Linking Demographic Processes of Juvenile Corals to Benthic Recovery Trajectories in Two Common Reef Habitats

Tropical reefs are dynamic ecosystems that host diverse coral assemblages with different life-history strategies. Here, we quantified how juvenile (<50 mm) coral demographics influenced benthic coral structure in reef flat and reef slope habitats on the southern Great Barrier Reef, Australia. Permanent plots and settlement tiles were monitored every six months for three years in each habitat. These environments exhibited profound differences: the reef slope was characterised by 95% less macroalgal cover, and twice the amount of available settlement substrata and rates of coral settlement than the reef flat. Consequently, post-settlement coral survival in the reef slope was substantially higher than that of the reef flat, and resulted in a rapid increase in coral cover from 7 to 31% in 2.5 years. In contrast, coral cover on the reef flat remained low (~10%), whereas macroalgal cover increased from 23 to 45%. A positive stock-recruitment relationship was found in brooding corals in both habitats; however, brooding corals were not directly responsible for the observed changes in coral cover. Rather, the rapid increase on the reef slope resulted from high abundances of broadcast spawning Acropora recruits. Incorporating our results into transition matrix models demonstrated that most corals escape mortality once they exceed 50 mm, but for smaller corals mortality in brooders was double those of spawners (i.e. acroporids and massive corals). For corals on the reef flat, sensitivity analysis demonstrated that growth and mortality of larger juveniles (21–50 mm) highly influenced population dynamics; whereas the recruitment, growth and mortality of smaller corals (<20 mm) had the highest influence on reef slope population dynamics. Our results provide insight into the population dynamics and recovery trajectories in disparate reef habitats, and highlight the importance of acroporid recruitment in driving rapid increases in coral cover following large-scale perturbation in reef slope environments.     

Phase shifts and the stability of macroalgal communities on Caribbean coral reefs

Caribbean coral reefs are widely thought to exhibit two alternate stable states with one being dominated by coral and the other by macroalgae. However, the observation of linear empirical relationships among grazing, algal cover and coral recruitment has led the existence of alternate stable states to be questioned; are reefs simply exhibiting a continuous phase shift in response to grazing or are the alternate states robust to certain changes in grazing? Here, a model of a Caribbean forereef is used to reconcile the existence of two stable community states with common empirical observations. Coral-depauperate and coral-dominated reef states are predicted to be stable on equilibrial time scales of decades to centuries and their emergence depends on the presence or absence of a bottleneck in coral recruitment, which is determined by threshold levels of grazing intensity and other process variables. Under certain physical and biological conditions, corals can be persistently depleted even while increases in grazing reduce macroalgal cover and enhance coral recruitment; only once levels of recruitment becomes sufficient to overwhelm the population bottleneck will the coral-dominated state begin to emerge. Therefore, modest increases in grazing will not necessarily allow coral populations to recover, whereas large increases, such as those associated with recovery of the urchin Diadema antillarum, are likely to exceed threshold levels of grazing intensity and set a trajectory of coral recovery. The postulated existence of alternate stable states is consistent with field observations of linear relationships between grazing, algal cover and coral recruitment when coral cover is low and algal exclusion when coral cover is high. The term ‘macroalgal dominated’ is potentially misleading because the coral-depauperate state can be associated with various levels of macroalgal cover. The term ‘coral depauperate’ is preferable to ‘macroalgal dominated’ when describing alternate states of Caribbean reefs.     

