Coral Reef Ecosystems Research Articles

Recent expansion of the Atlantic cownose ray (Rhinoptera bonasus) into Bermudian waters

Cownose rays (Family Rhinopteridae) are highly migratory pelagic rays that are generally restricted to continental shelves. Despite 100's of years of natural history records, cownose rays have never been reported in Bermuda, an atoll-like coral reef ecosystem that is separated from the continental mainland United States by ~1,000 km. Here we compile evidence that the Atlantic cownose ray (Rhinoptera bonasus) has recently established in Bermuda, supported by both morphological and genetic data. Potential ecological and inter-specific competition concerns are presented as well as probable physical mechanisms that facilitated this recent and presumed range expansion.

Christmas tree worm Spirobranchus spp. (Annelida: Serpulidae) as indicators of coral health at Weh Island, Aceh Province, Indonesia

Abstract. Afkar, Barus TA, John AH, Sarong MA. 2024. Christmas tree worm Spirobranchus spp. (Annelida: Serpulidae) as indicators of coral health at Weh Island, Aceh Province, Indonesia. Biodiversitas 25: 1743-1753. The research was conducted along 300-m long transects at 3 and 7 m depth in Beurawang Waters, Weh Island, Aceh Province, Indonesia, which aimed to analyze the association of christmas tree worms (Polychaeta: Serpulidae: Spirobranchus) with coral health conditions and determine the impact of their presence on the coral reef ecosystem. On average, Spirobranchus individuals were more commonly found at 3 m than at 7 m depth. Spirobranchus was found to be most associated with massive corals of the genus Porites. Spirobranchus tends to be most abundant in damaged coral reef colonies, which suggests that coral conditions could worsen if the abundance of Spirobranchus worms increases. Statistical analysis also shows an association between the abundance of Spirobranchus and the condition of coral reefs, with a 'strong' relationship value of 0.611. Therefore, it is necessary to consider coral transplantation as an effort to repair damaged coral substrates in Beurawang Waters.

The emerging and legacy persistent organic contaminants in corals of the South China Sea

Seawater warming, ocean acidification and chemical pollution are the main threats to coral growth and even survival. The legacy persistent organic contaminants (POCs), such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), and the emerging contaminants, including polybrominated diphenyl ethers (PBDEs), dechlorane plus (DPs) and novel brominated flame retardants (NBFRs) were studied in corals from Luhuitou fringing reef in Sanya Bay and Yongle atoll in Xisha Islands, the South China Sea (SCS). Total average concentrations of ∑16PAHs, ∑23OCPs, ∑34PCBs, ∑8PBDEs, ∑2DPs and ∑5NBFRs in 20 coral species (43 samples) from the SCS were 40.7 ± 34.6, 5.20 ± 5.10, 0.197 ± 0.159, 3.30 ± 3.70, 0.041 ± 0.042 and 36.4 ± 112 ng g−1 dw, respectively. PAHs and NBFRs were the most abundant compounds and they are likely to be dangerous pollutants for future coral growth. Compared to those found in other coral reef regions, these pollutants concentrations in corals were at low to median levels. Except for PBDEs, POCs in massive Porites were significantly higher than those in branch Acropora and Pocillopora (p < 0.01), as large, closely packed corals may be beneficial for retaining more pollutant. The current study contributes valuable data on POCs, particularly for halogenated flame retardants (HFRs, including PBDEs, DPs and NBFRs), in corals from the SCS, and will improve our knowledge of the occurrence and fate of these pollutants in coral reef ecosystems.

