Chinese Coastal Waters Research Articles

One becomes three: An integrative morphological and molecular analysis of the windowpane oyster Placuna (Bivalvia: Pectinida) reveals new species.

For decades, many marine animals have been considered to exhibit cosmopolitan or transoceanic distribution. This situation is prevalent in Asia, where many species were collected and named by American or European experts in the 1700s to early 1900s. Using the windowpane oysters Placuna-a small genus of bivalves with five recognized species-we show that careful analysis is required to reassess the validity of these species. Currently, only two species of Placuna (P. placenta and P. ephippium) widely reported in the Indo-Pacific region have been recorded from Chinese coastal waters. Here, we described two new species of Placuna from China. Placuna vitream sp. nov. can be distinguished from P. placenta by its larger ridge angle. Phylogenetic analysis using five gene fragments fully supported that P. vitream sp. nov. is a sister to the specimen from Singapore identified as P. placenta and more distant from other Placuna species with available molecular data. Besides, based on subfossil shells, we describe Placuna aestuaria sp. nov. that differs from its congeneric species by its broad hinge, medium ridge angle, and nearly straight ridges. Finally, we suggest a combination of hinge structure and ridge angle that can be used for identifying Placuna species and preparing a key to this genus. Our findings of two new species expand the diversity of Placuna and prompt reassessment of the many presumably widely distributed marine species in Asia.

Ontogenetic, Sexual, and Monthly Niche Segregation of Sepia esculenta in the Northern East China Sea Revealed by Stable Carbon and Nitrogen Isotopes.

Golden cuttlefish play a significant role in the food web of the East and Yellow Seas and are a valuable fishery resource in Chinese coastal waters. Samples of golden cuttlefish were obtained from the northern East China Sea between September 2021 and March 2022, and stable isotope methods were utilized in this study to examine the variations in the forage ecology of golden cuttlefish. Our findings reveal dynamic shifts in carbon and nitrogen stable isotopes (δ13C and δ15N), highlighting intricate foraging strategies tailored to growth and environmental changes. A notable trend emerges: an initial growth-linked rise in δ13C and δ15N enrichment, followed by seasonal fluctuations mirroring seasonal food availability. The ontogenetic niche evolution displays striking habitat shifts and trophic level escalation in small mantle length stages, transitioning to niche overlap and subtle trophic shifts later on. Sex-specific differences emerge, with females occupying higher trophic levels than males in most samples. This comprehensive study underscores the complexity and adaptability of golden cuttlefish feeding ecology, inviting further inquiry into their intricate relationships within the marine ecosystem.

Microplastics in Chinese coastal waters: A mini-review of occurrence characteristics, sources and driving mechanisms.

The oceans are facing global and irreversible pollution from microplastics, and China is not immune. In this mini-review, information on microplastics in four coastal waters of China and the natural and social environment of key basins were compiled. The results showed that microplastics were ubiquitous in the coastal waters, and the abundance and spatial distribution of microplastics varied significantly under different sampling methods. For trawl samples, microplastic abundance ranged from 0.045 to 1170.8 items m-3, among which the coastal waters of the East China Sea were the most polluted. For filtered samples, microplastic abundance ranged from 46 to 63,600 items m-3, and the coastal waters of the Yellow Sea were the most polluted. Meanwhile, human activities in basin were the key factors affecting microplastic pollution in coastal waters. The main terrestrial source in the coastal waters of the South China Sea was express packaging loss, whereas the main source in the other coastal waters was tyres and road markings wear from vehicle trip. The decoupling results of analytic hierarchy process showed that there was spatial heterogeneity in the impact of socio-economic and natural environmental factors in the basin on the distribution of microplastics in coastal waters. Among the five major basins, the impact weights of the latter were 20.00%, 83.34%, 66.66%, 50.00% and 25.00%, respectively. This study provides the first perspective of land-sea linkage to summarize the characteristics, sources and influencing factors of microplastics in Chinese coastal waters, providing ideas for reducing marine microplastic pollution from the source.

