Multimedia distributions, bioaccumulation, and trophic transfer of microcystins in the Geum River Estuary, Korea: Application of compound-specific isotope analysis of amino acids

To determine distributions, bioaccumulation, and trophic transfer of freshwater cyanobacterial toxins such as microcystins (MCs), surface water, suspended solids, sediments, and coastal organisms were collected from seven stations in inner and outer regions of the estuary dam in the Geum River Estuary in June and July 2017. Concentrations of MC variants (MC-LR, -RR, and -YR) in the multimedia samples were analyzed using a HPLCMS/MS. Trophic position (TP) of organisms (fish, bivalve, gastropod, decapod, and polychaete) was determined by nitrogen stable isotope analyses of both bulk tissues and amino acids. From July to August 2017, great concentrations of MCs were detected in discharged freshwater ranging from 0.4 to 75 mu g L-1. Considerable amounts of MCs are delivered to the Geum River Estuary in summer season. MCs spread far away as dissolved phases (18.7-49.5 mu g L-1) in July when large amount of freshwater was discharged during the rainy season. Concentrations of MCs in marine organisms varied among species, ranging from 40 to 870 mu g g(-1) dw. Bioaccumulated MCs tend to decrease with increasing TP of organisms, suggesting that MCs are biodiluted through the marine food web. Compound-specific isotope analysis (nitrogen of amino acids) provides more reliable TPs compared with those by bulk isotope analysis in a closed estuary (such as the Geum River Estuary) with large fluctuations in the isotope ratio of primary producers.This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (Ministry of Science and ICT) (No. NRF-2016R1E1A1A01943004 & No. 2017R1A4A1015393)

Temporal variation in riverine organic carbon concentrations and fluxes in two contrasting estuary systems: Geum and Seomjin, South Korea

In this study, surface water samples were collected at sites located in the lowest reaches of closed (Geum) (i.e. with an estuary dam at the river mouth) and open (Seomjin) estuary systems between May 2016 and May 2018. We analyzed concentrations and stable isotopes of particulate organic carbon (POC) and dissolved organic carbon (DOC) to assess OC sources, to estimate fluxes of riverine OC, and to assess some of the factors driving OC exports in these two contrasting Korean estuary systems. Our geochemical results suggest that the contribution of the phytoplankton-derived POC to the total POC pool was larger in the Geum River than in the Seomjin River. Notably, a heavy riverine algae bloom occurred in the Geum River in August 2016, resulting in a high carbon isotopic composition (-19.4%) together with low POC/PN ratio (˂ 10) and POC/Chl-a ratio (˂ 100). In contrast, potential DOC sources in both the Geum River and the Seomjin River were a mixture of C3-derived forest soils and cropland organic matter. During the study period, the catchment area-normalized fluxes of POC and DOC were 0.40x10(-3) tC/km(2)/yr and 6.5x10(-2) tC/km(2)/yr in the Geum River and 5.2x10(-4) tC/km(2)/yr and 8.6x10(-4) tC/km(2)/yr in the Seomjin River, respectively. It appears that the POC flux was more weakly associated with the water discharge in the Geum River than in the Seomjin River, but the DOC fluxes were in general controlled by the water discharges in both rivers. Accordingly, the estuary dam of the Geum River might be one of the most strongly influencing factors on seasonal patterns in POC fluxes into the adjacent coastal seas, strongly modifying water residence times and thus biogeochemical processes.We would like to thank Dokyun Kim, Ji Hwan Hwang, Jong-Ku Gal, Dong-Hun Lee, Dahae Kim, and Solbin Kim for their assistance during fieldwork. This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science and ICT (MSIT) -South Korea [NRF-2016R1A2B3015388, KOPRI-PN19100]

Biodegradation-induced signatures in sediment pore water dissolved organic matter: Implications from artificial sediments composed of two contrasting sources

