The Kuroshio Extension (KE) is a natural boundary region characterized by complex hydrodynamic processes in the western North Pacific Ocean that fuel spring phytoplankton blooms in high latitudes. This study looked at the spatial patterns and diversity of phytoplankton community and biomass associated with oceanographic profiles across the KE from the north to south in June 2011. Results showed that upper-ocean gradients were strongly correlated with observed spatial variability in phytoplankton communities (> 10 μm). Phytoplankton abundance, species richness, and Chl a biomass were generally higher in the Kuroshio–Oyashio transition region than in the KE axis and the southern KE. No bloom event was recorded in late spring. A total of 81 phytoplankton taxa belonging to 45 genera of four phyla were identified. Dominant taxa in both abundance and occurrence included the diatoms Chaetoceros radicans, C. curvisetus, C. convolutes, C. deblis, C. peruvianus, Pseudonitzchia delicatissima, Coscinodiscus asteromphalus, Thalassionema nitzschioides, T. frauenfeldii, Thalassiothrix longissima, the dinoflagellates Protoperidinium pyrifoprmus, and the Cyanobacterium Trichodesmium thiebautii. Depth-averaged abundance and Chl a were 2076 ± 3,615 cells L⁻¹ and 0.20 ± 0.10 mg m⁻³, respectively. Subsurface Chl a maxima (SCM) was mainly found at 50 m, while the abundance maximum differed regionally in the water column. A cluster analysis grouped phytoplankton communities into three assemblages related to geographic locations influenced by Oyashio and Kuroshio currents. Nutrient limitation rather than light led to low Chl a and abundance during late spring. Redundancy correspondence and spearman’s correlation further suggest that dissolved inorganic nitrogen was the major factor regulating phytoplankton distribution north of KE, while phosphate limitation was more prominent in the KE axis and the southern KE. The Oyashio and Kuroshio interaction caused evident variability in the hydrodynamic environment including the MLD and Z_eu of the region, and changes in chemical profiles such as nutrients, pH, and DO. The observed distributional shift in the spatial pattern of phytoplankton was attributed to upper-ocean environmental gradients within the KE axis and its northern and southern sections.

The invasion or aggregation of marine biota in coastal waters has become a common problem, threatening the safety of cooling water systems in the context of environmental and climate changes. However, studies on issues of coastal nuclear power plants from the view of marine ecology have mostly focused on the thermal effluent, entrainment effect on organisms, residual chlorine, radioactivity, etc. There is a lack of information on the safety of cooling water systems in nuclear power plants blocked by marine biota. Based on field and historical datasets, this study screened phytoplankton species that may potentially block the cooling water system of the Fuqing nuclear power plant on the Southeast China coast, identified the phytoplankton risk and a risk calendar, and established a catalog of risk phytoplankton species for the cooling water system. The screening criteria were simultaneously required as follows: (1) particle size of cells or group >2000 μm; (2) phytoplankton bloom or aggregation events occurred in surrounding areas; (3) and species abundance maintained at >0.5×10⁵ cells/L in the surrounding area. Nine high-risk species were screened out that can easily form colonies, clusters, and groups, including Thalassiosira diporocyclus, Thalassiosira subtilis, Noctiluca scintillans, Phaeocystis globosa, Pseudo-nitzschia pungens, Pseudo-nitzschia delicatissima, Skeletonema costatum, Skeletonema dohrnii, Paralia sulcata. Due to small cells or the formation of short chains, some dominant phytoplankton species, even those with advantages in abundance and occurrence, had difficulty threatening the reliability of cooling water systems in nuclear power plants. The outbreak of different phytoplankton species varied daily, and the risk of blockage was highest from April to July. The biological characteristics, ecological mechanisms underlying outbreaks of high-risk phytoplankton species are reviewed and discussed, suggesting a high degree of temporal and spatial variability of blockage risk. Finally, main prevention and control measures used against high-risk phytoplankton species are provided to imply new ideas and methods for nuclear power plants. These strategies have very important practical and scientific significance.

