Coloration in fishes plays central roles in communication, defense, and sexual selection, and is mediated by specialized pigment cells (chromatophores). In many species, red and orange hues derive from dietary carotenoids that are metabolically modified and intracellularly transported. The Garibaldi, Hypsypops rubicundus, a long-lived and iconic damselfish endemic to the eastern Pacific, displays a striking carotenoid-based orange-red coloration. To provide genomic resources for studying coloration genes in this species, we generated and assembled a high-quality genome using Oxford Nanopore long reads, yielding a 781.7 Mb assembly with 96% BUSCO completeness. As a proof of concept, we investigated the carotenoid-associated transport gene kif5b, which encodes a kinesin-1 motor protein involved in intracellular pigment mobilization. The kif5b gene in H. rubicundus comprises 25 exons and shows conserved organization relative to other damselfishes, but exhibits a unique amino acid substitution within a conserved nucleotide-binding motif (N3). Specifically, position 238 contains a leucine in H. rubicundus, whereas other damselfishes possess a glutamic acid or serine at this site. This substitution replaces a polar residue with a hydrophobic one, potentially affecting protein conformation or function. Phylogenetic analyses based on mitochondrial genomes and kif5b exons were largely congruent with published relationships. Our results establish the H. rubicundus genome as a valuable resource and identify a candidate molecular change that may contribute to its distinctive carotenoid-based coloration.
Outside the breeding season, small pelagic seabirds are particularly challenging to study due to their large geographic ranges and high mobility. Consequently, their non-breeding distribution and activity patterns are often poorly known. However, the non-breeding period is of critical importance, encompassing both migration and flight feather moult. We combined miniaturised geolocator-immersion loggers (GLS) with carbon and nitrogen bulk and compound-specific stable isotope analyses of rectrix feathers. Using this approach, we investigated the annual phenology, migratory routes, moult locations, non-breeding activity patterns and distribution of two Antarctic storm-petrel species: Wilson's Storm-petrel Oceanites oceanicus and Black-bellied Storm-petrel Fregetta tropica. Stable isotope data revealed a narrower isotopic niche and less intraspecific variation in trophic positions for Black-bellied Storm-petrels (n = 15) compared to Wilson's Storm-petrels (n = 15). GLS data suggested the non-breeding season of Wilson's Storm-petrels to last from around mid-April to end of November. All individuals (n = 7) migrated transequatorial in a clockwise pattern. Three individuals initially stayed at a non-breeding site in the South Atlantic Ocean. The main non-breeding sites of all individuals were in the North Atlantic Ocean, along the eastern coast of Canada and the United States, where flight feather moult took place from July to September, inferred from a period of reduced flight activity (measured by time on water). The foraging activity of Wilson's Storm-petrels was higher at night than during the day. This was not influenced by lunar phase but is likely linked to prey behaviour. The single successfully tracked Black-bellied Storm-petrel also crossed the equator but spent the non-breeding period in the Indian Ocean, mainly in the Arabian Sea. This indicates spatial segregation from Wilson's Storm-petrels. We present the first ever GLS tracking data of Wilson's and Black-bellied Storm-petrels, improving our understanding of their non-breeding behaviour. Future research including more individuals alongside environmental variables will be necessary to examine the drivers of the observed inter- and intraspecific non-breeding spatial and trophic segregation.
Emerging infectious diseases are novel threats to marine ecosystems. Although elucidating the temporal and spatial dynamics of such diseases is critical for managing ecosystems, it is generally challenging because many are invisible and cryptic, making it difficult to conduct long-term surveys at large spatial scales. Here, by analyzing web images on the social network platform X (formerly Twitter), I examined the infection dynamics of the parasitic copepod Lernaeenicus cf. ramosus, which causes pathological impacts on economically important marine fishes. Although previous studies indicated that infections increased after the 2000s in Japanese waters, there is no long-term data. Based on 3390 posts containing images of two host fish species (yellow grouper Epinephelus awoara and grub fish Parapercis sexfasciata) posted from 2012 to 2024, I found the copepods emerged and increased substantially around 2016-2019 in grub fish but declined in yellow grouper. Infection levels tended to be higher in autumn and winter, and methods of fish collection influenced the detectability of parasites. Moreover, I also identified new localities of the copepods, which fall outside of their previously known range, suggesting that their distribution is rapidly expanding north (east) ward. My study showed that analyzing web images sheds important insights into how aquatic diseases emerge and spread.
