Ocean warming is increasing the frequency, extent, and severity of tropical-coral bleaching and mortality. During 2014-2017, marine heatwaves caused the Third Global Coral Bleaching Event. We analyze data from 15,066 reef surveys globally during 2014-2017. Across all surveyed reefs, 80% and 35% experienced moderate or greater (affecting >10% of corals) bleaching and mortality, respectively. We assess the global extent of coral bleaching and mortality by applying bleaching response curves calibrated from surveyed reefs to predict bleaching globally, based on comprehensive remote-sensing of heat stress. These models predict that 51% and 15% of the world's coral reefs suffered moderate or greater bleaching and mortality, respectively, during one or multiple years, surpassing damage from any prior global coral bleaching event. Our findings demonstrate that the impacts of ocean warming on coral reefs are accelerating, with the near certainty that ongoing warming will cause large-scale, possibly irreversible, degradation of these essential ecosystems. With heat stress levels during this event surpassing those observed previously, the National Oceanic and Atmospheric Administration developed more extreme Bleaching Alert levels that are now being used during the ongoing Fourth Global Coral Bleaching Event.

Ecological transformation is underway on Caribbean reefs, including the flattening of structural complexity and shifts in species assemblages. As marine litter accumulates faster than it can be removed, marine organisms increasingly use litter for shelter and substrate. This study used commercial litter removal dives to assess the cryptofauna most affected by such activities. Following state and federal protocols, displaced taxa were recorded from marine litter retrieved during 18 dive events. Mobile organisms, stony corals, and soft corals were classified, with polychaete worms, Scleractinia corals, and crustaceans (e.g., Mithracidae crabs) comprising over 58% of all taxa observed. Taxa exhibited various interactions with specific litter types. Dives with more diverse litter types yielded significantly higher cryptofauna richness. Biomass estimates were calculated using length- or width-weight relationships for taxa found on the four most abundant litter types (plastic, cloth, metal, processed wood). Using medians and best-fit models for 21 identified taxa, the 18 dives removed an estimated total biomass of 1.34 kg. This equates to roughly 0.0014 kg of fauna per kilogram of litter. When scaled to PADI AWARE Dive Against Debris® removals specific to coral reef environments within the Florida Keys National Marine Sanctuary, we estimate that over 94 kg of biomass of taxa may have been removed over the past decade. These values likely underestimate the true impact especially once scaled to the many clean-up dives that occur each year. We recommend that conservation and management practices account for these largely understudied taxa. Further observations of litter-cryptofauna interactions will improve our ability to include taxon-specific impact estimates in past and future marine litter removal efforts.

Symbiotic relationships are a vital component of the stability and function of ecosystems. Despite their importance, our understanding of many key symbiotic relationships is rudimentary. Within freshwater ecosystems, crayfish are considered keystone species and ecosystem engineers, in addition to serving as a host to multiple ectosymbionts. Recent studies on crayfish symbioses have primarily focused on branchiobdellidan worms in isolation, showcasing context-dependent mutualistic and parasitic fitness outcomes for the crayfish hosts. However, in natural environments, branchiobdellidan worms often share their crayfish host with other symbiont taxa, such as freshwater ostracods, potentially leading to interactions that may have unique effects on their host's biology. In this study, we used a correlational approach to assess the relationships among ostracod and branchiobdellidan abundances, the direct sublethal effects of these symbionts, crayfish health, and crayfish behavioral measures, using regression analyses. In addition, to examine potential interactive effects of our symbiont variables, we used path analyses determining the direct, indirect, and total effects of both symbionts on crayfish health and behavior. We found that ostracod and branchiobdellidan abundance was significantly related to gill scarring on crayfish. Similarly, we found that gill scarring was significantly negatively related to hepatosomatic index, suggesting the possibility of parasitism occurring in these symbiotic relationships under certain contexts. Additionally, our regression analyses indicated symbiont abundance and gill scars were related to both locomotion and grooming behavior. However, these relationships were in opposite directions, suggesting these symbiotic relationships may result in behavioral tradeoffs. While we found no significant indirect effects, the total effects of our path analyses indicated that positive and negative reciprocal feedback loops may occur between symbiont abundance and direct sublethal symbiont effects on host crayfish. The results of this study provide further support for context-dependent outcomes in crayfish symbiotic relationships, with symbiont abundance and the direct sublethal effects of symbionts as potential drivers of fitness outcomes. However, the correlational nature of the study cannot provide direct evidence of either parasitism or mutualism, indicating that further work is necessary to determine the mechanistic links between both symbionts and their host crayfish. The results of this study highlight the importance of examining direct sublethal symbiont effects on crayfish hosts as well as multisymbiont interactions to understand the outcomes of crayfish symbiotic relationships in natural environments. Additionally, while the study is based on correlational analyses, the findings suggest novel directions for future studies to help further understand the symbiotic relationships of crayfish.