Five Karenia species along the Chinese coast: With the description of a new species, Karenia hui sp. nov. (Kareniaceae, Dinophyta)

Dinoflagellates within the genus Karenia are well known for their potential to cause harmful algal blooms and induce detrimental ecological consequences. In this study, five Karenia species, Karenia longicanalis, Karenia papilionacea, Karenia mikimotoi, Karenia selliformis, and a new species, Karenia hui sp. nov., were isolated from Chinese coastal waters. The new species exhibits the typical characteristics of the genus Karenia, including a linear apical groove and butanoyl-oxyfucoxanthin as the major accessory pigment. It is distinguished from the other Karenia species by a wide-open sulcal intrusion onto the epicone, a conical epicone with an apical crest formed by the rim of the apical groove, and a hunchbacked hypocone. It is most closely related to Karenia cristata, with a genetic divergence of 3.16 % (22 bp out of 883 bp of LSU rDNA). Acute toxicity tests indicated that the five Karenia species from China are all toxic to marine medaka Oryzias melastigma. Karenia selliformis and K. hui were very toxic to O. melastigma, resulting in 100 % mortality within 4 h and 24 h, respectively. Further analysis by high-performance liquid chromatography revealed that four species, K. selliformis, K. longicanalis, K. papilionacea and K. mikimotoi were capable of producing Gymnodimine-A (GYM-A). The highest GYM-A content was in K. selliformis (strain HK-43), in which the value was 889 fg/cell. No GYM-A was detected in the new species K. hui, however and its toxin remains unknown. Below we provide a comprehensive report of the morphology, phylogeny, pigment composition, and toxicity profiles of Karenia species along the Chinese coast. These findings contribute new insights for monitoring of Karenia species, with important toxicological and ecological implications.

Responses of microeukaryotic community structure to a Phaeocystis globosa bloom in a semi-enclosed subtropical bay

The occurrence of Phaeocystis globosa, a harmful algal bloom species in Chinese coastal waters, has significant impacts on marine organisms and poses a threat to the safety of coastal nuclear power plants. Although previous studies have established a close association between P. globosa blooms and the bacterial community, the relationship between the microeukaryotic community and P. globosa blooms remains poorly understood. In this study, the variations in the microeukaryotic community resulting from a P. globosa bloom were analyzed using 18S rRNA gene amplicon sequencing. The results indicated that the diversity of the microeukaryotic community during the bloom phase was significantly higher than that during the dissipation phase. The microeukaryotic community compositions varied significantly between the two phases of the P. globosa bloom. During the bloom phase, the dominant microeukaryotic was Viridiplantae, which was then replaced by Dinoflagellata during the dissipation phase. Co-occurrence network analysis showed that the relationship among the microeukaryotic community during the bloom phase was more complex than that during the dissipation phase, and the keystone taxa varied as the bloom progressed. Additionally, microeukaryotic community assembly was primarily driven by stochastic processes during the bloom phase based on the β-nearest taxon distance, whereas it was driven by both deterministic processes and stochastic processes during the dissipation phase. Overall, our findings provide novel insight into the mechanisms and interactions involved in microeukaryotic community dynamics in environments disturbed by P. globosa blooms.

Morphology, molecular phylogeny and biogeography revealed two new Pseudo‐nitzschia (Bacillariophyceae) species in Chinese waters

AbstractPseudo‐nitzschia is a group of widely distributed planktonic diatoms. Some species produce the neurotoxin domoic acid. Herein, two new Pseudo‐nitzschia species were described from Chinese coastal waters and the South China Sea after combining morphological and molecular data, together with biogeographical traits. Pseudo‐nitzschia punctionis sp. nov. was similar to Pseudo‐nitzschia bipertita morphologically, but differed in poroid structure, which was undivided in P. punctionis but divided in two sectors in P. bipertita. This difference corresponded to the presence of two hemicompensatory base changes (HCBCs) in the secondary structure of internal transcribed spacer 2. Pseudo‐nitzschia polymorpha sp. nov. was sister to Pseudo‐nitzschia limii phylogenetically, but distinct by the various shapes of perforations on the valve and copula, which was supported by four HCBCs. In a metabarcoding analysis, multiple new ribotypes were identified within the two new species, and intraspecific genetic divergences were analyzed. Metabarcoding data revealed that P. punctionis had a broader temperature range (12.9–30.5°C) than P. polymorpha (22.3–30.5°C). Within the two new species, different traits were found among the amplicon sequence variants regarding temperature and biogeography, representing different microevolutionary directions under environmental selection. The two new species had different biogeographical traits when compared to their closely related species. Domoic acid was detected in strains of P. punctionis at a concentration of 13.5–17.7 fg/cell, but the toxin was not found in strains of P. polymorpha. A combination of characters based on laboratory strains and field metabarcoding data provided more data for delimiting Pseudo‐nitzschia species and gave new insights into their diversity and biogeography.

