https://repository.kopri.re.kr/handle/201206/9683 2026-04-21T12:30:49Z https://repository.kopri.re.kr/handle/201206/13037 Title: Patterns, drivers and implications of ascidian distributions in a rapidly deglaciating fjord, King George Island, West Antarctic Peninsula Authors: Kim, Dong-U; Khim, Jong Seong; Ahn, In-Young Abstract: We report strong evidence for the utility of ascidian communities as sentinel organisms for monitoring nearshore Antarctic marine ecosystem response to climate-induced warming and glacial melting. Ascidians are one of the most common Antarctic epibenthic megafauna, but information on their distribution and the determinants is still scarce. In this study we investigated spatial patterns of ascidians in Marian Cove (MC), a rapidly deglaciating fjord in the West Antarctic Peninsula, one of the most rapidly warming regions on earth. We also analyzed key drivers structuring the communities and assessed their relevance to glacial retreat and following processes. The first applied ROV survey in MC discovered that ascidians were the most diverse (14 out of 64 taxa) taxa with the greatest abundance (~264 inds·m-2). Ascidian abundance and diversity greatly varied in space, by distance from glacier and/or depths, explaining ~64% of total megafaunal variations. Notably, in deep seabed (50？90 m) they shifted distinctly from early colonization communities near glacier (0.2 km to glacier) with predominance of two opportunistic species, Molgula pedunculata and Cnemidocarpa verrucosa, to mature communities at the most remote site (3.5 km). A set of analyses revealed that such shifts were related mostly to changes in sediment properties that develop in association with glacial retreat and consequent processes. Sediment composition, grain size and sorting collectively explained outward increasing physical stability apparently with decreased influence of glacial retreat, supporting ascidian community maturing at the deep and distant site. BIOENV analysis indicated that “distance” to glacier is one key factor influencing ascidian community structure in the deep seabed. Overall, the results of the analyses strongly indicated that physical disturbances (mainly sedimentation and ice scouring) accompanying glacial retreat are an important force shaping ascidian assemblages in the cove, and that these forces are altered by the distance from the glacier and water depth. Notably, in this fjord, the period of sea bed deglaciation was roughly proportional to the distance to glacier over the last six decades. This suggested that the ascidian shift identified in this study reflects a long-term successional process associated with glacial retreat in the past in MC, which in turn warrants to project future changes in this glacial fjord and possibly other similar environments. 2021-06-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/12082 Title: 30 years revisit survey for long-term changes in the Antarctic subtidal algal assemblage Authors: Ko, Young Wook; Choi, Han-Gu; Lee, Dong Seok; Kim, Jeong Ha Abstract: A long-term change of a subtidal macroalgal assemblage has been investigated in Maxwell Bay, King George Island (KGI) of the Antarctic coast by a revisit survey after 30 years. Field surveys were done by SCUBA diving at six sites in 2016-2018 to directly compare with the previous survey conducted in 1988-1993 at the same sites. The total number of macroalgal species was similar between the previous and the present survey, 25 and 27 species respectively. However, the macroalgal assemblage changed substantially with the average similarity of 48.2% between the two surveys. Also, the species-level abundance showed a high variability between surveys. On the other hand, over the 30 years interval there was little overall change at the between-site level hierarchical structure in the subtidal communities of Maxwell Bay. The sites near the penguin rookery consistently showed the highest biodiversity, indicating the importance of land-based nutrients input in Antarctic coastal habitats. A noticeable pattern change over 30 years was the increase of Desmarestia complex and Plocamium cartilagineum and the decrease of Himantothallus grandifolius. Both groups are still dominant, but the shift from Himantothallus to Desmarestia-Plocamium may reflects temperature rise on the Maxwell Bay coast compared to the past. 2020-05-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/12019 Title: Studies on the Changes in Coastal Marine Systems of the Antarctic Peninsula: A 2050 Outlook Authors: Ahn, In-Young 2020-02-28T00:00:00Z https://repository.kopri.re.kr/handle/201206/11005 Title: Ocean freshening and acidification differentially influence mortality and behaviorof the Antarctic amphipod Gondogeneia antarctica Authors: Park, Seojeong; Ahn, In-Young; Sin, Eunchong; Shim, JeongHee; Kim, Taewon Abstract: Increase in anthropogenic CO2 to the atmosphere causes rapid glacial retreat by regional warming and high CO2 dissolution to the Southern Ocean, resulting in declining trends of mean salinity and pH in seawater of the Antarctica. The Marian Cove, King George Island in the Western Antarctic Peninsula (WAP) is one of the regions that undergoes one of the highest rates of glacier retreat. Ocean freshening and acidification caused by meltwater intrusion near the glacier are inevitable, so the changes in the marine ecosystem are expected. One of the abundant gammarid amphipod species, Gondogeneia antarctica, occupies essential ecological niche in the WAP. To test the effects of the low salinity and low pH on the population, we exposed G. antarctica to 4 different treatments combining two salinity (34 and 27 psu) and two pH (pH 8.0 and 7.6) levels for 27 days. Mortality except cannibalized individuals significantly decreased under low salinity, while increased under low pH. Accordingly, low salinity increased cannibalism rates, while low pH reduced the food detection significantly. Shelter-using during the daytime decreased by low salinity and pH respectively, which indicates two stressors act as behavioral disruptors for the amphipods. Under low salinity conditions, swimming behavior during the daytime increased, whereas swimming during the nighttime decreased significantly. Although the interactions between low salinity and low pH were not observed during the experiments, the results suggest that each stressor due to glacier melting causes amphipods' abnormal behavior and eventually may threat population persistence in the cove. 2020-02-01T00:00:00Z