Tracing Geographic and Molecular Footprints of Copepod Crustaceans Causing Multifocal Purple Spots Syndrome in the Caribbean Sea Fan Gorgonia ventalina

The recent rise in ocean temperatures, accompanied by other environmental changes, has notably increased the occurrence and spread of diseases in Octocorallia, many species of which are integral to shallow tropical and subtropical coral reef ecosystems. This study focuses on the understanding of these diseases, which has been largely limited to symptomatic descriptions, with clear etiological factors identified in only a fraction of cases. A key example is the multifocal purple spots syndrome (MFPS) affecting the common Caribbean octocoral sea fan Gorgonia ventalina, linked to the gall-forming copepods of the genus Sphaerippe, a member of the widespread family, Lamippidae. The specialized nature of these copepods as endoparasites in octocorals suggests the potential for the discovery of similar diseases across this host spectrum. Our investigation employed four molecular markers to study disease hotspots in Saint Eustatius, Curaçao, northwest and southwest Cuba, and Bonaire. This led to the discovery of a group of copepod species in these varied Caribbean locations. Importantly, these species are morphologically indistinguishable through traditional methods, challenging established taxonomic approaches. The observed diversity of symbionts, despite the host species’ genetic uniformity, is likely due to variations in larval dispersal mechanisms. Our phylogenetic analyses confirmed that the Lamippidae copepods belong to the order, Poecilostomatoida (Copepoda), and revealed their sister group relationship with the Anchimolgidae, Rhynchomolgidae, and Xarifiidae clades, known for their symbiotic relationships with scleractinian corals. These results add to our understanding of the evolutionary and ecological interactions of copepods and their hosts, and the diseases that they cause, and are important data in a changing climate.

Puzzling parrotfishes: Radiocarbon age validation and updated longevity estimates for western Atlantic species in support of sustainable fisheries management

For management efforts to succeed in Caribbean fisheries, local fishers must support and be willing to comply with fishing regulations. This is more likely when fishers are included in a stock assessment process that utilizes robust scientific evidence, collected in collaboration with fishers, to evaluate the health of fish stocks. Caribbean parrotfishes are important contributors to coral reef ecosystem health while also contributing to local fisheries. Scientifically robust stock assessments require regional species-specific information on age-based key life history parameters, derived from fish age estimates. Evaluation of the accuracy of age estimation methods for fish species is a critical initial step in managing species for long-term sustainable harvest. The current study resulted from a collaborative research program between fish biologists and local fishers investigating age, growth, and reproductive biology of the seven parrotfish species landed in U.S. Caribbean fisheries; specifically, we validated age estimation for stoplight parrotfish Sparisoma viride and queen parrotfish Scarus vetula. This is the first study to directly validate age estimation for any parrotfish species through analysis of Δ14C from eye lens cores. Our age estimation validation results show that enumeration of opaque zones from thin sections of sagittal otoliths for a Sparisoma and a Scarus species provides accurate age estimates. The oldest stoplight parrotfish and queen parrotfish in the Δ14C age estimation validation series were 14 y and 16 y; while the oldest stoplight parrotfish and queen parrotfish we aged to-date using the Δ14C validated age estimation method were 20 y and 21 y, respectively. Fish longevity (maximum age attained/life span) is a key life history parameter used for estimation of natural mortality, survivorship, and lifetime reproductive output. Past reviews on parrotfishes from the Pacific and Atlantic concluded that most Caribbean/western Atlantic parrotfish species are relatively short-lived with estimated maximum ages ranging from 3–9 y. However, information from our collaborative research in the U.S. Caribbean combined with recently published age estimates for Brazilian parrotfish species indicate that many western Atlantic parrotfishes are relatively long-lived with several species attaining maximum ages in excess of 20 y.

Priority sites for coral aquaculture in Kume Island based on numerical simulation

