Historical reconstruction of anthropogenic mercury input from sedimentary records: Yeongsan Estuary, South Korea

Williams, J.,Dellapenna, T.,Louchouarn, P.,Lee, G.h. Academic Press in association with the Estuarine a 2015 Estuarine, coastal and shelf science Vol.167 No.2

The rapid economic growth of the Republic of Korea (S. Korea) within the last half-century has resulted in a pronounced increase in anthropogenic Hg emission from coal combustion, oil refining, cement production, and waste incineration. The record of increasing atmospheric sources have been investigated with a historical reconstruction of Hg accumulation in 30 sediment cores collected from the Yeongsan Estuary. Within the last several decades, this region has undergone severe anthropogenic alteration, including the construction of an estuarine dam forming the Yeongsan Lake, and installation of numerous seawalls that eliminated vast tidal flats and restricted estuarine circulation. Total mercury concentrations (T-Hg) measured in sediments deposited after 1980 (23.2 +/- 9.6 ng g<SUP>-1</SUP>; n = 273), were significantly higher than those reported for pre-industrial sediments (i.e. background values: 8.6 +/- 2.7 ng g<SUP>-1</SUP>; n = 274). An extensive survey of surface samples show that T-Hg concentrations are highest above the dam, with a gradient to lower values further offshore. The concomitant timing of enrichment of T-Hg within the sedimentary record and increased National emissions in Korea suggests that regional sources dominate the input to the Yeongsan Estuary. This indicates that with sufficient regional historic emission data, T-Hg might be utilized as a geochronologic tool to aid in corroborating traditional radioisotopic methods.

Pathways of organic matter through food webs of diverse habitats in the regulated Nakdong River estuary (Korea)

Choy, E.J.,An, S.,Kang, C.K. Academic Press in association with the Estuarine a 2008 Estuarine, coastal and shelf science Vol.78 No.1

The benthic macroinvertebrates of the Nakdong River estuary were sampled at three different habitats: two salt marsh (Scirpus triqueter and Phragmites australis) beds and a bare intertidal flat. Fishes were sampled in the main channel. The trophic importance of marsh vascular plants, microphytobenthos, and riverine and channel particulate organic matter to macroinvertebrate and fish production was studied using stable carbon and nitrogen isotope tracers. There was a dramatic change in coverage of macrophytes (salt marshes and seagrass) after the construction of an estuarine barrage in 1987 in the Nakdong River estuary, with the S. triqueter bed increasing, the P. australis bed decreasing, and Zostera marina habitats being nearly lost. Although the invertebrate δ<SUP>^13</SUP>C were within a narrower range than those of the primary producers, the values varied considerably among consumers in these habitats. However, the isotope signatures of consumers showed similarities among different habitats. Cluster analysis based on their isotopic similarity suggested that the isotope variability among species was related more to functional feeding groups than to habitats or taxonomic groups. While δ<SUP>13</SUP>C values of suspension feeders were close to that of the channel POM (mainly phytoplankton), other benthic feeders and predators had δ<SUP>13</SUP>C similar to that of microphytobenthos. Isotopic mixing model estimates suggest that algal sources, including microphytobenthos and phytoplankton, play an important role in supporting the benthic food web. Despite the huge productivity of emergent salt marshes, the contribution of the marsh-derived organic matter to the estuarine food webs appears to be limited to some nutrition for some invertebrates just within marsh habitats, with little on the bare intertidal flats or in the channel fish communities. Isotope signatures of the channel fishes also confirm that algal sources are important in supporting fish nutrition. Our findings suggest that benthic and pelagic microalgae made a large contribution to consumer diets, while marsh plants may not have a large role in supporting food webs in this estuarine system.

Microphytobenthic biomass and species composition in intertidal flats of the Nakdong River estuary, Korea

Du, G.,Son, M.,Yun, M.,An, S.,Chung, I.K. Academic Press in association with the Estuarine a 2009 Estuarine, coastal and shelf science Vol.82 No.4