Aim: Panulirus is the spiny lobster genus with the most living species, containing 22 recognised species split into two lineages distinguished by habitat preference. Diversification has been proposed to occur due to geographic events affecting the distribution of adults and the dispersal potential of long-lived larvae by oceanic currents. Previously, the most thorough biogeographic inference for Panulirus described diversification influenced by vicariance events resulting from plate tectonics and oceanic currents from the Palaeocene to the Pleistocene. We present updated comprehensive phylogenetic hypotheses and historical biogeography reconstruction models for the spiny lobster genus Panulirus. Location: Tropical and subtropical oceanic regions, especially the Indo-West Pacific. Taxon: The spiny lobster genus Panulirus (White 1847); infraorder Achelata, fam. Palinuridae. Methods: We assembled a dataset of 250 sequences representing mitochondrial (COI and 16S) and nuclear (18S, 28S and H3) gene fragments for 59 members of the Achelata, including 22 living Panulirus species and 4 subspecies. Phylogenetic relationships were reconstructed from all concatenated gene fragments and time-calibrated using fossils. Ancestral distributions across deep time were modelled, and informed historical biogeographic inferences were made. Results: The Achelata and the Palinuridae emerged in the Tethys during the Triassic epoch (similar to 231 and similar to 225 Mya, accordingly). After the ancestor of Panulirus diverged during the late Jurassic (similar to 164 Mya), Panulirus L1 and L2 originated in the Western and Indo-Pacific during the early (similar to 135 Mya) and late (similar to 87 Mya) Cretaceous, respectively. The genus Panulirus experienced the most diversification during the Eocene (similar to 52 Mya), then continued to diversify until the Pliocene (similar to 3 Mya), with the greatest concentration of ancestral species inhabiting the Indo-West Pacific. Main Conclusions: Divergence within the Achelata has been primarily driven by shifts in plate tectonics and oceanic current patterns. Dispersal and, secondarily, vicariance were supported as the main driving forces behind Panulirus diversification. Geographic events likely significantly impacted the dispersal and settlement of long-lived phyllosoma larvae, thus altering gene flow patterns.

The Florida Keys reef tract has rapidly shifted from a structurally complex, hard coral-dominated reef to a less rugose, soft coral-dominated reef. This transition has been facilitated by persistent anthropogenic stressors including recreational and commercial fishing and increased anthropogenic marine debris. During the summers of 2020–2022, benthic censuses were conducted to identify substrate and marine debris composition for 30 reefs in the middle Florida Keys. Inshore reefs contained higher rugosity, coral cover, and marine debris abundance primarily comprised of monofilament and rope from fishing traps. Plastic items (e.g., ropes and monofilament) overall had the highest species diversity. Additionally, marine debris appears to promote turf algae growth on inshore reefs. While is it not yet possible to determine if this pattern of high debris nearshore is due to proximity to onshore debris sources, accumulation due to higher rugosity snagging debris, or increased debris removal efforts offshore, these differences in marine debris types and abundances suggest variability in potential impacts of debris on marine biota on inshore versus offshore reefs. Therefore, the differential use of marine debris by associated biota should be considered in marine debris management practices.

