Potentially bloom-forming dinoflagellates in Korean coastal area

The frequency of harmful algal blooms (HABs) has been increasing dramatically since the 1980’s in Korean coastal waters, caused by the bloom-forming dinoflagellates. Water samples were collected in the southern coastal area, Korea. We isolated and successfully established 108 culture strains of potentially bloom-forming dinoflagellates. Here, we provided a list and descriptions of these potentially bloom-forming dinoflagellates in detail to help a better understanding of the morphological characteristics and molecular phylogenetic positions. Potentially bloom-forming dinoflagellates recorded during study periods included 6 Alexandrium species, 1 Akashiwo species, 2 Ceratium species, 1 Cochlodinium species, 3 Gonyaulax species, 3 Gymnodinium species, 4 Heterocapsa species, 2 Karlodinium species, 1 Lingulodinium species, 1 Noctiluca species, 4 Prorocentrum species, 1 Protoceratium species and 2 Scrippsiella species. The presence of potentially bloom-forming dinoflagellates in Korean coastal waters deserves more attention and efforts in HAB monitoring and in HAB management in the future. In addition, these live cultures could be also applied in more extensive scientific areas.olated and successfully established 108 culture strains of potentially bloom-forming dinoflagellates. Here, we provided a list and descriptions of these potentially bloom-forming dinoflagellates in detail to help a better understanding of the morphological characteristics and molecular phylogenetic positions. Potentially bloom-forming dinoflagellates recorded during study periods included 6 Alexandrium species, 1 Akashiwo species, 2 Ceratium species, 1 Cochlodinium species, 3 Gonyaulax species, 3 Gymnodinium species, 4 Heterocapsa species, 2 Karlodinium species, 1 Lingulodinium species, 1 Noctiluca species, 4 Prorocentrum species, 1 Protoceratium species and 2 Scrippsiella species. The presence of potentially bloom-forming dinoflagellates in Korean coastal waters deserves more attention and efforts in HAB monitoring and in HAB management in the future. In addition, these live cultures could be also applied in more extensive scientific areas.1

Seasonal productions of dinoflagellate cysts in relation to environmental characteristics in Jinhae-Masan Bay, Korea: One year sediment trap observation

To investigate dinoflagellate cyst production and seasonality in relation to major environmental factors, such as water temperature, salinity, chlorophyll-a (chl-a) and dissolved nutrients, and to propose dinoflagellate cysts as possible biological indicators for the reconstruction of past environmental conditions, a sediment trap study was conducted for one year, from March 2011 to February 2012, in Jinhae-Masan Bay, Korea. Marked increases in dinoflagellate cyst productionwere documented in Jinhae-Masna Bay during two distinct seasons (summer and late autumn) characterized by different environmental conditions. Summer (July and August) was characterized by relatively high water temperature, dissolved inorganic nitrogen (DIN), and chl-a concentrations and low salinity, whereas late autumn (November and December) exhibited high dissolved inorganic phosphorus, low water temperature and high salinity, compared to those of the summer. Fourteen dinoflagellate cyst taxa were identified. These assemblages were dominated by Brigantedinium species (round brown cyst), cysts of Scrippsiella species, Spiniferites species and cysts of Alexandrium species (ellipsoidal cyst). The total flux of dinoflagellate cysts ranged from 781 cysts m -2 day -1 to 5,602 cysts m -2 day -1, and the production of autotrophic dinoflagellate cysts was mainly restricted to the warmest months (July-September) and autumn.1

