The Crown-of-Thorns Starfish (CoTS) outbreaks is one of the important causes of the degradation of coral reefs, but it is still difficult to achieve early warning for such outbreaks. Here, we combined a decade-long record of surface-water environmental factor (2015–2024) from the Xisha Islands, including dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), chlorophyll a (Chl-a), pH, dissolved oxygen (DO), salinity (S), and temperature (T), with phytoplankton community observations collected during 2022–2024 to explore a candidate early-warning indicator system for CoTS outbreak risk. During the period from 2017 to 2018, DIN, DIP and Chl-a significantly increased, N/P decreased, indicating that significant changes in nutrients had already occurred before the CoTS outbreak. Between 2022 and 2024, Bacillariophyta dominated the phytoplankton community, with annual differences in diversity and evenness, indicating that the community structure was relatively sensitive to changes in nutrients. Two complementary predictive models were developed based on environmental factors and phytoplankton community structure data. Model 1 identified the period from 2017 to 2018 as the window with the highest risk of CoTS outbreak, while Model 2 determined 2022 as the year with the highest probability of outbreak support, with a lower probability from 2023 to 2024. This is consistent with the observed CoTS outbreak situation. These results indicate that early warning of CoTS outbreaks through the combined signals of nutrients, Chl-a and the structure of phytoplankton communities is more accurate than relying on any single factor.

The identification of ecological corridors is crucial for mitigating habitat fragmentation and conserving biodiversity. This study pioneered the use of environmental DNA (eDNA) metabarcoding to identify potential fish ecological corridors in Xiamen Bay, a subtropical semi-enclosed bay in Southeast China, addressing the challenge of delineating marine corridors for mobile species. We collected surface and bottom water samples from 29 sites across 10 transects during winter and summer of 2021. eDNA metabarcoding of the 12S rRNA gene (MiFish-U) revealed distinct seasonal shifts in fish community composition, with 46 and 112 species detected in winter and summer, respectively. The communities were predominantly composed of warm-water and temperate species, with a significant proportion of migratory taxa. Alpha and beta diversity analyses confirmed significant seasonal variations in community structure. Spatial analysis of habitat nodes identified ecological corridors with clear seasonal dynamics. In winter, a primary corridor connected the estuary to the western waters and Tong'an Bay, while a secondary corridor linked the Jiulong River Estuary to the southern waters of Xiamen Island. During summer, both corridors extended eastward, with the primary corridor reaching through the waters around Dadeng Island to the eastern waters and the secondary corridor expanding to the eastern waters of Xiamen Island. These corridors likely facilitate various critical ecological processes. Our findings demonstrate that eDNA metabarcoding is a powerful, spatially explicit tool for identifying ecological corridors in complex marine environments, offering a novel and efficient approach to inform marine spatial planning and conservation strategies.

Global climate change is profoundly altering Arctic marine biodiversity, yet baseline data on fish assemblages in the central Arctic Ocean remain critically scarce. The Chukchi Borderland-a Pacific-Atlantic water confluence zone experiencing the most pronounced sea ice retreat in the Arctic-is a frontline area for assessing fish diversity dynamics under climate change. In this study, we simultaneously conducted bottom trawling and environmental DNA (eDNA) metabarcoding to evaluate their complementarity in characterizing fish diversity and to detect species beyond their previously documented ranges. Trawling at 16 stations captured 72 specimens from 17 species, while eDNA metabarcoding of 69 seawater and sediment samples from 31 stations detected 16 species, of which only two were shared with the trawls, highlighting their complementarity. The detected taxa-including pelagic groups (Myctophidae, Gadidae) and demersal groups (Cottidae, Zoarcidae)-align with the region's biogeographic character. Log-transformed eDNA sequence reads were strongly correlated with species' site occurrence frequency, validating the site-occurrence model for inferring relative abundance in Arctic waters. Notably, six species-Artediellus atlanticus, Lycodes raridens, Zaprora silenus, and the Atlantic-affiliated Lycodes lavalaei, Lycodes gracilis, and Hippoglossoides platessoides-were detected beyond their historically recorded northern boundaries. We interpret these signals cautiously: they may reflect climate-driven northward expansions, but may equally indicate historically under-sampled resident populations given the extreme paucity of baseline surveys in the central Arctic Ocean. This study provides the first paired comparison of eDNA and trawling in the central Arctic Ocean and delivers new evidence essential for filling ecological baseline gaps in this rapidly changing region.

