DSpace Collection:

The complete mitochondrial genome of the ice krillEuphausia crystallorophias Holt & Tattersall, 1906 (Euphausiacea, Euphausiidae), from the Ross Sea, Antarctica

2024-04-01T00:00:00Z

Title: The complete mitochondrial genome of the ice krillEuphausia crystallorophias Holt & Tattersall, 1906 (Euphausiacea, Euphausiidae), from the Ross Sea, Antarctica Authors: Kim, Sung Hoon; Kim Taeho; Son, Wuju; Kim, Jeong-Hoon; La, Hyoung Sul Abstract: The mitogenome of Euphausia crystallorophias collected from the Ross Sea Region Marine Protected Area (RSR MPA) is described for the first time. The assembled mitogenome was 17,291 bp in length and consisted of two ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), 13 protein-coding genes (PCGs), and noncoding regions, all of which were identical to those of other euphausiid species. The most common start codon for the 13 PCGs was ATG, and the most common termination codon was TAA. The overall G + C content was 33.2% in the heavy strand. Euphausia crystallorophias was sister to E. superba in the phylogenetic analysis. The mitogenome of E. crystallorophias provided significant DNA molecular data for further identification and phylogenetic analysis within the euphausiids.

Contrasting optical properties of dissolved organic matter between oceanic regions near the Getz and Dotson ice shelves in the Amundsen Sea, West Antarctica

2024-01-01T00:00:00Z

Title: Contrasting optical properties of dissolved organic matter between oceanic regions near the Getz and Dotson ice shelves in the Amundsen Sea, West Antarctica Authors: 손주영; Jung, Jinyoung; Lee, Youngju; Kim, Tae-Wan; Park, Jisoo; 전미해; 박미옥 Abstract: The Amundsen Sea, located in West Antarctica, is experiencing rapid melting due to the intrusion of Circumpolar Deep Water, which is causing ice sheet thinning and basal melting. The resulting changes can affect the biogeochemical cycle of dissolved organic matter (DOM) by supplying iron from sea ice and/or glacier, thereby influencing primary production and ocean circulation. Therefore, it is crucial to understand the dynamics of the DOM in this region. In this study, our primary focus was to examine the optical properties of DOM in the oceanic regions adjacent to the West Getz Ice Shelf (WGIS) and the Dotson Ice Shelf (DIS). Significant differences in DOM optical properties, including the chromophoric DOM (CDOM) absorption coefficient at 350 nm (a350), spectral slope coefficient (S275-295), and specific UV absorbance at 254 nm (SUVA254), were observed between the WGIS and DIS regions (t-test, p < 0.05). Notably, the WGIS regions exhibited high a350 values. Additionally, the S275-295 and SUVA254 values, which serve as indices of molecular weight, indicated that the DOM pool in the WGIS regions was dominated by high molecular weight compounds with a substantial proportion of aromatic compounds. In contrast, the low values of a350 and SUVA254 along with the high S275-295 values in the DIS region suggested the dominance of low molecular weight CDOM associated with compounds of lower aromaticity. Furthermore, significant negative correlations were found between biomass of Phaeocystis antarctica (P. antarctica) and phosphate (PO4) in the WGIS regions (r2 = 0.82, p < 0.01 for WGIS 1 and r2 = 0.73, p < 0.01 for WGIS 2). However, no significant relationship was observed in the DIS region. These findings suggest that the high value and molecular weight of a350, extending from the surface layer to the deep layer, in the WGIS regions were associated with autochthonous sources, primarily driven by the colony-forming bloom of P. antarctica. These findings demonstrate that the quantity and quality of DOM in the Amundsen Sea are strongly affected by bloom conditions. The results emphasize that a combination of physical and biological processes interacts in complex ways to determine the characteristics of DOM in the Amundsen Sea.