노동시장참여 선택과 성별 임금격차

학위논문(석사) -- 서울대학교대학원 : 사회과학대학 경제학부, 2024. 2. Jungmin Lee.This paper studies selection into the workforce associated with gender wage inequality in South Korea where selection bias could potentially be colossal in light of the stark gender difference in the employment rate. To correct for selection into employment, I mainly employed the probabilistic imputation of unobserved wage offers based on observable characteristics and median regression upon the imputed sample. By exploiting the longitudinal nature of the panel data, I allow for selection on unobservables, along with selection on observables. The result shows that there has been a considerable negative selection into employment among women in South Korea and the extent of negative selectivity has been alleviated over time. Furthermore, the adjustment for selection reveals that the apparent closing of the gender wage gap is overstated, which only reflects a consistent change in the composition of women entering the workforce toward being highly skilled. The study explains the counterintuitive finding by presenting evidence that older elite women's positive selection into marriage and their subsequent withdrawal from the workforce have impeded the convergence of the gender wage gap driven by the increasing entry of younger elite women into employment. Keyword : wage inequality, gender wage gap, sample selection Student Number : 2020-28293본 연구는 한국의 엄청난 크기의 성별 고용률격차를 주목하며 성별 임금불평등에 관한 고용 선택편의를 보정하는 목적을 가진 연구이다. 고용 선택편의를 보정하기 위한 주요 방법론으로, 관측가능한 특성들을 이용한 확률적인 방법을 통해 관측되지 않은 임금값을 삽입(Imputation)한 후에 중앙값 회귀분석을 이용하였다. 패널데이터의 종단적 특성을 이용하여, 관측변수에 기반한 선택편의 뿐만 아니라 미관측변수에 기반한 편의까지 고려하였다. 2001년부터 2021년까지 시간당 임금을 분석해 본 결과, 여성들로부터 음의 선택편의가 존재한다는 사실 및 시간이 지남에 따라 그 편의의 크기가 점점 감소해왔음을 확인하였다. 이러한 결과는 관측되는 데이터로 확인했던 성별 임금격차의 지속적인 감소의 대부분은 여성들의 고용 선택편의에 기인한 것으로서, 실제로는 격차의 감소가 과대추정 되어 왔음을 시사한다. 또한, 출생코호트별 분석을 통하여 상대적으로 연령이 높은 코호트의 여성들 중 임금수준이 높은 이들이 혼인을 계기로 하여 노동시장에서 이탈하는 패턴을 관측하였다. 오히려 연령이 낮은 코호트의 여성들은 남성들과 마찬가지로 교육수준이 높아 잠재임금이 높을 수록 고용비율이 높다는 점에 비추어 볼 때, 우리나라에서 장기간 동안 존재해 온 여성들의 음의 고용 선택편의는 대부분 연령이 높은 여성들이 고정된 성역할 인식 등에 의한 영향에 의해 혼인을 기점으로 경제활동을 포기한 것이 반영된 것이라고 볼 수 있다.Chapter 1. Introduction 1 Chapter 2. Data 5 Chapter 3. Empirical Strategy 7 Chapter 4. Results 13 Chapter 5. Concluding Remarks 27 Bibliography 30 Abstract in Korean 32석

Magneto-Electric Property Variation of Rare-Earth modified BiFeO3 Multiferroics

Maste

실험적으로 유발한 신부전 개에서 소아용 혈액 투석기의 적용에 관한연구

학위논문(석사)--서울대학교 대학원 :수의학과 수의외과학전공,2000.Maste

지방재정조정제도 변화의 수평적 형평화 효과에 관한 연구 : 지방양여금과 지방교부세의 상대적 효과를 중심으로

학위논문(석사) --서울대학교 대학원 :행정학과(행정학전공),2008. 8.Maste

Morphological identification of Alexandrium species in Jinhae Bay, Korea

The outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by Alexandrium species in Jinhae Bay have been nearly annual events for many years,however morphological identification of Alexandrium species has not fully understand yet.In this study, we provide detailed morphological features, and discuss intraspecificvariability. 24 culture strains were established from water column or sediment trap samplesin Jinhae Bay, Korea. Four species were identified: Alexandrium affine, A.fundyense (A. tamarense complex group Ⅰ), A. insuetum and A. pacificum (A. tamarensecomplex group Ⅳ). A. affine was characterized by the shape of the apical pore plate,which is bullet-shaped with a attachment pore. A. insuetum had a Goniodoma&#8211 type 1’plateand highly reticulated thecal plates. A. fundyense was morphologically indistinguishablefrom A. pacificum. However, the variations of the apical pore complex and posterior sulcal plate were only observed in A. pacificum.derstand yet.In this study, we provide detailed morphological features, and discuss intraspecificvariability. 24 culture strains were established from water column or sediment trap samplesin Jinhae Bay, Korea. Four species were identified: Alexandrium affine, A.fundyense (A. tamarense complex group Ⅰ), A. insuetum and A. pacificum (A. tamarensecomplex group Ⅳ). A. affine was characterized by the shape of the apical pore plate,which is bullet-shaped with a attachment pore. A. insuetum had a Goniodoma&#8211 type 1’plateand highly reticulated thecal plates. A. fundyense was morphologically indistinguishablefrom A. pacificum. However, the variations of the apical pore complex and posterior sulcal plate were only observed in A. pacificum.2

