Development of temperature-based algorithms for the estimation of microphytobenthic primary production in a tidal flat: A case study in Daebu mudflat, Korea.

This study presents the results of field experiments that were designed to investigate the photophysiological characteristics of microphytobenthos (MPB) and to estimate primary production (PP) in Daebu mudflat, which is located at the west coast of Korea. A typical seasonal (or monthly) fluctuation of intertidal MPB PP was found in association with biotic (benthic Chl-a) and/or abiotic parameters (irradiance and temperature) over a period of three years. From a series of field-laboratory experiments using the oxygen micro-profiling method (totaling 28 surveys), three consistent phenomena were observed: 1) winter to early spring algal blooms, 2) seasonal changes in Q10, and 3) temperature dependent MPB photosynthesis-irradiance (P-I). In particular, both the chlorophyll-specific maximum photosynthetic capacity (Pbmax) and the saturated light intensity (Ik), derived from 126 P-I curves (1870 data sets of oxygen micro-profiling in the sediment), were significantly correlated with sediment temperature (p < 0.01). To develop an empirical MPB PP model, the relationships between P-I parameters and environmental variables were parameterized following established exponential forms (e.g., Q10). It was possible to estimate the MPB PP in Daebu mudflat area by using easily accessible explanatory factor, suitable to be used for future explorations of parameters such as sediment temperature, irradiance, chlorophyll concentration, and tidal height. The estimated annual MPB PP based on the empirical PP model were found to be greater than that in the Wadden Sea and average annual PP in the temperate zones of the world. Authors believe that the present approach of the MPB PP estimation could be combined with remote-sensing techniques (e.g., satellites) to support coastal ecosystem management.

DESCRIPTION OF A NEW NAVICULOID DIATOM GENUS MORENEIS GEN. NOV. (BACILLARIOPHYCEAE) FROM SAND FLATS IN KOREA(1).

This article describes a new diatom genus Moreneis from the Yellow Sea sand flats on the west coast of Korea. The new genus is characterized by a unique combination of morphological characteristics, including the shape of the plastids, which have not been previously observed in diatoms. The valve morphology resembles other genera belonging to Lyrellaceae, within which we place this genus. In terms of areolae structure, Moreneis resembles Petroneis and Placoneis; however, it differs from both genera with respect to the raphe system and plastid shape. Cells of Moreneis spp. have a single large plastid appressed to the girdle of the secondary side of the valve, with two lobes extended toward the primary side of the valve. Furthermore, the unique feature of Moreneis frustules is the raphe, which has both external central and apical endings bent in opposite directions. We differentiated four taxa, which we describe as new for science. However, based on our findings, several established species from Navicula should also be formally transferred to Moreneis, including N. alpha Cleve, N. besarensis Giffen, N. epsilon Cleve, N. menaiana Hendey, N. polae Heiden, and N. quadri-undulata F. Meister. Analysis of published data revealed that species belonging to Moreneis are numerous in tropical marine littoral waters, and in moderate climate zones, especially in the western Pacific, with only a few species occurring in the Mediterranean and Atlantic.

The impact of heavy metal pollution gradients in sediments on benthic macrofauna at population and community levels.

The effect of sediment pollution on benthos was investigated in the vicinity of a large sewage treatment outflow at Incheon North Harbor, Korea. Animal size, vertical distribution and standard community parameters were analyzed along a 3 km transect line (n = 7). Univariate parameters showed a general trend of increasing species diversity with increasing distance from the pollution source. Multi-dimensional scaling analysis led to the clear separation of 3 locational groups, supporting gradient-dependent faunal composition. The innermost location was dominated by small sub-surface dwellers while the outer locations by large mid to deep burrowers. Looking for the size-frequency distribution, most abundance species (Heteromastus filiformis) showed the presence of larger size animals with increasing proximity to the pollution source. Meanwhile, species-specific vertical distributions, regardless of the pollution gradient, indicated that such shifts were due to species replacement resulting from a higher tolerance to pollutants over some species.

Perfluorinated compounds in water, sediment, soil and biota from estuarine and coastal areas of Korea.

Soil, sediment, water, and biota collected from the western coast of Korea were analyzed to determine occurrence and sources of perfluorinated compounds (PFCs). PFCs were significantly concentrations of PFCs were measured in some water and biological samples, while concentrations of PFCs in soils and sediments were relatively low. The most widely detected compound was found to be perfluorooctanesulfonate (PFOS), with a maximum concentration in water of 450 ng/L and in fish of 612 ng/g, dw. PFOS concentrations in water and biota were both less than those thought to cause toxicity. However, in both cases concentrations were within a factor of 10 of the toxicity threshold concentration. Concentrations of PFCs were significantly greater downstream than those upstream on the same river, suggesting point sources. Overall, the detection of PFCs at relatively great concentrations in various environmental matrixes from this region of Korea suggests that further studies characterizing PFCs and their potential risk to both humans and wildlife are needed.

Land use in Korean tidal wetlands: impacts and management strategies.

