities. The workflow is presented for the Insular Caribbean and Florida, and at the national level for Cuba, Jamaica, Dominican Republic and Haiti. Our approach allows managers to consider uncertainty and multiple objectives for climate‐smart spatial management in coral reefs or any ecosystem across the globe. [ABSTRACT FROM AUTHOR]

Identifying organisms that play an important role in maintaining ecosystem function is a key aspect of resilience‐based management. For Australia's Great Barrier Reef (GBR), we found that the recovery ability of shallow exposed fore‐reefs is more than 14 times higher when tabular Acropora are present. The disproportionate role that tabular Acropora play appears to be driven by a combination of traits including high recruitment, high growth rate and, importantly, large maximum colony sizes. Despite this key role, tabular Acropora are highly sensitive to most pressures. We compile evidence suggesting that if tabular corals were to decline or disappear on the GBR, the potential for reef recovery on exposed fore‐reefs would be considerably slowed. We then consider the merits of placing special emphasis on the protection of tabular Acropora within the management of the GBR. Importantly, we recognise that an analysis of costs and benefits of such recognition is vital before any change is implemented. Actions might include targeted crown‐of‐thorns starfish control, anchoring restrictions and protection for tabular corals on reefs identified as essential for their larval dispersal. In addition, targeted communications about the critical importance of these highly recognisable corals may boost community support and participation in their protection. [ABSTRACT FROM AUTHOR]

The community of species, human institutions, and human activities at a given location have been shaped by historical conditions (both mean and variability) at that location. Anthropogenic climate change is now adding strong trends on top of existing natural variability. These trends elevate the frequency of "surprises"-conditions that are unexpected based on recent history. Here, we show that the frequency of surprising ocean temperatures has increased even faster than expected based on recent temperature trends. Using a simple model of human adaptation, we show that these surprises will increasingly challenge natural modes of adaptation that rely on historical experience. We also show that warming rates are likely to shift natural communities toward generalist species, reducing their productivity and diversity. Our work demonstrates increasing benefits for individuals and institutions from betting that trends will continue, but this strategy represents a radical shift that will be difficult for many to make. [ABSTRACT FROM AUTHOR]

In the face of increasing cumulative effects from human and natural disturbances, sustaining coral reefs will require a deeper understanding of the drivers of coral resilience in space and time. Here we develop a high‐resolution, spatially explicit model of coral dynamics on Australia's Great Barrier Reef (GBR). Our model accounts for biological, ecological and environmental processes, as well as spatial variation in water quality and the cumulative effects of coral diseases, bleaching, outbreaks of crown‐of‐thorns starfish (Acanthaster cf. solaris), and tropical cyclones. Our projections reconstruct coral cover trajectories between 1996 and 2017 over a total reef area of 14,780 km2, predicting a mean annual coral loss of −0.67%/year mostly due to the impact of cyclones, followed by starfish outbreaks and coral bleaching. Coral growth rate was the highest for outer shelf coral communities characterized by digitate and tabulate Acropora spp. and exposed to low seasonal variations in salinity and sea surface temperature, and the lowest for inner‐shelf communities exposed to reduced water quality. We show that coral resilience (defined as the net effect of resistance and recovery following disturbance) was negatively related to the frequency of river plume conditions, and to reef accessibility to a lesser extent. Surprisingly, reef resilience was substantially lower within no‐take marine protected areas, however this difference was mostly driven by the effect of water quality. Our model provides a new validated, spatially explicit platform for identifying the reefs that face the greatest risk of biodiversity loss, and those that have the highest chances to persist under increasing disturbance regimes. [ABSTRACT FROM AUTHOR]

