https://repository.kopri.re.kr/handle/201206/9682 Tue, 21 Apr 2026 12:29:32 GMT 2026-04-21T12:29:32Z 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. Tue, 01 Jun 2021 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13037 2021-06-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/11787 Title: Large Plastic Debris Dumps: New Biodiversity Hot Spots Emerging on the Deep-Sea Floor Authors: Song, Xikun; Lyu, Mingxin; Zhang, Xiaodi; Ruthensteiner, Bernhard; Ahn, In-Young; Guido, Pastorino; Yunan, Wang; Gu, Yifan; Ta, Kaiwen; Sun, Jie; Liu, Xi; Han, Jian; Ke, Caihuan; Peng, Xiaotong Abstract: Macroplastic debris recorded in the Mariana Trench and accumulated on some deep-sea canyons worldwide arouses great public concerns. Large plastic debris dumps found in canyons of the Xisha Trough, South China Sea become hotspots for deep-sea pollution, with one order of magnitude higher abundance than in other canyons. Here we adopted an integrative specimen-based approach to examine macroplastic items from large debris dumps in the Xisha Trough, and comparative items from continental shelves with rare macroplastics. On the investigated items, we found an epibenthic ecosystem with relatively high species diversity, comprised of 49 millimeter-sized fungi and invertebrate species dominated by scyphozoan polyps and brachiopod juveniles according to inhabiting density. These large dumps are functioning as new biodiversity hotspots hosting endemic species like soft corals or aplacophoran molluscs, providing a spawning habitat for gastropods and even specialized parasitic flatworms, and can be inferred as potential scattered regional sources releasing deep-sea coronate jellyfish. We hypothesize that macroplastics can boost population extension of sessile and some free-living (Mollusca) invertebrates and affect the deep-sea benthic-pelagic coupling process. The baseline of associated organisms needs to be set up and monitored in more canyons, where debris is transported to and accumulated at the highest density. Mon, 01 Feb 2021 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/11787 2021-02-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/12045 Title: Shift in polar benthic community structure in a fast retreating glacial area of Marian Cove, West Antarctica Authors: Bae, Hanna; Ahn, In-Young; Park, Jinsoon; Song, Sung Joon; Noh, Junsung; Kim, Hosang; Khim, Jong Seong Abstract: Glacier retreat is a major long-standing global issue; however, the ecological impacts of such retreats on marine organisms remain unanswered. Here, we examined changes to the polar benthic community structure of "diatoms" under current global warming in a recently retreated glacial area of Marian Cove, Antarctica. The environments and spatiotemporal assemblages of benthic diatoms surveyed in 2018-2019 significantly varied between the intertidal (tidal height of 2.5 m) and subtidal zone (10 and 30 m). A distinct floral distribution along the cove (similar to 4.5 km) was characterized by the adaptive strategy of species present, with chain-forming species predominating near the glacier. The predominant chain-forming diatoms, such as Fragilaria striatula and Paralia sp., are widely distributed in the innermost cove over years, indicating sensitive responses of benthic species to the fast-evolving polar environment. The site-specific and substrate-dependent distributions of certain indicator species (e.g., F.striatula, Navicula glaciei, Cocconeis cf. pinnata) generally reflected such shifts in the benthic community. Our review revealed that the inner glacier region reflected trophic association, featured with higher diversity, abundance, and biomass of benthic diatoms and macrofauna. Overall, the polar benthic community shift observed along the cove generally represented changing environmental conditions, (in)directly linked to ice-melting due to the recent glacier retreat. Fri, 01 Jan 2021 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/12045 2021-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/10868 Title: Tight trophic association between benthic diatom blooms and shallow-water megabenthic communities in a rapidly deglaciated Antarctic fjord Authors: Ha, Sun-Yong; Ahn, In-Young; Moon, Hye-Won; Choi, Bohyung; Shin, Kyung-Hoon Abstract: This study reports isotopic evidence of a unique and highly efficient trophic structure based on a rarely reported benthic diatom species in a rapidly warming Antarctic fjord (Marian Cove; MC). Recent surveys of MC revealed a very conspicuous feature, an intense, persistent benthic diatom bloom ('benthic diatom bush') overgrowing a variety of common megabenthic fauna, primarily filter feeders (bivalves, ascidians, and demosponges), which occurred widely at shallow depths. To ascertain if the benthic diatom bloom is consumed as a primary food source, δ13C and δ15N were analyzed in the associated filter feeders and other herbivores, as well as in the diatom bush and other potential food sources (microphytobenthos, sedimentary organic matter and macroalgae). The analysis showed that the δ13C values of all filter feeders (？23.5 to ？25.2‰) were very similar to those of the diatom bush (？23.1 to ？23.6‰), strongly suggesting that these benthic diatoms are the principal diet of the associated filter feeders. The isotopic signatures of the other food sources were very close to those of the diatom bush, indicating that the organic matter had the same origin, namely benthic diatoms. Given its quality, quantity and availability, the diatom bush could be regarded as the primary food source. The benthic diatom bush was predominated by the chain-forming centric diatom Paralia sp., which occurs in shallow coastal waters with a wide range of salinity in various geographic localities. Thus, the Paralia sp. bloom in this rapidly warming fjord also indicates its potential utility as an indicator of climate-induced environmental changes. Additional isotopic analysis of other common fauna showed that the benthic food web in this fjord comprised up to four trophic levels of consumers, with starfish and isopods at the apex. Given that filter feeders comprise the largest trophic group in the cove and many other Antarctic coastal waters, the results of this study strongly suggest that benthic diatoms are of prime importance in supporting the benthic food web in MC, and possibly other nearshore Antarctic waters. Further studies on the mechanism underlying benthic diatom blooms and their relevance to climate-induced processes would provide better project future scenarios for rapidly warming fjord ecosystems. Fri, 01 Mar 2019 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/10868 2019-03-01T00:00:00Z