Intertidal microphytobenthos (MPB) were investigated monthly from August 2006 to March 2008 at four different sites in the sand flats of Nakdong River estuary, Korea. Samples of surface sediment (ca. 1cm) were collected, and chlorophyll a was extracted as biomass estimation. Species identification and enumeration were carried out by light microscopy, assisted where necessary by scanning electronic microscopy. Biomass varied between 0.47 and 16.58μgcm<SUP>-3</SUP>, abundance changed from 5.25 to 414.75x10<SUP>3</SUP> cells cm<SUP>-3</SUP>, while the Shannon diversity indexes ranged between 0.69 and 2.35 H'. Thirty-nine MPB taxa were identified, primarily composed of epipelic diatoms, among which Amphora and Navicula were the most abundant genera. Based on the biomass, abundance, species composition and their dynamics, MPB assemblages of sampling sites were grouped into three distinct communities corresponding to their sediment composition characteristics. Multivariate correlation analysis revealed that biomass was positively related to mud and very fine sand, negatively related to fine and medium sand, but not significantly related to environmental factors such as pore water nutrients, light intensity and salinity, which fluctuated rapidly during emersion period. Cluster analysis corroborated the division of MPB communities according to site types on seasonal scales, and also showed seasonality between sites by cluster of all summer groups. Principal component analysis identified that variability in species composition was significantly affected by mud, very fine sand, fine sand, light intensity, and sediment temperature. This study suggests that sediment composition plays an important role in the functioning of intertidal MPB communities in estuarine ecosystems.

Salinity and bisphenol A alter cellular homeostasis and immune defense by heat shock proteins in the intertidal crab <i>Macrophthalmus japonicus</i>

Park, Kiyun,Kwak, Ihn-Sil Academic Press in association with the Estuarine a 2019 Estuarine, coastal and shelf science Vol.229 No.-

<P><B>Abstract</B></P> <P>Heat shock proteins (HSPs) play crucial roles in cellular metabolic processes, as well as in protective immune responses. In this study, we determined the cellular and immune-related functions of HSPs in the intertidal mud crab <I>Macrophthalmus japonicus</I> under osmotic and bisphenol A (BPA) exposure stress. We performed transcriptional profiling of six HSP genes (HSP70, HSP60, HSP90, HSP83, HSP40, and HSP21) in <I>M. japonicus</I> gills and hepatopancreas. Tissue-specific responses were observed as differentially expressed HSP transcripts in <I>M. japonicus</I>. Under osmotic stress, expression levels of HSP70, HSP90 and HSP40 mRNA increased at high salinity (40 psμ), and decreased at low salinity (10 psμ) in <I>M. japonicus</I> gills. In contrast, HSP60 expression was significantly diminished under high salinity, and increased under low salinity. HSP21 was down-regulated under all salinity changes over 1, 4, and 7 days. In the hepatopancreas, under osmotic stress, most HSP transcripts were up-regulated at an early exposure time point (day 1) with subsequent down-regulation (day 7). On day 4, HSP70, HSP60, HSP90 and HSP40 transcript levels increased in <I>M. japonicus</I>, whereas HSP83 and HSP21 transcript levels decreased in the hepatopancreas following most salinity changes. In addition, BPA exposure generally induced HSP responses in the gills. In particular, HSP70 and HSP83 were significantly up-regulated at all concentrations of BPA on days 1 and 4. However, induced responses of HSP transcripts diminished by day 7, except for HSP83 and HSP40. In the hepatopancreas, HSP70 and HSP90 mRNA expression showed significant up-regulation, whereas transcription of HSP60, HSP83, and HSP21 was down-regulated on days 1 and 4. These results suggested that HSPs are differently involved in the molecular adaptation and defense responses of crabs to BPA and osmotic stress.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Six HSPs gene responses of mud crab were quantified at osmotic and BPA stress. </LI> <LI> BPA exposure induced different expressions of HSPs following tissue type. </LI> <LI> Most HSPs showed up-regulation at high salinity change in <I>M. japonicus</I> crab. </LI> <LI> HSP90 and HSP83 expressed differently under salinity change and BPA exposure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Coastal environmental assessment and management by ecological simulation in Yeoja Bay, Korea

Lee, D.I.,Choi, J.M.,Lee, Y.G.,Lee, M.O.,Lee, W.C.,Kim, J.K. Academic Press in association with the Estuarine a 2008 Estuarine, coastal and shelf science Vol.80 No.4

An eco-hydrodynamic model was used to estimate the carrying capacity of pollutant loads and response of water quality to environmental change in Yeoja Bay, Korea. An energy-system model also was used to simulate the fluctuation in nutrients and organic matter in the bordering wetland. Most water quality factors showed a pulsed pattern, and the concentrations of nutrients and organic matter of seawater increased when input loads of nutrients increased due to freshwater discharge. The well-developed tidal zones and wetlands in the northern area of the bay were highly sensitive to input loads. Residence times of water, chemical oxygen demand (COD), and dissolved inorganic nitrogen (DIN) within the bay were estimated to be about 16 days, 43.2 days, and 50.2 days, respectively. Water quality reacted more sensitively to the effects of nitrogen and phosphorus input than to COD. A plan to reduce the present levels of COD and dissolved inorganic phosphorus (DIP) by 20-30% and DIN by at least 50% in pollutant loads is needed for satisfying the target water quality criteria. The natural removal rate of nutrients in wetlands by reeds was assessed to be approximately 10%.

