동중국해 북부의 과거 지표수 온도에 대한 프록시로서 C37 알케논의 사용. C37 알케논은 중국 북동해 해수에 존재하는 부유물질의 적합성을 판단하기 위한 것입니다. 알케논 농도의 계절적 변화를 확인하기 위해 매년 3개월 간격으로 샘플을 수집했습니다.
연구지역에서는 알케논이 연중 합성되었으며, 5월에 일시적으로 농도가 증가하였다. 표층 해수 시료의 알케논 회수 온도는 일반적으로 실제 온도와 일치했습니다. 이러한 결과는 대륙붕 지역의 해양 퇴적물에서 회수된 알케논 온도가 연평균 표면 수온을 반영한다는 사실과 일치합니다.
알케논 농도를 1차 생산의 대용으로 사용하는 것이 적절한지 결정하기 위해 엽록소-a 농도의 계절적 변화를 알케논 농도의 계절적 변화와 비교했습니다. 알케논과 알케논의 농도는 상반된 패턴을 보였는데, 이는 이 지역의 주요 1차 생산자가 석회질 편모가 아니기 때문인 것으로 생각된다. 따라서 알케논 농도를 동중국해 북부의 1차 생산성에 대한 대용으로 사용하는 것은 적절하지 않은 것 같습니다.
그러나 석회질 편모조류의 개체수와 비교할 때, 알케논 농도는 고착성 편모조류의 생산성을 나타내는 지표로 사용될 수 있을 것으로 생각된다.
Introduction
Sampling
Seawater samples were collected at three-month intervals from February 2007 to August 2010 (Feb., May, Aug. and Nov.) along three transects during the NFRDI Korea research cruises (Fig. 1). Surface seawater samples were collected using a membrane pump at stations and during transit between stations. Samples of 100 L were collected and immediately filtered through glass fiber filters (GF/F, Whatman, 0.7 μm) on ship.
Alkenone analysis
These alkenones were quantified using a flame ionization detector and fused silica capillary column (J&W DB-1, 60m＊0.32 mm＊0.25 μm, Agilent Technology) attached to a gas chromatograph (Agilent 7890A).
Results
Subsurface seawater
Therefore, the vertical distribution of the concentrations shows that the concentrations were highest near the surface (0-20 m). Alkenone concentrations in groundwater samples were relatively high in May 2008, May 2009, and August 2010, supporting seasonal alkenone concentrations from surface seawater samples. However, the temperatures in the summer were both 29℃ at the surface, and they dropped significantly below 10-30 m.
Therefore, the surface mixed layer in summer extends from the surface to approx. 20 m, and a seasonal thermocline existed below the surface mixed layer. Therefore, alkenone temperatures estimated from subsurface seawater samples generally appeared to correspond well to in situ temperatures, and the difference between them was generally within ±2℃ at each depth studied.
Discussion
Alkenone concentration as a productivity proxy
Seasonal changes in total C37 alkenone concentrations were compared with the concentration of chlorophyll-a (NFRDI dataset, 2007) to confirm the suitability of using alkenone concentration as a proxy for primary productivity in the study area. Therefore, the concentrations of chlorophyll-a from the western part were generally higher than in the eastern area. In spring and summer, the presence of the diluted Yangtze River plume in the study area increased stratification (and improved solar insolation) in the upper layers.
However, this could be offset by the nutrients supplied by the Yangtze River, so that chlorophyll-a concentrations indicated relatively high productivity in the western part of the study area in spring and summer. In contrast to the distribution of chlorophyll-a, alkenones were hardly detected anywhere in the study area in winter. In addition, alkenone concentrations were high in the eastern part of the study area in spring, although concentrations in the west were very low in spring.
Previous studies of phytoplankton population distributions in the northern ECS have suggested that diatoms dominate along the coast near the mouth of the Yangtze River, and dinoflagellates dominate near the front (Yoon et al., 2003). Therefore, using alkenone concentration as a proxy for primary productivity is not applicable in this area. 9 Chlorophyll-a concentration in surface seawater in February, May, August and November using data from NFRDI in Korea, 2007).
The distribution of total C37 alkenone concentration was compared with that of living coccolithophore abundance in the water column of the ECS. Oceanica abundance was higher than 5 cells/ml at both western and eastern parts in winter, but it was 0-3 cells/ml in summer (Sun et al., 2014). Consequently, simple calculations show that the total abundance of two species appears to be about 5-10 cells/ml in winter, 0-5 cells/ml in summer and 10-20 cells/ml in autumn.
Although there was no spring record for abundance of living coccolithophores in either data set, the alkenone producers appear to be year-round residents of the study area. Notably, the abundance of living coccolithophores was low in the western part and increased in the eastern part in autumn and winter, corresponding to total C37. This suggests that the total C37 alkenone concentration can be used as a haptophyte productivity proxy in the area.
Conclusions
이 논문은 귀중한 결과였다. 열심히 노력하여 얻은 데이터 하나하나의 중요성을 일깨워주시고, 항상 명확하고 객관적이며 과학적으로 생각하고 글로 표현할 수 있도록 지도해주시는 이경은 교수님에게 진심으로 감사의 말씀을 전하고 싶습니다. 비록 부족한 점이 많았지만, 논문을 쓰는 동안뿐만 아니라 다른 분야에서도 지도와 조언, 기회를 받았던 덕분에 학부 시절과 다르게 성장하고 발전할 수 있었다고 믿습니다.
바쁜 일정에도 불구하고 항상 관심을 가져주시고, 본 논문을 검토해주신 이희준 박사님과 장태수 교수님께 감사드립니다. 학교에 올 때마다 편안한 조언을 해준 지영이, 이번 논문의 자료 정리를 도와준 용기, 성혜, 늘 옆에서 묵묵히 도와준 시웅이, 실험실 생활 초기에 저의 고민을 들어주셨습니다. 제가 생활에 적응할 수 있도록 도와준 령아, 나연, 가희에게 늘 감사하다는 마음을 이 페이지를 통해 표현합니다. 그리고 멀리 사는 아들이 잘 지내는지 늘 걱정하면서도 늘 믿고 응원해주시는 부모님에게도 감사드립니다.
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