First report of the microgastropod Ammonicera japonica (Omalogyridae Habe, 1972) in Korea

The intertidal zone of Jeju Island, Korea, is characterized by well-developed volcanic rocks with high wave action. During low tide, numerous small tidal pools are formed on the rocky intertidal zone, which provide shelter and habitats for benthic organisms. Previous investigation indicated that many species of micromolluscans inhabit the tidal pools; however, only a few studies have reported the ecology and identification of these microshells. In this study, we have identified a microgastropod, Ammonicera japonica Habe, 1972 (Omalogyridae), from a tidal pool on the southern coast of Jeju Island. Morphological identification of the species was based on scanning electron microscopy (SEM) of the protoconch and teleoconch. A. japonica was found to be associated with encrusting coralline algae distributed on the bottom of the tidal pools. This is the first report of A. japonica from Korea, and the specimen was registered at the National Marine Biodiversity Institute of Korea (MABIK MO00157413)

Factors controlling the vertical zonation of the intertidal seagrass, Zostera japonica in its native range in the northwestern Pacific

The desiccation tolerance of the intertidal seagrass Zostera japonica has been demonstrated in a number of studies; however, the factors limiting expansion of intertidal seagrass species into subtidal zones remain controversial. We transplanted Z. japonica shoots from the intermediate intertidal zone into the plots with and without Z. marina shoots in both the lower intertidal and shallow subtidal zones to investigate the factors controlling Z. japonica growth in these zones. Daily photon flux density at the Z. japonica canopy level was attenuated by both water depth and coexisting Z. marina shoots but more strongly by Z. marina shoots than water depth in the transplant plots. The shoot density and biomass of Z. japonica transplants were significantly lower in transplant plots in the subtidal zone than in the lower intertidal zone. Although the photon flux density was significantly lower in transplant plots containing Z. marina shoots, the growth of Z. japonica transplants did not differ significantly between plots with and those without Z. marina shoots. Z. japonica transplants exhibited photoacclimatory responses such as increased shoot height and chlorophyll content under the lower-light conditions, offsetting the reduced light availability so that no significant differences in transplant growth occurred between plots with and those without Z. marina shoots. As the growth of Z. japonica transplants decreased significantly in the subtidal zone, the interactive effects of environmental stresses associated with tidal inundation and reduced light availability may restrict penetration of the intertidal seagrass Z. japonica into the subtidal zone. The persistence of high photosynthetic performance after air exposure and a regular arrangement of the densely overlapped leaves atop wet sediments may be desiccation tolerance mechanisms for Z. japonica in the intertidal zone

Exploring the Impacts of Anthropogenic Disturbance on Seawater and Sediment Microbial Communities in Korean Coastal Waters Using Metagenomics Analysis

The coastal ecosystems are considered as one of the most dynamic and vulnerable environments under various anthropogenic developments and the effects of climate change. Variations in the composition and diversity of microbial communities may be a good indicator for determining whether the marine ecosystems are affected by complex forcing stressors. DNA sequence-based metagenomics has recently emerged as a promising tool for analyzing the structure and diversity of microbial communities based on environmental DNA (eDNA). However, few studies have so far been performed using this approach to assess the impacts of human activities on the microbial communities in marine systems. In this study, using metagenomic DNA sequencing (16S ribosomal RNA gene), we analyzed and compared seawater and sediment communities between sand mining and control (natural) sites in southern coastal waters of Korea to assess whether anthropogenic activities have significantly affected the microbial communities. The sand mining sites harbored considerably lower levels of microbial diversities in the surface seawater community during spring compared with control sites. Moreover, the sand mining areas had distinct microbial taxonomic group compositions, particularly during spring season. The microbial groups detected solely in the sediment load/dredging areas (e.g., Marinobacter, Alcanivorax, Novosphingobium) are known to be involved in degradation of toxic chemicals such as hydrocarbon, oil, and aromatic compounds, and they also contain potential pathogens. This study highlights the versatility of metagenomics in monitoring and diagnosing the impacts of human disturbance on the environmental health of marine ecosystems from eDNA

Physiological and Biochemical Responses of the Green Tide-Forming Algae, <i>Ulva</i> Species, under Different Nutrient Conditions on Jeju Island, Korea

In this study, we investigated the physiological and biochemical responses of Ulva species to variation in nutrient availability. Sampling was conducted at two sites on Jeju Island, Korea, namely, Handong, which is close to seven intensive land-based fish farms, and Hado, which has no apparent nearby nutrient sources. We examined the water column nutrient concentrations, nitrate reductase (NR) activity, nitrate uptake efficiency, tissue C, N, and P content, and stable isotope ratios of Ulva species. Water column NH4+, NO3− + NO2−, and PO43− concentrations were significantly higher at Handong than at Hado. NR activity and tissue N content of Ulva species were significantly higher at Handong than at Hado. Notably, nitrate uptake efficiency was inversely proportional to NR activity and tissue N content. The physiological and biochemical responses of Ulva species were closely related to dissolved inorganic nitrogen, which stimulates Ulva species to regulate growth. Additionally, the δ15N values of Ulva tissues at both sites were within the previously reported range for fresh groundwater. Therefore, the main nitrogen source for Ulva growth may be submerged groundwater with high nutrient concentrations. Our results provide invaluable information for estimating dissolved inorganic nitrogen levels in water, which may facilitate development of management policies

Study sites in Aenggang Bay and Koje Bay on the southern coast of the Korean peninsula.