Biodegradation is one of the main processes causing the changes in amount, composition and properties of organic matter in sediment and water-sediment interface. The degradation processes of sediment organic matter lead to a release of dissolved organic matter (DOM) into the pore water via hydrolysis and depolymerization of particulate organic matter (POM). Whereas the pore waters represent a reactive zone in sediment closely linked to biogeochemistry of the substrate, they are still poorly characterized under diagenetic processes. In this study, we examined the DOM alterations in sediment pore water originating from the mixtures of two contrasting POM sources at known ratios through controlled incubation experiments with two different oxygen conditions (i.e., oxic versus anoxic). The changes in pore water DOM were tracked using fluorescence and absorbance spectroscopy and size exclusion chromatography. The results based on the sediments artificially mixed of two end-member sources (e.g., soil and algae) showed that the most affected parameter during the biodegradation process was the amount of the pore water DOM. It was also demonstrated that the changes in the spectroscopic and molecular properties were more dependent on the POM sources and the mixing ratios rather than on the oxygen conditions. This study provides insights into the responding features of DOM in a reactive sediment zone as pore water to the main biogeochemical process. (C) 2019 Elsevier B.V. All rights reserved.This work was supported by National Research Foundation of Korea (NRF) grants and was funded by the Korean government (MSIP) (No. 2017R1A4A1015393 and 2017033546). Additional support was provided by the National Research Council of Science and Technology (NST) grant by the Korea government (MSIP) (No. CAP-17-05-KIGAM)

Evaluation of alkane indexes for quantifying organic source from end member mixing experiments based on soil and algae

The identification for the sources of organic matters (OMs) is necessary to better understand biogeochemical cycling of carbon in aquatic environments. Hence, we intend to evaluate quantitative contributions of OM sources by using typical n-alkane indexes. In this regard, the end-member mixing experiment was designed as an example of theoretical system, which was physically mixed by two contrasting OM sources (e.g. soil and algae). Two sources showed distinct patterns with the long-chain alkanes (e.g., mainly C-25, C-27, C-29, C-31 and C-33) for soil, but mid-chain alkanes (e.g., mainly C-19, C-21, C-23 and C-25) for algae. However, typical n-alkane indexes such as average chain length (ACL), carbon preference index (CPI), and aquatic plants % (Pmar-aq), except for terrestrial/aquatic ratio (TAR), were not well reflected for different proportions of mixed OM sources, indicating the overestimated contribution of soil sources. With respect to source tracking capability of n-alkane indexes, the calculated regression slope indicated non-linear relationships (R-2 = 0.52-0.67) in ACL, CPI, and Pmar-aq, and linear relationships (R-2 = 0.86) in TAR, while the most precise capability was found for carbon isotopic compositions (delta C-13) of C-25 alkane (linear relationships; R-2 = 0.97) calculated from the isotope mixing model. Thus, the present study suggests that a binary mixing model of C-25 alkanes concentrations combined with their isotopic values should be a promising tool for quantifying each contribution of autochthonous and/or allochthonous OM in natural aquatic environments.This work was supported by National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIP) (No. 2017R1A4A1015393). We would like to thank B. Choi, S. Kang, D. Kim, and S. Kim for their analytical assistance in the laboratory at Hanyang University

Sources of organic matter in two contrasting tropical coastal environments: The Caribbean Sea and the eastern Pacific