Global and local stresses such as increased water temperature and terrestrial sediment runoff significantly affect coral reef ecosystems. Over the past three decades, the increase in the intensity and frequency of coral bleaching has been a significant problem in tropical and subtropical coastal seas, and maintaining healthy coral reef ecosystems has long been a challenge. Coral cover in Shimajiri Bay on Kume Island, located in the Nansei Islands (Okinawa Prefecture, southern Japan), has declined due to exposure to high water temperatures, an outbreak of coral predators, and sediment (red soil) inflow from the land. From such a background, coral aquaculture has been implemented at a few stations in the bay. Therefore, it is essential to conduct aquaculture in suitable locations for coral growth and survival. This study aimed to select suitable locations for coral culture with high spatial resolution in an enclosed bay that was greatly affected by red soil runoff, mainly from a sugarcane field. A freshwater and red soil runoff model for the watershed was merged with a coastal hydrodynamic, red soil dispersal, and accumulation model at a spatial resolution of 75 m for Shimajiri Bay. The simulation results were validated using in situ continuous and routine observations. Simulations were conducted over ten years. Locations not subjected to high water temperature in the bay or river loading were selected based on topography, simulated water temperature, salinity, and red soil content of sea sediment. This coupled model enables us to evaluate the growth and survival conditions of cultured corals with high spatiotemporal resolution and quantitatively consider the reduction target of red soil runoff to realize robust coral growth and survival.

Impact of marine debris on coral reef ecosystem of Palk Bay, Indian Ocean

Abstract Coral reef ecosystems are highly sensitive to pollution from marine debris, especially if the regions are noted for tourism and fishing. Palk Bay on the south east coast of India is a famous tourist and fishing region, where the marine debris accumulation poses a great threat to the coastal ecosystem. In this study during 2018–2020, the marine debris distribution and their interactions with coral reefs of Palk Bay were monitored from five stations. Derelict fishing gears (DFGs), including ropes (51 ± 2%) and fishing lines (43 ± 2.5%), were the dominant debris forms recorded. Among the reef‐forming corals, Acropora sp. colonies experienced maximum physical injury and mortality from DFG entanglement. Plastic materials and anchors caused considerable physical damage and tissue loss in Porites sp, without any mortality. Manual debris removal as a potential debris management method was assessed by regularly removing the accumulated debris from the test reef locations of all five stations, whereas the control reef locations were left undisturbed. Test reef locations showed a significant increase in live coral cover and coral recruit density in 2020, against that in 2018, compared with the control locations. Continuous accumulation and interaction of marine debris with the coral colonies of control reef locations resulted in significant reduction of live coral cover and coral recruit density at the control reef locations. This study illustrates the impact of unsustainable fishing and other anthropogenic activities such as tourism and waste disposal on coral reef ecosystems like Palk Bay. The findings of this study demonstrates that manual removal of debris is an important strategy for marine debris management in coral reef ecosystem. Considering the importance of coral reefs in the livelihood of the coastal communities, it is important to tackle the marine debris issue through regular debris removal with stakeholder participation, awareness campaigns and strict legal and management measures.

Rehabilitating coral reefs in the Anthropocene

Coral reefs provide food and livelihoods for hundreds of millions of coastal people in over 100 countries. Recent global estimates for the total value of goods and services that they can generate indicate around US$ 105,000-350,000 per hectare per year, but local estimates of current total economic value can be one to two orders of magnitude lower. Unfortunately, coral reefs are under threat both from local human stressors (for example, sediment and nutrient run-off from agriculture, sewage discharges, dredging, destructive fishing, land 'reclamation', overfishing) and, increasingly, from stressors related to global climate change (not only El Niño Southern Oscillation-related marine heatwaves, which cause mass bleaching and mortality of corals, but also more frequent and powerful tropical cyclones and ocean acidification). Four successive mass-bleaching events on Australia's iconic Great Barrier Reef between 2016 and 2022 (plus another one currently underway) have focused world attention on the need for urgent action to protect coral reefs. It is clear that coral reef ecosystems will continue to decline unless anthropogenic greenhouse gas emissions are reduced and innovative management strategies are developed to assist adaptation.

Context-dependent multimodal behaviour in a coral reef fish.