<p>Study sites in Aenggang Bay and Koje Bay on the southern coast of the Korean peninsula.</p

Photoacclimatory Responses of <i>Zostera marina</i> in the Intertidal and Subtidal Zones

<div><p>Photoacclimatory responses of the seagrass <i>Zostera marina</i> in the intertidal and subtidal zones were investigated by measuring chlorophyll <i>a</i> fluorescence parameters, photosynthetic pigments, leaf δ¹³C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETR_max) and minimum saturation irradiance (E_k) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (<i>F</i>_<i>v</i>/<i>F</i>_<i>m</i>) were higher in subtidal plants. The intertidal plants also had significantly greater Stern–Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ¹³C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO₂ for photosynthesis during emersion. Effective quantum yield (<i>ΔF</i>/<i>F</i>_<i>m</i><i>´</i>) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of <i>Z</i>. <i>marina</i> in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones.</p></div

Data from: Population genetic structure of eelgrass (Zostera marina) on the Korean coast: current status and conservation implications for future management

Seagrasses provide numerous ecosystem services for coastal and estuarine environments, such as nursery functions, erosion protection, pollution filtration, and carbon sequestration. Zostera marina (common name "eelgrass") is one of the seagrass bed-forming species distributed widely in the northern hemisphere, including the Korean Peninsula. Recently, however, there has been a drastic decline in the population size of Z. marina worldwide, including Korea. We examined the current population genetic status of this species on the southern coast of Korea by estimating the levels of genetic diversity and genetic structure of 10 geographic populations using eight nuclear microsatellite markers. The level of genetic diversity was found to be significantly lower for populations on Jeju Island [mean allelic richness (AR) = 1.92, clonal diversity (R) = 0.51], which is located approximately 155 km off the southernmost region of the Korean Peninsula, than for those in the South Sea (mean AR = 2.69, R = 0.82), which is on the southern coast of the mainland. South Korean eelgrass populations were substantially genetically divergent from one another (FST = 0.061-0.573), suggesting that limited contemporary gene flow has been taking place among populations. We also found weak but detectable temporal variation in genetic structure within a site over 10 years. In additional depth comparisons, statistically significant genetic differentiation was observed between shallow (or middle) and deep zones in two of three sites tested. Depleted genetic diversity, small effective population sizes (Ne) and limited connectivity for populations on Jeju Island indicate that these populations may be vulnerable to local extinction under changing environmental conditions, especially given that Jeju Island is one of the fastest warming regions around the world. Overall, our work will inform conservation and restoration efforts, including transplantation for eelgrass populations at the southern tip of the Korean Peninsula, for this ecologically important species

<i>Zostera marina</i>.

<p><b>Recovery of effective quantum yield after 0, 1, 3, 5, and 12 h of re-immersion for the intertidal (A and C) and subtidal plants (B and D) previously exposed to air for 1, 2, 3, 4, 5, and 6 h emersion periods.</b> Values are means ± standard errors (n = 10).</p

Schematic summary of the morphological and photoacclimatory responses of intertidal and subtidal <i>Zostera marina</i> plants.

<p>Schematic summary of the morphological and photoacclimatory responses of intertidal and subtidal <i>Zostera marina</i> plants.</p

Data from: Population genetic structure of eelgrass (Zostera marina) on the Korean coast: current status and conservation implications for future management

Seagrasses provide numerous ecosystem services for coastal and estuarine environments, such as nursery functions, erosion protection, pollution filtration, and carbon sequestration. Zostera marina (common name "eelgrass") is one of the seagrass bed-forming species distributed widely in the northern hemisphere, including the Korean Peninsula. Recently, however, there has been a drastic decline in the population size of Z. marina worldwide, including Korea. We examined the current population genetic status of this species on the southern coast of Korea by estimating the levels of genetic diversity and genetic structure of 10 geographic populations using eight nuclear microsatellite markers. The level of genetic diversity was found to be significantly lower for populations on Jeju Island [mean allelic richness (AR) = 1.92, clonal diversity (R) = 0.51], which is located approximately 155 km off the southernmost region of the Korean Peninsula, than for those in the South Sea (mean AR = 2.69, R = 0.82), which is on the southern coast of the mainland. South Korean eelgrass populations were substantially genetically divergent from one another (FST = 0.061-0.573), suggesting that limited contemporary gene flow has been taking place among populations. We also found weak but detectable temporal variation in genetic structure within a site over 10 years. In additional depth comparisons, statistically significant genetic differentiation was observed between shallow (or middle) and deep zones in two of three sites tested. Depleted genetic diversity, small effective population sizes (Ne) and limited connectivity for populations on Jeju Island indicate that these populations may be vulnerable to local extinction under changing environmental conditions, especially given that Jeju Island is one of the fastest warming regions around the world. Overall, our work will inform conservation and restoration efforts, including transplantation for eelgrass populations at the southern tip of the Korean Peninsula, for this ecologically important species