Taxonomy and phylogeny of Chaetoceros species of the section Stenocincta (Bacillariophyceae), with emendation of C. affinis and C. willei and description of three new species

ABSTRACT Species of Chaetoceros sect. Stenocincta are frequently observed in marine phytoplankton. To study species diversity within the section Stenocincta, monoclonal strains were established from Chinese coastal waters and Norwegian Sea. Following detailed morphological observations and molecular evidence inferred from nucleus-encoded large subunit ribosomal DNA, the descriptions of C. affinis and C. willei are emended based on isolates from their respective type localities. Additionally, three new species are described. Chaetoceros donghaiensis sp. nov. is characterized by short straight chains, with thin setae only, and terminal setae that tend to cross distally. Chaetoceros forceps sp. nov. is unique by its thick terminal setae, each with an inflation near the end, with each pair forming a V-shape, resembling forceps. Chaetoceros lepidus sp. nov. is characterized by short, straight chains, narrowly elliptical valve faces, setae all located in the apical plane, and arched intercalary setae in opposite directions to the chain axis in broad girdle views. Three other distinct clades, which may also represent new species, were discerned in the LSU rDNA phylogeny, but more morphological characters are needed before formal proposals can be made. These species/clades formed a well-supported monophyletic lineage, supporting the current circumscription of section Stenocincta. This section is characterized by colonies in straight chains, cells with one chloroplast only, narrow lanceolate apertures, and terminal setae generally thicker than intercalary ones or both similar and thin. However, in C. diversus the terminal setae are thin and distinctly thicker pairs of intercalary setae are usual.

Changes of eutrophication degree in Dongshan Bay in China affected by the COVID-19 outbreak

At the background of the outbreak of COVID-19 pandemic, water samples were collected in Dongshan Bay from 2019 to 2020, to study spatial and temporal changes of nutrients concentration and eutrophication degree with a new assessment model–PE3. Results showed that the spatial distribution of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and dissolved silica (DSi) generally decreased from Zhangjiang River estuary to the mouth of the bay and from west to east both in spring and summer. This pandemic seems to have little influence on the spatial distribution of DIP and DSi. However, DIN concentration decreased much greatly from 2019 to 2020, meanwhile N replaced P to be the potentially limited nutrient factor for the growth of phytoplankton. And average eutrophication degree of the bay assessed by PE3 increased from 1 in 1988 to 5 in 2008 and 6 in 2019 respectively, and decreased to 4 in 2020. It was suggested that after this pandemic, DIN concentration and eutrophication degree may decrease a lot in Chinese coastal waters.

Long-term changes in Noctiluca scintillans blooms along the Chinese coast from 1933 to 2020.

Noctiluca scintillans is one of the most common harmful algal species and widely known due to its bioluminescence. In this study, the spatial distribution, seasonal variations, and long-term trends of N. scintillans blooms in China and the related drivers were analyzed and discussed. From 1933 to 2020, a total of 265 events of N. scintillans blooms were recorded in Chinese coastal waters, with a total duration of 1052 days. The first N. scintillans bloom occurred in Zhejiang in 1933, and only three events were recorded before 1980. From 1981 to 2020, N. scintillans caused harmful algal blooms (HABs) almost every year, both the average duration and the proportion of multiphase HABs showed an increasing trend. 1986-1992, 2002-2004, and 2009-2016 were the three peak periods with a frequency of no less than five events of N. scintillans blooms per year. In terms of spatial distribution, N. scintillans blooms spread from the Southeast China Sea to the Bohai Sea after 2000, Guangdong, Fujian, and Hebei were the three provinces with the highest numbers of recorded events of N. scintillans blooms. Moreover, 86.8% of the events of N. scintillans blooms occurred in spring (March, April, and May) and summer (June, July, and August). Among environmental factors, the dissolved inorganic phosphate, dissolved silicate and chemical oxygen demand were significantly correlated with the cell density of N. scintillans during N. scintillans blooms, and most of N. scintillans blooms were recorded in the temperature range of 18.0-25.0°C. Precipitation, hydrodynamics, water temperature, and food availability might be the main factors affecting the spatial-temporal distribution of N. scintillans blooms along the Chinese coast.

