ABSTRACT Mass mortality of Diadematidae urchins, caused by the Diadema antillarum scuticociliatosis Philaster clade (DScPc), affected the Caribbean in spring 2022 and subsequently spread to the eastern Mediterranean, Red Sea, and western Indian Ocean. A key question around Diadematidae scuticociliatosis (DSc), the disease caused by the scuticociliate, is whether the urchin microbiome varies between scuticociliatosis-affected and grossly normal urchins. Tissue samples from both grossly normal and abnormal Diadema antillarum were collected in the field during the initial assessment of the DSc causative agent and from an experimental challenge of DScPc culture on aquacultured D. antillarum. Specimens were analyzed using 16S rRNA gene amplicon sequencing. Additional abnormal urchin samples were collected from the most recent outbreak site in the western Indian Ocean (Réunion Island). At reference (i.e., unaffected by DSc) sites, Kistimonas spp., Propionigenium spp., and Endozoicomonas spp. were highly represented in amplicon libraries. DSc-affected urchin amplicon libraries had lower taxonomic richness and a greater representation of taxa related to Fangia hongkongensis and Psychrobium spp. Amplicon libraries of urchins experimentally challenged with the DSc pathogen had some shifts in microbial composition, but F. hongkongensis was not a part of the core bacteria in DSc-challenged specimens. DSc-affected Echinothrix diadema from Réunion Island showed a similar high representation of F. hongkongensis as that seen on Caribbean D. antillarum. Our results suggest that DSc alters Diadematidae microbiomes and that F. hongkongensis may be a candidate bacterial biomarker for DSc in environmental samples. The mechanism driving microbiome variation in host–pathogen interactions remains to be explored.IMPORTANCEThe mass mortality of Diadematidae urchins due to Diadema antillarum scuticociliatosis (DSc) has had significant ecological impacts, spreading from the Caribbean to the eastern Mediterranean, Red Sea, and western Indian Ocean. This study investigates whether the microbiome of urchins varies between those affected by DSc and those that are not. Using 16S rRNA gene amplicon sequencing, researchers found that DSc-affected urchins had lower taxonomic richness and a greater representation of Fangia hongkongensis and Psychrobium spp. The findings indicate that F. hongkongensis could serve as a bacterial biomarker for DSc in environmental samples, providing a potential tool for early detection and management of the disease. Understanding these microbiome changes is crucial for developing strategies to mitigate the spread and impact of DSc on marine ecosystems.

The Caribbean spiny lobster (Panulirus argus) fishery in Florida, valued at millions of dollars annually, relies mostly on wooden-slat traps baited with live, sublegal-size lobsters to attract legal-size individuals. However, this practice leads to confinement-related mortality due to starvation and depredation. We investigated the escape rates and mortality of bait lobsters using long-term deployable cameras, documenting behavior of bait lobsters in traps. Although previous research found that long-term confinement of these bait lobsters results in their poor health and mortality, these estimates of mortality relied on periodic observations of traps that could not differentiate causes and timing of mortality. To identify how the long-term confinement of bait lobsters affects their likelihood for escape or mortality, we deployed traps with one lobster for each of the following treatments: healthy/fed or starved for 2, 4, or 6 weeks. Long-term deployable cameras and infrared lights mounted on traps were used to observe the fate (i.e., escape or mortality) of these lobsters over a 2-week trap soak period typical in the fishery. We conducted 12 deployments of 103 total traps over 1 year and found that escape varied with duration of lobster starvation. Our study confirmed escape rates from past studies (1.26 +/- 0.43 % of lobsters per day) and revealed "serial confinement," where escaped lobsters re-entered traps, potentially prolonging their confinement and mortality risk. Starvation, caused by long-term confinement, resulted in increased mortality, with smaller lobsters (<68 mm carapace length) facing higher risk of mortality. Video documentation allowed for the first time to differentiate between starvation mortality and depredation within traps; depredation by octopuses (Octopus briareus) and triggerfish (Ballistes spp.) posed a substantial threat, reducing trap catch efficiency. Our video documentation showed that the presence of dead lobsters in traps further decreased catch rates for the duration (similar to 5d) the carcass remained in the trap, underscoring the negative impact on fishery yield. Our findings emphasize the need for the fishery to explore management strategies to mitigate mortality of sublegal-size lobsters in traps due to long-term confinement, including trap reduction, use of escape gaps, and shorter trap soak times, akin to successful practices in other spiny lobster fisheries. The study highlights the utility of long-term deployable cameras in assessing trap functioning and catch dynamics, offering insights for sustainable management of Florida's lobster fishery while preserving its cultural and economic significance.