Variability of Inflowing Current Into the Dotson Ice Shelf and Its Cause in the Amundsen Sea

2024-01-01T00:00:00Z

Title: Variability of Inflowing Current Into the Dotson Ice Shelf and Its Cause in the Amundsen Sea Authors: Yang, Heewon; Kim, Tae-Wan; 김영기; 유재일; Park, Jisoo; Cho Yang-Ki Abstract: The inflow of warm and salty Circumpolar Deep Water affects the melting of the ice shelf on the Amundsen Sea, a significant contributor to global sea level rise. Multi-year mooring data (2014-2016 and 2018-2020) from the front of the Dotson Ice Shelf show the modified Circumpolar Deep Water layer was thicker during 2018-2020 than during 2014-2016. During 2014-2016, Ocean surface stress curl influenced the barotropic process and strengthened southward velocity, while during 2018-2020, it caused lift and downwelling of thermocline depth, increasing the impact of the baroclinic process in ocean circulation. The heat transport to the ice shelf during 2018-2020 (57.42 MW m-1) was half as much as it was during 2014-2016 (111.06 MW m-1) due to a weaker lower layer current. The difference in ocean circulation between two periods, caused by a difference in warm layer thickness, ultimately impacts the heat transport entering the ice shelf cavity. Warm and salty water from the deep ocean flows into the ice shelf cavities in the West Antarctic, causing the ice to melt and contribute to global sea level rise. We measured the current and water properties in front of the Dotson Ice Shelf during 2014-2016 and 2018-2020 and found that the warm layer was thicker during the latter period. Unlike during 2014-2016 when ocean surface stress curl created a spatial imbalance in sea level and affected the southward current due to pressure gradients, during 2018-2020, ocean surface stress curl changed the density by causing upwelling and downwelling. This density change influenced the velocity variation toward the ice shelf. Although the mCDW layer was ticker, the heat influx to the ice shelf during 2018-2020 was half as much as it was during 2014-2016. The difference in ocean current during these two periods, due to differences in the warm layer thickness, ultimately affects how much heat is transported into the ice shelf cavity. The modified circumpolar deep water layer was thicker in 2018-2020 than that during 2014-2016 The baroclinic effect plays a more important role in the variability of the current entering the ice shelf during 2018-2020 Differences in the seasonal cycle of the ocean surface stress curl can affect ocean circulation by changing ocean conditions

Phytoplankton Variability in Response to Glacier Retreat in Marian Cove, King George Island, Antarctica in 2021-2022 Summer

2023-01-01T00:00:00Z

Title: Phytoplankton Variability in Response to Glacier Retreat in Marian Cove, King George Island, Antarctica in 2021-2022 Summer Authors: 심초롬; 민준오; Lee. BoYeon; 홍서연; Ha, Sun-Yong Abstract: 세종기지가 위치한 마리안 소만은 기후 변화로 인한 빙하후퇴로 다량의 융빙수가 유입되고 있다. 이러한 빙하후퇴에 따른 생태계 반응을 예측하기 위해, 해양 환경 변화의 지시자인 식물플랑크톤 생체량 및 크기 구조와 물리, 화학적 매개변수에 대한 현장 조사를 2021년 12월, 2022년 1월 두 차례 수행하였다. 2022년 1월의 수온과 염분은 평균 1.41 ± 0.13 ℃, 33.9 ± 0.10 psu로 2021년 1월의 수온과 염분인 0.87 ± 0.17 ℃, 34.1 ± 0.12 psu보다 상대적으로 고온, 저염의 양상을 보였다. 조사시기 동안 영양염류는 대체로 높은 농도를 보여 식물플랑크톤의 제한요소로 작용하지 않은 것으로 판단된다. 식물플랑크톤 생체량의 지표인 엽록소는 2021년 12월, 2022년 1월에 각각 1.03 ± 0.64 μg L-1, 0.66 ± 0.15 μg L-1로 나타났으며 부유물질은 전체 조사기간 평균 24.9 ± 3.54 mg L-1로 나타났다. 부유물질의 농도가 높은 소만 내측에서 엽록소는 낮은 농도를 보였는데 이는 융빙수로부터 유입되는 고농도의 부유물질로 인해 수층 내 빛이 강하게 제한되어 식물플랑크톤의 성장이 저해된 것으로 판단된다. 또한, 빙벽 주변 정점에서 크기가 작은 미소 식물플랑크톤이 전체 식물플랑크톤 생체량에서 70% 이상 차지하는 것으로 나타났으며 이는 융빙수 유입으로 유발된 저조도 환경에서 미소 식물플랑크톤의 기여도가 증가할 수 있음을 시사한다. 따라서 본 연구는 빙하후퇴 지역에서 유입되는 담수와 부유물질이 식물플랑크톤의 생체량 및 군집구조 조절 요인이 될 수 있음을 시사하며, 결과 자료는 추후 마리안 소만의 탄소순환 변동을 파악하는 기초자료로 활용될 수 있다.