The endosymbiotic communities of corals are major contributors to the evolutionary success of scleractinian corals as the main reef-building organisms in modern coral reefs. The most studied endosymbiotic taxa associated with scleractinian corals are dinoflagellate family Symbiodiniaceae (previously the genus Symbiodinium), but corals are truly holobionts with a myriad of other microorganisms living together in what is known as the coral microbiome. The goal of this research was to characterize the genetic variability of the microbiome (based on 16S rRNA) and Symbiodiniaceae (based on ITS2) associated with the eurybathic Caribbean sheet coral Agaricia lamarcki along a depth gradient. This plating-crustose coral is found along a wide depth distribution from shallow coastal reefs at approximately 10 m down to mesophotic depths at > 75 m in southwest Puerto Rico. Environmental conditions vary across this gradient, leading us to expect significant differences in zooxanthellae clades and microbiome community composition. We collected fragments of 36 A. lamarcki colonies along a shallow-mesophotic depth gradient from 20 to 70 m at Black Wall in southwest Puerto Rico. PCR and Next-generation sequencing targeting 16S rRNA and ITS2 genes were performed on DNA extracted from coral biomass containing coral tissue and surface mucus layer. Despite no differences in alpha-diversity/richness metrics, our study found significant differences in coral-associated bacterial community composition between shallower reefs (20-30 m) and mesophotic reefs (50-70 m). Contrastingly, we found no significant differences in the Symbiodiniaceae composition of A. lamarcki across the depth gradient, indicating a uniform algal endosymbiont community in this location. Given the increasing loss of shallow water coral reefs, understanding coral adaptation mechanisms to mesophotic environmental conditions becomes ever more important to establish proper management and conservation efforts.
Global climate forcing and anthropogenic pressures are increasingly destabilizing marine ecosystems, pushing high-productivity upwelling zones toward unpredictable ecological tipping points. In the southeastern Caribbean, the eastern Venezuelan coastal region supports one of the world's most significant fisheries for the sardine Sardinella aurita, a species whose population stability is governed by a narrow thermal window (18 degrees C-25 degrees C). Utilizing two decades (2002-2023) of high-resolution MODIS-Aqua satellite data, we applied an early warning signal (EWS) framework based on critical slowing down (CSD) theory to diagnose the loss of resilience in this vital habitat. By contrasting the coastal sardine fishing area (SFA) with the offshore exclusive economic zone (EEZ), we analyzed temporal trends in sea surface temperature (SST) variance (standard deviation) and temporal autocorrelation (AR(1)). Our results reveal a significant divergence in thermal stability: while minimum and mean SSTs show increasing persistence (AR(1)), signaling a classic loss of resilience, the maximum SST in the coastal domain exhibits a sharp increase in volatility (SD) and erratic behavior. These "anti-CSD" signals in maximum SST indicate that extreme thermal events, such as marine heatwaves, are becoming more frequent and intense, frequently trespassing the physiological thresholds of S. aurita. By prioritizing physics-based indicators of habitat stability over confounded fishery-dependent data, this study demonstrates that the coastal sardine habitat is approaching a nonlinear regime shift. These findings provide a robust, proactive diagnostic tool for fisheries management, offering a critical lead time for adaptive strategies before biological collapses become statistically detectable.