Animals are expected to respond flexibly to changing circumstances, with multimodal signalling providing potential plasticity in social interactions. While numerous studies have documented context-dependent behavioural trade-offs in terrestrial species, far less work has considered such decision-making in fish, especially in natural conditions. Coral reef ecosystems host 25% of all known marine species, making them hotbeds of competition and predation. We conducted experiments with wild Ambon damselfish (Pomacentrus amboinensis) to investigate context-dependent responses to a conspecific intruder; specifically, how nest defence is influenced by an elevated predation risk. We found that nest-defending male Ambon damselfish responded aggressively to a conspecific intruder, spending less time sheltering and more time interacting, as well as signalling both visually and acoustically. In the presence of a model predator compared to a model herbivore, males spent less time interacting with the intruder, with a tendency towards reduced investment in visual displays compensated for by an increase in acoustic signalling instead. We therefore provide ecologically valid evidence that the context experienced by an individual can affect its behavioural responses and multimodal displays towards conspecific threats.

Deciphering the environmental adaptation and functional trait of core and noncore bacterial communities in impacted coral reef seawater

Microorganisms play pivotal roles in different biogeochemical cycles within coral reef waters. Nevertheless, our comprehension of the microbially mediated processes following environmental perturbation is still limited. To gain a deeper insight into the environmental adaptation and nutrient cycling, particularly within core and noncore bacterial communities, it is crucial to understand reef ecosystem functioning. In this study, we delved into the microbial community structure and function of seawater in a coral reef under different degrees of anthropogenic disturbance. To achieve this, we harnessed the power of 16S rRNA gene high-throughput sequencing and metagenomics techniques. The results showed that a continuous temporal succession but little spatial heterogeneity in the bacterial communities of core and noncore taxa and functional profiles involved in nitrogen (N) and phosphorus (P) cycling. Eutrophication state (i.e., nutrient concentration and turbidity) and temperature played pivotal roles in shaping both the microbial community composition and functional traits of coral reef seawater. Within this context, the core subcommunity exhibited a remarkably broader habitat niche breadth, stronger phylogenetic signal and lower environmental sensitivity when compared to the noncore taxa. Null model analysis further revealed that the core subcommunity was governed primarily by stochastic processes, while deterministic processes played a more significant role in shaping the noncore subcommunity. Furthermore, our observations indicated that changes in function related to N cycling were correlated to the variations in noncore taxa, while core taxa played a more substantial role in critical processes such as P cycling. Collectively, these findings facilitated our knowledge about environmental adaptability of core and noncore bacterial taxa and shed light on their respective roles in maintaining diverse nutrient cycling within coral reef ecosystems.

Variation in population assemblage of Acanthuridae and Scaridae across human concentration levels during a bleaching event affecting the coral reefs of Guna Yala, Panama

