Search Results (9)

Phyllodoce koreana was first described in 1985 in Gwangyang Bay, a semi-enclosed bay in Korea affected by significant organic input from the Seomjin River and dredging activities near the Gwangyang Port. Since then, this Korean endemic species has received limited attention in taxonomic and ecological studies. Phyllodoce koreana is known for its resilience to mild disturbances but is vulnerable to severe environmental changes. In this study, P. koreana specimens were collected from organically polluted Asian stalked tunicate aquaculture farms at eight sites in Jindong Bay, a location with environmental conditions similar to those of Gwangyang Bay, over the course of five sampling events from March to November. Both bays experience benthic hypoxia in summer due to elevated water temperatures and organic matter accumulation. Phyllodocid specimens were primarily collected in March and November 2023, non-hypoxic periods, suggesting potential seasonal adaptations to environmental fluctuations. The morphological features of the collected specimens were consistent with the original description of P. koreana, confirming their identification. Additionally, we reported previously overlooked morphological details, contributing to a more comprehensive taxonomic understanding of the species. We also present, for the first time, the complete mitochondrial genome of this species, comprising 15,559 bp, which provides essential genetic data for future taxonomic and phylogenetic studies. The phylogenetic analysis of protein-coding genes shows that, among 17 related polychaete species, P. koreana (family Phyllodocidae) is closely related to the family Goniadidae. Future research should expand our knowledge of polychaete taxonomy by integrating additional mitochondrial genomes and investigating the role of conserved gene synteny within Polychaeta. Full article

Microplastic distribution surveys centered on Korea’s Gwangyang Bay and southern coastal waters. Gwangyang Bay seawater averaged 3.17 ± 1.23 particles/L, and sediments averaged 462.4 ± 143.9 particles/kg. The southern coastal seawater averaged 0.10 ± 0.09 particles/L, and the sediments averaged 50.6 ± 29.7 particles/kg. Microplastics flowing from land, through physical modeling of ocean currents in Gwangyang Bay and southern coastal waters, pass through the Yeosu Strait and flow into the southern coastal waters. At the same time, it is judged that the southern coastal waters showed somewhat lower abundance than the Gwangyang Bay waters because they move toward the Korean Strait due to the Jeju warm current water and Tsushima current water, strongly generated in summer. In addition, the seawater microplastic abundance showed a higher abundance than that on the site adjacent to the land in the southern coastal waters, which is the study area. On the other hand, the results for sediment microplastic abundance were opposite to the surface seawater microplastic results. Therefore, it is judged that entering one source of pollution does not affect the distribution of microplastics in Gwangyang Bay and southern coastal waters, but rather this occurs in different forms. Full article

The biochemical composition of seston along a salinity gradient were examined in the low-turbidity, temperate, estuarine embayment, Gwangyang Bay in Korea. Seasonal variations in sestonic protein (PRT), carbohydrate (CHO), and lipid (LIP) concentrations were analyzed to assess the effects of physiological status and taxonomic composition of phytoplankton. The concentrations of biochemical compounds displayed a close relationship with chlorophyll a (Chla). PRT:CHO ratios were high (>1.0) in the estuarine channel in warmer months and in whole bay in February, indicating a N-replete condition for phytoplankton growth. High CHO:LIP ratios (>2.5) in the saline deep-bay area during the warmer months (>2.0) emphasized the importance of temperature and photoperiod over nutritional conditions. The low POC:Chla (<200), molar C:N (~7) ratios, and biopolymeric carbon concentrations coupled with high primary productivity indicated a low detrital contribution to the particulate organic matter pool. Diatom dominance throughout the year contributed to consistently high carbohydrate concentrations. Furthermore, generalized additive models highlighted that phytoplankton community (i.e., size) structure may serve as an important descriptor of sestonic biochemical composition. Collectively, our results suggest that physiological and taxonomic features of phytoplankton play prominent roles in determining the biochemical composition of seston, supporting the fact that the ecosystem processes in Gwangyang Bay are largely based on phytoplankton dynamics. Full article

Spotnape ponyfish (Nuchequula nuchalis) is a dominant species that is broadly distributed from estuarine to deep-bay areas, reflecting a euryhaline habitat. Apolipoprotein AI (ApoAI) is a main component of plasma lipoproteins and has crucial roles in lipid metabolism and the defense immune system. In this study, we characterized the N. nuchalis ApoAI gene and analyzed the expression of the ApoAI transcript in N. nuchalis collected at various sites in the estuary and the deep-bay area which have different salinities. Owing to the fish’s mobility, we conducted stable isotope analyses to confirm the habitat characteristics of N. nuchalis. Carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) from N. nuchalis indicated different feeding sources and trophic levels in the estuarine and deep-bay habitats. The characterized N. nuchalis ApoAI displayed residual repeats that formed a pair of alpha helices, indicating that the protein belongs to the apolipoprotein family. In the phylogenetic analysis, there was no sister group of N. nuchalis ApoAI among the large clades of fish species. The transcriptional expression level of ApoAI was higher in N. nuchalis inhabiting the deep-bay area with a high salinity (over 31 psu) than in N. nuchalis inhabiting the top of the estuary with a low salinity (6~15 psu). In addition, the expression patterns of N. nuchalis ApoAI were positively correlated with environmental factors (transparency, pH, TC, and TIC) in the high salinity area. These results suggest that ApoAI gene expression can reflect habitat characteristics of N. nuchalis which traverse broad salinity ranges and is associated with functional roles of osmoregulation and lipid metabolism for fish growth and development. Full article

