Owing to the significant differences in environmental characteristics and explanatory factors among estuarine and coastal regions, research on diatom transfer functions and database establishment remains incomplete. This study analysed diatoms in surface sediment samples and a sediment core from the Lianjiang coast of the East China Sea, together with environmental variables. Principal component analysis of the environmental variables showed that sea surface salinity (SSS) and sea surface temperature were the most important factors controlling hydrological conditions in the Lianjiang coastal area, whereas canonical correspondence analysis indicated that SSS and pH were the main environmental factors affecting diatom distribution. Based on the modern diatom species–environmental variable database, we developed a diatom-based SSS transfer function to quantitatively reconstruct the variability in SSS between 1984 and 2021 for sediment core HK3 from the Lianjiang coastal area. The agreement between the reconstructed SSS and instrument SSS data from 1984 to 2021 suggests that diatom-based SSS reconstruction is reliable for studying past SSS variability in the Lianjiang coastal area. Three low SSS events in AD 2019, 2013, and 1999, together with an increased relative concentration of freshwater diatom species and coarser sediment grain sizes, corresponded to two super-typhoon events and a catastrophic flooding event in Lianjiang County. Thus, a diatom-based SSS transfer function for reconstructing past SSS variability in the estuarine and coastal areas of the East China Sea can be further used to reflect the paleoenvironmental events in this region.

To explore the occurrence phases and enrichment mechanism of rare earth elements (REEs) in cobalt-rich crusts, this study analyzes the mineral composition and REE contents of the samples from Marcus-Wake Seamounts by XRD, ICP-OES and ICP-MS. The results show that, (1) the cobalt-rich crusts contain the major crystalline mineral (vernadite), the secondary minerals (quartz, plagioclase and carbonate fluorapatite), and a large amount of amorphous ferric oxyhydroxides (FeOOH). (2) The cobalt-rich crusts contains higher Mn (10.83% to 28.76%) and Fe (6.14% to 18.86%) relative to other elements, and are enriched in REEs, with total REE contents of 1 563−3 238 µg/g and Ce contents of 790−1 722 µg/g. Rare earth element contents of the old crusts are higher than those of the new crusts. Moreover, the non-phosphatized crusts have positive Ce and negative Y anomalies, and yet the phosphatized crusts have positive Ce and positive Y anomalies, indicating that cobalt-rich crusts is hydrogenetic and REEs mainly come from seawater. (3) Analytical data also show that the occurrence phases of elements in cobalt-rich crusts are closely related to their mineral phases. In the non-phosphatized crusts, REEs are adsorbed by colloidal particles into the crusts (about 67% of REEs in the Fe oxide phase, and about 17% of REEs in the Mn oxide phase). In contrast, in the phosphatized crusts (affected by the phosphatization), REEs may combine with phosphate to form rare earth phosphate minerals, and about 64% of REEs are enriched in the residual phase containing carbonate fluorapatite, but correspondingly the influence of Fe and Mn oxide phases on REEs enrichment is greatly reduced. In addition, the oxidizing environment of seawater, high marine productivity, phosphatization, and slow growth rate can promote the REE enrichment. This study provides a reference for the metallogenesis of cobalt-rich crusts in the Pacific.

To protect the sustainability of the benefits from seas and near coastal areas, which have under the effect of the very complex hydrodynamic conditions and intensive human activities, without disrupting the balance of nature, it is necessary to image the status of the seafloor features. Therefore, this study presents the deformations, depositional conditions, underwater constructions, and the other non-natural impacts on the seafloor of the nearshore area at western Istanbul (between Küçükçekmece and Büyükçekmece lagoons) where it intensely used by the citizens. The results of the study may provide some guidance for understanding the impacts and risk factors of uses that are or will be conducted in coastal and/or near-coastal areas. Construction planning for civil coastal structures and areas should be done in great harmony with nature, minimizing negative environmental impacts. Although sediment distribution in the area is generally quite complex, the current state of the region, wave action, hydrodynamic conditions, the amount of material transported from the land, and bathymetry are important influencing factors. The seafloor has been damaged primarily by anchor deformation and associated bottom scanning, as well as disturbing trawl tracks. The seafloor was observed as partially shallowing near the constructions (such as natural gas pipelines, fishermen’s shelter, and port piles) of coastal areas and associated with sand deposits. Therefore, scanning the seafloor using side-scan sonar may provide valuable frequency data to prevent future disruptions.