Spiny lobsters (Decapoda: Palinuridae) in the genus Panulirus are targets of lucrative fisheries globally and have relevant ecological functions in tropical and subtropical environments. Only a few, but increasing, number of genetic and genomic resources exist for them. Nuclear and mitochondrial genome assemblies can provide insights into their phylogenetic relationships and support fishery management strategies in species that are heavily exploited. Herein, using Illumina short reads whole genome sequencing, we assembled the nuclear and mitochondrial genomes of a total of 14 species. Genomic DNA was extracted from specimens deposited at Clemson University Crustacean Collection and sequenced in a HiSeq X Ten system. The number of paired-end (PE) reads generated for the different studied species varied between 219,917,346 in P. argus and 70,215,423 in P. cygnus. Nuclear and mitochondrial genomes were ‘de novo’ assembled. Nuclear genomes ranged between 1,624,400,357 bp in P. guttatus and 935,571,898 bp in P. cygnus with scaffold numbers varying between 466,583 in P. versicolor and 852,228 in P. longipes. Mitochondrial genomes varied between 15,613 bp and 15,768 bp in P. pascuensis and P. versicolor, respectively. The totality of the short reads, nuclear, and mitochondrial genome assemblies are available at NCBI's GenBank.

Caribbean spiny lobsters are known to undergo migration as adults, but the dispersal and homing ability of subadults and juveniles is not well characterized. Given that settlement habitat for juveniles is inshore seagrass / hardbottom and reproductive habitat is offshore coral reefs, dispersal during ontogeny serves as a bottleneck potentially limiting adult population density. Previous studies have examined factors associated with movement and den selection by juvenile lobsters such as shelter type, predators, and conspecific density. Their attraction to odors of healthy conspecifics plays a significant role in aggregation of lobsters in casitas and traps. But what is unknown is whether juvenile lobsters possess the map and compass orientation found in adults. To examine the ontogeny of homing ability, we conducted multiple mark / displace tracking studies using acoustic telemetry in juvenile hardbottom and subadult coral patch reef habitats. All lobsters regardless of size tend to relocate to new crevice shelters when handled, even if returned to their original shelter. Thus, for non-displaced lobsters tagged and returned to their point of capture, distance and angle travelled appears to be random with distance increasing as function of body size. However, for juvenile and subadult lobsters tagged and displaced away from their point of capture, the distance and angle travelled when released is significantly directed toward the point of capture. Thus, it appears that the map and compass ability of Caribbean spiny lobsters appears early in ontogeny and may allow for individuals to safely explore unfamiliar locations while retaining knowledge of how to return to known shelter. This ability to expand their known habitat map while maintaining knowledge of critical diurnal shelter locations is expected to facilitate their ontogenetic dispersal to adult habitat.

Human-made debris is entering the ocean at alarming rates. These artificial structures are becoming habitats for small marine taxa known as cryptofauna. Cryptofauna are among the most essential reef taxa; however, little is known about these organisms, let alone their fate considering degrading coral reefs and increasing anthropogenic disturbance. The current study explores differences in naturally occurring cryptofauna biodiversity compared to those inhabiting benthic marine debris. To explore this difference, we measured invertebrate diversity from autonomous reef monitoring structures (ARMS) located on patch reefs along the middle Florida Keys reef tract. ARMS were used as a proxy for natural structure to compare to marine debris removed from five reef locations. Plastic debris was the most abundant of all the debris material collected. Wood and concrete were identified as covariates since they are sourced from wooden lobster traps. Taxa diversity varied significantly between ARMS and debris, indicating that each structural unit contained significantly different and diverse communities. The most influential taxa identified included commensal shrimps, hermit crabs, brittle stars, segmented worms, and several families of crabs. Additionally, while functional richness increased with taxa richness for ARMS communities, debris communities showed decreasing functional richness and high functional similarity, suggesting a specialization of debris-specific taxa. Overall, these data assist in better understanding of the marine community ecology surrounding anthropogenic marine debris for future debris removal and management practices for comprehensive reef health.