Decadal‐scale rates of reef erosion following El Niño‐related mass coral mortality

As the frequency and intensity of coral mortality events increase under climate change, understanding how declines in coral cover may affect the bioerosion of reef frameworks is of increasing importance. Here, we explore decadal‐scale rates of bioerosion of the framework building coral Orbicella annularis by grazing parrotfish following the 1997/1998 El Niño‐related mass mortality event at Long Cay, Belize. Using high‐precision U‐Th dating and CT scan analysis, we quantified in situ rates of external bioerosion over a 13‐year period (1998–2011). Based upon the error‐weighted average U‐Th age of dead O. annularis skeletons, we estimate the average external bioerosion between 1998 and 2011 as 0.92 ± 0.55 cm depth. Empirical observations of herbivore foraging, and a nonlinear numerical response of parrotfish to an increase in food availability, were used to create a model of external bioerosion at Long Cay. Model estimates of external bioerosion were in close agreement with U‐Th estimates (0.85 ± 0.09 cm). The model was then used to quantify how rates of external bioerosion changed across a gradient of coral mortality (i.e., from few corals experiencing mortality following coral bleaching to complete mortality). Our results indicate that external bioerosion is remarkably robust to declines in coral cover, with no significant relationship predicted between the rate of external bioerosion and the proportion of O. annularis that died in the 1998 bleaching event. The outcome was robust because the reduction in grazing intensity that follows coral mortality was compensated for by a positive numerical response of parrotfish to an increase in food availability. Our model estimates further indicate that for an O. annularis‐dominated reef to maintain a positive state of reef accretion, a necessity for sustained ecosystem function, live cover of O. annularis must not drop below a ~5–10% threshold of cover.     

Micro-topography mediates interactions between corals,algae, and herbivorous fishes on coral reefs

Processes occurring during the early life stages of corals are important for the replenishment of coral assemblages and the resilience of coral reefs. However, the factors influencing early life stages of corals are not well understood, and the role of micro-topographic complexity for habitat associations of juvenile corals is largely unexplored. This study investigated the microhabitat distribution patterns of early life stages of corals and a potential macroalgal competitor (Turbinaria ornata) across two reef zones (reef crest and outer reef flat) on Lizard Island, Great Barrier Reef. In both reef zones, both corals and T. ornata were significantly more abundant in concealed microhabitats than in semi-concealed or open microhabitats (GLMM: P < 0.001). The prevalence of juvenile corals and T. ornata within concealed environments suggests that they might be effective refuges from grazing by herbivorous fishes. The density of juvenile corals was positively related, and density of T. ornata negatively related to the abundance of two groups of herbivorous fishes, pairing rabbitfishes, and surgeonfishes in the genus Zebrasoma (BEST ENV-BIO: r _s  = 0.72, P < 0.01), which feed in concealed microhabitats. This correlative evidence suggests that crevices may be important for early life stages of both coral and macroalgae, and that a specific suite of crevice-feeding fishes may influence benthic community dynamics in these microhabitats.     

Effects of herbivores, nutrient enrichment, and their interactions on macroalgal proliferation and coral growth

We conducted a 20-week manipulative field experiment on shallow forereefs of the Florida Keys to assess the separate and interactive effects of herbivory and nutrient enrichment on the development of macroalgal communities and the fitness of the corals Porites porites and Siderastrea siderea. Excluding large herbivorous fishes produced macrophyte blooms both with and without nutrient enrichment. In contrast, there were no direct effects of nutrient enrichment. There were, however, small, but significant, interactive effects of herbivory and enrichment on macroalgal cover. Following nutrient enrichment, total macroalgae and the common seaweeds Dictyota spp. were suppressed in the presence, but not in the absence, of large herbivorous fishes—suggesting that fishes were selectively feeding on nutrient-enriched macrophytes. Access by large herbivores prevented algal overgrowth of corals, but these large fishes also directly grazed both corals. Excluding fishes did not alter survivorship of either coral species, but did decrease parrotfish grazing scars on both corals and increased the net growth of P. porites. Nutrient additions had no direct effects on the survivorship of corals, but there was a trend (P = 0.097) for nutrients to stimulate the growth of P. porites. The preponderance of experiments available to date indicates that loss of key herbivores is a major factor driving macroalgal blooms on coral reefs; anthropogenic nutrient pollution generally plays a more minor role.     