That coral reefs are in decline worldwide, particularly in the Caribbean, will come as no surprise. This decades-long decline has reached a potential tipping point as the weight of the effects of climate change have come decidedly to bear on the planet’s most diverse marine ecosystem. Whether coral reefs can persist without restorative intervention is debatable, which has prompted a surge in coral reef restoration projects focusing primarily on the cultivation and transplantation of coral fragments onto degraded reefs. But that widespread approach does little to address the underlying causes of coral loss, one of which is the proliferation of macroalgae that are deleterious to corals. An emerging solution to this problem is the enhancement of herbivory on coral reefs through improved management of herbivores, artificial enhancement of herbivore settlement, or their mariculture and subsequent stocking. This review explores the nuances of the biology of well-studied Caribbean coral reef herbivores (fishes, sea urchins, and crabs) as it relates to their mariculture and investigates the promise of herbivore stocking onto coral reefs as a restoration strategy. Fish, urchin, and crab herbivores differ appreciably in life histories, which confers advantages and disadvantages with respect to their mariculture and effectiveness as grazers. Mariculture of herbivorous marine fish for reef restoration is essentially non-existent so the reestablishment of grazing fish abundance on coral reefs focuses primarily on their protection through fishery regulations, but only at a few locations in the Caribbean. Mariculture of herbivorous urchins and crabs for restoration purposes is in its infancy, but promising especially for crabs whose larval rearing is less difficult. Perhaps the biggest challenge for the mariculture of either taxon is “scaling-up” from research settings to large-scale mariculture needed for stocking. Numerous studies extol the benefits of functional redundancy and complementarity for coral reef ecosystem stability, but whether this principal applies to the restoration of grazing function is untested. We identify gaps in our knowledge of best practices for the restoration of grazing function on coral reefs and conclude with some practical guidance on the establishment of targets for macroalgal reduction, along with strategic advice on grazer stocking in a given reef habitat.

The functional loss of herbivory on Caribbean coral reefs following an epizootic-driven die-off of the long-spined urchin ( Diadema antillarum ) in the 1980s and its lack of recovery has inspired efforts to re-establish an ecologically viable population throughout the region. An area of focus is to develop scalable methods for producing D. antillarum through aquaculture from gametes for release onto coral reefs. We had earlier observed that aquaculture- produced D. antillarum lacked the strong diurnal sheltering behavior exhibited by wild individuals. Based upon those findings, subsequent cohorts of aquaculture-produced individuals were therefore maintained under a natural diurnal cycle of UV-filtered sunlight and provided ample access to structure that mimicked its natural shelter. An examination of the sheltering behavior of D. antillarum from one of these cohorts found the pronounced diurnal sheltering behavior typical of wild individuals. This observation underscores the potential that the behavioral deficit observed in earlier hatchery-propagated D. antillarum can be mediated and ecologically functional individuals can be produced through this aquaculture process.

The marine aquarium trade in the United States operates primarily in Florida, and though the trade’s effects on many marine taxa are largely unknown, local declines have been observed for some harvested species. To reverse local declines in the abundance of the giant Caribbean sea anemone Condylactis gigantea, state managers prohibited harvest of this popular aquarium organism in late 2012. To assess the recovery of C. gigantea following the moratorium, we monitored relative abundance at 45 fixed locations in South Florida from 2013 to 2016. Seventeen of the sites were locations provided to us by commercial aquarium-trade collectors. The remaining sites were locations at which C. gigantea was presumably not being exploited. We found increased densities at only 4 of those 17 sites, while densities at the remaining sites remained unchanged. We also examined genome-wide single nucleotide polymorphism data to assess genetic diversity and population structure of 82 individuals from seven locations (three collection and four non-collection locations) across South Florida. Observed genetic diversity was comparable in all locations. But the location in the eastern Gulf of Mexico showed a significant FIS value, suggesting inbreeding that might be attributed to a small number of occupants. Condylactis gigantea is generally well mixed across South Florida, though a relatively weak pattern of genetic differentiation was detected. These results suggest limited reproductive success and dispersal that is restricted by hydrological and geographical barriers. We highlight the importance of periodic population and genetic monitoring to assess changes in relative abundance and genetic diversity.

