Distribution of calanoid copepod eggs in seabed sediments of Masan Bay, Korea

The distribution of calanoid copepod eggs was studied in the bottom sediment of Masan Bay (South Sea, Korea), where hypoxic conditions develop every summer, during a hopoxic period (August 2011) and a normoxic period (April 2012). In addition, an analysis was carried out concerning the relationship between seabed environments and the distribution pattern of morphologically normal and abnormal eggs. In August all stations showed hypoxic condition with sea bottom dissolved oxygen below 1.2 mg L-1, whereas in April they showed normoxic condition with sea bottom dissolved oxygen above 5.0 mg L-1. A measurement taken in the inner part of the bay during the hypoxic period gave a low pH ( 20 mol L-1) at sediment–water interface, whereas during the normoxic period there was no significant difference between stations. As for the abundance of eggs found in sediment, a higher range of density (between 0.61 and 2.01 × 106 eggs m-2) was observed during the hypoxic period compared to the normoxic period, and this level of abundance was higher than the levels reported to be observed at various global locations. The hypoxic period showed high proportion (maximum 77.1%) of abnormal eggs, including empty egg shells, in the inner part of the bay; whereas the normoxic period showed homogeneous distribution of normal eggs (> 80%) among all stations. The generation of abnormal eggs that either failed to develop to hatching or hatched into deformed nauplii is presumed to be related to the high concentration of H2S and low pH caused by hypoxia. This study will discuss the influences of hypoxia and seabed environments on hatching success of calanoid copepod eggs.1

A study on availability of in-situ determination in the potential production and size-specific distribution of a jellyfish population

마산만, 통영만 등 남해안의 내만에서 보름달물해파리가 대량으로 발생하는 것이 종종 관찰되고 2003년에는 서해안과 남해안에 대형해파리가 대량으로 출현하여 어업생산에 피해를 유발하기도 하였다. 그러나 한국산 해파리에 대해서는 분류, 생활사 등 기초적인 연구조차도 매우 부족한 실정이다. 해파리의 생활사, 분포, 생리생태, 발생과정 등 기본적인 연구들의 바탕위에 해파리 개체군의 규모와 이동에 대한 연구를 수행함으로서 해파리 대량발생의 원인을 규명하여 이에 대한 대처방안과 함께 피해방지 대책이 마련될 수 있을 것이다. 또한 우리나라 해역에 분포하는 해파리들의 잠재 생산력을 측정할 수 있을 것이다.본 연구에서는 마산만에서 보름달물해파리의 성장과 정량적 개체군을 파악하였으며, 실험실에서 수행한 보름달물해파리의 생활사 단계별 특징들을 이용하여 보름달물해파리의 잠재 생산력을 측정할 수 있는 방법을 알아보고자 하였다.2

A study of semantic and syntactic violations in Korean Language processing by high-resolution EEG 고해상도 EEG를 이용한 한국어처리에서의 의미적 통사적 오류에 대한 연구

Thesis (master`s)--서울대학교 대학원 :협동과정 인지과학전공,2003.Maste

Marine ecological study using marine mesocosm

해양에서 사용되는 실험용 폐쇄생태계 (Enclosed Experimental Ecosystem)는 자연생태계로부터 격리시킨 인위적으로 만든 생태계를 말한다. 이러한 실험 장치는 연구자가 조사목적에 맞게 환경요인을 조절할 수 있고, 실험을 반복할 수 있으며, 필요에 따라 세밀한 조작이 가능하다. 이러한 점은 생태계의 변화를 모니터링 하는 데 장점이 있어 기초학문 연구뿐만 아니라 독성실험 및 환경오염에 대한 생태계의 반응 실험 등 응용분야에서도 활용도가 높다. 이미 미국, 캐나다, 유럽 등의 여러 나라에서 폐쇄생태계를 이용한 연구를 오래전부터 진행해 오고 있다. 폐쇄생태계를 활용한 해양생태계 연구가 많은 장점이 있지만 임해 연구시설, 많은 연구 인력과 연구비가 소요되므로 우리나라에서는 최근까지도 연구가 미흡한 실정이다. 그러나 한국해양연구원에서는 1999년 거제도 장목 남해연구소에 폐쇄생태계를 설치하여 플랑크톤 동태 및 유기오염물질의 이동에 관한 예비실험을 시작하였으며 (한국해양연구소 2000a), 2000년에는 실험 폐쇄생태계 8개를 동시에 사용하여 실험할 수 있는 대규모의 mesocosm을 설치하여 본격적인 실험에 착수할 준비를 갖추었다. 이러한 시설을 이용하여 질산염 (NO3+NO2)변화와 N/P ratio 변화에 따른 식물플랑크톤 현존량과 우점종의 변화 및 투입한 초식자에 따른 식물플랑크톤의 변화를 조사하였다. 각 실험의 조사결과에 대해 토론하고자 한다.2