Abstract Coral reefs are the ocean's most productive ecosystem, supporting a huge amount of biodiversity, and are relied upon by millions of people worldwide. As we progress into the Anthropocene, coral reef ecosystems are increasingly threatened by a swath of pressures. Of the most impactful are El-Niño Southern Oscillation-related heat pulses, which result in the bleaching and potential mortality of coral reefs. Bleaching events, in synergy with other threats, are increasing algal-dominated reefs, which impact the productiveness of coral reef ecosystems. Herbivorous fish are the prominent algal consumers and are essential in controlling algal blooms. Species from the family Acanthuridae and Scaridae are the most conspicuous of herbivorous fish on coral reefs, and through a diverse array of physiological differences compose several unique functional groups. The population distribution of Acanthuridae and Scaridae are directly correlated with coral reef characteristics and composition and can suffer from bleaching events as well. Despite their importance in maintaining reef health and improving resilience to disturbances, there is a very scarce collection of literature that describes the population assemblage of Acanthuridae and Scaridae spp. during bleaching events. This study aims to contribute to this underreported phenomenon. Visual surveys of Acanthuridae and Scaridae species were conducted to measure the average density, mean size, and biomass in terms of coral reef characteristics across a human concentration gradient in Guna Yala, Panama. Results suggest a similar overall abundance of herbivorous fish between the two reef locations, with significantly larger sizes and biomass of A. coeruelus, S. aurofrenatum, S. viride, and S. iseri in reefs further away from human concentration. This correlates with significantly higher rugosity on these reefs. The mean size of each respective species appears to be lower than previously reported across the Caribbean. Additionally, the biomass distribution was strikingly skewed by S. viride which corresponds to almost ¾ of the total biomass. This indicates that the current bleaching event is having drastic impacts on the distribution of herbivorous fish populations, which is exacerbated by proximity to human concentration. This can have very negative consequences for the recovery of these reefs following the bleaching event. Of specific concern are the coral reefs closer to humans. Data from benthic composition surveys show that macroalgae cover and overall coral bleaching are significantly higher compared to reefs far from humans. This study provides vital information that may be useful for future studies to identify coral reef resilience to bleaching events through the scope of Acanthuridae and Scaridae population distribution. Lay Summary The ocean is a crucial and largely unexplored part of our planet. One area that has begun to receive sufficient scientific attention is coral reefs. This is because, despite only covering less than 1% of the ocean’s surface, coral reefs support a quarter of all marine life. This rich environment provides more than a billion people with their primary source of protein and offers coastal protection to hundreds of millions of people. However, the future of coral reefs is under threat. Due to climate change and human pressures, coral reefs are facing mortality on a worldwide scale. Of the most lethal are bleaching events, when the water temperature rises past the threshold of coral, and they turn white and die. At the same time, corals face a daily threat from increasing algae coverage, which can smother and kill the coral. These threats have intensified in the recent few decades and may permanently alter the biodiversity and productivity of coral reefs. Understanding these changes is of utmost importance, and one way to do so is to study the animals that eat algae and give coral a chance to thrive—herbivorous fish. This paper analyzes the population distribution of two herbivorous fish families: Acanthuridae (surgeonfish) and Scaridae (parrotfish) during a bleaching event. Learning how a bleachingevent can impact the presence of these essential species among coral reefs has rarely been accomplished in scientific literature, so this paper offers valuable contributions to a more comprehensive understanding of reef health during bleaching events and our changing world.

Status of pink ear emperor (Lethrinus lentjan) fishery in the Sinjai and Bone waters, South Sulawesi, Indonesia

The pink ear emperor (Lethrinus lentjan) is a type of coral fish belonging to the Lethrinidae family, they usually eat mainly at night, namely benthic invertebrates or fish. L. lentcan included in the main family of food coral fish that live in coral reef ecosystems and in sandy bottom coastal waters. Good management of fisheries resources is by utilizing fish populations without having to deplete fishery resources. If fishing is carried out continuously without taking into account the ability to renew, over exploitation will occur. The research was conducted from March to May, 2023, in Sinjai and Bone waters, south sulawesi Indonesia which focused on fishing ports with L. lentjan landing potential. The highest class length was obtained in Sinjai Regency and in Bone regency which was negative allometric. Lc in Sinjai regency uses basic gillnet, and in Bone regency 21.9 uses basic longline. Gender comparison between L. lentjan males and females in Sinjai regency is 45% : 55%. Meanwhile for Bone regency it is 41% : 59%. L. lentjan males and females have a ratio of 1: 1.43 with the results of the chi square test tcount &lt; ttable, this condition shows that H0 accepted, there is no real difference between the number of male and female biota. gonad maturity level L. lentjan in Sinjai regency it is 24 cm with a length range of 23 – 25 cm, and in Bone regency it is 24.6 cm with a length range of 24-25 cm.

Combining environmental DNA and visual surveys can inform conservation planning for coral reefs

Environmental DNA (eDNA) metabarcoding has the potential to revolutionize conservation planning by providing spatially and taxonomically comprehensive data on biodiversity and ecosystem conditions, but its utility to inform the design of protected areas remains untested. Here, we quantify whether and how identifying conservation priority areas within coral reef ecosystems differs when biodiversity information is collected via eDNA analyses or traditional visual census records. We focus on 147 coral reefs in Indonesia's hyper-diverse Wallacea region and show large discrepancies in the allocation and spatial design of conservation priority areas when coral reef species were surveyed with underwater visual techniques (fishes, corals, and algae) or eDNA metabarcoding (eukaryotes and metazoans). Specifically, incidental protection occurred for 55% of eDNA species when targets were set for species detected by visual surveys and 71% vice versa. This finding is supported by generally low overlap in detection between visual census and eDNA methods at species level, with more overlap at higher taxonomic ranks. Incomplete taxonomic reference databases for the highly diverse Wallacea reefs, and the complementary detection of species by the two methods, underscore the current need to combine different biodiversity data sources to maximize species representation in conservation planning.