During this research, the average surface temperature, salinity, dissolved oxygen, and pH were 24.65 ± 1.53 (°C), 34.21 ± 0.07 (PSU), 6.85 ± 0.18 (mg/L), and 8.36 ± 0.03, respectively. Based on these environmental parameters, stations were arranged into three groups. Group A represents stations located around Keelung Island with the relative highest average dissolved oxygen, lowest average temperature, and pH values. Instead, the lowest average dissolved oxygen and highest average temperature, salinity, and pH values were recorded at the offshore stations. Keelung Island area was charged by cold water masses, which were driven by the Northeast monsoon, and stations in group C were affected by the Kuroshio Current. Kueishan Island area was mainly affected by mixed water masses resulting from the Kuroshio intrusion and monsoon-derived cold water. In this study, a total of 108 copepod species were identified, with an average abundance of 774.24 ± 289.42 (inds. m⁻³). Most species belong to the orders Calanoida and Poecilostomatoida, with an average relative abundance (RA) of 62.96% and 30.56%, respectively. Calanoid copepodites were the most dominant group, with a RA of 28.06%. This was followed by Paracalanus aculeatus, with a RA of 18.44%. The RA of Clausocalanus furcatus and Canthocalanus pauper was 4.80% and 3.59%, respectively. The dominant species P. aculeatus, C. pauper, Paracalanus parvus, and Temora turbinata were positively correlated with dissolved oxygen and negatively correlated with temperature in the surface waters. pH showed a negative correlation with P. parvus and T. turbinata, while the temperature was negatively correlated with these two dominant species. Indicator species were selected by an indicator value higher than 50%. Temora turbinata, Calanopia elliptica, C. pauper, Euchaeta concinna, Temora discaudata, Acartia pacifica, Macrosetella gracilis, Corycaeus speciosus, and P. parvus were considered as monsoonal cold water indicator species in Group A. Indicator copepod species for the Kuroshio Current were Farranula concinna, Copilia mirabilis, Candacia aethiopica, Corycaeus agilis, Farranula gibbula and Acrocalanus monachus in the study area. Paracandacia truncata, Oncaea clevei, P. aculeatus, and Centropages furcatus were considered suitable indicators for mixed water masses.

Taxonomic information is important to fisheries management and conservation. In this study, we collected 95 specimens of larval fish from Hawaiian waters and a total of 92 mitochondrial COI barcode sequences were obtained, representing 20 species, 18 genera and 12 families. The determined average Kimura-2-parameter distances within species, genera, families, and orders were 0.72%, 25.99%, 26.30%, and 27.50%, respectively, and the mean interspecific distance was found to be 36-fold higher than the mean intraspecific distance. Phylogenetic tree analysis showed that individuals belonging to the same species were clustered together and could be clearly distinguished. The findings of this study can make a valuable contribution to our knowledge of the diversity and dispersal of larval fish in Hawaiian waters.

Ostracods are small bivalved crustaceans widely distributed in aquatic environments and in total 99 species have been recorded in genusEuphilomedesKornicker, 1967. In this study, we further describe two new species of benthic ostracods in this genus,Euphilomedes liuruiyiisp. nov. andEuphilomedes pentacanthossp. nov., collected from the Taiwan Strait in China. These two species can be easily distinguished from their congeners by some crucial morphological characteristics, including the carapace shape, the numbers of main and secondary furcal claws, and their arrangement of furcal claws. In addition the first antenna, endopod of second antenna, frontal organ, mandible and the seventh limb also differentiate these two species from related species.

Background: The Polyplacophora class, which includes all chitons, is distinguished by its unique eight-piece interlocking armor, showcasing a vast diversity in marine environments. However, the detailed evolutionary relationships within the Chitonidae family remain largely unknown. The mitochondrial genome is essential for understanding these relationships, but there has been a significant lack of such genomic information, especially for the Liolophura genus. Methods: We generated the first mitogenome of Liolophura japonica by assembling Illumina reads with GetOrganelle, polishing with Pilon, annotating genes with MitoZ and MITOS2, and inferring phylogeny from 13 concatenated protein-coding genes (PCGs) using MAFFT and IQ-TREE. Results: The mitogenome is 15,209 base pairs long and includes 13 protein-coding genes, 22 transfer RNAs, and 2 ribosomal RNAs. The mitogenome exhibited a slight AT bias common in Chitonidae and showcased structural uniqueness with no control region found. Notably, all protein-coding genes demonstrated evidence of purifying selection, with Ka/Ks ratios below 1, highlighting evolutionary conservation. Phylogenetic analysis reveals a close relationship between L. japonica, Acanthopleura loochooana Broderip & Sowerby 1829, and Acanthopleura vaillantii Rochebrune, 1882, potentially warranting future taxonomic re-evaluation. This research emphasizes the crucial role of mitochondrial genomes in mollusk phylogeny and sets the stage for advanced genetic studies within this group. Conclusions: The significance of this study lies in its contribution to understanding the mitochondrial genome of L. japonica, a key species within the Polyplacophora class. By analyzing its mitogenome, we aim to enhance our understanding of evolutionary processes in chitons and other mollusks.