정신분열병 고위험군에서 전주위적 청각정보처리 이상 : 뇌자도를 이용한 정신분열병과 대조군 비교 연구

Thesis(doctors) --서울대학교 대학원 :협동과정 인지과학전공,2009.8.Docto

Physical and chemical characteristic of Korea via ship

연구 기간 동안 22척의 선박에서 24 개의 선박평형수를 샘플링하여 평형수 내의 환경과 식물플랑크톤 및 동물플랑크톤에 대한 조사가 수행되었다. 선박평형수 내 수온은 조사 항의 주변수와 유사한 양상을 보인다. 조사 선박 중에서 평형수를 엔진 실의 얇은 유압라인에서 채수한 경우 주변수와 온도차이가 크게 나타났다. 염분은 중국의 Jangjiang River, 미국의 Delaware River와 Hudson River에서 선박평형수를 실은 선박에서 낮은 값이 관측되었으며, 이런 선박의 경우 영양염 농도가 높게 나타나, 담수가 영양염의 공급원으로 추정된다. 이러한 선박평형수가 국내의 항에 들어와 평형수를 배출할 경우 점오염원으로서 역할을 할 수 있을 것으로 추정된다. 부유물질은 오히려 외해에서 평형수를 실은 선박이 높게 나왔는데, 이는 조사된 선박평형수가 dead ballast였기 때문으로 파악된다. 엽록소-a,와 활성 엽록소-a의 농도는 선박평형수의 보관일수와 유사한 상관성을 보여, 우리나라 주변국간의 선박평형수 처리면제 권에 대한 논의에 있어서 신중해야 함을 보여준다. 유압라인에서 채수한 경우 주변수와 온도차이가 크게 나타났다. 염분은 중국의 Jangjiang River, 미국의 Delaware River와 Hudson River에서 선박평형수를 실은 선박에서 낮은 값이 관측되었으며, 이런 선박의 경우 영양염 농도가 높게 나타나, 담수가 영양염의 공급원으로 추정된다. 이러한 선박평형수가 국내의 항에 들어와 평형수를 배출할 경우 점오염원으로서 역할을 할 수 있을 것으로 추정된다. 부유물질은 오히려 외해에서 평형수를 실은 선박이 높게 나왔는데, 이는 조사된 선박평형수가 dead ballast였기 때문으로 파악된다. 엽록소-a,와 활성 엽록소-a의 농도는 선박평형수의 보관일수와 유사한 상관성을 보여, 우리나라 주변국간의 선박평형수 처리면제 권에 대한 논의에 있어서 신중해야 함을 보여준다.2

Interannual and seasonal changes in zooplankton community in a monsoonal coastal bay

Environmental and zooplankton data were analyzed over a 10-year period (2001–2010) to investigate interannual and seasonal patterns of zooplankton dynamics and to identify major factors controlling these dynamics at an estuarine station in the southern coastal waters of Korea. There was a strong positive association in the interannual variation between freshwater discharge and copepod abundance, even though phytoplankton biomass was negatively associated with runoff. Copepod abundance was lowest in the summer when the abundance of predators such as chaetognaths and Noctiluca scintillans was highest. The high density of heterotrophic dinoflagellates (>103 cells m-3) adversely affected both the copepod abundance and, more markedly, the zooplankton diversity. Both the interannual pattern of zooplankton richness and the ratio of gelatinous zooplankton abundance to that of copepods increased with the increase in salinity and temperature following reduced river discharge. The overall shift in the zooplankton community during the study period may indicate range expansion of warm water zooplankton from offshore waters as well as better environmental conditions for them to grow in this bay water. This outcome also appears to reflect ecological processes related to the increase in sea surface temperature that has been underway in the offshore waters.tation in the southern coastal waters of Korea. There was a strong positive association in the interannual variation between freshwater discharge and copepod abundance, even though phytoplankton biomass was negatively associated with runoff. Copepod abundance was lowest in the summer when the abundance of predators such as chaetognaths and Noctiluca scintillans was highest. The high density of heterotrophic dinoflagellates (>103 cells m-3) adversely affected both the copepod abundance and, more markedly, the zooplankton diversity. Both the interannual pattern of zooplankton richness and the ratio of gelatinous zooplankto1