Effects of herbivore exclusion and nutrient enrichment on coral reef macroalgae and cyanobacteria

Although phase shifts on coral reefs from coral-dominated to algal-dominated communities have been attributed to the effects of increased nutrient availability due to eutrophication and reduced herbivore abundance due to overfishing and disease, these factors have rarely been manipulated simultaneously. In addition, few studies have considered the effects of these factors on benthic, filamentous cyanobacteria (blue-green algae) as well as macroalgae. We used a combination of herbivore-exclusion cages and nutrient enrichment to manipulate herbivore abundance and nutrient availability, and measured the impacts of these treatments on macroalgal and cyanobacterial community structure. In the absence of cages, surface cover of the cyanobacterium Tolypothrix sp. decreased, while surface cover of the cyanobacteria Oscillatoria spp. increased. Cyanobacterial cover decreased in partial cages, and Tolypothrix sp. cover decreased further in full cages. Lower cyanobacterial cover and biomass were correlated with higher macroalgal cover and biomass. Dictyota bartayresiana dominated the partial cages, while Padina tenuis and Tolypiocladia glomerulata recruited into the full cages. Palatability assays demonstrated that herbivore-exclusion shifted macroalgal species composition from relatively unpalatable to relatively palatable species. Nutrient enrichment interacted with herbivore exclusion to increase the change in cover of D. bartayresiana in the uncaged and fully caged plots, but did not affect the final biomass of D. bartayresiana among treatments. Nutrient enrichment did not significantly affect the cover or biomass of any other taxa. These results stress the critical role of herbivory in determining coral reef community structure and suggest that the relative palatabilities of dominant algae, as well as algal growth responses to nutrient enrichment, will determine the potential for phase shifts to algal-dominated communities.     

Effects of herbivory,nutrients, and reef protection on algal proliferation and coral growth on a tropical reef

Maintaining coral reef resilience against increasing anthropogenic disturbance is critical for effective reef management. Resilience is partially determined by how processes, such as herbivory and nutrient supply, affect coral recovery versus macroalgal proliferation following disturbances. However, the relative effects of herbivory versus nutrient enrichment on algal proliferation remain debated. Here, we manipulated herbivory and nutrients on a coral-dominated reef protected from fishing, and on an adjacent macroalgal-dominated reef subject to fishing and riverine discharge, over 152 days. On both reefs, herbivore exclusion increased total and upright macroalgal cover by 9-46 times, upright macroalgal biomass by 23-84 times, and cyanobacteria cover by 0-27 times, but decreased cover of encrusting coralline algae by 46-100% and short turf algae by 14-39%. In contrast, nutrient enrichment had no effect on algal proliferation, but suppressed cover of total macroalgae (by 33-42%) and cyanobacteria (by 71% on the protected reef) when herbivores were excluded. Herbivore exclusion, but not nutrient enrichment, also increased sediment accumulation, suggesting a strong link between herbivory, macroalgal growth, and sediment retention. Growth rates of the corals Porites cylindrica and Acropora millepora were 30-35% greater on the protected versus fished reef, but nutrient and herbivore manipulations within a site did not affect coral growth. Cumulatively, these data suggest that herbivory rather than eutrophication plays the dominant role in mediating macroalgal proliferation, that macroalgae trap sediments that may further suppress herbivory and enhance macroalgal dominance, and that corals are relatively resistant to damage from some macroalgae but are significantly impacted by ambient reef condition.     

Geomorphology and community structure of Middle Reef, central Great Barrier Reef, Australia: an inner-shelf turbid zone reef subject to episodic mortality events

Middle Reef is an inshore turbid zone reef located 4 km offshore from Townsville, Queensland, Australia. The reef consists of four current-aligned, interconnected reef patches that have reached sea level and formed reef flats. It is regularly exposed to high turbidity (up to 50 mg l⁻¹) generated by wave-driven sediment resuspension or by episodic flood plumes. Middle Reef has a high mean hard coral cover (>39%), relatively low mean macro-algal cover (<15%) and a coral community comprising at least 81 hard coral species. Cluster analysis differentiated six benthic communities which were mapped onto the geomorphological structure of the reef to reveal a spatially patchy community mosaic that reflects hydrodynamic and sediment redistribution processes. Coral cover data collected annually from windward slope transects since 1993 show that coral cover has increased over the last ~15 years despite a history of episodic mortality events. Although episodic mortality may be interpreted as an indication of marginality, over decadal timescales, Middle Reef has recovered rapidly following mortality events and is clearly a resilient coral reef.     