Stoplight parrotfish, Sparisoma viride , are hermaphroditic fish that exhibit a complex social structure in which terminal phase (TP) males control a territory of initial phase (IP) individuals (mostly female, rarely male) called a harem. These fish are prolific herbivores that maintain the health of coral reefs by consuming or removing algae that competes with coral for space. In this study, we estimate the influence of food availability, structural complexity, and conspecific density on territory size in S. viride TP males on reef sites in the middle Florida Keys. Divers estimated the territory sizes of both TP and IP individuals by following fish and dropping markers. Divers also estimated the substrate composition, conspecific density, and physical complexity around these territories. TP territories were roughly circular and only overlapped with IP individuals on the outer edges of the TP territory, resulting in TP territories being significantly larger. While TP territory size was positively influenced by the body size of the TP male and negatively influenced by the number of IP individuals, the average ratio of IP:TP individuals was 2.99:1 (± 0.31 SE, range 1–12) for each TP territory regardless of body size. These results suggest that TP males adjust their territory sizes to maintain an apparent optima for the number of females within harems and that the density of conspecifics can potentially influence the timing of sexual transitions in these fish. These results also suggest that S. viride have a polygynous mating structure that is driven by female defense rather than resource defense.

Marine diseases have caused large scale decreases in coral cover across the Caribbean and are unfortunately projected to increase as sea surface temperatures rise. Identifying the main drivers of disease transmission is essential for our understanding and response to diseases in the future. This study investigates the effects of direct-contact, waterborne, Symbiodiniaceae composition, and butterflyfish foraging on the transmission rates of stony coral tissue loss disease (SCTLD) across Montastraea cavernosa (MCAV) coral fragments. M. cavernosa fragments were placed in direct contact with diseased Orbicella and Montastraea colonies with the purpose of creating disease MCAV fragments for experimental trials with butterflyfish. Three treatments were used to investigate waterborne transmission (control), mechanically injury to a healthy coral (limited), and direct contact feeding across a diseased and healthy coral (unlimited). After the experimental trials, the composition of Symbiodiniaceae was analyzed for every MCAV fragment. Direct contact transmission took on average 3.9 days in 2019 and 11.9 days in 2020 with significantly quicker rates of transmission between donor diseased Orbicella and Montastraea than Montastraea to Montastraea . The composition of Symbiodiniaceae differed significantly between the fragments used in 2019 (dominated by Durusdinium ) than in 2020 (dominated by Cladocopium spp.). The limited treatment had the quickest time to transmission compared to the unlimited and control treatments. Symbiodiniaceae differences between 2019 and 2020 might explain differences in transmission rates and overall susceptibility between the years. The species of Symbiodiniaceae may play a role in the susceptibility of corals to the transmission of SCTLD. Additionally, we also have some suggestive evidence that butterflyfish do not directly increase infection rates, but instead might be increasing infection recovery.

Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.

Throughout the Caribbean, coral reefs are transitioning from rugose, coral-dominated communities to flat, soft coral-dominated habitats, triggering declines in biodiversity. To help mitigate these losses, artificial structures have been used to re-create substrate complexity and support reef inhabitants. This study used natural and artificial structures to investigate the factors influencing the use of habitat by reef fish. During 2018 and 2019, divers added artificial structures and monitored the fish assemblages associating with both the artificial structures and naturally occurring corals. Overall, there were more fish on natural structures than on artificial structures. While structure shape did not influence fish use, there was a non-significant trend for increased use of larger structures. Fish observations did not differ across a gradient of shallow, complex reefs to deeper, flatter reefs; however, analyses of feeding guilds revealed clearer patterns: herbivores and omnivores were positively associated with low rugosity reefs where macroalgal abundance was higher, whereas invertivores preferred more rugose reefs. These results suggest that as reefs lose structural complexity, fish communities may become dominated by herbivores and omnivores. It also appears that the addition of artificial structures of the type used here may not mitigate the effects of structure loss on reef fish assemblages.