Indo-Pacific sun corals (Tubastraea spp.) are aggressive competitors capable of disrupting the structure and function of natural reef habitat in the western Atlantic. Sun corals observed on rope debris entangled on an artificial reef in the Florida Keys suggest a potential dispersal mechanism for the colonization of natural reef habitat.

Echinoderm mass mortality events shape marine ecosystems by altering the dynamics among major benthic groups. The sea urchin Diadema antillarum, virtually extirpated in the Caribbean in the early 1980s by an unknown cause, recently experienced another mass mortality beginning in January 2022. We investigated the cause of this mass mortality event through combined molecular biological and veterinary pathologic approaches comparing grossly normal and abnormal animals collected from 23 sites, representing locations that were either affected or unaffected at the time of sampling. Here, we report that a scuticociliate most similar to Philaster apodigitiformis was consistently associated with abnormal urchins at affected sites but was absent from unaffected sites. Experimentally challenging naïve urchins with a Philaster culture isolated from an abnormal, field-collected specimen resulted in gross signs consistent with those of the mortality event. The same ciliate was recovered from treated specimens postmortem, thus fulfilling Koch's postulates for this microorganism. We term this condition D. antillarum scuticociliatosis.

The scleractinian corals of the genus Tubastraea Lesson, 1830 are currently globally dispersed and even so still present a confused taxonomy due to the overlap of morphological characters between the species. In this study, we investigate Tubastraea species previously found in the western Atlantic, based on the molecular marker (ITS gene) and morphology, to determine the accuracy of their descriptions. We identified three morphotypes from Brazil which were genetically delimited into two species: Tubastraea coccinea (Morphotypes I and II) and Tubastraea sp. (Morphotype III). Although morphotype I has morphological patterns of Tubastraea aurea (Quoy & Gaimard, 1833) there was no molecular divergence to support the species differentiation and continue to be recognized as a morphological variant of T. coccinea . The third morphotype is both morphologically and genetically distinct from T. coccinea and is also not representative of the species Tubastraea tagusensis Wells, 1982 despite earlier descriptions describing T. tagusensis in Brazil. Morphotype III exhibited distinct morphological characteristics among the other morphotypes, mainly due to greater polyp projection. In addition, it has fusions between septa, a characteristic that differentiates it from T. tagusensis . Nevertheless, molecular phylogenetic analyses showed that Brazilian Tubastraea fell into two well-supported monophyletic clades, and samples collected in the United States overlapped in both clades. Florida samples exhibited fewer morphotypes and showed greater genetic diversity, presenting haplotypes in four other internal clades. This study highlights the need for an integrative approach to conduct a deeper species delimitation of Tubastraea , essential for managing bioinvasion events by sun corals.

This photograph documents a batwing coral crab ( Carpilius corallinus ) preying on the sea urchin ( Diadema antillarum ) on a coral reef site enhanced with artificial shelter and staghorn coral. This interaction illustrates an interaction that to be better understood to develop a restoration strategy that harnesses positive ecological processes.

Corals throughout the Caribbean have experienced major declines since the 1970s. In response, many agencies have focused their conservation and restoration efforts on outplanting nursery-grown coral fragments onto degraded reefs. Predation on newly outplanted corals can be an important but often unmonitored factor contributing to the declining health and survival of these fragments. In this study, we outplanted 360 boulder coral fragments (Montastraea cavernosa, Orbicella faveolata, Pseudodiploria clivosa), sourced from both ex situ and in situ nurseries, at three locations in the Florida Keys. Each location included one inshore and one offshore site. Ten fragments of each species and source were outplanted at each site (60 corals per site). Transplants were monitored for finfish predation, live tissue area, and survival at 1, 2, 6, and 12 wks post-outplanting. We found the highest finfish predation for all species during the 1 wk monitoring period. Predation during this first week varied by location and reef type, with two locations showing higher predation on offshore sites and one location experiencing increased predation on the inshore site. We also found that coral fragments produced in the ex situ nursery experienced higher initial predation compared to fragments produced in the in situ nursery. However, overall coral survival at 12 wks post-outplanting was 96%, suggesting there was no effect of initial predation on survival. Our results indicate that coral restoration efforts may be affected by intense, initial predation on newly-outplanted boulder coral colonies, but this initial predation may not lead to an increase in mortality.

