Jeju, Island of World Peace

1. Necessity

The waters around Jeju, an island located off the southernmost tip of the Korean Peninsula, flow northward with the Tsushima Warm Current and the Yellow Sea Warm Current moving from south to east and from south to west, respectively. Depending on the season, Jeju’s waters are intricately affected by water masses with different properties, such as the Chinese Coastal Water, the Korean Southern Coastal Water, and the Korean West Sea Cold Water Zone. This diversity creates good conditions for migration routes and wintering grounds of different fish varieties in the neritic waters of Jeju Island. Of the waters around the Korean Peninsula, the region features the most diverse marine flora and fauna and provides habitats for various living species. Due to climate change, however, it has been reported that the subsea desertification near Jeju Island has caused the disappearance of macro-algal communities (e.g. Sargassum spp., kelp, Ecklonia cava, Eisenia bicyclis, etc.) and the emergence of epiphytic coccolithophorid – a valueless species as food organisms for commercial clam resources (e.g. abalone, horned turban, etc.) – with an increasing occurrence of soft coral reefs. As such, understanding the global carbon cycle is crucial to comprehending and forecasting global warming and other climate change-related phenomena. The ocean is critical for storing carbon (38,000 Gt C). Sixteen times more carbon dioxide (100 Gt yr^-1) than the amount released into the atmosphere by human activities (6 Gt yr^-1) is circulated by the exchange of gases between the ocean and atmosphere. Carbon dioxide introduced into the ocean due to the exchange of gases between the ocean and the atmosphere is transformed into different forms of organic carbon during the photosynthesis process. Most organic carbon (97%) exists in the form of dissolved organic carbon (DOC) of 700 Gt C, similar to the amount of carbon dioxide in the atmosphere (750 Gt C). As such, DOC plays a crucial role in the carbon cycle. However, most of the studies on DOC have focused on the oceanic province. Although the significance of the neritic environment of the marine carbon cycle has been recognized, few studies have addressed the mechanism of cycling, generation, and removal of DOC. Jeju Island – Korea’s representative pristine environment – is well-known to be very sensitive to climate change. It is therefore necessary to identify the movements of DOC affected by climate change and complete the Carbon Balance Model by quantifying carbon in the neritic environment of Jeju Island.

 

2. Domestic and International Research Trends

Although there has been dramatic advancement over the past 30 years in the studies of the process of the marine carbon cycle and quantitative flux measurement, much has been incompletely understood in terms of the origin, generation, movement, and removal of DOC, as well as the carbon balance of the neritic seas. The trends and prospects of the latest domestic and international research and the problems of preceding research trends on the two topics are as follows:

(1) Origin, generation, movement, and degradation of dissolved organic carbon (DOC)

– In the ocean, the DOC has a concentration of 34-150 μM. Between 1980-2000, however, great controversy erupted over how DOC was measured. According to preceding studies, the high-temperature oxidation methods are more efficient in DOC measurement, take a shorter time for analysis, and require smaller samples for analysis (100-1000 μl) compared to the peroxide oxidation and ultraviolet oxidation methods. However, the results revealed that much higher concentrations of DOC (300 μM) were reported due to contamination from the device. The recent large-scale distribution of Deep Sea Reference by the University of Miami has greatly improved the reliability of DOC measurements using high-temperature oxidation.

– Therefore, research has been actively conducted around the world to trace the origin of the DOC in the oceans and to understand the generation process of the non-biodegradable DOC. As tracers for terrestrial dissolved organic matter, using ¹³C, ¹⁴C, CDOM (colored dissolved organic matters), and C-H-O values has been attempted. However, the origin and generation process of DOM remains insufficiently identified because the analytic methods for the components have yet to be well-established and are difficult to measure, thus forcing researchers to limit the areas of study to certain subjects or phenomena depending on their majors. Therefore, in order to understand the origin and generation process of DOM in the oceans, it is necessary to comprehensively understand the generation, movement, and degradation processes of DOM, while many tracers as possible should be applied at the same time.

(2) Are the neritic seas the source of carbon supply or of carbon removal?

Neritic seas exhibit substantial changes in pCO2 by region, function of the source of carbon supply, or that of carbon removal. Even when assuming that the oceans stay relatively consistent, the complexity of carbon supply channels and removal processes makes it difficult to measure regional pCO2. Decades of neritic pollution, climate change, and change in the neritic terrestrial environment have made it even more difficult to measure pCO2 by region and/or time. Additionally, preceding studies on the carbon matter balance ignored the influx of carbon and nutritive salts from undersea groundwater, while the findings of recent studies have revealed that the amount of undersea groundwater is absolutely crucial. Therefore, clearly understanding the carbon balance of neritic waters is critical to creating a carbon cycle model that can predict future climate changes and to establish neritic carbon reduction policies.