Aim: Use a fishery‐independent metric to model and map regional‐scale fishing impact, and demonstrate how this metric assists with modelling current and potential fish biomass to support coral‐reef management. We also examine the relative importance of anthropogenic and natural factors on fishes at biogeographical scales. Location: Reefs of five jurisdictions in Micronesia. Methods: A subset of 1,127 fish surveys (470 surveys) was used to calculate site‐specific mean parrotfish lengths (a proxy for cumulative fishing impact), which were modelled against 20 biophysical and anthropogenic variables. The resulting model was extrapolated to each 1 ha reef cell in the region to generate a fishing impact map. The remaining data (657 surveys) were then used to model fish biomass using 15 response variables, including fishing impact. This model was used to map estimated current regional fish standing stocks and, by setting fishing impact to 0, potential standing stocks. Results: Human population pressure and distance to port were key anthropogenic variables predicting fishing impact. Total fish biomass was negatively correlated with fishing, but the influence of natural gradients of primary productivity, sea surface temperature, habitat quality and larval supply was regionally more important. Main conclusions: Mean parrotfish length appears to be a useful fishery‐independent metric for modelling Pacific fishing impact, but considering environmental covariates is critical. Explicitly modelling fishing impact has multiple benefits, including generation of the first large‐scale map of tropical fishing impacts that can inform conservation planning. Using fishing impact data to map current and potential fish stocks provides further benefits, including highlighting the relative importance of fishing on fish biomass and identifying key biophysical variables that cause maximum potential biomass to vary significantly across the region. Regional‐scale maps of fishing, fish standing stocks and the potential benefits of protection are likely to lead to improved conservation outcomes during reserve network planning. [ABSTRACT FROM AUTHOR]

Despite being one of the most important and well-studied coral reefs in the world, the full extent of coral habitat of the Great Barrier Reef (GBR) is not well mapped and there is no current and comprehensive map of the GBR's geomorphic zonation or benthic composition. This paper demonstrates an approach that integrates ecological coral habitat mapping with empirical modelling to map the geomorphic zonation and benthic composition of the “shallow offshore reefs” of the GBR, using the Capricorn Bunker Group (CBG) as a case study. The approach combined environmental data sets and geo-ecological rule sets to identify geomorphic zones. The benthic composition of individual geomorphic zones was mapped for: shallow reef flat zones, using object-based image analysis with context driven rules based on coral reef ecology; and reef slope zones, using levels of wave exposure to predict the distribution of coral types. The environmental data sets used were field-based benthic composition data, Landsat 8 OLI satellite image-derived bottom reflectance, water depth and slope (15 m × 15 m pixel size) data, reef impact data, and modelled wave exposure. The study showed that the combination of geomorphic-ecological rules and models with remote sensing imagery provided robust mapping results over a large (~2500 km 2 ) reef system, of which 245 km 2 was mapped as shallow coral reefs and 88 km 2 of that was mapped as areas containing coral. Most importantly, the method produced defined the geomorphic zones and benthic composition of a study area that is significantly larger than the majority of coral reef remote sensing mapping projects previously published. With some modifications, the methods presented have the potential to be applied to the full extent of the shallow offshore reefs of the GBR, or any large reef globally. Monitoring and management of coral reefs for conservation and other purposes, at regional to global scales will benefit from the ability to produce and use this type of essential information on a regular basis. [ABSTRACT FROM AUTHOR]

A strong driver of water quality change in the Great Barrier Reef (GBR) is the pulsed or intermittent nature of terrestrial inputs into the GBR lagoon, including delivery of increased loads of sediments, nutrients, and toxicants via flood river plumes (hereafter river plumes) during the wet season. Cumulative pressures from extreme weather with a high frequency of large scale flooding in recent years has been linked to the large scale reported decline in the health of inshore seagrass systems and coral reefs in the central areas of the GBR, with concerns for the recovery potential of these impacted ecosystems. Management authorities currently rely on remotely-sensed (RS) and in situ data for water quality monitoring to guide their assessment of water quality conditions in the GBR. The use of remotely-sensed satellite products provides a quantitative and accessible tool for scientists and managers. These products, coupled with in situ data, and more recently modelled data, are valuable for quantifying the influence of river plumes on seagrass and coral reef habitat in the GBR. This article reviews recent remote sensing techniques developed to monitor river plumes and water quality in the GBR. We also discuss emerging research that integrates hydrodynamic models with remote sensing and in situ data, enabling us to explore impacts of different catchment management strategies on GBR water quality. [ABSTRACT FROM AUTHOR]