In this study, we evaluate sources of organic matter (OM) in two contrasting tropical coastal environments in Colombia, using a combination of glycerol dialkyl glycerol tetraethers (GDGTs) and n-alkane lipid biomarkers. A clear difference between the less productive Caribbean Sea and the more productive eastern Pacific is observed, with higher terrestrial contributions into the eastern Pacific strongly associated with riverine inputs. Although higher land plant-derived n-alkanes can be transported as eolian dust, our results suggest mainly riverine sources for our samples. When looking at the branched GDGT compositions, in situ production could be identified in most Caribbean stations and some of the more coastal sites in the Pacific with #rings(te)(tra) index values of above 0.7. The remaining stations in the eastern Pacific display soil-eroded GDGTs inputs associated with river discharges and deposited in the proximity of the coast. Marine production as measured by short chain n-alkanes and crenarchaeol are also higher in the eastern Pacific. It appears that the terrestrial inputs would bring nutrients as well as OM fueling both auto- and heterotrophs making the eastern Pacific overall more productive. We also observe OM of petrogenic origin, albeit in a low amount, especially in coastal Caribbean sites located near main harbors. This study helps improve the understanding of the complex mixture of OM inputs, origins and transport mechanisms into Colombian coastal areas. The present work emphasizes the need to integrate climate, geological setting and hydrology to fully understand the carbon cycle at a regional scale.This work was partially funded by FAPA project "Biomarcadores lipidicos para reconstrucciones paleoclimaticas" [R.3.2015.2423; Los Andes University] to CH. This work was also supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT [MSIT, No. NRF-2016R1A2B3015388, KOPRI-PN19100] to J-H. K. This project was conceived by CG and CH as part of the project "Distribucidn de palinomorfos marinos y terrestres en sedimentos marinos superficiales del Mar Caribe y el Pacifico tropical oriental en relacion con parametros ambientales" funded by COLCIENCIAS [project 1204-569-34184]. We are grateful to Centro de Innovacidn y Tecnologia from the Institute Colombiano de Petroleo (ICP), Laboratorio Biologia Marina Uniandes (BIOMAR), Lamont Doherty Earth Observatory (LDEO), Ocean Drilling Program (ODP, OIDP), and EAFIT University for providing samples

Algal Contribution to the Occurrence of Refractory Organic Matter in Lake Paldang, South Korea: Inferred from Dual Stable Isotope (13C and 15N) Tracer Experiment

효과적인 물환경관리계획을 수립하기 위해서는 다양한 기원의 유기물이 난분해성 유기물 농도 증가에 영향을 줄 수 있는지 여부를 파악하는 것이 중요하다. 특히 상당량의 광합성 산물은 식물플랑크톤에 의해 매일 생성되고 있지만, 이들이 수계 내 난분해성 유기물에 기여하는지에 대한 정보는 부족하다. 본 연구에서는 13C 및 15N 추적자 첨가 실험을 통해 조류기원 유기물이 생분해 (60일, 암배양) 및 산화제 (과망간산칼륨) 처리 후 분해되지 않고 잔존하는지 여부를 확인하였다. 생분해 실험 결과 광합성을 통해 생성된 총 유기탄소 (TO13C), 입자성 유기탄소 (PO13C), 입자성 질소 (P15N)는 각각 26%, 20%, 17%가 비 생분해성 유기물로 잔존하였다. 또한 상당량의 PO13C가 과망간산칼륨에 의해 산화되지 않고 잔존하였다 (초기: 12%, 60일 암배양 후: 38%). 이는 미생물에 의해 사용된 후 남아있는 조류 기원 유기물이 난분해성 유기물에 기여할 수 있음을 의미 한다. 또한 미생물에 의해 변형된 조류기원 유기물의 양은 COD 산화율 및 유기물 지표 간 격차에 영향을 줄 것으로 사료된다. While a fairly large amount of organic matter is produced daily via phytoplankton photosynthesis in Lake Paldang, South Korea, knowledge of the role of algal-derived organic matter (OM) as a refractory OM source is not adequate. To understand the contribution of algal-derived OM to the refractory pool, biodegradation experiment and KMnO4 oxidation experiment were conducted for 60 days using 13C and 15N labeled natural phytoplankton assemblage. The assemblage was collected from Lake Paldang on May 20, 2010. The photosynthetically produced total organic carbon (TO13C), particulate organic carbon (PO13C), and particulate nitrogen (P15N) remained at 26%, 20%, and 17% of the initial concentrations, respectively, in the form of non-biodegradable organic matter. In addition, 12% and 38% of PO13C remained after KMnO4 treatment on Day 0 and 60, respectively. These results indicate that photosynthetic products could be an important source of refractory organic matter after microbial degradation. Moreover, the microbially transformed algal-derived OM could contribute to the oxidation rate of the chemical oxygen demand

Reconstructing spring sea ice concentration in the Chukchi sea over recent centuries: insights into the application of the PIP25 index