The Diadema antillarum population in the Florida Keys has not recovered since the Caribbean-wide mass mortality event of the early 1980s. Concomitantly, coral reefs have degraded to the point that there has been a loss of habitat complexity and thus of refuge from predation, possibly creating a bottleneck to the recovery of D. antillarum. With interest rising in using D. antillarum in coral reef ecosystem restoration, we initiated this study to investigate some factors that may limit the survival of D. antillarum. First, we conducted a field experiment to determine whether D. antillarum survival was size-specific by tethering urchins from four size classes (test diameters: 21–30 mm, 31–40 mm, 41–50 mm, and ≥51 mm) on a degraded, offshore reef. We found that size did not offer any protection against predation as there was no difference in survival among size classes. Next, we tethered another set of urchins, approximately 60 mm in test diameter, at the same location but provided half with artificial shelter in the form of halved terracotta flowerpots. We found that urchins that were provided artificial shelter had significantly higher survival than those that did not have access to artificial shelter. Finally, because certain behaviors in D. antillarum are density-dependent, we conducted a laboratory experiment to evaluate whether D. antillarum sheltering behavior was also density dependent. This experiment showed that sheltering behavior decreased significantly as stocking density increased. Our results indicate that restoration practitioners must be cognizant of and facilitate urchin behaviors that maximize survival (e.g., shelter use) and, more importantly, that successful restoration of D. antillarum in Florida will require that suitable refuge be available, either in the form of overhead cover provided by highly rugose reef habitat or by enhancing degraded habitat with artificial shelter. Thus, we suggest that incorporating artificial shelter into the dual-pronged approach of simultaneous urchin and coral restoration may facilitate the recovery of Florida's reefs.

Coastal ecosystems are constantly buffeted by anthropogenic forces that degrade habitats and alter ecological processes and functions; in turn, this habitat degradation diminishes the ecosystem goods and services on which humans rely. Within the last few decades, the field of restoration ecology has burgeoned into a discipline that marries scientific rigor with functional restoration practice-an idea championed by Pete Peterson and his research. Here, we describe our efforts to restore the hard-bottom sponge communities of Florida Bay, FL (USA)-a once-diverse subtropical lagoon severely degraded by cyanobacteria blooms-and the scientific and practical lessons learned from those efforts. Sponge community restoration yielded insights into basic sponge biology and ecology (e.g., density-dependent growth rates) and hastened the recovery of ecological processes (e.g., rates of sedimentation, structuring of water column characteristics, soundscape productions). Because the results of our initial restoration efforts were promising, our collaboration among academic researchers, natural resource managers, and non-governmental organizations has begun scaling up restoration efforts to re-establish the sponge communities over large areas of degraded hard-bottom to "jump start" the ecological recovery of Florida Bay. Though our efforts show promise for ecological recovery, restoration will require a concerted effort by scientists, resource managers, and citizens to stem the anthropogenic drivers of ecological degradation of this unique South Florida ecosystem.