A new strategy based on a cascade amplification strategy biosensor for on-site eDNA detection and outbreak warning of crown-of-thorns starfish

Population outbreaks of the crown-of-thorns starfish (COTS) seriously threaten the sustainability of coral reef ecosystems. However, traditional ecological monitoring techniques cannot provide early warning before the outbreaks, thus preventing timely intervention. Therefore, there is an urgent need for a more accurate and faster technology to predict the outbreaks of COTS. In this work, we developed an electrochemical biosensor based on a programmed catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) cyclic amplification strategy for sensitive and selective detection of COTS environmental DNA (eDNA) in water bodies. This biosensor exhibited excellent electrochemical characteristics, including a low limit of detection (LOD = 18.4 fM), low limit of quantification (LOQ = 41.1 fM), and wide linear range (50 fM – 10 nM). The biosensing technology successfully allowed the detection of COTS eDNA in the aquarium environment, and the results also demonstrated a significant correlation between eDNA concentration and COTS number (r = 0.990; P < 0.001). The reliability and accuracy of the biosensor results have been further validated through comparison with digital droplet PCR (ddPCR). Moreover, the applicability and accuracy of the biosensor were reconfirmed in field tests at the COTS outbreak site in the South China Sea, which has shown potential application in dynamically monitoring the larvae before the COTS outbreak. Therefore, this efficient electrochemical biosensing technology offers a new solution for on-site monitoring and early warning of the COTS outbreak.

Microorganisms uniquely capture and predict stony coral tissue loss disease and hurricane disturbance impacts on US Virgin Island reefs.

Coral reef ecosystems are now commonly affected by major climate and disease disturbances. Disturbance impacts are typically recorded using reef benthic cover, but this may be less reflective of other ecosystem processes. To explore the potential for reef water-based disturbance indicators, we conducted a 7-year time series on US Virgin Island reefs where we examined benthic cover and reef water nutrients and microorganisms from 2016 to 2022, which included two major disturbances: hurricanes Irma and Maria in 2017 and the stony coral tissue loss disease outbreak starting in 2020. The disease outbreak coincided with the largest changes in the benthic habitat, with increases in the percent cover of turf algae and Ramicrusta, an invasive alga. While sampling timepoint contributed most to changes in reef water nutrient composition and microbial community beta diversity, both disturbances led to increases in ammonium concentration, a mechanism likely contributing to observed microbial community shifts. We identified 10 microbial taxa that were sensitive and predictive of increasing ammonium concentration. This included the decline of the oligotrophic and photoautotrophic Prochlorococcus and the enrichment of heterotrophic taxa. As disturbances impact reefs, the changing nutrient and microbial regimes may foster a type of microbialization, a process that hastens reef degradation.