Zostera marina, commonly referred to as eelgrass, is a marine flowering plant frequently growing in some water-saturated sediments along the coastal regions of Japan. We examined the bacterial communities in the sediment of three eelgrass areas to compare the bacterial composition of vegetated sediments (eelgrass sediments) with that of nearby unvegetated sediments. We also revealed the core bacterial groups commonly detected in all eelgrass beds examined. The bacterial communities varied between the eelgrass sediment and the surrounding unvegetated sediment. Deltaproteobacteria and Epsilonproteobacteria were showed significantly higher relative abundance in eelgrass sediment compared to the unvegetated sediment. As core taxa, 38 OTUs/phylotypes consistently appeared across the three eelgrass sediments and are considered unique to the eelgrass beds, indicating potential specific interactions with Z. marina. The most prevalent core taxa in eelgrass sediment were Gammaproteobacteria, Deltaproteobacteria, and Flavobacteriia, which include members involved in key biogeochemical processes. Additionally, environmental variables such as temperature, salinity, pH, DO, and total organic carbon (TOC), emerged as the key drivers of variation within the bacterial community. This study contributes to the understanding of bacterial diversity associated with Z. marina sediments and highlights differences in microbial community composition between eelgrass and adjacent unvegetated sediments. Deeper sequencing in future studies will further improve the resolution of rare bacterial diversity associated with eelgrass sediments.
Estuaries play a crucial role in maintaining marine biodiversity and providing key ecosystem services, but they are increasingly impacted by local anthropization and global climate change. Developing effective management strategies requires a deep understanding of the genetic structure and diversity of marine species, including how their populations are connected across their distributional range. Here, we used cytochrome oxidase 1 (COI) data to test the hypothesis of significant genetic structuring in the semiterrestrial crab Armases rubripes along its distribution, from the Caribbean to the Western South Atlantic coastline. Patterns of genetic diversity, population structure, and demographic history were assessed, and phylogenetic analysis was performed. Our results support this hypothesis, revealing a potential cryptic species complex, with species-level divergence between the Caribbean and Brazilian regions. These two regions exhibit exclusive haplotypes, with up to 16 mutational steps between them, and were recovered as well-supported clades in our phylogenetic reconstructions and high genetic distances that are consistent with interspecific differentiation. We also uncovered unexpected genetic structure within the Brazilian coast, revealing distinct South and North groups among our sampling sites. The analysis of historical demography suggests that Caribbean clade remained stable over time, while Brazilian South group showed signs of recent demographic expansion. Overall, our results suggest that A. rubripes is likely a species complex, with Caribbean and Brazil representing separate evolving lineages.
The endosymbiotic jellyfish Cassiopea andromeda represents a yet untapped marine species that could be targeted as a new source for bioproducts, including food and feed. Also, the potential use of contained valuable ingredients, such as carotenoids and other antioxidants, under controlled aquaculture conditions might be a particularly promising pathway. However, this requires close knowledge about physiology and culture conditions. In this study, the effects of different stress parameters such as different light spectra, light intensities, UV and extreme temperatures on C. andromeda were investigated. The following response parameters were measured: pigments, photosynthetic efficiency, bell pulsation rate, antioxidant activity (AOA) and respiration. The carotenoid peridinin and chlorophyll a were detected as dominant light-harvesting pigments. Three different experiments were performed. Over a four week treatment interval under four different light conditions, C. andromeda that were exposed to light spectra lacking blue color (lambda = 400-500 nm) showed a decreasing content of chlorophyll, peridinin and all other detected pigments, while photosynthetic efficiency and AOA were not affected by any light spectra changes. Critical thresholds for both photosynthetic efficiency and respiration were detected beyond 39 degrees C. UV seemed to have a similar effect on respiration as low temperatures, while UV did not seem to significantly affect bell pulsation rate and symbiont density. This study contributes to the development of an environmentally controlled C. andromeda indoor aquaculture system, revealing optimal temperature and light regimes. Accordingly, C. andromeda holds promise as a resource for pigment production that may offer value as a supplement for functional foods and nutraceuticals.