Microplastics (MPs) have become emerging contaminants of global concern, yet their presence in the reproductive tissues of Antarctic marine mammals remains poorly understood. In this study, COI gene sequencing confirmed that 59 naturally expelled placentas, collected accidentally from Prydz Bay, East Antarctica, originated from the Weddell seal Leptonychotes weddellii. MPs were isolated from placental tissues and characterized. A total of 30 MP items were detected, with an average abundance of 0.024 ± 0.029 items/g (wet weight). Fibers dominated (73.33 %), followed by films (16.67 %) and fragments (10.00 %). Red (60.00 %) and blue (23.33 %) were the most common colors. Particle sizes ranged from 48.69 to 1207.97 μm, with 26.67 % of MPs smaller than 200 μm. Fourier transform infrared spectroscopy (FTIR) revealed five polymer types, with acrylic (53.33 %) and polyester (23.33 %) being the most prevalent. These results provide the first report of MPs in the placenta of Antarctic marine mammals and establish baseline evidence of MPs presence at the maternal-fetal interface, supporting further assessment of potential implications for placental function and early development.

Eelpouts (family Zoarcidae) serve as an ideal model for investigating adaptive radiation in polar fishes and the parallel evolution of functional genes. However, collection of Antarctic specimens remains highly constrained by logistical difficulties. Here, we present a high-quality, chromosome-level genome assembly for Lycenchelys nigripalatum, reconstructed by combining Illumina short reads, PacBio high-fidelity (HiFi) long reads, and Hi-C chromatin interaction data. The final assembly spans 700.14 Mb with a scaffold N50 of 28.04 Mb, successfully anchored onto 24 pseudo-chromosomes. Technical validation demonstrated exceptional genome integrity and accuracy, yielding a Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness score of 99.31% and a base-level quality value (QV) of 62.44. Genome annotation identified 18,956 protein-coding genes and revealed that transposable elements comprise 22.79% of the genome. This high-resolution genome provides a foundation for elucidating the molecular mechanisms underlying polar adaptation and environmental transitions in Antarctic eelpouts.

Artificial illumination generated during deep-sea mining may impose physiological disturbances on mesopelagic fishes that have long adapted to extremely dim environments, however, the quantitative relationship between light stress intensity/duration and biological responses remains unclear. In this study, Epinephelus lanceolatus was used as a model species to investigate transcriptomic changes in eye and brain tissues under no light (0 lx), weak light (900 lx), and strong light (2000 lx) conditions, aiming to define the biological thresholds of light-induced effects. The results revealed that the eye was highly sensitive to light exposure, with weak light significantly upregulating genes related to visual signal transduction and energy metabolism, whereas the brain exhibited fewer transcriptional changes and maintained homeostasis, showing a differentiated response pattern of "active eye-stable brain". Short-term exposure (24 h) primarily induced acute stress and rapid metabolic adjustments, while long-term strong-light exposure (72 h) led to circadian rhythm disruption, mitochondrial dysfunction, and persistent metabolic burden, potentially impairing growth and reproduction. Based on these mechanistic insights, we propose a dual-threshold model of "adaptive threshold-stress threshold": ≤103 lx as a low-risk level and ≥ 103 lx as a high-risk level. Accordingly, it is recommended that deep-sea mining operations restrict illumination within the weak-light range (≤103 lx), avoid prolonged continuous exposure, and adopt intermittent, directional, and tiered lighting strategies. Incorporating light intensity, duration, and frequency into environmental risk assessments, alongside noise and sediment plume impacts, will support integrated risk management and help mitigate ecological impacts on mesopelagic nekton.