Climate change has led to significant fluctuations in marine ecosystems, including alterations in the structure and function of food webs and ecosystem status. Coastal ecosystems are critical to the functioning of the earth’s life-supporting systems. However, temporal variations in most of these ecosystems have remained unclear so far. In this study, we employed a linear inverse model with Markov Chain Monte Carlo (LIM-MCMC) combined with ecological network analysis to reveal the temporal variations of the food web in Haizhou Bay of China. Food webs were constructed based on diet composition data in this ecosystem during the year of 2011 and 2018. Results indicated that there were obvious temporal variations in the composition of food webs in autumn of 2011 and 2018. The number of prey and predators for most species in food web decreased in 2018 compared with 2011, especially for Trichiurus lepturus, zooplankton, Amblychaeturichthys hexanema, and Loligo sp. Ecological network analysis showed that the complexity of food web structure could be reflected by comprehensive analysis of compartmentalized indicators. Haizhou Bay ecosystem was more mature and stable in 2011, while the ecosystem’s self-sustainability and recovery from disturbances were accelerated from 2011 to 2018. These findings contribute to our understanding of the dynamics of marine ecosystems and highlight the importance of comprehensive analysis of marine food webs. This work provides a framework for assessing and comparing temporal variations in marine ecosystems, which provides essential information and scientific guidance for the Ecosystem-based Fisheries Management.

The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph. In this study, six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity. These strains, namely Marinobacter guineae M3B^T, Marinobacter aromaticivorans D15-8P^T, Marinobacter vulgaris F01^T, Marinobacter profundi PWS21^T, Marinobacter denitrificans JB02H27^T, and Marinobacter sp. ST-1M (with a 99.93% similarity to the 16S rDNA sequences of Marinobacter salsuginis SD-14B^T), were screened out of 32 Marinobacter strains by autotrophic thiosulfate oxidization medium. The population of cells grew in a chemolithotrophic medium, increasing from 10⁵ cells/mL to 10⁷ cells/mL within 5 d. This growth was accompanied by the consumption of thiosulfate 3.59 mmol/L to 9.64 mmol/L and the accumulation of sulfate up to 0.96 mmol/L, and occasionally produced sulfur containing complex particles. Among these Marinobacter strains, it was also found their capability of oxidizing thiosulfate to sulfate in a heterotrophic medium. Notably, M. vulgaris F01^T and M. antarcticus ZS2-30^T showed highly significant production of sulfate at 9.45 mmol/L and 3.10 mmol/L. Genome annotation indicated that these Marinobacter strains possess a complete Sox cluster for thiosulfate oxidation. Further phylogenetic analysis of the soxB gene revealed that six Marinobacter strains formed a separate lineage within Gammaproteobacteria and close to obligate chemolithoautotroph Thiomicrorhabdus arctica. The results indicated that thiosulfate oxidizing and chemolithoautotrophic potential in Marinobacter genus, which may contribute to the widespread of Marinobacter in the global ocean.

The conventional theory of concerted evolution has been used to explain the lack of sequence variation in ribosomal RNA (rRNA) genes across diverse eukaryotic species. However, recent investigations into rRNA genes in flatfish genome have resulted in controversial findings. This study focuses on 18S rRNA genes of the widely distributed tongue sole, Cynoglossus abbreviatus (Pleuronectiformes: Cynoglossidae), aiming to explore sequence polymorphism. Five distinct 18S rDNA sequence types (Type A, B, R1, R2, and R3) were identified, suggesting a departure from concerted evolution. A combination of general criteria and variations in highly conserved regions were employed to detect pseudogenes. The results pinpointed Type A sequences as potential pseudogenes due to significant sequence variations and deviations in secondary structure within highly conserved regions. Three types (Type R1, R2, and R3) were identified as recombinants between Type A and B sequences, with simple crossing over and gene conversion as the most likely recombination mechanisms. These findings not only contribute to rRNA pseudogene identification but also shed light on the evolutionary dynamics of rRNA genes in teleost genomes.

In the coastal environment, the co-occurrence of antibiotic and nanoplastic pollution is common. Investigating their individual and combined toxicity to marine organisms is of great necessity. In the present study, the reproductive toxicity of sulfamethazine (SMZ) and nanoplastics (polystyrene, PS) via the dietary route on the spermatogenesis of marine medaka (Oryzias melastigma) was examined. After 30 d of dietary exposure, SMZ alone decreased the gonadosomatic index (GSI) value (~35%) and the proportion of undifferentiated type A spermatogonia (A_und) (~40%), probably by disrupting the testicular sex hormone production, the spermatogenesis-related growth factor network and the balance of apoptosis. Individual exposure to PS did not affect the GSI value or the proportions of germ cells at different developmental stages, but dysregulated the expression of several spermatogenesis-related genes. Interestingly, the presence of PS alleviated the decreased GSI value caused by SMZ. This alleviation effect was achieved by enhancing the spermatogonia differentiation instead of reversing the suppressed self-renewal of A_und, suggesting that the mixture of PS and SMZ could cause reproductive effects in a different way. These findings expand our knowledge of threats of ubiquitous antibiotic and nanoplastic pollution to fish reproduction and population.