The seagrass ecosystems of the Tropical Northwestern Atlantic (TNA) host three described species of sea anemones in the genus Bunodeopsis Andres, 1881 (Enthemonae: Metridioidea: Acuticulata): B. antilliensis, B. globulifera, and B. pelagica. Due to their small size and nocturnal nature, many aspects of their basic biology and distribution remain unknown. To investigate their ecology and distribution, we surveyed five TNA ecoregions: Greater Antilles (Puerto Rico), Southern Caribbean (Cura & ccedil;ao), Southwestern Caribbean (Colombia and Panama), Western Caribbean (Belize and Mexico), and the Southern Gulf of Mexico (Mexico). Specimens were identified to genus, documented in situ and captively maintained for behavioral observations. Field methods combined nighttime snorkel observations and collection with macro and timelapse photography to document behavior, morphology, and asexual reproduction. We observed extensive morphological variation and presumably clonal aggregations in situ. Captive observations corroborated previously reported modes of asexual reproduction including pedal and vesicular scission, as well as revealed the previously unreported mode of transverse fission. Field observations revealed novel ecological interactions including predation on amphinomid polychaetes, association with the sacoglossan Elysia crispata, and predation by a reptantian ribbonworm (Nemertea: Reptantia). In Belize, standardized diurnal and nocturnal quadrat surveys at fixed distances from shore quantified Bunodeopsis spp. detectability, which was significantly greater at night regardless of observation depth. Nighttime detectability was approximately three times higher than during the day, supporting the conclusion that the lack of an abundance of reports of Bunodeopsis spp. is likely an artifact of underdetection than true rarity. The new occurrences reported here more than double previous records on GBIF, contributing resolution to the distribution of Bunodeopsis spp. Across five ecoregions in the TNA. These findings underscore the ecological importance of this genus of sea anemones in seagrass ecosystems and emphasize the need for surveys that target small, nocturnal, and understudied marine invertebrates.
Diverse invertebrate communities inhabiting carbonate rocks at methane seeps may rely on a mix of local chemosynthetic production and sinking photosynthetic organic matter, with relative importance shaped by environmental conditions. We investigate the contribution of chemosynthetic carbon to macrofaunal diets at six Southern California methane seeps (275-1020 m depth) and the influence of seep site, seepage habitat, water depth, and oxygen on trophic structure, using stable isotope analyses, Bayesian mixing models, and generalized additive models. Macrofauna exhibit wide isotopic ranges and methane-derived carbon (MDC) contributions, with several species deriving > 80% of their diet from chemosynthetic sources, including pyropeltid limpets, provannid snails, and dorvilleid and nereidid polychaetes. Negative delta N-15 values and high MDC in a trichobranchid polychaete and sponge are consistent with N-2 fixation or incorporation of N-fixing microbial biomass. Taxa historically not considered as 'seep fauna' (e.g., bryozoans and cnidarians) also incorporate substantial chemosynthetic input, challenging their classification as 'background' taxa. Community-wide trophic structure varied strongly by seep habitat, with active seepage habitats showing higher chemosynthetic reliance, trophic diversity, and isotope ranges. Seep production export into surrounding systems was greater at deeper seeps, suggesting a stronger trophic sphere of seep influence where photosynthetic input is more limited. This increased reliance on chemosynthesis with depth appears to reverse the typical positive delta N-15-depth relationship observed in non-chemosynthetic fauna. Low oxygen seems to favor a restricted number of species with specialized trophic niches. Macrofauna isotopic variability across seep sites likely reflects differences in fluid flux regime and geochemistry. Our study demonstrates that chemosynthetic production plays a broad role in supporting the deep-sea communities off Southern California and reveals complex, and potentially novel, trophic interactions at methane seeps. These findings underscore the importance of incorporating trophic diversity and associated functional heterogeneity in conservation planning, especially as environmental changes reshape deep-sea ecosystems, warranting more nuanced protection frameworks.