 

3. The Mechanism of the Cycling of Materials Introduced into the Seas

Currently, almost no quantitative analysis has been conducted of the physiochemical effects of groundwater due to snowfall in Jeju, where a considerable amount of snow falls every year. And little research has been conducted on the impact assessment of groundwater recharge and spring water created due to snowfall on the island. Snow from the atmosphere penetrates into the aquifer through the process of freezing and thawing, after which the penetrated groundwater is released into neritic waters alongside high concentrations of terrestrial materials (e.g. nutritive salts, heavy metals, carbon, and organic matter) through various biogeochemical reactions in the aquifer. Given this, it is necessary to qualitatively and quantitatively assess terrestrial materials contained in groundwater while considering the impacts of snowfall in Jeju, where groundwater outflows are relatively high compared to other regions. The assessment is crucial in terms of water resources on land as well as of environmental changes in marine ecosystems.

In particular, Jeju Island is located in the transition zone from subtropical to temperate climate, which makes the island’s temperature and precipitation higher than those of Korea’s inland regions. Moreover, groundwater is very important as a water resource on Jeju Island because 40-45% of its mean annual precipitation is absorbed underground due to the highly permeable volcanic rock formation, leaving no surface water available. Many of preceding studies focused on the research and development of groundwater created due to precipitation. With a large amount of snowfall around the summit of Mt. Halla from mid-November to April – although the total amount of snowfall is smaller than that of inland areas – the snowfall in the highlands of Mt. Halla is expected to have a significant impact on the changes in the amount of groundwater. Nonetheless, no research has been conducted from this perspective. The continuous rise in temperature due to climate change will likely affect the amount of snowfall in the alpine region of Mt. Halla, eventually affecting Jeju’s main water supply, that is, groundwater recharge. Also important is to grasp the influence of nutritive salts, heavy metals, and major ions on the groundwater environment, including organic substances from the atmosphere.

Furthermore, a recent study has reported that nutritive salts that contain nitrates emitted by China have melted into the sea through rain and snow, increasing the level of nutritive salts in the neritic waters off the Korean Peninsula over the past decades (Kim et al., 2011). In the analysis of the entire Pacific Ocean, Korea’s East Sea showed the highest concentration of nutritive salts, which were found to be one-fifth the concentration in Hawaiian waters. This confirmed that the nutritive salts originated from air pollutants emitted in China and other East Asian states. The study also forecast that the increasing concentration of nitrates in the atmosphere will cause the increase in the influx of nitrates into the ocean, eventually diminishing the amount of small phytoplankton while augmenting that of large plankton that causes red tide.

 

4. A Research Proposal on the Direction of the Marine Environment-Related Policies Reflecting Climate Change

Research on the marine environment is deemed to provide basic data for global climate change forecasting and carbon cycle models as well as lay the foundation for setting future policy directions for Jeju Island’s marine environment, which is sensitive to climate change. In this perspective, I propose the following potential research areas:

(1) Changes in the cycling of water and nutritive salts and the feedback effect concerning climate change

– A study on the water cycle and water balance reflecting climate change: The purpose of this study is to secure future water resources and accurately forecast climate change.

– A study on the iron cycle reflecting climate change: This study calculates the iron supply through aerosols to broaden the understanding of biochemical movements of micro-nutritive salts, which are essential for biological production. It will also help recognize the importance of marine-atmospheric interaction.

– A study on the cycling of nutritive salts reflecting climate change: This study aims to understand how limiting factors in biological production appear depending on the marine environment. As biological production in the oceans is related to the reduction of carbon dioxide – a major greenhouse gas – it will be considered important as a timely research topic at an international level.

(2) Ocean acidification and global ecological change due to climate change

– A study on ocean acidification due to climate change: The increase in carbon dioxide in the atmosphere causes the acidification of the ocean. Therefore, the different scenarios on the increasing level of carbon dioxide allow for the varied prediction of ocean acidification and the resulting changes in the marine ecosystems. It also creates a feedback effect concerning climate change.

– A study on the changes in the global ecosystems due to climate change: Fundamental research is needed on how the changes in terrestrial vegetation and ecosystems due to climate change affects the changes in water cycle, greenhouse gases, and aerosols, and on what feedback it eventually gives to climate change.

Jwa, Min-seok is a Senior Researcher of Jeju Research Institute. Earned a Ph.D. in the College of Ocean Sciences of Jeju National University. Authored “Physiological Responses of Intrinsic Small Abalone Haliotis Diversicolor Aquatilis under High Temperature Stress by Low-Level 60Co, Gamma Irradiation-Mediated Hormetic Effect” (2020) and “Current Situation and Economic Analysis of Flatfish Aquaculture in Jeju” (2020). Study underway on the distribution status of marine products from Jeju Island.