Coral reefs in the Florida Keys have degraded in recent decades, prompting efforts to re-establish populations of staghorn coral, Acropora cervicornis , to restore structure and ecological function. However, predation on these corals by the corallivorous gastropod, Coralliophila galea , has been a substantial and chronic impediment to restoration efforts. Therefore, we conducted a series of manipulative laboratory experiments and a 2-week, in situ proof-of-concept trial to determine whether Thais deltoidea , a carnivorous gastropod that co-occurs with C. galea , can control C. galea corallivory and thus improve A. cervicornis survival. Our laboratory results showed that T. deltoidea preys upon C. galea , although it is not a preferred prey choice. Nevertheless, treatments with T. deltoidea had significantly higher percentages of live coral tissue than when T. deltoidea was absent. This occurred not only because T. deltoidea consumed C. galea , but also because the presence of T. deltoidea elicited an escape response in C. galea , significantly reducing the amount of time C. galea spent feeding on A. cervicornis colonies. This trophic relationship was also seen in our in situ proof-of-concept trial. We observed significantly fewer C. galea on A. cervicornis when T. deltoidea was present which led to a higher, if not statistically significant, percentage of live tissue on our A. cervicornis outplants. Ecological processes need to be incorporated into coral reef ecosystem restoration to achieve positive outcomes. Integrating T. deltoidea into coral restoration efforts may improve success by mitigating C. galea corallivory through the non-consumptive, risk-adverse, escape response that T. deltoidea provokes, initiating a trophic cascade that improves the long-term survival of outplanted corals. Further research is needed to determine the long-term efficacy of this approach, but the addition of gastropod trophodynamics to coral reef ecosystem restoration may prove useful.

Florida Bay nutrient budgets have shown that the majority of existing and influent nitrogen (N) is in organic forms. Consequently, local remineralization processes have been found to regulate the supply of dissolved inorganic nitrogen (DIN). Sponges have dominated benthic animal biomass in Florida Bay and are known to influence local DIN concentrations through remineralization organic matter, yet the role of these organisms in local N budgets is largely unaddressed. We quantified the role of sponges in N cycling in Florida Bay during 2012-2013 by constructing an N budget for a sponge-rich basin. Surveys of sponge biomass conducted in Mystery Basin found sponges at 57 of the 59 assessed stations. Sponge population maxima reached 21 individuals m(-2) and biomass contributions as high as 4.4 L-sponge m(-2). We estimated an average areal DIN contribution from total sponge biomass of 0.59 +/- 0.28 mmol N m(-2) d(-1). However, calculated fluxes from the 59 stations exhibited significant spatial variability associated with changes in the size and species composition of the sponge community; peak N fluxes reached 3.5 +/- 0.9 mmol N m(-2) d(-1) in areas with large populations of high microbial abundance sponges. The average flux from the sponge community was the largest of the estimated sources of DIN to Mystery Basin, representing roughly half of the overall N sourcing. This N satisfied more than half of the demand by primary productivity. These results indicate that sponges are important sources of inorganic N to Florida Bay environments.

Along the Florida reef tract, stony-coral-tissue-loss disease (SCTLD) has caused extensive mortality of more than 20 scleractinian coral species. The pathogen is unknown, but its epizoology indicates that the disease, facilitated by water currents, has progressed linearly along the tract, affecting reefs at the scale of hundreds of kilometers. To inform ongoing disease mitigation efforts, we examined the small-scale spatial and temporal epidemiology of SCTLD. We established a series of sites in the middle Florida Keys at offshore and inshore locations that had not yet shown signs of SCTLD. We then conducted high-frequency monitoring from February 2018 through September 2019 and documented the onset of SCTLD and its progression through the sites. SCTLD was first observed at one site during early February 2018 and by early March 2018 all sites showed signs of the disease. A dynamic multistate model suggested that disease transmission was independent of coral density and found little evidence of a positive association between a colony showing signs of SCTLD and the condition or distance to its neighboring colonies. The model did, however, indicate that the probability of a colony showing signs of SCTLD increased with increasing colony surface area. These results are consistent with the water-borne transmission of a pathogen that progressed rapidly through the survey area. However, by the end of our survey the progression of SCTLD had slowed, particularly at inshore sites. Many affected colonies no longer exhibited progressive tissue mortality typical of the disease, suggesting the existence of differentially resilient colonies or coral communities, meriting their use for future coral rescue and propagation and disease research. These results are useful for refining ongoing SCTLD mitigation strategies, particularly by determining when disease rates are sufficiently low for direct intervention efforts designed to arrest disease progression on individual coral colonies will be most effective.