The interactive roles of zooplankton grazing (top-down) and nutrient (bottom-up) processes on phytoplankton distribution in a temperate estuary were investigated via dilution and nutrient addition experiments. The responses of size-fractionated phytoplankton and major phytoplankton groups, as determined by flow cytometry, were examined in association with zooplankton grazing and nutrient availability. The summer bloom was attributed to nanoplankton, and microplankton was largely responsible for the winter bloom, whereas the picoplankton biomass was relatively consistent throughout the sampling periods, except for the fall. The nutrient addition experiments illustrated that nanoplankton responded more quickly to phosphate than the other groups in the summer, whereas microplankton had a faster response to most nutrients in the winter. The dilution experiments ascribed that the grazing mortality rates of eukaryotes were low compared to those of the other groups, whereas autotrophic cyanobacteria were more palatable to zooplankton than cryptophytes and eukaryotes. Our experimental results indicate that efficient escape from zooplankton grazing and fast response to nutrient availability synergistically caused the microplankton to bloom in the winter, whereas the bottom-up process (i.e., the phosphate effect) largely governed the nanoplankton bloom in the summer. Full article

The nonlinearity and complexity of coastal ecosystems often cause difficulties when analyzing spatial and temporal patterns of ecological traits. Environmental DNA (eDNA) monitoring has provided an alternative to overcoming the aforementioned issues associated with classical monitoring. We determined aquatic community taxonomic composition using eDNA based on a meta-barcoding approach that characterizes the general ecological features in the Gwangyang Bay coastal ecosystem. We selected the V9 region of the 18S rDNA gene (18S V9), primarily because of its broad range among eukaryotes. Our results produced more detailed spatial patterns in the study area previously categorized (inner bay, main channel of the bay and outer bay) by Kim et al. (2019). Specifically, the outer bay zone was clearly identified by CCA using genus-level identification of aquatic organisms based on meta-barcoding data. We also found significant relationships between environmental factors. Therefore, eDNA monitoring based on meta-barcoding approach holds great potential as a complemental monitoring tool to identify spatial taxonomic distribution patterns in coastal areas. Full article

Our study focuses on methodological comparison of plankton community composition in relation to ecological monitoring and assessment with data sampling. Recently, along with the advancement of monitoring techniques, metabarcoding has been widely used in the context of environmental DNA (eDNA). We examine the applicability of eDNA metabarcoding for effective monitoring and assessment of community composition, compared with conventional observation using microscopic identification in a coastal ecosystem, Gwangynag Bay in South Korea. Our analysis is based primarily on two surveys at a total of 15 study sites in early and late summer (June and September) of the year 2018. The results of our study demonstrate the similarity and dissimilarity of biological communities in composition, richness and diversity between eDNA metabarcoding and conventional microscopic identification. It is found that, overall, eDNA metabarcoding appears to provide a wider variety of species composition, while conventional microscopic identification depicts more distinct plankton communities in sites. Finally, we suggest that eDNA metabarcoding is a practically useful method and can be potentially considered as a valuable alternative for biological monitoring and diversity assessments. Full article

Our study aims to identify the spatial characteristics of water quality and sediment conditions in relation to fisheries resources, since the productivity of fisheries resources is closely related to the ambient conditions of the resource areas. We collected water quality samples and sediment contaminants from twenty-one sites at Gwangyang Bay, Korea, in the summer of 2018. Our study sites covered the area from the Seomjin River estuary to the inner and outer bays. To spatially characterize physicochemical features of Gwangyang Bay, we used Self-Organizing Map (SOM), which is known as a robust and powerful tool of unsupervised neural networks for pattern recognition. The present environmental conditions of Gwangyang Bay were spatially characterized according to four different attributes of water quality and sediment contamination. From the results, we put emphasis on several interesting points: (i) the SOM manifests the dominant physicochemical attributes of each geographical zone associated with the patterns of water quality and sediment contamination; (ii) fish populations appear to be closely associated with their food sources (e.g., shrimps and crabs) as well as the ambient physicochemical conditions; and (iii) in the context of public health and ecosystem services, the SOM result can potentially offer guidance for fish consumption associated with sediment heavy metal contamination. The present study may have limitations in representing general features of Gwangyang Bay, given the inability of snapshot data to characterize a complex ecosystem. In this regard, consistent sampling and investigation are needed to capture spatial variation and to delineate the temporal dynamics of water quality, sediment contamination, and fish populations. However, the SOM application is helpful and useful as a first approximation of an environmental assessment for the effective management of fisheries resources. Full article

Spatial interpolation is employed to improve exposure estimates and to assess adverse health effects associated with environmental risk factors. Since various studies have reported that high ozone (O₃) concentrations can give rise to adverse effects on respiratory symptoms and lung function, we investigated the association between O₃ levels and lung function using a variety of spatial interpolation techniques and evaluated how different methods for estimating exposure may influence health results for a cohort from an industrial complex (Gwangyang Bay) in South Korea in 2009. To estimate daily concentrations of O₃ in each subject, four different methods were used, which include simple averaging, nearest neighbor, inverse distance weighting, and kriging. Also, to compare the association between O₃ levels and lung function by age-groups, we explored ozone’s impacts on three age-related groups: children (9–14 years), adults (15–64 years), and the elderly (≥65 years). The overall change of effect size on lung function in each age group tended to show similar patterns for lag and methods for estimating exposure. A significant negative association was only observed between O₃ levels and FVC and FEV₁ for most of the lag and methods in children. The largest effect of O₃ levels was found at the average for the lung function test day and last 2 days (0–2 days). In conclusions, the spatial interpolation methods may benefit in providing individual-level exposure with appropriate temporal resolution from ambient monitors. However, time-activity patterns of residents, monitoring site locations, methodological choices, and other factors should be considered to minimize exposure misclassification. Full article