Rays are common marine mesopredators that use coastal and estuarine habitats during multiple life history stages for critical functions. They are long-lived, late to mature, and have low reproductive output, making them vulnerable to and slow to recover from population threats such as overfishing and habitat loss. Considering this, examining ray abundance, assemblage structure and distribution, as well as identifying ray habitat use patterns, especially over long time periods, is important. Fishery-independent sampling (tangle nets, bottom longlines, and rod and reel) was used to examine ray species composition, distribution, and abundance in St. Joseph Sound over a 10-year period. Six different ray species were caught, with three species making up 93.5% of the catch: southern stingray (Hypanus americanus), cownose ray (Rhinoptera sp.), and bluntnose stingray (Hypanus say). Ray abundance and assemblage composition varied across the study area, potentially due to differences in abiotic or biotic conditions. Analyses revealed that this area is used by multiple ray species for multiple life history functions, including use by cownose rays as a pupping area. This study represents the first in-depth analysis of the batoid community in St. Joseph Sound, and collectively, the results suggest that the study area serves as important habitat supporting ray communities in the coastal and inshore waters of the eastern Gulf of Mexico.
The current study examines the population structure and reproductive traits of the porcelain crab Petrolisthes rufescens (Heller 1861) among the samples collected from the rocky intertidal region of Shivrajpur village, located on the Saurashtra coast of Gujarat. Understanding the population ecology of this species is crucial for its significant role in ecological processes, such as nutrient cycling, and its potential susceptibility to environmental stressors. Specimens were collected over 12 consecutive months (March 2019-February 2020) from a 500 m(2) area during low tide using the hand-picking method. A total of 1191 individuals were collected, comprising 552 males, 475 non-ovigerous females, and 164 ovigerous females. Adult male individuals were significantly larger than adult non-ovigerous females, with an average carapace length of 9.28 +/- 1.32 mm compared to 8.56 +/- 1.12 mm in females. The overall and monthly sex ratios were slightly female-biased (1:1.2). The size-frequency distribution in both males and females showed an apparent bimodal pattern. Ovigerous females were present year-round, suggesting that reproduction occurs on a continuous basis. However, a relatively higher proportion of ovigerous females were observed during March-May and August-October at the Shivrajpur coast over the study period. Reproductive biology was assessed by examining egg characteristics, including total number, size, weight, and alongside the carapace length of ovigerous females. A significant positive correlation was found between the size of ovigerous females and their reproductive output, including total egg count (197 +/- 87.53), egg mass weight (10.78 +/- 8.26 mg), and egg size (0.59 +/- 0.09 mm). This study provides baseline data for future research on the species' response to environmental changes and the increasing anthropogenic pressures affecting coastal ecosystems.
Sipunculans are unsegmented marine annelids distributed from intertidal to deep sediments, playing important roles in nutrient cycling and ecosystem health. The Sipunculus nudus species complex is exploited as food and bait in several regions, yet reproductive data at the population level remain scarce, especially for Atlantic populations. Understanding morphological correlates of body size and reproduction is essential for sustainable management. Over 17 months, 434 individuals of S. cf. nudus were collected monthly from intertidal sediments in Salvador, Brazil. External (total length, posterior length, width) and internal (number of longitudinal muscle bands, nephridia length, intestinal coils) measurements were taken. Coelomic fluid was examined to determine sex and gamete maturity, and oocytes and spermatocyte clusters were staged and measured. Population structure was analyzed using correlation analyses, DistLM, and dbRDA; reproductive investment via generalized linear models; and sex ratios by chi-square tests. Environmental data (temperature, salinity, tide, rainfall) were included in redundancy analyses. Posterior length strongly correlated with total length and was identified as a reliable size proxy, while nephridial length distinguished mature from immature individuals. The population showed a near 1:1 sex ratio, with males producing larger spermatocyte clusters relative to size, while female oocyte diameter was size-independent. Gametes at multiple maturation stages occurred year-round, indicating continuous reproduction unaffected by environmental variation. These findings reveal morphological indicators of reproductive status and suggest stable, size-dependent reproductive strategies that may enhance population resilience under harvesting pressure. The study provides key baseline data for managing exploited Sipunculus populations.