Preface

This special issue on Advances in Ecosystem-Scale Coral Reef Visual Surveys focuses on large-scale monitoring efforts that inform ecological and management topics that are highly relevant and timely as coral reefs worldwide continue to decline. For the past two decades, probability surveys have been implemented by federal, state, territorial, county, and academic partners. The probability surveys’ randomized design, large spatial scale, consistent methodology, participant expertise, and consistent temporal data collection have resulted in high quality, geographically comprehensive coral reef ecosystem data in the US Atlantic Ocean and Caribbean Sea. More recent advances in these long-term, periodic jurisdictional assessments have broad applicability to other coral reef jurisdictions looking to implement ecosystem-scale surveys. In particular, this special issue captures the many advances in ecosystem-scale coral reef visual surveys as it relates to the following themes: (1) Survey statistical design; (2) Reef fish, coral, and motile invertebrate ecology; and, (3) Ecosystem and fisheries management.Collectively, the ten visual census publications herein underscore the importance of these data to assess the present status and trends of the coral reef communities and specific assemblages (e.g., fishery-targeted species, benthic communities; Grove et al. 2024a, Viehman et al. 2024), habitat use (i.e., by species, life stage, guilds; Heidmann et al. 2024, Herbig et al. 2024), responses to anthropogenic stressors (Aeby et al. 2024) and episodic events (e.g., hurricanes; Langwiser et al. 2024), and to inform the fisheries management process (e.g., reliable fishery-independent indices; Ault et al. 2024) and support management actions (e.g., no-take marine reserves, size and bag limits; Keller et al. 2024). Notable advances in these long-term, large-scale surveys include an expansion to a new region (i.e., mesophotic reefs; Grove et al. 2024b, Heidmann et al. 2024) and to a new species (i.e., spiny lobster, Richter and Feeley 2024) in the US Caribbean. In addition, multiple publications use visual census data for new applications such as analyses (e.g., comparing uncalibrated survey indices, Langwiser et al. 2024), ecosystem status reports (Viehman et al. 2024, Grove et al. 2024a) and to inform the efficacy of place-based investments (i.e., restoration, Herbig et al. 2024), a current focus of coral reef conservation.As the breadth of research on these three visual census themes continues to expand in the US Atlantic and Caribbean, we hope to include related, subsequent publications as a second section to this special issue.

Phylogenetic Relationship of Diadema: Emphasis on The Two Distinct Clades of D. Setosum With The Inclusion of Long Spine Black Sea Urchin From Malaysian Borneo

Diadema urchins (family Diadematidae) are ecologically important bioindicators of coral reef ecosystems and seagrass beds. Diadema urchins which are widely distributed and broadcast spawners, have been frequently utilized as model invertebrate species for zoogeography research of the Indo-West Pacific region. So far, Malaysian Borneo, located at the geographic center of Maritime Southeast Asia, has been under-sampled. This study aims to fill this sampling gap and provide the first record of Diadema setosum from Malaysian Borneo using genetic diagnostics to conclusively establish the clade-level identity of the species. According to Cytochrome Oxidase I gene analysis, Diadema is monophyletic. Seven species of Diadema namely Diadema palmeri, Diadema clarki, Diadema mexicanum, Diadema antillarum, Diadema paucispinum, Diadema africanum, and Diadema savignyi, formed their subclades with strong bootstrap values, demonstrating interspecific variation. The findings of this study provide further evidence for the presence of two distinct monophyletic clades, with all D. setosum individuals forming a monophyletic clade that later split into two distinct subclades, dividing Red Sea population (D. setosum-b) and Indo-West Pacific populations (D. setosum-a), supported by a significant genetic divergence value ranging from 6.3% to 9.1%. This study also revealed notable levels of nucleotide and population subdivision between the D. setosum from the Indo-West Pacific and the Red Sea populations (Nst = 0.891; Fst = 0.886) with a low number of migrants per generation (Nm = 0.065). This may suggest geographic isolation due to ecological factors preventing each other from surviving in the territory of the other, or that the two clades of D. setosum were a separate species. Additional morphological and molecular analysis is required in the future to ascertain the level of divergence and further resolve the taxonomic confusion within the genus Diadema.

A novel biosensing strategy on the dynamic and on-site detection of Vibrio coralliilyticus eDNA for coral health warnings