In this study, we aimed to reconstruct spring (April?June) sea ice changes in the western Arctic Ocean over recent centuries (ca. the last 250 years) by measuring biomarker distributions in a multicore (ARA01B-03MUC) retrieved from the Chukchi Shelf region and to evaluate outcomes against known or modelled estimates of sea ice conditions. Specifically, we analyzed for the Arctic sea ice proxy IP25 and assessed the suitability of a further highly branched isoprenoid (HBI) lipid (HBI III), epi-brassicasterol, and dinosterol as complementary biomarkers for use with the so-called phytoplankton marker-IP25 index (PIP25; PIIIIP25, PBIP25, and PDIP25, respectively). The presence of IP25 throughout core ARA01B-03MUC confirms the occurrence of seasonal sea ice at the study site over recent centuries. From a semi-quantitative perspective, all three PIP25 indices gave different trends, with some dependence on the balance factor c, a term used in the calculation of the PIP25 index. PIIIIP25-derived spring sea ice concentration (SpSIC) estimates using a c value of 0.63, determined previously from analysis of Barents Sea surface sediments, were likely most reliable, since SpSIC values were high throughout the record (SpSIC >78%), consistent with the modern context for the Chukchi Sea and the mean SpSIC record of the 41 CMIP5 climate models over recent centuries. PBIP25-based SpSIC estimates were also high (SpSIC 108%?127%), albeit somewhat over-estimated, when using a c value of 0.023 obtained from a pan-Arctic distribution of surface sediments. In contrast, PDIP25 values using a pan-Arctic c value of 0.11, and PIP25 data based on the mean biomarker concentrations from ARA01B-03MUC, largely underestimated sea ice conditions (SpSIC as low as 13%), and exhibited poor agreement with instrumental records or model outputs. On the other hand, PBIP25 values using a c factor based on mean IP25 and epi-brassicasterol concentrations exhibited a decline towards the core top, which resembled recent decreasing changes in summer sea ice conditions for the Chukchi Sea; however, further work is needed to test the broader spatial generality of this observation.We thank the crew of the R/V ARAON for retrieving the sediment core, Calyso Racine (Bordeaux University) for providing a map, and four reviewers for their critical and constructive comments. The study was supported by grants from the Korea Polar Research Institute (PE19130), the National Research Foundation of Korea grant funded by the Korean government (2015M1A5A1037243, PN19090), and the University of Plymouth

Major AhR-active chemicals in sediments of Lake Sihwa, South Korea: Application of effect-directed analysis combined with full-scan screening analysis

This study utilized effect-directed analysis (EDA) combined with full-scan screening analysis (FSA) to identify aryl hydrocarbon receptor (AhR)-active compounds in sediments of inland creeks flowing into Lake Sihwa, South Korea. The specific objectives were to (i) investigate the major AhR-active fractions of organic extracts of sediments by using H4IIE-luc in vitro bioassay (4 h and 72 h exposures), (ii) quantify known AhR agonists, such as polycyclic aromatic hydrocarbons (PAHs) and styrene oligomers (SOs), (iii) identify unknown AhR agonists by use of gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOFMS), and (iv) determine contributions of AhR agonists to total potencies measured by use of the bioassay. FSA was conducted on fractions F2.6 and F2.7 (aromatics with log K-ow 5-7) in extracts of sediment from Siheung Creek (industrial area). Those fractions exhibited significant AhR-mediated potency as well as relatively great concentrations of PAHs and SOs. FSA detected 461 and 449 compounds in F2.6 and F2.7, respectively. Of these, five tentative candidates of AhR agonist were selected based on NIST library matching, aromatic structures and numbers of rings, and available standards. Benz[b]anthracene, 11H-benzo[a]fluorene, and 4,5-methanochrysene exhibited significant AhR-mediated potency in the H4IIE-luc bioassay, and relative potencies of these compounds were determined. Potency balance analysis demonstrated that these three newly identified AhR agonists explained 1.1% to 67% of total induced AhR-mediated potencies of samples, which were particularly great for industrial sediments. Follow-up studies on sources and ecotoxicological effects of these compounds in coastal environments would be required.The authors appreciate anonymous reviewers for their valuable comments and suggestions and improvements to this article. This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIP) (2017R1A4A1015393, 2016R1E1A1A01943004, and 2017R1E1A1A01075067). This work was also supported by the project entitled "Development of techniques for assessment and management of hazardous chemicals in the marine environment (2014-0342)" funded by the Ministry of Oceans and Fisheries of Korea. Prof. Giesy was supported by the Canada Research Chairs program of the Natural Sciences and Engineering of Canada