The impact of invasive alien species (IAS) is one of the direct factors causing global biodiversity decline and economic losses, and predicting the potential invasion risks of invasive species is crucial for developing prevention and control strategies. In recent years, an increasing number of studies have shown that invasive species undergo rapid shifts in climate niche in invaded areas. Accurately quantifying the dynamic shifts in the climate niche of invasive species in invaded areas is crucial for developing a more accurate framework for early warning of invasive species risks. Pomacea canaliculata is a freshwater snail found in South America and has become one of the most aggressive aquatic species in the world. Since its introduction to China in 1981, it has rapidly spread and caused multiple serious damages to agriculture, ecology, and public health. Therefore, based on multi-source distribution data of P. canaliculata, this study calculated the climate niche overlap by Schoener' s D, quantified the niche shifts between the P. canaliculata in native and invaded areas (China) via the COUE scheme (a unified terminology representing niche centroid shift, overlap, unfilling, and expansion), and analyzed their changes on a time scale. The results revealed that there have been significant climate niche shifts (Schoener's D < 0.2, niche similarity tests p > 0.01, niche equivalence tests p < 0.01) between the native and invaded areas (China) of P. canaliculata, which does not support the climate niche conservation hypothesis. The minimum temperature of the coldest month (Bio 6) and precipitation seasonality (Bio 15) were the key climate variables driving the climatic niche shift, and P. canaliculata can survive in colder and more arid regions than their native counterparts. The changes in the niche shifts in P. canaliculata on a time scale show significant temporal heterogeneity, and its invasion behavior in China presents a discontinuous and phased expansion pattern, with strong adaptability to new environments. The results are of great significance for the future development of more accurate ecological niche model (ENM), the formulation of more targeted prevention and control strategies, and the study of adaptive evolution mechanisms of invasive species.

Anisarchus medius (Reinhardt, 1837) is a widely distributed Arctic fish, serving as an indicator of climate change impacts on coastal Arctic ecosystems. This study presents a chromosome-level genome assembly for A. medius using PacBio sequencing and Hi-C technology. The PacBio assembly totaled 739.07 Mb across 697 contigs, with a Contig N50 of 10.004 Mb. Hi-C mapping yielded 23 chromosomes, with a successful mapping rate of 90.53% and a Scaffold N50 of 30.20 Mb. Genome BUSCO integrity was 97.05%. Repetitive sequences accounted for 240.83 Mb (32.58%) of the genome. Non-coding RNA annotations included 4,928 rRNAs, 9,663 tRNAs, 347 snRNAs, and 21 snoRNAs. A total of 30,345 protein-coding genes were identified, encoding 46,603 proteins, with a BUSCO completeness of 94.98%. Molecular pathway related to the endocrine system, carbohydrate metabolism, folding, sorting, and degradation, signal transduction, and transport and catabolism contribute to A. medius adaptation to extreme Arctic environments. This high-quality genome provides valuable genetic resources for understanding Arctic adaptations and supporting polar ecological conservation and management.

The international community has reached a consensus to facilitate knowledge of living resources in the Central Arctic Ocean (CAO), where the demersal fishes remain largely unexplored. The Chukchi Borderland is currently one of the few viable areas for bottom trawling within the CAO because it possesses some gentle terrain and has experienced severe seasonal sea ice retreat. In this region, we report an unexpectedly speciose demersal fish fauna with unique zoogeographic patterns based on the most extensive fish surveys conducted by the Chinese National Arctic Research Expedition (CHINARE). Several fish species were recorded here for the first time, which is crucial for updating their geographic ranges and assessing their distribution shifts. Cods (Gadidae), eelpouts (Zoarcidae), and sculpins (Cottidae) were the dominant families, which may have diverse origins and intensified competition that revealed by otolith chemistry and stable isotope analyses. The key species, polar cod (Boreogadus saida), exhibits high mobility and flexible feeding strategies that contribute to its high biomass. Fish assemblages in the Chukchi Borderland have been significantly influenced by sea ice and oceanic inflows, thereby the individual northwards movement and rising biota and nutrients in this region are assumed to increase its fish species richness and biomass. Our findings highlight the importance of scientific monitoring and research in comprehending the impacts of climate change on fish, which is essential for future conservation and sustainable fisheries management in the CAO.