The coastal landscapes in southwestern Korea include a diverse array of tidal wetlands and salt marshes. These coastal zones link the ecological functions of marine tidal wetlands and freshwater ecosystems with terrestrial ecosystems. They are rich in biological diversity and play important roles in sustaining ecological health and processing environmental pollutants. Korean tidal wetlands are particularly important as nurseries for economically important fishes and habitats for migratory birds. Diking, draining, tourism, and conversion to agricultural and urban uses have adversely affected Korean tidal wetlands. Recent large development projects have contributed to further losses. Environmental impact assessments conducted for projects affecting tidal wetlands and their surrounding landscapes should be customized for application to these special settings. Adequate environmental impact assessments will include classification of hydrogeomorphic units and consideration of their responses to biological and environmental stressors. As is true worldwide, Korean laws and regulations are changing to be more favorable to the conservation and protection of tidal wetlands. More public education needs to be done at the local level to build support for tidal wetland conservation. Some key public education points include the role of tidal wetlands in maintaining healthy fish populations and reducing impacts of nonpoint source pollution. There is also a need to develop procedures for integrating economic and environmental objectives within the overall context of sustainable management and land uses.

Characterization of trace organic contaminants in marine sediment from Yeongil Bay, Korea: 2. Dioxin-like and estrogenic activities.

This study employed mechanism-specific in vitro bioassays to help characterize the occurrence and distribution of dioxin-like and estrogenic contaminants in sediment from Yeongil Bay, Korea. Approximately 85% of the sediments tested induced significant dioxin-like activity in the H4IIE-luc bioassay, while approximately 50% induced significant estrogenic activity in the MVLN bioassay. Instrumentally-derived estimates of 2,3,7,8-tetrachlorodibenzo-p-dioxin and 17beta-estradiol equivalents tended to underestimate the magnitude of response observed in the bioassays, suggesting that compounds detected by chemical analysis did not account for all the activity associated with Yeongil Bay sediments, or that non-additive interactions were occurring. The greatest dioxin-like and estrogenic activity was associated with the mid-polarity Florisil fractions (F2) expected to contain polycyclic aromatic hydrocarbons (PAHs) as well as chlorinated dioxins and furans. As in previous studies of Korean coastal sediment, more polar fractions (F3) generated more modest responses both in terms of magnitude and the number of samples responding.

Characterization of trace organic contaminants in marine sediment from Yeongil Bay, Korea: 1. Instrumental analyses.

Concentrations of polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides (HCB, HCHs, CHLs, and DDTs), polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and bisphenol A (BPA) were measured in 26 marine sediments collected from Yeongil Bay, Korea, in order to characterize their spatial distribution and sources. PCBs (2.85-26.5 ng/g, dry wt.) were detected mainly in the inner bay locations Mean OC pesticide ranged from 1.16 ng/g dry wt. for HCH to 0.05 ng/g dry wt. for HCB). PAH concentrations ranged from <10.0 to 1870 (mean: 309)ng/g dry wt., and were predominated 3- and 4-ring congeners. Concentrations of APs, such as nonylphenol, octylphenol, butylphenol (means 89.1, 4.61, 11.0 ng/g dry wt., respectively), were greater at locations proximal to municipal wastewater discharges. Concentrations of PCBs and PAHs were great near shipyards and industrial complexes. Vertical profiles of PAHs and APs indicated that they have been associated with sediments since the 1950s.

Instrumental and bioanalytical measures of dioxin-like and estrogenic compounds and activities associated with sediment from the Korean coast.

Sediments from inland areas and open bays along the Korean coast were analyzed to examine the distribution of dioxin-like and estrogenic compounds. Concentrations of target chemicals varied considerably among locations (Lake Shihwa, Masan Bay, and Kwangyang Bay) and between inland and coastal areas. Principal component analysis (PCA) of contaminants measured in sediments showed that all of the inland locations from Lake Shihwa were highly contaminated, and the variations among locations were explained predominantly by the distribution of alkylphenols and polycyclic aromatic hydrocarbons (PAHs). PCA of PAH congener profiles among locations indicated that automobiles were a major source of PAH contamination. Dioxin-like and estrogenic activities associated with sediment from inland sites were approximately three- and six-fold, respectively, greater than those associated with open bay locations. The target dioxin-like and estrogenic compounds measured in raw extracts of sediments accounted for approximately 20% and 40% of the activities measured in the sediment extracts. The results suggest that a combination of instrumental and bioanalytical measurements of dioxin-like and estrogenic compounds is a valuable approach to screen, identify, and prioritize the risks posed by contaminants in complex environmental matrices.

Analysis of trace organic contaminants in sediment, pore water, and water samples from Onsan Bay, Korea: instrumental analysis and in vitro gene expression assay.