Dinoflagellate cyst assemblages in surface sediments from Yellow Sea, Korea

To investigate the distribution, abundance and species composition of dinoflagellate cysts in the Yellow Sea, surface sediment samples were collected at 37 sites, including the Korean dump site. Twenty-one dinoflagellate cyst taxa were identified, with the assemblages dominated mainly by Spiniferites bulloideus, Operculodinium centrocarpum and cyst of Alexandrium catenella/tamarense type. A high frequency of O. centrocarpum in the Yellow Sea was observed for the first time, and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water mass and the Changjiang (Yangtze) River runoff. Total cyst concentrations ranged from 23 to 48,442 cysts g-1 dry weight, and high cyst concentrations were recorded adjacent to the dumping site. This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea, which in turn leads to high levels of dinoflagellate cyst production.tified, with the assemblages dominated mainly by Spiniferites bulloideus, Operculodinium centrocarpum and cyst of Alexandrium catenella/tamarense type. A high frequency of O. centrocarpum in the Yellow Sea was observed for the first time, and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water mass and the Changjiang (Yangtze) River runoff. Total cyst concentrations ranged from 23 to 48,442 cysts g-1 dry weight, and high cyst concentrations were recorded adjacent to the dumping site. This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea, which in turn leads to high levels of dinoflagellate cyst production.1

Alexandrium pacificum (Group IV) is causative species for past paralytic shellfish poisoning outbreaks in Jinhae-

Paralytic shellfish poisoning (PSP) caused the deaths of four people in coastal area of Korea, mainly Jinhae-Masan Bay and adjacent areas, in April 1986 and in 1996. The PSP outbreaks were caused by the consumption of mussels, Mytilus edulis. The organism that caused PSP was identified, from morphological data only, as Alexandrium tamarense which is recently renamed as A. catenella, however recent studies have shown that the morphological diagnostic characteristics used to identify Alexandrium species have uncertainties and molecular tools and other criteria should be considered as well. The organism that caused past PSP outbreaks and incidents in Korea therefore need to be carefully reconsidered. The aim of this study was to re-evaluate the species really responsible for past outbreaks of PSP in Jinhae-Masan Bay, Korea. The temporal production and fluxes of the resting cysts of Alexandrium species were investigated for one year (from March 2011 to February 2012) using a sediment trap, and the morphology and phylogeny of vegetative cells germinated from the resting cysts were analysed. The production of Alexandrium species peaked in August and November, when temporal discrepancies were found in the water temperature (22.4 and 22.7 °C in August, 19.1 and 19.6 °C in November) and salinity (29.5 and 26.1 psu in August, 30.5 and 31.8 psu in November). The morphological data revealed that Alexandrium species is. The organism that caused PSP was identified, from morphological data only, as Alexandrium tamarense which is recently renamed as A. catenella, however recent studies have shown that the morphological diagnostic characteristics used to identify Alexandrium species have uncertainties and molecular tools and other criteria should be considered as well. The organism that caused past PSP outbreaks and incidents in Korea therefore need to be carefully reconsidered. The aim of this study was to re-evaluate the species really responsible for past outbreaks of PSP in Jinhae-Masan Bay, Korea. The temporal production and fluxes of the resting cysts of Alexandrium species were investigated for one year (from March 2011 to February 2012) using a sediment trap, and the morphology and phylogeny of vegetative cells germinated from the resting cysts were analysed. The production of Alexandrium species peaked in August and November, when temporal discrepancies were found in the water temperature (22.4 and 22.7 °C in August, 19.1 and 19.6 °C in November) and salinity (29.5 and 26.1 psu in August, 30.5 and 31.8 psu in November). The morphological data revealed that Alexandrium species1

Morphological features of dinoflagellate cysts in southern coastal areas of Korea

Marine dinoflagellate are a major component in plankton communities and play an important role as primary produced in marine ecosystem. Some 200 of the approximate 2000 exsisting species of marine dinoflagellates are known to form resting cysts in a part of their life cycle. Although the morphological characteristics and distribution of dinoflagellate cysts have been widely investigated in many coastal areas of the world, the knowledge-base in Korean coastal areas remains limited. Here we provide the description of dinoflagellate cysts to help a better understanding of the morphological features of dinoflagellate cysts observed in southern coastal areas of Koreaing cysts2