In the context of ongoing outbreaks of the crown-of-thorns starfish, the outbreak of the South China Sea's crownof-thorns starfish (Acanthaster solaris) has severely threatened coral reef ecosystems, highlighting the urgent need for research on related control and eradication technologies. Biological control offers environmental friendliness and long-term effectiveness, making research on predator fish species crucial for managing the crown-of-thorns starfish outbreaks. This study investigates the feeding effects of seven common coral reef fish species in the South China Sea on crown-of-thorns starfish larvae, aiming to identify suitable predator fish species for South China Sea reefs. Additionally, the study develops and validates eDNA quantitative detection technology for the most effective predator, providing technical support and data for subsequent stock enhancement, release effectiveness evaluation, and fishery management. The results indicate that Pomacentrus coelestis significantly outperforms other species in terms of both feeding amount and feeding rate on brachiolaria, making it the most optimal predator identified in this study with a consumption rate of 403 larvae/day. There is a significant positive correlation between the density of the P. coelestis and eDNA concentration, with eDNA concentration stabilizing after 96 h of cultivation. The linear function (eDNA concentration = 267,120,000 density - 234,320,000) shows a good fit (R2 = 0.985), making it generally effective for assessing the resource levels of P. coelestis in stable water environments.

AimRecent climate-driven changes in the Antarctic marine environment, marked by regional differences between West and East Antarctica, may alter ecosystem dynamics. As key components of the food web, fish might reflect these changes. This study examines fish biodiversity patterns across four typical Antarctic seas by integrating eDNA analysis with bottom trawl surveys, focusing on biodiversity shifts and range alterations in response to varying levels of climate change exposure.LocationFour ecologically distinct Antarctic regions: The Adjacent Waters of Antarctic Peninsula (AAP), the Amundsen Sea-Bellingshausen Sea (ASBS), the Prydz Bay-Cooperation Sea (PBCS), and the Cosmonaut Sea (CS).MethodsDuring the 37th Chinese National Antarctic Research Expedition, we integrated eDNA metabarcoding (from both pelagic and benthic water layers) with bottom trawl surveys across four regions (AAP, ASBS, PBCS, and CS) to characterise regional fish community.ResultsEnvironmental DNA metabarcoding and trawl surveys detected 40 and 27 Antarctic fish species, respectively. Environmental DNA proved effective in complementing traditional methods and capturing early life stages, especially with a refined local reference database. Species belonging to the suborder Notothenioidei dominated across all surveyed regions. Ten species exhibited range extensions beyond previously documented distributions, likely reflecting historical data gaps, with the exception of Patagonotothen sp.Main ConclusionseDNA metabarcoding showed potential for monitoring Antarctic ichthyoplankton. Fish diversity in the four studied seas aligns with the general pattern in the Southern Ocean, while ASBS was identified as a previously overlooked fish diversity hotspot. The southward detection of Patagonotothen sp. may signal climate-driven shifts in species distribution. Future research integrating eDNA with interdisciplinary approaches holds promise for advancing the monitoring of climate change impacts on Antarctic marine ecosystems.

Recurring outbreaks of crown-of-thorns starfish (COTS) are one of the greatest threats to corals and have caused catastrophic damage to coral reef ecosystems in recent decades. As obligate corallivores, COTS can tolerate toxic coral mucus, and the sharp spines covering their bodies provide protection from predators. While both of these characteristics are known to contribute to the vitality of COTS and aggravate the impact of COTS outbreaks, the genetic mechanisms underlying their adaptation remain unclear. In this study, we generated a chromosome-level COTS genome and suggested the importance of chromosome fusion in coral-feeding adaptation. In addition, high expression levels of EP4 receptors in the COTS spine apex indicated their potential ability to use the coral prostaglandin PGE2, which might further activate the skeletogenic gene regulatory network responsible for the growth of the spine and body plan of COTS. A comparison of the historical population sizes of COTS from different locations revealed a unique trend in the Coral Triangle, suggesting a potentially higher risk of outbreaks in this region. Our results provide a molecular basis for the adaptive evolution of COTS and a better understanding of its interactions in coral reef ecosystems.