Effect of human activity on Lake Saroma (Japan) during the past 150 years: Evidence by variation of diatom assemblages

Katsuki, K.,Seto, K.,Nomura, R.,Maekawa, K.,Khim, B.K. Academic Press in association with the Estuarine a 2009 Estuarine, coastal and shelf science Vol.81 No.2

Diatom assemblages of the surface and in core sediment samples from Lake Saroma (Japan) were examined for the purpose of evaluating anthropogenic effect on the coastal environmental changes. Before the first inlet excavation, the lake's water quality and ecology were controlled by water exchange with the Okhotsk Sea as well as lake-level variation. However, large-scale ecological modification occurred, mainly due to artificial excavation and shellfish industrial farms. A distinct record of the succession of the dominant diatom taxa was preserved in core sediments. Low-oxygen water was prevalent in the lake in 1929, before the first inlet excavation. Immediately after the first inlet excavation, the low-oxygen water in the western basin of the lake began to disappear, in a trend that became increasing transparent, which has been attributed to an increasing rate of water exchange. However, the lacustrine environment of bottom sediments resumes deterioration 20years after since the first artificial excavation: the resultant deposition of river-mouth materials into the deep basin caused eutrophication and environmental disturbance of the lake bottom. At the same time, the eutrophication of surface water became intensified with the onset of intense scallop culturing beginning in 1966. Increasing organic loads deposited onto the bottom layer in the form of excreta from the scallop nursery led to more oxygen deficiency and the elution of nitrogen and phosphorus from the sediment, which again brought about eutrophication of the surface layer. Such environmental change was reflected in a decrease of benthic diatom taxa and an increase of planktonic taxa, trends which have continued until today. Particularly, the numbers of diatom assemblage have been decreasing all over the lake during the last 10years, which suggests that Lake Saroma's present-day deterioration and eutrophication will continue or become even worse.

Lithogenic and biogenic particle deposition in an Antarctic coastal environment (Marian Cove, King George Island): Seasonal patterns from a sediment trap study

Khim, B.K.,Shim, J.,Yoon, H.I.,Kang, Y.C.,Jang, Y.H. Academic Press in association with the Estuarine a 2007 Estuarine, coastal and shelf science Vol.73 No.1-2

<P><B>Abstract</B></P><P>Particulate suspended material was recovered over a 23-month period using two sediment traps deployed in shallow water (∼30m deep) off the King Sejong Station located in Marian Cove of King George Island, West Antarctica. Variability in seasonal flux and geochemical characteristics of the sediment particles highlights seasonal patterns of sedimentation of both lithogenic (terrigenous) and biogenic particles in the coastal glaciomarine environment. All components including total mass flux, lithogenic particle flux and biogenic particle flux show distinct seasonal variation, with high recovery rates during the summer and low rates under winter fast ice. The major contributor to total mass flux is the lithogenic component, comprising from 88% during the summer months (about 21gm<SUP>−2</SUP>d<SUP>−1</SUP>) up to 97% during the winter season (about 2gm<SUP>−2</SUP>d<SUP>−1</SUP>). The lithogenic particle flux depends mainly on the amount of snow-melt (snow accumulation) delivered into the coastal region as well as on the resuspension of sedimentary materials. These fine-grained lithogenic particles are silt-to-clay sized, composed mostly of clay minerals weathered on King George Island. Biogenic particle flux is also seasonal. Winter flux is ∼0.2gm<SUP>−2</SUP>d<SUP>−1</SUP>, whereas the summer contribution increases more than tenfold, up to 2.6gm<SUP>−2</SUP>d<SUP>−1</SUP>. Different biogenic flux between the two summers indicates inter-annual variability to the spring–summer phytoplankton bloom. The maximum of lithogenic particle flux occurs over a short period of time, and follows the peak of biogenic particle flux, which lasts longer. The seasonal warming and sea-ice retreat result in change in seawater nutrient status and subsequent ice-edge phytoplankton production. Meanwhile, the meltwater input to Marian Cove from the coastal drainage in January to February plays a major role in transporting lithogenic particles into the shallow water environment, although the tidal currents may be the main agents of resuspension in this kind of sheltered bay.</P>

Tidal variability in benthic silicic acid fluxes and microphytobenthos uptake in intertidal sediment

Leynaert, A.,Longphuirt, S.N.,An, S.,Lim, J.H.,Claquin, P.,Grall, J.,Kwon, B.O.,Koh, C.H. Academic Press in association with the Estuarine a 2011 Estuarine, coastal and shelf science Vol.95 No.1