Meiofaunal studies in both shelf and deep-water benthic habitats of the Gulf of Mexico (GOM) have increased notably over the last decade, including research focused on specific taxa such as kinorhynchs. In this study, a grid of 63 sampling sites was sampled, covering depths from 49.7 to 3708 m and encompassing most of the southwestern GOM, to study the factors influencing meiofaunal distribution, which is fundamental to understanding marine ecosystem structure. We analyzed the diversity patterns of kinorhynchs in the southern Gulf of Mexico (sGOM) with two main objectives: (1) to describe the diversity of kinorhynchs collected from shallow to deep stations, and (2) to assess the effects of environmental variables on kinorhynch species richness and taxonomic composition. A total of 54 kinorhynchs were collected from 36 sites, representing 14 taxa distributed in one class: Cyclorhagida and three orders Kentrorhagata, Echinorhagata and Xenosomata. Order Echinorhagata was the most diverse and abundant, represented by the genera Echinoderes and Fissuroderes. Followed by order Kentrorhagata with genera Antygomonas, Centroderes, and Sphenoderes. Ecological analyses indicated a pattern toward a linking depth and granulometry with the structure of kinorhynch assemblages across the southern Gulf of Mexico.
This study provides the first detailed assessment of the spatio-temporal distribution of benthic amphipods in Chilika Lagoon. Seasonal changes in species composition, diversity, and distribution were analyzed across four lagoon sectors, along with environmental factors influencing these patterns. Thirteen species belonging to seven genera and families were recorded, with Aoridae, Eriopisidae, and Maeridae being dominant. Permutational Multivariate Analysis of Variance (PERMANOVA) and Canonical Analysis of Principal Coordinates (CAP) analyses revealed clear separation between post-monsoon/winter assemblages and those from pre-monsoon/monsoon seasons. Amphipod communities differed markedly from earlier records, likely due to long-term ecological changes in the lagoon, though Quadrivisio bengalensis and Victoriopisa chilkensis persisted, indicating their resilience. Principal Component Analysis (PCA) and Distance-based Linear Models (DistLM) showed amphipod diversity significantly correlated positively with dissolved oxygen and pH, and negatively with depth and temperature. General Linear Model (GLM) identified dissolved oxygen as the primary driver that can model the amphipod distribution in the studied area. The results of Canonical Correspondence Analysis (CCA) demonstrated that amphipod species show varying degrees of specialization, with F. odishi exhibiting a strong environmental affinity, while most taxa display broader ecological tolerance. In contrast, Quadrivisio bengalensis , Quadrivisio chilikensis , and Ampelisca sp. were associated with higher temperature and higher total organic carbon (TOC). Overall, this study establishes a much-needed ecological baseline for benthic amphipods in Chilika Lagoon, demonstrating the species-specific responses to environmental conditions and offering a framework for detecting future ecological change.
Merluccius productus, commonly referred to as the Pacific Hake, is well known as a relevant species in the structure and functioning of its marine food web networks, acting as a foraging species. Additionally, it represents an important resource for the fishing industry. Nevertheless, little is known about its feeding habits. Therefore, this work describes the diet of the Pacific hake inhabiting the Gulf of California. Samples were obtained from six exploratory fishing research trips conducted between 2014 and 2017. The Prey-Specific Index of Relative Importance (%PSIRI) was used to quantify the dietary components of the Pacific hake. Additionally, to determine its feeding strategy, a similarity analysis was conducted and the Levin's Index and Morisita-Horn Index were calculated. The sampling included 1772 organisms with sizes ranging from 13.3 to 98.4 cm TL. The analysis of 39.2% of stomachs revealed the presence of different prey items, allowing the identification of 23 distinct prey types grouped into three categories: bony fish, crustaceans, and mollusks. The Prey-Specific Index of Relative Importance indicated that the diet is mainly composed of Solenocera mutator (25.2%), fish remains (24.9%), Nyctiphanes simplex (18.7%), and Benthosema panamense (8.3%), collectively accounting for 77.1% of the diet composition. The low Levin's index value (Bi = 0.19) classified the Pacific hake as a specialized predator, while the Morisita-Horn index indicated a moderate level of dietary overlap (C lambda = 0.42). The temporal similarity analysis revealed an overall similarity of 60%, allowing the identification of three distinct groups. Notably, Group B, composed of stomach contents from F-2014 and C-2014, exhibited a higher similarity of 76.1%. The highest contribution to the similarity of this group was represented by the euphausiids N. simplex (41.03%). Our results suggest that M. productus primarily feeds on highly abundant and available prey species in its environment, predominantly pelagic crustaceans, performing vertical migration to feed. The high frequency of crustaceans such as S. mutator and N. simplex, along with the fish B. panamense, further supports the classification of M. productus as a specialized predator.