Heat stress and coral diseases are the predominant factors causing the degradation of coral reef ecosystems. Over recent years, Vibrio coralliilyticus was identified as a temperature-dependent pathogen causing tissue lysis in Pocillopora damicornis and one of the primary pathogens causing bleaching and mortality in other corals. Yet current detection techniques for V. coralliilyticus rely primarily on qPCR and ddPCR, which cannot meet the requirements for non-invasive and real-time detection. Herein, we developed an effective electrochemical biosensor modified by an Au-MoS2/rGO (AMG) nanocomposites and a specific capture probe to dynamically detect V. coralliilyticus environment DNA (eDNA) in aquarium experiments, with a lower limit of detection (0.28 fM) for synthetic DNA and a lower limit of quantification (9.8 fg/µL, ∼0.86 copies/µL) for genomic DNA. Its reliability and accuracy were verified by comparison with the ddPCR method (P > 0.05). Notably, coral tissue started to lyse at only 29 °C when the concentration of V. coralliilyticus increased abruptly to 880 copies/µL, indicating the biosensor could reflect the types of pathogen and health risks of corals under heat stress. Overall, the novel and reliable electrochemical biosensing technology provides an efficient strategy for the on-site monitoring and early warning of coral health in the context of global warming.

Sipuncula (Peanut Worms) in Indonesia Waters: A Review

Sipunculans, or peanut worms, are unsegmented worm-like marine organisms with distinctive trunk-like bodies. They play important roles in marine ecosystems, such as bioerosion, bioturbation, and food sources. Sipunculans are also harvested as human food in some regions worldwide. Despite their importance, a comprehensive understanding of the Sipuncula in Indonesia is still limited. This work aimed to compile a study of the distribution, ecology, and potency of Sipuncula species in Indonesian waters. The distribution of Sipuncula species in Indonesian waters was recorded from the northernmost to the easternmost part of Indonesia. So far, nineteen species have been found in Indonesian waters and are dominated by Sipunculus nudus. In Indonesia, Sipuncula exhibits a diverse range of habitats, they can be found in seagrass, mangrove and coral reef ecosystems, in both sandy and muddy sediments. Sipunculans found in Indonesia have ecosystem function as bioturbator, shell-utilizer, and coral-symbiotic species. Sipuncula also has potency as a food and nutraceutical for human health maintenance because it contains highly nutritious such as protein, carbohydrates, ash, lipids, moisture, minerals, amino acids, and fatty acids. In some areas in Indonesia, local communities use Sipuncula as a traditional food source and fishing bait. Given its significance for marine ecosystems and human livelihoods in Indonesia, future management strategies should include regulations on catch size and management practices, data collection, promotion of sustainable fishing practices, and research on Sipuncula biology and ecology. Addressing these knowledge gaps will help to ensure the sustainable use and conservation of Sipuncula in Indonesia.

Transcriptome analysis of the bipotential gonads of hermaphroditic bivalve species Tridacna crocea unravels the potential genes responsible for spermatogenesis

Sex is an integral part of the evolution of species and often takes the form of intersex and sexual change in mollusks. As a major member of the deep-sea coral reef ecosystem, Tridacna crocea has complex gonadal development mechanisms and reproductive strategies, and the regulation model of spermatogenesis needs to be further explored. In this study, gonadal transcripts of T. crocea in resting, spermatogonia and sperm stage were evaluated. According to the statistics of bioinformatics analysis, a total of 10,260 DEGs were identified, including 3021 genes shared by three developmental stages. Through dynamic expression analysis, we identified the expression patterns and functional classification of genes that regulate spermatogenesis. These candidate genes were involved in regulatory mechanisms such as nucleotide binding, cell cycle, sexual reproduction and DNA replication. Subsequently, based on functional screening, PPI analysis was performed on the target gene cluster to learn the network relationships among candidate genes and other genes closely related to candidate genes. The results showed that in addition to candidate genes (zmcm6, gins2, mcm9, blm, mcm4, psmc3ip, haus, ccnb3, spice, rad1, rad17, ncapg, bub1b, lin9, tipin, and cks), several genes that have been shown to be associated with gonadal development were present in the network (such as fanci, aurka, kif20a and nek2), suggesting the reliability of the results. Finally, the expression levels of candidate genes between individuals at different developmental stages were compared with transcriptional expression profiles, which further proved that these candidate genes were related to T. crocea gonad development traits. These results make up for the lack of research on T. crocea gametogenesis, spermatogenesis and gonad development, and provide a reference for the research on Tridacna reproductive mechanism.