Persistent organic pollutants and alkylphenols (APs) were determined in sediment and water samples from Onsan Bay, Korea, by using instrumental analysis and in vitro gene expression cell bioassay. Polycyclic aromatic hydrocabons (PAHs) were the predominant compounds in sediments with concentrations as great as 573 ng/g dry weight. The PAH concentrations were elevated in sediment from inland rivers that flow through Onsan City (mean: 116 ng/g dry wt) and discharge into Onsan Bay. Concentrations of polychlorinated biphenyls (PCBs) in sediments ranged from <1.00 to 56.2 ng/g dry weight. Among different organochlorine (OC) pesticides analyzed (hexachlorobenzene, hexachlorocyclohexanes, chlordanes, and DDTs), DDT concentrations were the greatest, ranging from <0.01 to 7.58 ng/g dry weight. The spatial gradient of contaminant concentrations suggested that streams and rivers are the major sources of PCBs, PAHs, and APs to the bay. Maximum concentrations of nonylphenol, octylphenol, and bisphenol A in sediments were 860, 11, and 204 ng/g dry weight, respectively. Screening of Onsan Bay sediment samples for dioxinlike activity with the H4IIE-luc in vitro cell bioassay revealed that 17 of 22 samples contained significant dioxinlike activity. Further fractionation of sediment extracts indicated that mid-polar and more polar fractions were responsible for the significant dioxinlike activity. Based on a mass balance analysis, PAHs apparently accounted for only a small portion of dioxinlike responses elicited by sediment extracts. Only one raw extract of sediment elicited a significant estrogenic response by MVLN cells. The combination of instrumental analysis and in vitro bioassay was useful to assess sediment quality and characterize the causative agents or potential toxic compounds present.

Toxicokinetics and time-dependent PAH toxicity in the amphipod Hyalella azteca.

The relationship between toxicokinetics and time-dependent PAH toxicity to Hyalella azteca was examined to test the constant critical body residue (CBR) model. A constant CBR model is based on the assumption that the body residue for 50% mortality is constant for each PAH across exposure times. With a constant CBR, kinetic parameters determined through kinetic experiments would be similar to those estimated from time series toxicity data. Time-dependent toxicity was investigated using three types of data: time series LCW data, LT50(c), and CBR values measured at multiple exposure times for live and dead animals. Kinetic parameters were measured independently. The constant CBR model did not predict the PAH toxicity time course for H. azteca. Since a first-order kinetic model predicted the bioaccumulation of the parent PAH except for naphthalene, this result is not due to a failure to predict the internal dose (body residue). The influence of metabolites on toxicity was negligible except for naphthalene. The LC50 values at multiple exposure times decreased to an incipient lethal concentration after H. azteca reached steady state. Measured CBR values also decreased with increasing exposure time. Thus, the time course of PAH toxicity is determined not only by the bioconcentration kinetics but also by the cumulative toxicity with increasing exposure time. Therefore, time-to-death or hazard models must be developed as a complement to toxicokinetic models to describe and predict the toxicity time course.

Prediction of time-dependent PAH toxicity in Hyalella azteca using a damage assessment model.

A damage assessment model (DAM) was developed to describe and predict the toxicity time course for PAH in Hyalella azteca. The DAM assumes that death occurs when the cumulative damage reaches a critical point and was described by a combination of both first-order toxicokinetic and toxicodynamic models. In aqueous exposures, body residues increase in proportion to the water concentration. Damage is assumed to accumulate in proportion to the accumulated residue and damage recovery in proportion to the cumulative damage when damage is reversible. As a result, the toxicity time course, LC50(t), is determined by both a damage recovery rate and an elimination rate. The constant critical body residue (CBR) and the critical area under the curve (CAUC) models can be derived as two extreme cases from the DAM, and all three models were reanalyzed using a hazard modeling approach. As a result, the critical cumulative damage (D(L)) is the determinant of the concentration-time response relationship and not simply the CBR or the CAUC. Finally, from the DAM, two parameters, a damage recovery rate constant kr and the killing rate kt, were estimated and found to be relatively constant for selected PAH.

Purification and characterization of metallothionein-like cadmium binding protein from Asian periwinkle Littorina brevicula.

Although mussels and oysters in the ocean are known to act as bioconcentrators for contaminants such as heavy metals, their ability to survive in heavily polluted water is relatively limited. The Asian periwinkle, Littorina brevicula, is one species that can accumulate a variety of environmental heavy metals, and the expression of its metal binding protein (MBP) is induced by cadmium. To better characterize this protein and its detoxification mechanism against cadmium, the present work examined the induction of a cadmium binding protein (Cd-BP) in Littorina brevicula exposed to 400 microg/l CdCl(2) for 30 days. The induced Cd-BP was purified by chromatography from the supernatants of homogenized organs (digestive gland, gonad, gill and kidney). This Cd-BP was found to consist of 103 amino acids, was rich in Cys (21 residues), and partial C-terminal sequence obtained by MALDI-TOF MS analysis revealed a Cys-XXX-Cys motif, which resembles a typical feature of mollusc metallothionein (MT). The Cd-BP molecular weight of 9.8 kDa is a little larger than that of other MTs.