The mangrove oyster (Crassostrea gasar) plays a key ecological role in Amazonian estuaries by filtering suspended organic particles, microalgae, phytoplankton, and bacteria, contributing to water quality and nutrient cycling. Its gut microbiota is shaped by complex interactions with the surrounding aquatic environment, reflecting the ecological conditions of its habitat. We applied a high phylogenetic resolution metabarcoding approach to investigate the richness, structure, and dynamics of bacterial communities associated with C. gasar and their environments. Samples were collected from four Amazonian farming sites-Santo Ant & ocirc;nio de Urindeua (SAU), Nova Olinda (NO), Pereru de F & aacute;tima (PF), and Lauro Sodr & eacute; (LS)-during both rainy and dry seasons. Total microbial DNA was extracted from water, sediment and oyster gut samples, and full-length 16S rRNA genes were sequenced using the PromethION 2 Solo platform (Oxford Nanopore Technologies). The microbiomes of oysters and water are both significantly influenced by abiotic factors. Redundancy analysis identified salinity and pH as the primary environmental drivers structuring bacterial communities. Seasonal decreases in these parameters during the rainy season led to increased alpha diversity, while their temporal fluctuations drove beta diversity patterns, resulting in distinct bacterial assemblages between rainy and dry periods across all sampling sites. The pan-microbiome encompassed 5409 taxa, with a core bacteriome of 2330 taxa dominated by Actinomycetota, Pseudomonadota, Mycoplasmatota, and Bacillota. Ecologically significant genera included Sphaerochaeta (organic matter fermentation), Crinalium (nitrogen fixation), Corynebacterium (pathogen defense), and Enterobacter (nutrient cycling), reflecting functional diversity in oyster-associated microbial communities. The presence of Salmonella during low rainfall underscores potential ecological risks. These findings reveal that oyster-associated microbiomes exhibit taxonomic shifts in response to seasonal environmental variation, with potential implications for ecosystem functioning. The detection of functionally important taxa (nitrogen fixation, organic matter degradation, pathogen defense) across environmental gradients provides insights into microbial ecological dynamics in Amazonian estuarine oyster farming.
Populations at a species' distribution edges often present reduced gene flow, increased impact of genetic drift, and impoverished genetic variation, globally compromising their ability to adapt to environmental changes. This study assessed the genetic diversity, structure, and connectivity of the Mediterranean endemic seagrass Posidonia oceanica at its easternmost distribution limit, from diverse thermal regimes around Cyprus, contextualised within a set of 16 Turkish populations in the Levantine and Aegean Seas (eastern Mediterranean). The genetic assessments were based on sets of 13 to 16 microsatellite loci, depending on the analysis. Our findings revealed lower genotypic and allelic richness in the Cypriot populations, which also presented lower connectivity and higher differentiation among them in comparison to the Turkish ones. Additionally, the genetic and genotypic diversity and the connectivity of Cypriot populations were highly variable, with populations presenting high diversity and connectivity, while others exhibited extremely low diversity and high isolation. The discrepancies among the Cypriot populations were potentially due to differences in the sexual reproductive output related to the different thermal regimes around the island and the presence of barriers to gene flow along the island's southern coastline. This study advances our understanding of the genetic connectivity and genetic diversity of range-edge P. oceanica populations in the Eastern Mediterranean. This knowledge can guide the management of conservation and ecosystem restoration initiatives for this habitat-forming seagrass species.