Under projections of global climate change and other stressors, significant changes in the ecology, structure and function of coral reefs are predicted. Current management strategies tend to look to the past to set goals, focusing on halting declines and restoring baseline conditions. Here, we explore a complementary approach to decision making that is based on the anticipation of future changes in ecosystem state, function and services. Reviewing the existing literature and utilizing a scenario planning approach, we explore how the structure of coral reef communities might change in the future in response to global climate change and overfishing. We incorporate uncertainties in our predictions by considering heterogeneity in reef types in relation to structural complexity and primary productivity. We examine 14 ecosystem services provided by reefs, and rate their sensitivity to a range of future scenarios and management options. Our predictions suggest that the efficacy of management is highly dependent on biophysical characteristics and reef state. Reserves are currently widely used and are predicted to remain effective for reefs with high structural complexity. However, when complexity is lost, maximizing service provision requires a broader portfolio of management approaches, including the provision of artificial complexity, coral restoration, fish aggregation devices and herbivore management. Increased use of such management tools will require capacity building and technique refinement and we therefore conclude that diversification of our management toolbox should be considered urgently to prepare for the challenges of managing reefs into the 21st century. [ABSTRACT FROM AUTHOR]

Employing ecological approaches to fisheries management or comprehensive marine spatial planning requires that species assemblage structure be accounted for. Fish and invertebrate spatial distributions from the National Marine Fisheries Service demersal trawl survey conducted in the Georges Bank – Gulf of Maine region were analyzed by bootstrapped principal component analysis (PCABtsp) and normal PCA (PCANrml). PCABtsp produced confidence limits for eigenvalue stopping rules and for eigenvectors to identify significantly correlated species. Stopping rules identified the first six principal components (PCs) as relevant. Initially, summer and fall survey data from 1963 to 2006 were analyzed, but high eigenvector variation led to reductions in the species and time series used. Confidence interval variation was achieved through removal of highly migratory species and restriction of the time series. PC scores were mapped using inverse distance weighted interpolation to reveal multispecies spatial arrangements. Core areas of species groupings and overlapping zones of higher diversity can be delineated and, even under high fishing pressure with large compositional changes, the assemblages maintained robust spatial organization. This spatial organization could be employed to protect appropriate species groups and minimize bycatch. Careful analysis of survey data can help ensure area-based management schemes are consistent with ecological scales. [ABSTRACT FROM AUTHOR]

1. Environmental variables are often used as indirect surrogates for mapping biodiversity because species survey data are scant at regional scales, especially in the marine realm. However, environmental variables are measured on arbitrary scales unlikely to have simple, direct relationships with biological patterns. Instead, biodiversity may respond nonlinearly and to interactions between environmental variables. 2. To investigate the role of the environment in driving patterns of biodiversity composition in large marine regions, we collated multiple biological survey and environmental data sets from tropical NE Australia, the deep Gulf of Mexico and the temperate Gulf of Maine. We then quantified the shape and magnitude of multispecies responses along >30 environmental gradients and the extent to which these variables predicted regional distributions. To do this, we applied a new statistical approach, Gradient Forest, an extension of Random Forest, capable of modelling nonlinear and threshold responses. 3. The regional-scale environmental variables predicted an average of 13-35% (up to 50-85% for individual species) of the variation in species abundance distributions. Important predictors differed among regions and biota and included depth, salinity, temperature, sediment composition and current stress. The shapes of responses along gradients also differed and were nonlinear, often with thresholds indicative of step changes in composition. These differing regional responses were partly due to differing environmental indicators of bioregional boundaries and, given the results to date, may indicate limited scope for extrapolating bio-physical relationships beyond the region of source data sets. 4. Synthesis and applications. Gradient Forest offers a new capability for exploring relationships between biodiversity and environmental gradients, generating new information on multispecies responses at a detail not available previously. Importantly, given the scarcity of data, Gradient Forest enables the combined use of information from disparate data sets. The gradient response curves provide biologically informed transformations of environmental layers to predict and map expected patterns of biodiversity composition that represent sampled composition better than uninformed variables. The approach can be applied to support marine spatial planning and management and has similar applicability in terrestrial realms. [ABSTRACT FROM AUTHOR]

