Assessing the effectiveness of artificial structures as a monitoring tool for benthic diversity in temperate reefs is crucial to determining their relevance in reef conservation and management. In this study, we utilized Autonomous Reef Monitoring Structures (ARMS) to evaluate sessile benthic communities that colonized ARMS units after 12 and 34 months of immersion within distinct habitats (coral-dominated and macroalgae-dominated habitats) in Jeju Island, Korea. We used two methods: image analysis of the ARMS plates and DNA metabarcoding of the ARMS units. We found significant differences in the sessile benthic community between the plate faces, installation periods, and habitats. DNA metabarcoding also revealed differences in sessile benthic diversity among habitats. Additionally, we identified the Lithophyllum genus within the crustose coralline algae community, whose dominance might trigger a transition to coral-dominated habitats in Jeju Island. We recommend integrating ARMS image analysis with DNA metabarcoding to enhance and complement studies focusing on benthic diversity. By utilizing ARMS, this study provides valuable information for understanding sessile benthic communities and biodiversity, contributing to an enhanced understanding of the responses of ecological communities to climate change.

Benthic habitat zonation is described from in situ observations and seabed photographs taken from the coastal area of Weno Island, Chuuk, Micronesia. Habitat groups, types, and boundaries are defined by visible substratum characteristics (i.e., in situ and by digital imaging of photo-quadrats along transect lines), and by cluster and ordination analyses using relative coverage percentage of identified classification categories. The statistical similarity between habitat groups is determined by Analysis of similarity (ANOSIM). Benthic habitat groups with significant influence on the determination of habitat type are isolated by the similarity percentage (SIMPER) test. In addition to the standard practices of using transect lines and collecting data in accordance with the already well-implemented and thoroughly-tested benthic habitat classification scheme for tropical reef monitoring, we applied simple statistics that enable comparative data interpretation. Our simple, repeatable methods provide a framework for benthic habitat-related monitoring research that allows the comparison of results across regions.

Since coastal wetlands have been severely degraded and polluted by human activities, they have increasingly become a significant source of greenhouse gases (GHGs), so understanding the characteristics of their emissions is critical for devising future climate change mitigation strategies. This study modified a model based on carbon balance to forecast carbon stored and CO₂, CH₄ emissions in four types of typical tidal flats—Phragmites australis (PA), Spartina alterniflora (SA), Suaeda japonica (SJ), and Bare Tidal Flat (BTF) in Korea’s Ganghwa province from 2017 to 2047. The model was built using biomass data from salt plant species collected in different locations. The results indicate that the total annual simulated flow of CH₄ increased over time in all four areas, most notably in SA, while CO₂ remained relatively stable. The mean CO₂ and CH₄ fluxes in the four types of representative tidal flats were in the range of 0.03 to 19.1 mg m⁻² d⁻¹ and 0.007 to 5.23 mg m⁻² d⁻¹, respectively, across all seasons. Besides, the results indicate that the amount of carbon accumulated in the top soil increases linearly over time in nearly all areas studied, ranging from 0.01 to 0.13 (kgC m⁻² yr⁻¹). In general, the study provides a model for Korean tidal flats that incorporates carbon storage and GHG emissions in the intertidal zone in order to develop potential GHG reduction scenarios.

The top shell, Turbo sazae, occurs commonly in the shallow rocky subtidal area of Jeju Island off the south coast of Korea, and it is one of the most valuable gastropod resources supporting the local shellfish industry. T. sazae landings in Jeju have declined dramatically in recent years, although the factors involved in this decline are yet to be identified. Recent studies also have reported that T. sazae is expanding its distribution range to the east coast of Korea, possibly due to the increasing seawater temperature. In this study, we investigated the hemocyte responses of T. sazae to elevated seawater temperatures in order to gain a better understanding of its immunological response to higher water temperatures. In this experiment, we exposed top shells to a gradual increase in seawater temperature, ranging from 22 °C to 30 °C, over a span of 9 days. We employed flow cytometry to assess various cellular immune responses, including hemocyte viability, phagocytosis capacity, and the production of reactive oxygen species (ROS) in T. sazae. The results showed that top shells exposed to elevated seawater temperature exhibited a significant decrease in phagocytosis capacity and an increase in ROS production after 3 days of the experiment. These findings indicate that an elevated seawater temperature imposes a stressful condition on T. sazae, characterized by reduced phagocytosis capacity and increased oxidative stress.