Primary Productivity and Photosynthetic Pigment Production Rates of Periphyton and Phytoplankton in Lake Paldang using 13C Tracer

팔당호 수변지역 내 부유조류와 부착조류의 일차생산력은 부착조류의 일차생산력이 더 높게 나타났다. 따라서 수변 지역이나 하천에서는 부착조류에 의한 유기물 생성이 주요한 수생태계 에너지 공급원이 될 것으로 판단된다. 본 연구를 통해 국내에서 처음으로 지표색소의 생산속도 분석결과가 제시되었는데 향후 일차생산력을 측정하는 데 있어서 조류의 총 일차생산력으로 국한된 측정 방법을 좀 더 세분화 하여 특정 조류의 기여도 및 개별 생산력을 판단하는 데 유용하게 사용될 것으로 사료된다. The primary productivity and production rate of photosynthetic pigment of periphyton and phytoplankton were estimated using a 13C stable labeling technique in May 2011, in the waterfront of Lake Paldang. Primary productivity of periphyton (28.15 mgC m-2 d-1) was higher than phytoplankton production (0.14 mgC m-2 d-1). The net production rates of photosynthetic pigments (Chl a and Fucoxanthin) of periphyton were 2.53 ngC m-2 d-1 and 0.12 ngC m-2 d-1, respectively. On the other hand, the net production rate of pigments on phytoplankton (Chl a : 0.023 ngC m-2 d-1, Fucoxanthin: 0.002 ngC m-2 d-1) was lower than that of periphyton. Specific production rates of individual pigments of phytoplankton to the total primary productivity indicate the predominance of diatom (Fucoxanthin) species in phytoplankton assemblage in Lake Paldang. The net individual production rate of pigments by 13C tracer was a useful tool to estimate the contribution of each phytoplankton class for total primary productivity, and it is possible to calculate the seasonal contribution of each phytoplankton class to the total primary productivity in the aquatic ecosystems. This study is the first report on photosynthetic pigment production rates of periphyton and phytoplankton

Differentiation of endogenous and exogenous γ-Hydroxybutyrate in rat and human urine by GC/C/IRMS

Gamma (gamma)-hydroxybutyric acid (GHB) has been reported to be an endogenous compound in the mammalian brain. It used to treat symptoms of alcohol, opioid, and drug withdrawal and cataplexy of narcolepsy. However, it is often used for criminal purposes because it is colorless, tasteless, and has short half-life. For this reason, there is a need for a method of distinguishing between endogenous and exogenous GHB administration. Therefore, urine from rat before administration of GHB and GHB urine after the single intraperitoneal injection of GHB as 30 mg/100 g were collected from Sprague-Dawley rats (7 weeks old, 10 males and females). Negative control urine, urine from individuals suspected of taking GHB, and urine from victims who were GHB-involved crime were collected. In urine samples, GHB was extracted with two-step SPE and collected fraction was derivatized and analyzed by GC/MS and GC/C/IRMS. In GC/MS and GC/C/IRMS analysis of rat urine, there was a statistically significant difference between urine from rat before administration of GHB and GHB rat urine (p < 0.05). In GC/MS analysis of human urine samples, there was no significant difference among human urine groups (negative control, suspects' urine, and victims' urine), but in GC/C/IRMS analysis of human urine samples, there was a statistically significant difference among human urine groups (p = 0.0001). Through these results, GC/C/IRMS can be more effective tool to identify endogenous and exogenous GHB in urine than GC/MS. This study can build a drug management system in forensic investigation agency and offer interpretation method to forensic science and court.This study was funded by National Forensic Service (NFS) (grant number is 2017-04, the development of analysis method for identification of endogenous and exogenous GHB) and Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology, Republic of Korea (grant number is 2016R1A6A1A03007648)