Parrotfish predation on massive Porites on the Great Barrier Reef

Parrotfish grazing scars on coral colonies were quantified across four reef zones at Lizard Island, Northern Great Barrier Reef (GBR). The abundance of parrotfish grazing scars was highest on reef flat and crest, with massive Porites spp. colonies having more parrotfish grazing scars than all other coral species combined. Massive Porites was the only coral type positively selected for grazing by parrotfishes in all four reef zones. The density of parrotfish grazing scars on massive Porites spp., and the rate of new scar formation, was highest on the reef crest and flat, reflecting the lower massive Porites cover and higher parrotfish abundance in these habitats. Overall, it appears that parrotfish predation pressure on corals could affect the abundance of preferred coral species, especially massive Porites spp, across the reef gradient. Parrotfish predation on corals may have a more important role on the GBR reefs than previously thought.     

Macroalgal herbivory on recovering versus degrading coral reefs

Macroalgal-feeding fishes are considered to be a key functional group on coral reefs due to their role in preventing phase shifts from coral to macroalgal dominance, and potentially reversing the shift should it occur. However, assessments of macroalgal herbivory using bioassay experiments are primarily from systems with relatively high coral cover. This raises the question of whether continued functionality can be ensured in degraded systems. It is clearly important to determine whether the species that remove macroalgae on coral-dominated reefs will still be present and performing significant algal removal on macroalgal-dominated reefs. We compared the identity and effectiveness of macroalgal-feeding fishes on reefs in two conditions post-disturbance—those regenerating with high live coral cover (20–46 %) and those degrading with high macroalgal cover (57–82 %). Using filmed Sargassum bioassays, we found significantly different Sargassum biomass loss between the two conditions; mean assay weight loss due to herbivory was 27.9 ± 4.9 % on coral-dominated reefs and 2.2 ± 1.1 % on reefs with high macroalgal cover. However, once standardised for the availability of macroalgae on the reefs, the rates of removal were similar between the two reef conditions (4.8 ± 4.1 g m^?2 h^?1 on coral-dominated and 5.3 ± 2.1 g m^?2 h^?1 on macroalgal-dominated reefs). Interestingly, the Sargassum-assay consumer assemblages differed between reef conditions; nominally grazing herbivores, Siganus puelloides and Chlorurus sordidus, and the browser, Siganus sutor, dominated feeding on high coral cover reefs, whereas browsing herbivores, Naso elegans, Naso unicornis, and Leptoscarus vaigiensis, prevailed on macroalgal-dominated reefs. It appeared that macroalgal density in the surrounding habitat had a strong influence on the species driving the process of macroalgal removal. This suggests that although the function of macroalgal removal may continue, the species responsible may change with context, differing between systems that are regenerating versus degrading.     

Benthic Composition of a Healthy Subtropical Reef: Baseline Species-Level Cover,with an Emphasis on Algae,in the Northwestern Hawaiian Islands

The Northwestern Hawaiian Islands (NWHI) are considered to be among the most pristine coral reef ecosystems remaining on the planet. These reefs naturally contain a high percent cover of algal functional groups with relatively low coral abundance and exhibit thriving fish communities dominated by top predators. Despite their highly protected status, these reefs are at risk from both direct and indirect anthropogenic sources. This study provides the first comprehensive data on percent coverage of algae, coral, and non-coral invertebrates at the species level, and investigates spatial diversity patterns across the archipelago to document benthic communities before further environmental changes occur in response to global warming and ocean acidification. Monitoring studies show that non-calcified macroalgae cover a greater percentage of substrate than corals on many high latitude reef sites. Forereef habitats in atoll systems often contain high abundances of the green macroalga Microdictyon setchellianum and the brown macroalga Lobophora variegata, yet these organisms were uncommon in forereefs of non-atoll systems. Species of the brown macroalgal genera Padina, Sargassum, and Stypopodium and the red macroalgal genus Laurencia became increasingly common in the two northernmost atolls of the island chain but were uncommon components of more southerly islands. Conversely, the scleractinian coral Porites lobata was common on forereefs at southern islands but less common at northern islands. Currently accepted paradigms of what constitutes a “healthy” reef may not apply to the subtropical NWHI, and metrics used to gauge reef health (e.g., high coral cover) need to be reevaluated.     