The Southern Ocean, a critical marine region on Earth, is undergoing significant environmental changes due to global climate change, including reductions in sea ice extent, ocean acidification, and alterations in the Antarctic Circumpolar Current (ACC). The Cosmonaut Sea, notable for its dynamic sea ice and rich biological activity, remains one of the least explored regions in the Southern Ocean, with limited data on its marine mammal populations. This study conducted during the 38th Chinese National Antarctic Research Expedition (CHINARE) from January to March 2022, collected systematic data on marine mammal occurrences. Species distribution modeling (SDM) was used to assess the influence of environmental variables on the distribution of the most abundant marine mammal species observed in the Cosmonaut Sea, including humpback whales (Megaptera novaeangliae), crabeater seals (Lobodon carcinophaga), and Antarctic minke whales (Balaenoptera bonaerensis). Our results indicated significant performance variations among the different algorithms, with ensemble model yielding more accurate predictions. Environmental variables such as water depth, sea surface height, and mixed layer thickness were identified as significant factors influencing habitat suitability for different species. Humpback whales were found to have the widest distribution range, followed by Antarctic minke whales and crabeater seals. Generally, the study provides the first comprehensive analysis of marine mammal distribution in the Cosmonaut Sea, highlighting the effectiveness of ensemble models in ecological predictions. The findings emphasize the importance of integrating high-resolution data and incorporating predator-prey interactions in future studies to improve our understanding and conservation of these complex ecosystems.

The lanternfishes are mesopelagic fish that are highly productive as common bycatch of deep-sea shrimp trawlers, but they are often neglected or discarded. Despite being one of the dominant lanternfish species in the Arabian Sea, little is known about the life history of Diaphus thiollierei and its role in marine ecosystems. In this study, 103 D. thiollierei were collected in the Arabian Sea during October–November 2020 to study population growth based on sagittal otolith daily ages; and 10 fish collected during April–May 2021 were subjected to otolith microchemistry analysis to reconstruct the vertical migration in their life history using LA-ICP-MS technique. The standard length–dry weight (SL-DW) relationships for D. thiollierei revealed both negative allometric growth and a significant difference between the sexes. Using daily growth annuli counts on the sagittal section of otoliths, the von Bertalanffy growth equation for D. thiollierei was determined. The pattern of four elemental ratios (Sr to Ca, Mg to Ca, Li to Ca, and Ba to Ca) in sagittal otolith suggested that, in general, D. thiollierei descended continually after hatching until the post-larval (PL) stage when they reached a depth of approximately 200 m. Subsequently, from the PL stage to the post-metamorphosis II (PM II) stage, D. thiollierei likely further sank from 200 m to a depth of approximately 300 m, and then in the daytime they were at a depth of approximately 300–800 m to take refuge from predators. This pilot study explored to unravel the vertical migration during life history in D. thiollierei from sagittal otoliths, whereas further investigation on otolith is needed to better delineate the population ecology in detail, and thus to provide basic information for the exploitation of the lanternfish resource and the understanding of their ecological roles.

Eelpouts (Zoarcidae) are known for their bipolar distributions and distinctive biogeographic histories. However, limited genomic data have hindered our understanding of their adaptive evolution. In this study, we present a thoroughly annotated chromosome-level genome assembly of pale eelpout (Lycodes pallidus) generated through the integration of Illumina, PacBio circular consensus, and Hi-C sequencing techniques. The final assembly spans 753.4 Mb, with its high quality confirmed by a scaffold N50 of 28.6 Mb and a Benchmarking Universal Single-Copy Ortholog (BUSCO) completeness of 99.3%. In comparison to other eelpouts and related fishes, the L. pallidus genome is larger and exhibits greater repetitive element content, accounting for approximately 45% of its total length. We annotated 21,419 protein-coding genes, a significant proportion of which are involved in signal transduction mechanisms and transcription. These findings provide valuable genetic resources for elucidating the evolutionary mechanisms underlying polar fish adaptation.