This paper reports about an informal learning experience - Something Very Fishy (SVF) - which is focused on ocean conservation and climate change. Results from 49 elementary school student workbooks indicated that experiencing SVF improved their understanding of ocean conservation, increased their interest in pursuing science careers, but did not affect their actions towards conservation. Survey results from 40 undergraduate students who helped run SVF indicated that the more efficacious they felt about communicating marine science and the more identified they felt with the scientific community, the more inclined they were to choose careers involving science communication. Survey results from 27 elementary school teachers, who accompanied their students to SVF, indicated perceived norms around teaching marine science and climate change affected their intentions to teach those topics in their classrooms. The paper concludes with implications of these findings on the future of SVF and programs alike, and research directions for environmental conservation in informal settings.

Synopsis Climate and ocean literacy are two of the most important challenges facing society today. However, many students lack exposure to these topics upon entering college. As a result, these students must rely on learning climate literacy and ocean conservation through experiences outside of those provided in the traditional undergraduate classroom. To fill this gap, we initiated a marine science professional development program to expose undergraduate students to ocean literacy principles and climate change concepts through marine ecology research and educational outreach. This study evaluates the effects of our undergraduate experiential learning for individuals involved in our research team, our educational outreach team, or both. Clemson University alumni that participated in our program were surveyed to determine educational and professional gains in three areas related to: (1) knowledge; (2) careers; and (3) attitudes. Multiple linear and logistic regressions were used to understand the relationships between gains and program type, mentor experience, and duration of program enrollment. In addition, we evaluated demographic covariates including age, ideology, and gender. Our study found that perceived knowledge of marine science and science communication skills increased with positive mentor experience. Alumni that rated their experience with their mentors highly also indicated that the program was important to their careers after graduation. Students who participated in any program for a prolonged period were more likely to indicate that marine science was important to their careers. These students were also more likely to continue their education. Additionally, we saw that a sense of belonging and identity in science, as well as the understanding of climate change threat on the marine environment, all increased with longer program involvement, more than the type of experience (research versus outreach). Overall, we found that both the research and outreach programs offered opportunities for advancements in knowledge, careers, and attitudes. These results provide evidence that experiential learning has the potential to increase student engagement and understanding of climate change and ocean literacy communication as well as a sense of belonging in science-oriented fields.

Since 2014, stony coral tissue loss disease (SCTLD) has rapidly spread throughout the Florida reef tract infecting and killing dozens of coral species. Previous studies have found that corallivorous fishes, such as butterflyfishes, are positively correlated with coral disease prevalence at both local and regional scales. This study investigates the association of SCTLD infection and butterflyfish abundance and behaviors on ten reefs in the middle Florida Keys. Divers conducted video surveys of reef fish abundance and disease prevalence in June 2017, 2018, and 2019; before, during, and after the outbreak of SCTLD infections. SCTLD prevalence increased from 3.2% in 2017 to 36.9% in 2018 and back to 2.7% in 2019. Butterflyfish abundances also showed a similar pattern with a twofold increase in abundance in 2018 over abundances in 2017 and 2019. To better understand the association of individual species of butterflyfishes and diseased corals, 60 coral colonies (20 healthy, 20 diseased, 20 recently dead) were tagged and monitored for butterflyfish activity using both diver-based AGGRA fish counts and 1-h time-lapse videophotography collected in the summers of 2018 and 2019. All reef fishes were more abundant on corals with larger surface areas of live tissue, but only the foureye butterflyfish preferred corals with larger surface areas of diseased tissues. Estimates of association indicate that foureye butterflyfish were found significantly more on diseased corals than either healthy or recently dead corals when compared with the other species of butterflyfishes. Foureye butterflyfish were observed to feed directly on the SCTLD line of infection, while other butterflyfish were not. Furthermore, association of foureye butterflyfish with particular diseased corals decreased from 2018 to 2019 as the SCTLD infections disappeared. Our findings suggest that foureye butterflyfish recruit to and feed on SCTLD-infected corals which may influence the progression and/or transmission of this insidious coral disease.