Distributions of coral reef macroalgae in a back reef habitat in Moorea,French Polynesia

On tropical reefs where macroalgae are subjected to continuous herbivore pressure, spatial refuges typically are identified as large-scale, landscape interfaces that limit foraging behavior. However, algal distributions and community assemblages may also rely on the availability of smaller scale spatial refuges within the reef. The results of this study demonstrate that the patterns of macroalgal distribution across the back reef of Moorea, French Polynesia, are maintained by herbivores interacting with the small-scale structural complexities of the coral reef landscape. Although the majority of space available for colonization is composed of exposed surfaces, macroalgae rarely are found in the open. Instead, macroalgal occurrence is highest in the protected narrow crevices and hole microhabitats provided by massive Porites spp. coral heads. These distributions are determined initially by post-settlement mortality of young algal recruits in exposed habitats. Rates of consumption for two of the most common macroalgal species found in refuges across the back reef, Halimeda minima and Amansia rhodantha, indicate that algal recruits in exposed habitats are limited by herbivory. While algal abundance and community structure are highly dependent upon herbivore grazing, the availability of small-scale spatial refuges ultimately shapes the distinct community patterns and distributional boundaries of coral reef macroalgae in the back reefs of Moorea.     

Direct evaluation of macroalgal removal by herbivorous coral reef fishes

Few studies have examined the relative functional impacts of individual herbivorous fish species on coral reef ecosystem processes in the Indo-Pacific. This study assessed the potential grazing impact of individual species within an inshore herbivorous reef fish assemblage on the central Great Barrier Reef (GBR), by determining which fish species were able to remove particular macroalgal species. Transplanted multiple-choice algal assays and remote stationary underwater digital video cameras were used to quantify the impact of local herbivorous reef fish species on 12 species of macroalgae. Macroalgal removal by the fishes was rapid. Within 3 h of exposure to herbivorous reef fishes there was significant evidence of intense grazing. After 12 h of exposure, 10 of the 12 macroalgal species had decreased to less than 15% of their original mass. Chlorodesmis fastigiata (Chlorophyta) and Galaxaura sp. (Rhodophyta) showed significantly less susceptibility to herbivorous reef fish grazing than all other macroalgae, even after 24 h exposure. Six herbivorous and/or nominally herbivorous reef fish species were identified as the dominant grazers of macroalgae: Siganus doliatus, Siganus canaliculatus, Chlorurus microrhinos, Hipposcarus longiceps, Scarus rivulatus and Pomacanthus sexstriatus. The siganid S. doliatus fed heavily on Hypnea sp., while S. canaliculatus fed intensively on Sargassum sp. Variation in macroalgal susceptibility was not clearly correlated with morphological and/or chemical defenses that have been previously suggested as deterrents against herbivory. Nevertheless, the results stress the potential importance of individual herbivorous reef fish species in removing macroalgae from coral reefs.     