Sthenoteuthis oualaniensis is one of the most commercially important marine cephalopod species distributed throughout tropical and subtropical waters of the Indo-Pacific Seas. The Indian Ocean is a main fishing ground for S. oualaniensis with a high population density. To explore the distribution of S. oualaniensis in the east equatorial Indian Ocean, four surveys were carried out using light-lift-net fishing vessels. Meanwhile, marine environmental data were also collected, including the sea surface temperature, sea temperature at 100 m depth, mixed layer depth, sea surface chlorophyll-a concentration, sea surface height, and eddy kinetic energy. Generalized Additive Models were used to analyze the relationship between the catch per unit effort (CPUE) for S. oualaniensis and environmental factors. The results showed that the average CPUE of S. oualaniensis was 14.55 kg/h in the four surveys, which was considerably lower than in the South China Sea and Northwest Indian Ocean. In terms of seasonal distribution, the high-CPUE stations were closer to the continental shelf in spring, while they shifted towards the deeper and offshore water in autumn, demonstrating a seasonal migration trend. Pearson correlation analysis showed that CPUE reflected a significant negative correlation with both sea temperature at 100 m depth and eddy kinetic energy (p < 0.001). The Generalized Additive Models revealed that sea surface height was the most significant factor affecting CPUE with a variance explanation of 30.1%. Furthermore, the optimal CPUE prediction model was established by stepwise regression, which contains two factors, sea surface height and eddy kinetic energy, with a variance explanation of 34.9%. This study provides insights into the environmental factors influencing the distribution of S. oualaniensis, which is essential for the sustainable utilization and management of this species.

Yellow seabream (Acanthopagrus latus), a species of significant economic importance, predominantly inhabits the warm waters of the Indo-Western Pacific. While previous studies have explored the genetic diversity of A. latus using microsatellites and other nuclear markers, a comprehensive understanding of its genetic characteristics and adaptive evolution using whole-genome resequencing (WGR) remains limited. In this study, we collected 60 individuals from six distinct geographic locations and performed WGR, achieving an average sequencing depth of 12.59×, which resulted in the identification of 19,488,059 high-quality single-nucleotide polymorphisms (SNPs). The nucleotide polymorphism (πθ) across all populations was consistent, ranging from 0.003042 to 0.003155, indicating low genetic differentiation among populations. Comparative analyses revealed that populations other than that in Xiamen (XM) have undergone adaptive evolution, potentially linked to traits such as growth and development, feeding, immunity, and movement. This study explores the population genetics and adaptive evolutionary patterns of Acanthopagrus latus at the genomic level, providing an essential foundation for the conservation and management of this economically important species in the future.

Acanthopagrus latus and Rhabdosargus sarba are economically important marine species along the coast of China, with similar external morphological characteristics and living habits, with wide distribution and strong adaptability. To investigate the molecular mechanisms underlying the adaptive evolution of these two species, we conducted whole-genome resequencing of 10 individuals of both species from the coastal waters of Wuyu Island, Fujian, China, using high-throughput sequencing technology. We obtained SNP, InDel, CNV, and SV variation information and annotated these variations, constructing a genomic variation database for both species. By comparing the resequencing data with reference genomes, we identified 9,829,511 SNP loci in the population of A. latus and 34,051,056 SNP loci in the population of R. sarba. Using whole-genome SNP data, we employed Fst and ROD methods to identify candidate genomic regions under selection. Functional annotation and enrichment analysis using GO and KEGG databases revealed potential adaptive evolution in R. sarba associated with immune response, feeding, growth and development, and locomotion, while A. latus showed potential adaptive evolution associated with immune response, nervous system, growth and development, and metabolism.