In the Gulf of Maine area (GoMA), as elsewhere in the ocean, the organisms of greatest numerical abundance are microbes. Viruses in GoMA are largely cyanophages and bacteriophages, including podoviruses which lack tails. There is also evidence of Mimivirus and Chlorovirus in the metagenome. Bacteria in GoMA comprise the dominant SAR11 phylotype cluster, and other abundant phylotypes such as SAR86-like cluster, SAR116-like cluster, Roseobacter, Rhodospirillaceae, Acidomicrobidae, Flavobacteriales, Cytophaga, and unclassified Alphaproteobacteria and Gammaproteobacteria clusters. Bacterial epibionts of the dinoflagellate Alexandrium fundyense include Rhodobacteraceae, Flavobacteriaceae, Cytophaga spp., Sulfitobacter spp., Sphingomonas spp., and unclassified Bacteroidetes. Phototrophic prokaryotes in GoMA include cyanobacteria that contain chlorophyll (mainly Synechococcus), aerobic anoxygenic phototrophs that contain bacteriochlorophyll, and bacteria that contain proteorhodopsin. Eukaryotic microalgae in GoMA include Bacillariophyceae, Dinophyceae, Prymnesiophyceae, Prasinophyceae, Trebouxiophyceae, Cryptophyceae, Dictyochophyceae, Chrysophyceae, Eustigmatophyceae, Pelagophyceae, Synurophyceae, and Xanthophyceae. There are no records of Bolidophyceae, Aurearenophyceae, Raphidophyceae, and Synchromophyceae in GoMA. In total, there are records for 665 names and 229 genera of microalgae. Heterotrophic eukaryotic protists in GoMA include Dinophyceae, Alveolata, Apicomplexa, amoeboid organisms, Labrynthulida, and heterotrophic marine stramenopiles (MAST). Ciliates include Strombidium, Lohmaniella, Tontonia, Strobilidium, Strombidinopsis and the mixotrophs Laboea strobila and Myrionecta rubrum (ex Mesodinium rubra). An inventory of selected microbial groups in each of 14 physiographic regions in GoMA is made by combining information on the depth-dependent variation of cell density and the depth-dependent variation of water volume. Across the entire GoMA, an estimate for the minimum abundance of cell-based microbes is 1.7×1025 organisms. By one account, this number of microbes implies a richness of 105 to 106 taxa in the entire water volume of GoMA. Morphological diversity in microplankton is well-described but the true extent of taxonomic diversity, especially in the femtoplankton, picoplankton and nanoplankton - whether autotrophic, heterotrophic, or mixotrophic, is unknown. [ABSTRACT FROM AUTHOR]

• We assessed the contribution of multiple stressors to reef state and performance. • Cumulative metrics of acute stressors were stronger predictors of reef health. • Water quality impacts are better detected on reef performance than reef state. • Temporal constraints in water quality data limit detectability of their effects. • Metrics based on coral types can be better indicators than total coral metrics. Coral bleaching, cyclones, outbreaks of crown-of-thorns seastar, and reduced water quality (WQ) threaten the health and resilience of coral reefs. The cumulative impacts from multiple acute and chronic stressors on "reef State " (i.e., total coral cover) and "reef Performance " (i.e., the deviation from expected rate of total coral cover increase) have rarely been assessed simultaneously, despite their management relevance. We evaluated the dynamics of coral cover (total and per morphological groups) in the Central and Southern Great Barrier Reef over 25 years, and identified and compared the main environmental drivers of State and Performance at the reef level (i.e. based on total coral cover) and per coral group. Using a combination of 25 environmental metrics that consider both the frequency and magnitude of impacts and their lagged effects, we find that the stressors that correlate with State differed from those correlating with Performance. Importantly, we demonstrate that WQ metrics better predict Performance than State. Further, inter-annual dynamics in WQ (here available for a subset of the data) improved the explanatory power of WQ metrics on Performance over long-term WQ averages. The lagged effects of cumulative acute stressors, and to a lesser extent poor water quality, correlated negatively with the Performance of some but not all coral groups. Tabular Acropora and branching non- Acropora were the most affected by water quality demonstrating that group-specific approaches aid in the interpretation of monitoring data and can be crucial for the detection of the impact of chronic pressures. We highlight the complexity of coral reef dynamics and the need of evaluating Performance metrics in order to prioritise local management interventions. [ABSTRACT FROM AUTHOR]