Glider Network Observation Unraveling A Cyclonic Eddy in the Northwestern Pacific Subtropical Countercurrent

The North Pacific Subtropical Countercurrent (STCC) is a zonal current consisting of a weak eastward current near the surface and a westward current (north equatorial current, NEC) below. Previous studies have proved that this region is an extremely active region of the North Pacific eddy. The activity of mesoscale eddy in this region can directly or indirectly affect the periodic variations of the Kuroshio and the Chinese coastal waters. In order to study the structure of mesoscale eddies in this region and their impact on the upper ocean, five Petrel-II underwater gliders were conducted as a network to collect hydrographic properties from December 09 2020 to February 05, 2021. It is found that a cyclonic eddy passed through the glider network from east to west during the observation period, and the glider grid almost covers the whole eddy. The radius, amplitude and propagation velocity of the eddy were analyzed. The underwater gliders were equipped with CTD sensors, collected about 1200 full thermohaline profiles. The observation results indicated that the cyclonic eddy can influence over 400 m in the vertical, which caused the isotherm rising up to 40 m. Analysis based on satellite sea surface temperature (SST) and sea level anomaly (SLA) data suggest that the cyclonic eddy is probably locally generated.

Interspecies calibration for biomonitoring metal contamination in coastal waters using oysters and mussels

Differences in metal bioaccumulation among species make it difficult to compare biomonitoring results obtained using different marine bivalve species. To address this challenge and improve the interpretation of biomonitoring data, we studied the toxicokinetic mechanisms underlying these differences and developed a method to estimate seawater metal concentrations based on metal concentrations in the organisms. We transplanted six common species of oysters and mussels found in Chinese coastal waters into the Jiulong River estuary and monitored metal concentrations in the organisms, water, and suspended particles every three days over a six-week period. A one-compartment first-order toxicokinetic model was used to describe the relationship between metal bioaccumulation and metal concentrations in the environment. The model parameters, including aqueous uptake (ku) and dietary assimilation (kp) rate constants, and elimination rate constant (ke), were estimated using a Markov Chain Monte Carlo fitting method with a priori information from a systematic review we conducted. The toxicokinetic model successfully fitted the temporal changes in metal bioaccumulation in all six bivalve species and explained the interspecies differences. Using the calibrated models, we were able to calculate metal concentrations in the seawater at the bivalve collection sites and enable comparisons of biomonitoring data across multiple species. In conclusion, we have established a toxicokinetic framework to explain interspecies differences in metal bioaccumulation in six commonly found bivalves and provided a useful tool for interpreting biomonitoring data in coastal environments.

Remote Sensing Analysis of Typhoon-Induced Storm Surges and Sea Surface Cooling in Chinese Coastal Waters

Inthis study, remote sensing measurements were utilized to examine the characteristics of storm surges and sea surface cooling in Chinese coastal waters caused by typhoons. Altimetric data from satellite altimeters were used to determine the magnitude, cross-shelf decaying scale, and propagating speed of storm surges from typhoons. The results were in agreement with estimates obtained from a theoretical model and tide gauge data, showing that the two storm surges propagated as continental shelf waves along the southeastern coast of China. The sea surface cooling, driven by Typhoons 1319Usagi and 1323Fitow, was analyzed using the remote sensing sea surface temperature product, named the global 1 km sea surface temperature (G1SST) dataset, revealing a considerable decrease in the temperature, with the largest decrease reaching 4.5 °C after the passage of 1319Usagi, in line with buoy estimates of 4.6 °C. It was found that 1323Fitow and 1324Danas jointly impacted the southeastern coast of China, resulting in a significant temperature drop of 4.0 °C. Our study shows that incorporating remotely sensed measurements into the study of oceanic responses to typhoons has significant benefits and complements the traditional tide gauge network and buoy data.

Metatranscriptomics and metabarcoding reveal spatiotemporal shifts in fungal communities and their activities in Chinese coastal waters.

Fungal communities are diverse and abundant in coastal waters, yet, their ecological roles and adaptations remain largely unknown. To address these gaps, ITS2 metabarcoding and metatranscriptomic analyses were used to capture the whole suite of fungal diversity and their metabolic potential in water column and sediments in the Yellow Sea during August and October 2019. ITS2 metabarcoding described successfully the abundance of Dikarya during August and October at the different examined habitats, but strongly underrepresented or failed to identify other fungal taxa, including zoosporic and early-diverging lineages, that were abundant in the mycobiome as uncovered by metatranscriptomes. Metatranscriptomics also revealed enriched expression of genes annotated to zoosporic fungi (e.g., chytrids) mainly in the surface water column in October. This enriched expression was correlated with the two-fold increase in chlorophyll-a intensity attributed to phytoplanktonic species which are known to be parasitized by chytrids. The concurrent high expression of genes related to calcium signalling and GTPase activity suggested that these metabolic traits facilitate the parasitic lifestyle of chytrids. Similarly, elevated expression of phagosome genes annotated to Rozellomycota, an early-diverging fungal phylum not fully detected with ITS2 metabarcoding, suggested that this taxon utilizes a suite of feeding modes, including phagotrophy in this coastal setting. Our data highlight the necessity of using combined approaches to accurately describe the community structure of coastal mycobiome. We also provide in-depth insights into the fungal ecological roles in coastal waters, and report potential metabolic mechanisms utilized by fungi to cope with environmental stresses that occur during distinct seasonal months in coastal ecosystems.