Habitat partitioning reduces competition among ecologically similar species and promotes their coexistence within the same environment. In this study, we evaluated the abundance, microhabitat use, reef occupancy, spatial overlap, and agonistic interactions of the sympatric territorial damselfishes Stegastes acapulcoensis and Stegastes flavilatus at La Entrega reef, Oaxaca, Mexico. Using visual censuses, habitat characterizations, in situ observations, and non-invasive video recordings, we found that S. acapulcoensis exhibited higher abundance than S. flavilatus across all reef zones. Both species exhibited clear habitat partitioning along the reef zones, with S. acapulcoensis occupying sites with high percentages of live coral and algae, as well as large shelters, while S. flavilatus used sites characterized by high rugosity and the presence of rock, sand, and rubble. Although S. flavilatus defended larger territories than S. acapulcoensis (6.6 +/- 4.9 m(2) vs. 4.5 +/- 1.5 m(2), respectively), S. acapulcoensis occupied a greater proportion of the reef area (58% vs. 18%). Spatial overlap between species was limited (10%-25%) but increased up to 40% among individuals of size class III in the deep zone, where the availability of preferred microhabitats for both species was substantially lower. Both species displayed a higher frequency of agonistic interactions toward conspecifics; however, interspecific interactions increased in the deep zone. Our results suggest that the spatial partitioning of S. acapulcoensis and S. flavilatus is driven by differences in microhabitat selection, resulting in relatively low spatial overlap and predominantly intraspecific aggression. Our findings show that the fine-scale selection of species-specific microhabitats and interspecific agonistic interactions drive spatial segregation and maintain ecological differentiation between S. acapulcoensis and S. flavilatus, thereby promoting their coexistence even in overlapping reef zones within structurally complex systems.
Deep-sea corals and sponges form ecologically significant habitats that support biodiversity hotspots and contribute to important ecosystem functions such as carbon and nutrient cycling as well as benthic-pelagic coupling. However, quantifying their contributions to ecosystem functioning requires examination not only of the fine spatial distribution of community composition but also community size structure, because larger individuals are expected to contribute more to ecosystem functions than smaller ones. Here we create novel cumulative abundance profiles (CAPs) by combining body size structure with species abundance data to identify ecological drivers of sponge and coral community composition and size structure. Data were collected from 226 drop camera images captured near Saglek Bank, on the northern Labrador shelf and upper slope in the northwest Atlantic. The density of four coral and 17 sponge morphospecies were recorded from each image. The surface area covered by coral and sponge specimens was measured (1458 measurements in total) and converted to size estimates using data from live specimens collected with a rock dredge. Cumulative abundance profiles were then constructed and combined with cluster analysis to identify distinct community assemblages. In addition, distance-based redundancy analysis was used to identify environmental drivers influencing cluster community composition and/or size structure. Finally, organic carbon turnover was calculated for each cluster using published respiration data. Three assemblages were identified with differing composition and size structures. One of these was characterized by large coral and sponge morphospecies and individuals. The spatial distribution of this cluster was controlled by interactions between substrate type, terrain position index (TPI) and orientation of the slope (eastness). When analysing composition or size structure separately, dissolved oxygen and current speed respectively were also identified as key parameters. This finding indicates that substrate type and TPI influence the presence of coral and sponges in the study area, while dissolved oxygen may constrain which morphospecies are present and bottom currents restrict the size of individuals. As predicted, high levels of carbon turnover were driven by large sponge and coral individuals, likely maintained in part by the sponge loop in which sponges recycle dissolved organic matter into particulate organic matter. This study gives the first demonstration of how CAPs can be used to analyse spatial variation in deep-sea benthic community composition and size structure and appropriately quantify contribution to ecosystem functions such as carbon turnover.