EFFECT OF THE HIGH CO2 ON GROWTH OF PHYTOPLANKTON SPECIES: LABORATORY STUDY

Cultured phytoplankton, Cylindrotheca closterium, Melosira nummuloides, Nitzschia sp., Phaeodictylum triconutum, Prorocentrum minimum were subjected to test the growth rates under the different conditions of CO2 concentration. Two different CO2 concentrations were defined as 'normal condition' (pCO2: 200ppm) and 'high condition' (pCO2: 980ppm). The experiment was performed under the nutrient enriched-condition. The temperature was maintained 25±1 ℃ under the equally lit light cycle (12 hr. light : 12 hr. dark). Nitzschia sp. and M. nummuloides showed higher chlorophyll-a concentration under the high condition than under the normal condition. However, higher chlorophyll-a concentration was measured for P. minimum under the normal condition than under the high condition. These results may reflect that the highly concentrated CO2 environment increased the growth rate of Nitzschia sp. and M. nummuloides, while the growth rate of P. minimum was retarded under the high condition. There was no a clear difference of growth rate between high and normal conditions in the case of C. closterium and P. triconutum. The researches are in progress and will argue on the matter of the rapid variations of phytoplankton community structure and primary productivity which is induced by the increase of global CO2 level.1

Applicability of the fluorescein diacetate (FDA) and Calcein-AM to determine the viability of marine organism

To evaluate whether marine phytoplankton species were rapidly able to apply on viability of living cells or not, the organism test was designed by staining methods of fluorescein diacetate (FDA) and Calcein-AM on each target species, such as bacillariphyceae, dinophyceae, raphidophyceae, chrysophyceae, haptophyceae and chlorophyceae. FDA method was the best dye for determining live cells of almost phytoplankton species, except several diatoms tested in this study. On the other hand, although fluorescence of Calcein-AM was very clear for a longer time, green fluorescence quantity per cell volume lacked in the tested almost species. In particular, gut of living zooplankton stained by Calcein-AM was strongly detected the green fluorescence than that of FDA staining cells or dead organisms. According to the Flow-CAM methods, green fluorescence values of stained cells by FDA were significantly higher than those of Calcein-AM treatments and control, implying that the Flow-CAM using FDA assay would adapt as important tool on the distinguish of living cells. Our results suggest that the FDA and Calcein-AM methods might be adapted to the phytoplankton and zooplankton, respectively, though species-specific characters are greatly different by organisms.2

A pitfall of understanding planktonic protozoan community dynamics on sampling time intervals

To determine a reasonable sampling interval for analyzing ciliate plankton dynamics, ciliate plankton samples were collected daily from Aug. 2008 to Oct. 2009 in Jangmok Bay of Geoje Island. Species composition and abundances were analyzed and environmental parameters (temperature and salinity) were also examined. According to the sampling time intervals of daily, weekly, biweekly, monthly, and seasonal samplings, the temporal patterns of ciliate abundance change were compared. The temporal pattern in daily interval was described detail change of the ciliate abundance. Abundance data collected in weekly interval was enough reflected in the daily result while those in monthly and seasonal intervals were distorted comparing with the daily pattern. In particular, daily observation is necessary for finding an ecological signal on the species level such as indicative species monitoring. It is suggested that data harvesting in the weekly interval is desirable to understand well the variation of ciliate abundances. Ciliate populations in Jangmok Bay were characterized by abrupt appearance and disappearances of many species, and such fluctuation impose important constraints upon designing sampling regimes.2