Transcript annotation of Chinese sturgeon (Acipenser sinensis) using Iso-seq and RNA-seq data

Chinese sturgeon (Acipenser sinensis) is a critically endangered fish inhabiting the Yangtze River and Chinese coastal waters. Numerous research projects and conservation efforts have focused on artificial propagation and release to restore this endangered species. However, genomic and full-length transcriptomic sequencing of Chinese sturgeon has rarely been reported. In this study, a total of 10 Chinese sturgeon tissues were used for PacBio Iso-seq and RNA-seq analyses. A total of 19,538 full-length transcripts were obtained with sizes from 51 bp to 7,033 bp. Moreover, cluster analysis of gene families and phylogenetic analysis of 14 species were performed. Furthermore, lncRNAs and coding sequence (CDS) were identified in all Chinese sturgeon tissues. Finally, gene expression profiles and differentially expressed genes (DEGs) were analyzed among 10 tissues in Chinese sturgeon. Taken together, full-length transcripts and the gene expression profile from Chinese sturgeon tissues will provide gene sequences and expression information for future functional genomic study and be very helpful for comprehensive understanding of the genetic mechanism of endangerment in Chinese sturgeon.

Effects of ocean acidification and eutrophication on the growth and photosynthetic performances of a green tide alga Ulva prolifera

With the impact of fossil fuel burning and industrialization, atmospheric CO2 concentration will reach about 1000 ppmv in 2100, and more and more CO2 will be absorbed by ocean, resulting in ocean acidification. The Chinese coastal waters are showing unexpectedly high levels of acidification due to a combination of global ocean acidification and severe regional eutrophication, which is caused by natural accumulation or human activities such as aquacultural tail water input, potentially affecting macroalgal blooms. However, little is known about the combined effects of ocean acidification and entrophication on the eco-physiology of bloom-forming macroalgae. This study investigated Ulva prolifera, a dominant species causing green tide in the South Yellow Sea, and explored its growth and physiological responses under the combination conditions of ocean acidification and enriched nutrients. In this study, U. prolifera thalli were cultured under two CO2 conditions (air and 1000 μatm) and two nutrient conditions (High Nutrient, HN, 135 μmol L-1 N and 8.5 μmol L-1 P; Normal Nutrient, NN, 27 μmol L-1 N and 1.7 μmol L-1 P). The results showed that eutrophication conditions obviously enhanced the relative growth rate and photosynthetic performance of U. prolifera. Elevated pCO2 had no significant effect on U. prolifera growth and photosynthetic performance under normal nutrient conditions. However, under eutrophication conditions elevated pCO2 inhibited U. prolifera growth. Moreover, eutrophication conditions markedly improved the contents of chlorophyll a, chlorophyll b and nitrate reductase activity and inhibited the soluble carbohydrate content, but elevated pCO2 had no significant effect on them under nutrient-replete conditions. In addition, elevated pCO2 significantly reduced the carotenoid content under eutrophication conditions and had no effect on it under normal nutrient conditions. These findings indicate that seawater eutrophication would greatly accelerate U. prolifera bloom, which may also be suppressed to a certain extent by ocean acidification in the future. The study can provide valuable information for predicting the future outbreaks of U. prolifera green tide in nearshore regions.

The Response of Oceanic Dimethylsulfide Fluxes Off the Chinese Coastal Waters to Altered Changjiang (Yangtze) Nutrient Inputs

The Response of Oceanic Dimethylsulfide Fluxes Off the Chinese Coastal Waters to Altered Changjiang (Yangtze) Nutrient Inputs

A New Species of Box Jellyfish (Cnidaria: Tripedaliidae: Tripedalia) from Hong Kong, China.