Widespread and persistent Ecosystem Disruptive Algal Blooms dominated by marine picocyanobacteria (Synechococcus) commonly occur in the subtropical lagoonal estuary of Florida Bay (U.S.A). These blooms have been linked to a decline in natural sheet flow over the past century from upstream Everglades National Park. Remote sensing algorithms for monitoring cyanobacteria blooms are highly desired but have been mainly developed for freshwater and coastal systems with minimal bottom reflectance contributions in the past. Examination of in situ optical properties revealed that Synechococcus blooms in Florida Bay exhibit unique spectral absorption and reflectance features that form the basis for algorithm development. Using a large, multi-year match-up dataset (2002-2012; n = 682) consisting of in situ pigment concentrations and Moderate Resolution Imaging Spectroradiometer (MODIS) Rayleigh-corrected reflectance (R-rc(lambda)), classification criteria for detecting cyanobacteria blooms with chlorophyll-a concentrations (Chl-a) similar to 5-40 mg m(-3) were determined based on a new approach to combine the MODIS Cyanobacteria Index, CIMODIS, and spectral shape around 488 nm, SS(488). The inclusion of SS(488) was required to prevent false positive classifications in seagrass-rich, non-bloom waters with high bottom reflectance contributions. 75% of cyanobacteria blooms were classified accurately based on this modified CI approach with < 1% false positives. A strong correlation observed between cyanobacteria bloom in situ Chl-a and CIMODIS r(2) = 0.80, n = 32) then allowed cyanobacterial chlorophyll-a concentrations (Chl(cl)) to be estimated. Model simulations and image-based analyses showed that this technique was insensitive to variable aerosol properties and sensor viewing geometry. Application of the approach to the entire MODIS time-series (2000 present) may help identify factors controlling blooms and system responses to ongoing management efforts aimed at restoring flow to pre-drainage conditions. The method may also provide insights for algorithm development for other lagoonal estuaries that experience similar blooms.

Strong physical disturbance from hurricanes can disrupt coral reef ecosystems and precipitate a regime shift toward algal dominance, particularly in the absence of grazing pressure to regulate algal growth post-storm. Here, we examine the influence of Hurricane Irma on a keystone grazer, Diadema antillarum, and the surrounding coral reef benthic community in the Florida Keys. D. antillarum densities and test diameters, as well as percent cover of coral reef benthic groups, were measured at 10 sites in the middle and upper Keys before and after Irma. Significant decreases in mean D. antillarum density and median test diameter were observed following the storm. There was a correlation between the magnitude of decline in D. antillarum density and the magnitude of sediment deposition on reefs, suggesting that abrasion or burial from sediment transport may have contributed to D. antillarum mortality. We detected significant decreases in the percent cover of sponges and hydrocorals following the storm, but no change in scleractinian coral cover, which was very low (3% mean cover) at the onset of the study. Macroalgal cover increased at sites in the upper Keys and decreased at sites in the middle Keys. There was no relationship between post-storm D. antillarum density and the change in percent cover of macroalgae or turf-algal-sediment matrix (TAS), likely due to low overall abundance of the grazer. We predict that coral reefs will remain in an algal-dominated ecosystem state due to, among other factors, increasing frequency of strong hurricanes that impact the D. antillarum population.

Lack of recovery of the sea urchin Diadema antillarum in the Caribbean region following a widespread epizootic in 1983–1984 has garnered great interest due to the role of this species as a grazer of macroalgae that exclude reef-building corals. In the Florida Keys, USA, previous research suggests that reestablishment of D. antillarum is limited by low fertilization success and a lack of larval supply. However, the physical mechanisms determining larval supply in the Florida Keys remain poorly resolved. Here, we use coupled biological and physical oceanographic datasets of D. antillarum larval supply to settlement collectors, sea surface temperatures and heights, and the Okubo Weiss parameter to examine a link between influx of larvae to the middle Florida Keys and Tortugas Eddy activity in the Straits of Florida. The greatest magnitude of settlement over 3 months of measurements occurred from late May to late June 2015, coinciding with the passage and dissociation of a Tortugas Eddy. Settlement occurred on collectors only at offshore bank-barrier reef sites, consistent with a temperature signal of a passing eddy at these sites. No D. antillarum were observed by divers at sites 1 yr following settlement on the collectors. The results indicate that despite the lack of population recovery, D. antillarum larval influx can occur during intermittent oceanographic events.