This study aims at identifying the microevolutionary processes responsible for the onset of the remarkable phylogeographic structure already recorded for the endangered giant clam Tridacna squamosa across its distribution range. For this purpose, the evolutionary, biogeographic and demographic histories of the species were comprehensively reconstructed in a mitochondrial dataset comprising nearly the whole available published cytochrome c oxidase 1 gene sequences of T. squamosa. Relatively higher level of genetic diversification was unveiled within T. squamosa, in comparison to earlier macro-geographic investigations, whereby five mitochondrial clusters were delineated. The resulting divergent gene pools in the Red Sea, western Indian Ocean, Indo-Malay Archipelago and western Pacific were found to be driven by Early Pleistocene glacial vicariance events among refugial lineages. Accentuated genetic diversification of the species across the Indo-Malay Archipelago was successively triggered by historical dispersal event during the Mid-Pleistocene MIS19c interglacial. This latter historical event might have also enabled genetically distinct giant clams from the Indo-Malay Archipelago to subsequently colonize the western Pacific, accounting for the genetic diversity hotspot detected within this region (comprising three divergent mitochondrial clusters). Late Pleistocene demographic expansion of T. squamosa, during the Last Interglacial period, could have contributed to forging spatial distribution of the so far delineated genetic entities across the Indo-Western Pacific. Overall, being resilient to major climate shifts during the Pleistocene through adaptation and consequent diversification, T. squamosa could be used as a model species to track the impact of climate change on genetic variability and structure of marine species. In particular, the new information, provided in this investigation, may help with understanding and/or predicting the consequences of ongoing global warming on genetic polymorphism of endangered coral reef species among which Tridacna sp. are listed as ecologically important.

More than 30 species of benthic Prorocentrum have been identified, some of which produce okadaic acid (OA) and its derivatives, dinophysistoxins (DTXs), which cause diarrhetic shellfish poisoning (DSP). Increasing numbers of benthic Prorocentrum species have been reported in tropical and subtropical waters of China. In contrast, only a few benthic Prorocentrum species have been reported in temperate waters. In this study, morphological descriptions obtained using light microscopy, scanning electron microscopy and molecular characterization of one Prorocentrum clipeus strain isolated from the Yellow Sea are presented. Prorocentrum clipeus cells were nearly circular in shape, with a collar, ridge, and one protrusion. The periflagellar area was wide U-shaped, with two curved projections on platelet 1a. Nine periflagellar platelets of different sizes were observed. The morphology closely fits that of the species isolated from other locations. Phylogenetic analysis based on the molecular sequences of the small subunit (SSU) rDNA, internal transcribed spacer (ITS), and large subunit (LSU) rDNA was performed. A comprehensive metabolomic analysis incorporating target, suspect and non-target screenings was first applied to investigate the intracellular and extracellular metabolite profiles of the current isolate of P. clipeus. According to the results of the target and suspect screenings, 179 metabolites or toxins produced by DSP-related algal species, including OA, dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2) and pectenotoxin-2 (PTX2), were not detected. Non-target screening involving feature-based molecular networking (FBMN) provided a global view of major metabolites produced by the P. clipeus DF128 strain and revealed 23 clusters belonging to at least 13 compound classes, with organometallic compounds, lipids and lipid-like molecules, phenylpropanoids and polyketides, and benzenoids as major types. To date, this is the first record of the characterization of P. clipeus in samples from Chinese waters. Our results support the wide distribution of epibenthic Prorocentrum species.

Isopod crustaceans of the family Dajidae are exclusively marine ectoparasites. The genus Notophryxus G. O. Sars, 1883 currently includes nine nominal species, which are very rarely reported as the chances for encountering these specimens are unpredictable. Our comprehension of the taxonomy, biology, ecology, and life cycle of species belonging to the Notophryxus genus is notably lacking. All nominal species of Notophryxus genus are reviewed here to obtain a comprehensive and integrative taxonomic understanding of this genus, in an attempt to address the lacunae. This paper also documents the rediscovery of an ectoparasitic isopod from the genus Notophryxus in Indian waters, after 55 years. Adult isopod specimens obtained from the outer reefs of Amini Island in the Lakshadweep archipelago, Southeastern Arabian Sea, display morphological congruence to Notophryxus globularis G. O. Sars, 1885. The only previous report on this species dates back to 1885 from G.O. Sars' description of N. globularis as an ectoparasite on the euphausiid Thysanoessa gregaria G. O. Sars, 1883 in the North Pacific. This discovery represents a range extension of N. globularis from the North Pacific to the Arabian Sea. Two cryptoniscid larvae and three adult females of N. globularis (with dwarf males) were found attached to four adult mysid specimens of Siriella aequiremis Hansen, 1910. The present study provides an improved diagnosis of N. globularis with the aid of light microscopy images and line drawings which was not given in the original G. O. Sars, 1885 report. This research also provides a concise description of cryptoniscid larvae from the same sampling location and same host which is most likely to be N. globularis larvae.