We describe a box jellyfish, Tripedalia maipoensis sp. nov., based on samples collected from a shrimp pond in Hong Kong. This new species is morphologically distinct from other species of the family Tripedaliidae by the following combination of characters: (1) three pedalia at each bell corner; (2) each pedalium with one tentacle; and (3) velarium with forked canals. Phylogenetic analyses based on a concatenated dataset of the 16S, 18S and 28S rRNA genes show that T. maipoensis sp. nov. is sister to the morphologically similar species T. cystophora, but the two species exhibit 17.4% divergence in the 16S rRNA gene, supporting T. maipoensis sp. nov. as a distinct species. This new species represents the fourth described species of Tripedaliidae, and the first record of the family in Chinese coastal waters.

Genetic diversity monitoring of Chiloscyllium plagiosum from coastal Xiamen between generations

Chiloscyllium plagiosum (Bennett, 1830) is a productive shark species found in the Chinese coastal waters. However, populations of this species have declined due to factors such as increased fishing pressure, habitat loss, and habitat destruction. Therefore, monitoring the genetic signatures of C. plagiosum is an urgent need. Using the coastal waters of Xiamen as the research area, C. plagiosum specimens were collected from 2017 to 2021 to detect changes in their genetic diversity across several years. The genetic diversity of C. plagiosum from the coastal area of Xiamen fluctuated between generations and remained relatively high in general compared to that of fishing waters which is possibly related to the coastal waters of Xiamen being in a protected marine area where C. plagiosum is not affected by fishing pressure. The genetic differentiation between C. plagiosum populations in different years was extremely low, primarily arising from within the population, indicating that the recruitment stock of C. plagiosum in the coastal waters of Xiamen was sufficient for adequate gene exchange. The results of the historical demography revealed that a population expansion of C. plagiosum had historically occurred, and its effective population experienced rapid growth after expansion. The coastal waters of Southern Fujian are the center of the expansion of the ancestral C. plagiosum population along the southern coast of China; therefore, the genetic diversity and genetic structure of this species require further study to understand the changing patterns of its genetic characteristics, prevent the decline of its germplasm resources in the wild, and protect fishery resources.

Residue Analysis and Assessment of the Risk of Dietary Exposure to Domoic Acid in Shellfish from the Coastal Areas of China.

Harmful algal blooms in Chinese waters have caused serious domoic acid (DA) contamination in shellfish. Although shellfish are at particular risk of dietary exposure to DA, there have been no systematic DA risk assessments in Chinese coastal waters. A total of 451 shellfish samples were collected from March to November 2020. The presence of DA and four of its isomers were detected using liquid chromatography-tandem mass spectrometry. The spatial-temporal distribution of DA occurrence and its potential health risks were examined. DA was detected in 198 shellfish samples (43.90%), with a maximum level of 942.86 μg/kg. DA was recorded in all 14 shellfish species tested and Pacific oysters (Crassostrea gigas) showed the highest average DA concentration (82.36 μg/kg). The DA concentrations in shellfish showed distinct spatial-temporal variations, with significantly higher levels of occurrence in autumn than in summer and spring (p < 0.01), and particularly high occurrence in Guangdong and Fujian Provinces. The detection rates and maximum concentrations of the four DA isomers were low. While C. gigas from Guangdong Province in September showed the highest levels of DA contamination, the risk to human consumers was low. This study improves our understanding of the potential risk of shellfish exposure to DA-residues.

The preliminary DNA barcoding dataset of fishes from Chinese coastal waters

DNA barcoding is a molecular method for species identification based on a short standardized DNA sequence derived from the 5’ region of the cytochrome c oxidase subunit I (COI) gene, which is widely applied in marine fish identification. In this study, DNA barcodes were generated for 1,671 specimens representing 309 morphological marine fish species belonging to 223 genera and covering 101 families from Chinese coastal waters. The mean Kimura 2-parameter (K2P) genetic distances within species, genera, families, and orders were 0.20%, 20.94%, 24.45%, and 25.34%, respectively. As expected, the mean interspecific distance was higher than the mean intraspecific distance. Phylogenetic trees based on Bayesian inference (BI) and neighbor-joining (NJ) methods agreed with the taxonomic classifications. A total of 306 operational taxonomic units (OTUs) were reidentified via automatic barcode gap discovery (ABGD) analysis. An estimated nucleotide substitution matrices showed a transversion bias compared to transitional mutation. The amino acid variations of the barcoding region were also examined, and 13 amino acid sites exhibited high variability. Overall, our findings confirmed that DNA barcoding is a highly reliable mean of identifying fish species in Chinese coastal waters, and that the barcode library established here would facilitate the monitoring and management of the marine fishery resources in China.