Chronic low-level nutrient enrichment benefits coral thermal performance in a fore reef habitat

Global- and local-scale anthropogenic stressors have been the main drivers of coral reef decline, causing shifts in coral reef community composition and ecosystem functioning. Excess nutrient enrichment can make corals more vulnerable to ocean warming by suppressing calcification and reducing photosynthetic performance. However, in some environments, corals can exhibit higher growth rates and thermal performance in response to nutrient enrichment. In this study, we measured how chronic nutrient enrichment at low concentrations affected coral physiology, including endosymbiont and coral host response variables, and holobiont metabolic responses of Pocillopora spp. colonies in Mo'orea, French Polynesia. We experimentally enriched corals with dissolved inorganic nitrogen and phosphate for 15 months on an oligotrophic fore reef in Mo'orea. We first characterized symbiont and coral physiological traits due to enrichment and then used thermal performance curves to quantify the relationship between metabolic rates and temperature for experimentally enriched and control coral colonies. We found that endosymbiont densities and total tissue biomass were 54% and 22% higher in nutrient-enriched corals, respectively, relative to controls. Algal endosymbiont nitrogen content cell⁻¹ was 44% lower in enriched corals relative to the control colonies. In addition, thermal performance metrics indicated that the maximal rate of performance for gross photosynthesis was 29% higher and the rate of oxygen evolution at a reference temperature (26.8 °C) for gross photosynthesis was 33% higher in enriched colonies compared to the control colonies. These differences were not attributed to symbiont community composition between corals in different treatments, as C42, a symbiont type in the Cladocopium genus, was the dominant endosymbiont type found in all corals. Together, our results show that in an oligotrophic fore reef environment, nutrient enrichment can cause changes in coral endosymbiont physiology that increase the performance of the coral holobiont.

     

Evaluation of algal regulation by herbivorous fishes on Caribbean coral reefs

The role of herbivorous fishes in maintaining low macroalgal cover was evaluated on coral reefs on several reef sites from Guadeloupe, either protected or not. Grazing by herbivorous fishes was assessed on different algal facies using fish-bite counts. Algal consumption by fish was estimated as well as algal production. Bite counts revealed that herbivorous fishes feed preferentially on algal turf and avoid brown macroalgae. The algal consumption varied between 0.4 and 2.8 g m⁻² days⁻¹ and was higher inside marine protected areas than outside. Comparison with algal production revealed that herbivorous fishes did not succeed in regulating algal growth. The insufficient number of grazers may lead to the dominance of stable assemblages of macroalgae on coral reefs, preventing the recovery of reef into previous coral-dominated ecosystems.     

Grazing pressure of herbivorous coral reef fishes on low coral-cover reefs

The impact of grazing by herbivorous fishes (Acanthuridae, Scaridae, and Pomacentridae) on low coral-cover reefs was assessed by measuring rates of benthic algal production and consumption on inshore and offshore reefs in the upper Florida Keys. Algal production rates, determined in situ with caged and uncaged experimental plates, were low (mean 1.05 g C m⁻² day⁻¹) and similar among reef types. Algal consumption rates were estimated using two different models, a detailed model incorporating fish bite rates and algal yield-per-bite for one species extrapolated to a guild-wide value, and a general regression relating fish biomass to algal consumption. Algal consumption differed among reef types: a majority of algal production was consumed on offshore reefs (55–100%), whereas consumption on inshore patch reefs was 31–51%. Spatial variation in algal consumption was driven by differences in herbivorous fish species composition, density, and size-structure among reef types. Algal consumption rates also varied temporally due to seasonal declines in bite rates and intermittent presence of large-bodied, vagile, schooling species. Spatial coherence of benthic community structure and temporal stability of algal turf over 3 years suggests that grazing intensity is currently sufficient to limit further spread of macroalgal cover on these low coral-cover reefs, but not to exclude it from the system.     