Silicic acid (DSi) benthic fluxes play a major role in the benthic-pelagic coupling of coastal ecosystems. They can sustain microphytobenthos (MPB) development at the water-sediment interface and support pelagic diatoms when river DSi inputs decrease. DSi benthic fluxes have been studied at the seasonal scale but little is known about their dial variations. This study measured the amplitude of such variations in an intertidal area over an entire tidal cycle by following the alteration of DSi pore water concentrations at regular intervals over the flood/ebb period. Furthermore we independently estimated the potential DSi uptake by benthic diatoms and compared it to the variations of DSi pore water concentrations and fluxes. The microphytobenthos DSi demand was estimated from primary production measurements on cells extracted from the sediment. There were large changes in DSi pore water concentration and a prominent effect of tidal pumping: the DSi flushed out from the sediment at rising tide, occurs in a very short period of time, but plays a far more important role in fueling the ecosystem (800 μmol-Si m<SUP>-2</SUP> d<SUP>-1</SUP>), than diffusive fluxes occurring throughout the rest of the tidal cycle (2 μmol-Si m<SUP>-2</SUP> d<SUP>-1</SUP>). This process is not, to our knowledge, currently considered when describing the DSi cycling of intertidal sediments. Moreover, there was a large potential MPB requirement for DSi (812 μmol-Si m<SUP>-2</SUP> d<SUP>-1</SUP>), similar to the advective flow periodically pumped by the incoming tide, and largely exceeded benthic diffusive fluxes. However, this DSi uptake by benthic diatoms is almost undetectable given the variation of DSi concentration profiles within the sediment.

Linking groundwater-borne nutrients and dinoflagellate red-tide outbreaks in the southern sea of Korea using a Ra tracer

Lee, Yong-Woo,Kim, Guebuem Academic Press in association with the Estuarine a 2007 Estuarine, coastal and shelf science Vol.71 No.1-2

<P><B>Abstract</B></P><P>We have measured nutrients, photosynthetic pigments, and two radium isotopes (<SUP>223</SUP>Ra and <SUP>224</SUP>Ra) in coastal groundwater and seawater during the summer of 2002 and 2003 in the southern sea of Korea, where harmful dinoflagellate blooms (hereafter red tides) have been occurring every year since 1982. In this region, the amount of submarine groundwater discharge (SGD) is known to be two orders of magnitude higher than the surface runoff. Good correlations of dissolved inorganic nitrogen (DIN) and silicate (DSi) with groundwater-borne <SUP>224</SUP>Ra (half life=3.66days) in the initial red-tide waters of 2002 confirm that the source of these nutrients is SGD. In addition, the DIN/DIP ratios in 2002 and total dissolved nitrogen/phosphorus (TDN/TDP) ratios in 2003 in red-tide waters ranged from 30 to 300, similar to those observed in groundwater. The spatial and temporal variations of nutrients and photosynthetic pigments showed that red tides broke out when DIN or DIP (dissolved inorganic phosphorus) were almost depleted, limiting the growth of diatoms. Thus, our observations reveal that the emergence of harmful dinoflagellate red tides might be facilitated by inter-specific competition of phytoplankton species when inorganic nutrients are limited and dissolved organic nutrients, converted from groundwater-borne nutrients, are sufficient.</P>

Quantitative estimation of intertidal sediment characteristics using remote sensing and GIS

Choi, J.K.,Ryu, J.H.,Lee, Y.K.,Yoo, H.R.,Woo, H.J.,Kim, C.H. Academic Press in association with the Estuarine a 2010 Estuarine, coastal and shelf science Vol.88 No.1

High spatial resolution satellite data (IKONOS) combined with in situ data was used to quantitatively estimate the spatial distribution of tidal flat characteristics for the Hwangdo tidal flat, Cheonsu Bay, Korea. The classification result was accurate in terms of a comparison with the in situ data, and the overall accuracy was 90.7%, which confirmed the validity of the classification. GIS analysis based on a probabilistic model was applied to a quantitative estimation of the relationship between each surface sediment facies and the spectral reflectance. Mud flat facies showed a high positive correlation (R<SUP>2</SUP>=0.91), and sand flat facies showed a high negative correlation (R<SUP>2</SUP>=1.00), which was a good reflection of the sedimentary characteristics of Hwangdo tidal flat. Relationships between each sediment facies and DEM also showed good agreement with the topographic characteristics in the study area. The study revealed that intertidal surface sediment classification using high resolution remote sensing imagery and in situ data successfully shows spectral and topographic characteristics of the study area. It was noted that spectral reflectance was affected by a combination of environmental factors, including grain size, topography, and remnant surface water. It is possible to determine the type of tidal flat through quantitative estimates of the spatial distribution of surface sediments according to their spectral reflectance.