Empirical models of transitions between coral reef states: effects of region, protection, and environmental change

There has been substantial recent change in coral reef communities. To date, most analyses have focussed on static patterns or changes in single variables such as coral cover. However, little is known about how community-level changes occur at large spatial scales. Here, we develop Markov models of annual changes in coral and macroalgal cover in the Caribbean and Great Barrier Reef (GBR) regions. We analyzed reef surveys from the Caribbean and GBR (1996-2006). We defined a set of reef states distinguished by coral and macroalgal cover, and obtained Bayesian estimates of the annual probabilities of transitions between these states. The Caribbean and GBR had different transition probabilities, and therefore different rates of change in reef condition. This could be due to differences in species composition, management or the nature and extent of disturbances between these regions. We then estimated equilibrium probability distributions for reef states, and coral and macroalgal cover under constant environmental conditions. In both regions, the current distributions are close to equilibrium. In the Caribbean, coral cover is much lower and macroalgal cover is higher at equilibrium than in the GBR. We found no evidence for differences in transition probabilities between the first and second halves of our survey period, or between Caribbean reefs inside and outside marine protected areas. However, our power to detect such differences may have been low. We also examined the effects of altering transition probabilities on the community state equilibrium, along a continuum from unfavourable (e.g., increased sea surface temperature) to favourable (e.g., improved management) conditions. Both regions showed similar qualitative responses, but different patterns of uncertainty. In the Caribbean, uncertainty was greatest about effects of favourable changes, while in the GBR, we are most uncertain about effects of unfavourable changes. Our approach could be extended to provide risk analysis for management decisions.     

Herbivory facilitates growth of a key reef‐building Caribbean coral

The decline of reef‐building corals in conjunction with shifts to short‐lived opportunistic species has prompted concerns that Caribbean reef framework‐building capacity has substantially diminished. Restoring herbivore populations may be a potential driver of coral recovery; however, the impact of herbivores on coral calcification has been little studied. We performed an exclusion experiment to evaluate the impact of herbivory on Orbicella faveolata coral growth over 14 months. The experiment consisted of three treatments: full exclusion cages; half cage procedural controls; and uncaged control plates, each with small O. faveolata colonies. We found that herbivorous fish exclusion had a substantial impact on both macroalgal cover and coral growth. Fleshy macroalgae reached 50% cover within some exclusion cages, but were almost absent from uncaged control plates. Critically, O. faveolata calcification rates were suppressed by almost half within exclusion cages, with monthly coral growth negatively related to overgrowth by fleshy macroalgae. These findings highlight the importance of herbivorous fishes for coral growth and the detrimental impact of macroalgal proliferation in the Caribbean. Policy makers and local managers should consider measures to protect herbivorous fishes and reduce macroalgal proliferation to enable coral communities to continue to grow and function.     

Abrolhos bank reef health evaluated by means of water quality, microbial diversity, benthic cover, and fish biomass data

The health of the coral reefs of the Abrolhos Bank (Southwestern Atlantic) was characterized with a holistic approach using measurements of four ecosystem components: (i) inorganic and organic nutrient concentrations, [1] fish biomass, [1] macroalgal and coral cover and (iv) microbial community composition and abundance. The possible benefits of protection from fishing were particularly evaluated by comparing sites with varying levels of protection. Two reefs within the well-enforced no-take area of the National Marine Park of Abrolhos (Parcel dos Abrolhos and California) were compared with two unprotected coastal reefs (Sebasti?o Gomes and Pedra de Leste) and one legally protected but poorly enforced coastal reef (the "paper park" of Timbebas Reef). The fish biomass was lower and the fleshy macroalgal cover was higher in the unprotected reefs compared with the protected areas. The unprotected and protected reefs had similar seawater chemistry. Lower vibrio CFU counts were observed in the fully protected area of California Reef. Metagenome analysis showed that the unprotected reefs had a higher abundance of archaeal and viral sequences and more bacterial pathogens, while the protected reefs had a higher abundance of genes related to photosynthesis. Similar to other reef systems in the world, there was evidence that reductions in the biomass of herbivorous fishes and the consequent increase in macroalgal cover in the Abrolhos Bank may be affecting microbial diversity and abundance. Through the integration of different types of ecological data, the present study showed that protection from fishing may lead to greater reef health. The data presented herein suggest that protected coral reefs have higher microbial diversity, with the most degraded reef (Sebasti?o Gomes) showing a marked reduction in microbial species richness. It is concluded that ecological conditions in unprotected reefs may promote the growth and rapid evolution of opportunistic microbial pathogens.