Significance of salinity and silicon levels for growth of a formerly estuarine eelgrass (Zostera marina) population (Lake Grevelingen, The Netherlands)

Since the early 1980s, the eelgrass, Zostera marina L., population in the saline Lake Gevelingen, The Netherlands, is rapidly declining. An earlier study, in which long-term data on eelgrass coverage in this former estuary were correlated with several environmental variables, showed only one significant correlation: coverage was positively related to water column silicon levels. In addition, a negative correlation with salinity was observed, but this was not significant. In the present study, the effect of silicon and the effect of salinity on the development of Z. marina were investigated experimentally. Enhancement of dissolved silicon concentrations in the water did not stimulate Z. marina above-ground production or an increase in final above- and below-ground biomass. The highly significant correlation between eelgrass coverage and water column silicon levels, thus, remains to be explained. The results of the growth experiments did, however, demonstrate a clear effect of salinity on Z. marina growth. Plants cultured at 22 psu showed a higher production of shoots and leaves, resulting in more above-ground biomass, than plants grown at 32 psu. In addition, below-ground biomass was also higher at 22 psu. Measurements of chlorophyll a fluorescence, performed with a PAM-fluorometer, indicated a reduction of photosynthesis in the high-salinity treatments. Thus, low salinity stimulates development of Z. marina from Lake Grevelingen. Eelgrass from such a historically estuarine area may be more sensitive to high salinities than other, more marine populations. Recovery of the autochthonous eelgrass population is expected to be favoured when the estuarine conditions of the seagrass area are re-established, or when restoration programmes are carried out with allochthonous ecotypes that are less sensitive to high salinities. Received: 23 June 1998 / Accepted: 19 November 1998     

Identification of potential biomarkers for diazinon exposure to Japanese Medaka (Oryzias latipes) using annealing control primers

A new differential display-polymerase chain reaction (PCR) method based on annealing control primers was used to screen and identify potential biomarkers from differentially expressed genes (DEGs) in medaka exposed to sub-lethal concentration of diazinon (100 ppb). Among the differentially expressed genes identified, the majority were in functional categories of protein biosynthesis, transport and metabolism according to the gene ontology classification. The differential expression of ribosomal protein genes was quantified by real time PCR. The genes encoding ribosomal proteins including L3 and S17 were selected as potential biomarkers for diazinon exposure in medaka fish.     

Radium isotopes in the Ulsan Bay

In order to estimate the fluxes of Ra isotopes, we measured 224Ra, 226Ra, and 228Ra activities in the Ulsan Bay mixing zone. The convex upwards curvature of the plot of Ra isotope activities versus salinity for the mixing zone suggests that Ra isotopes are supplied from particles entering the mixing zone from both the river and bottom sediments. This addition increases the estuarine flux of 226Ra and 228Ra to the outer sea by factors of 15 and 95 over the flux attributable to Ra dissolved in the riverine water alone. In order to estimate the residence time of the water in Ulsan Bay, we applied a mass balance model to the distribution of 224Ra and 226Ra activities in the Ulsan Bay mixing zone with the inflow from the Taehwa River. The obtained residence times of the waters in the Ulsan Bay were estimated to be 6.8-11.4 d. The waters in the upper part of the estuary have long residence times whereas those in the lower part, in contact with the open sea, have shorter residence times. The mean residence time of the water in the Ulsan Bay was estimated to be 9.1 d.     

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.     

Compositional data analysis and geochemical modeling of CO2–water–rock interactions in three provinces of Korea

Environmental Geochemistry and Health - The CO2-rich spring water (CSW) occurring naturally in three provinces, Kangwon (KW), Chungbuk (CB), and Gyeongbuk (GB) of South Korea was classified based...     

Morphological variation of dinoflagellate Prorocentrum lima (Ehrenberg) Dodge with geographical difference

Prorocentrum lima (Ehrenberg) Dodge, one of the cosmopolitan dinoflagellates, is basically benthic and is found on the surface of macroalgae and detritus. The identification of this species requires detailed morphological observation because of its close similarity to other benthic Prorocentrum species. The purpose of this study is to detect the morphological variability of P. lima using culture clones collected from several areas to find an adequate way of subdividing the species. In this study, 33 clones of P. lima were collected from Saipan, Tahiti, Indonesia, Japan and Bermuda, and their thecal valves and periflagellar area were observed by means of light microscopy with differential interference contrast optics and scanning electron microscopy. In general cells have two centrally located pyrenoids and a posterior nucleus. The surface of both valves has many valve pores except the center. Evenly spaced marginal pores are located along the edge of the valves. P. lima samples studied herein were subdivided into four major types (ellipsoidal, general, short, and elongate ovoid) according to their shapes, length-to-width ratio and number of valve pores. The length-to-width ratios of ellipsoidal, general, short, and elongate ovoid types were 1.32, 1.33-1.43, 1.20-1.27, and 1.53-1.60 microm respectively. Also there were slight differences in the number of valve pores. The number of valve pores examined in this study ranges from 40 to 97: ellipsoidal, general, and short ovoid types range from 40 to 91, while an elongate ovoid type ranges from 80 to 97. The combination of valve shape, number of valve pores and length-to-width ratio provides useful information on the morphological variation of P. lima.     

Cadmium accumulation and elimination in tissues of juvenile olive flounder, Paralichthys olivaceus after sub-chronic cadmium exposure

Experiments were carried out to investigate the accumulation and elimination of cadmium (Cd) in tissues (gill, intestine, kidney, liver and muscle) of juvenile olive flounder, Paralichthys olivaceus, exposed to sub-chronic concentrations (0, 10, 50, 100 microg l(-1)) of Cd. Cd exposure resulted in an increased Cd accumulation in tissues of flounder with exposure periods and concentration, and Cd accumulation in gill and liver increased linearly with the exposure time. At 20 days of Cd exposure, the order of Cd accumulation in organs was gill > intestine > liver > kidney > muscle and after 30 days of exposure, those were intestine > gill > liver > kidney > muscle. An inverse relationship was observed between the accumulation factor (AF) and the exposure level, but AF showed an increase with exposure time. During the depuration periods, Cd concentration in the gill, intestine and liver decreased immediately following the end of the exposure periods. No significant difference was found Cd in concentration in the kidney and muscle during depuration periods. The order of Cd elimination rate in organs were decreased intestine > liver > gill during depuration periods.     

Degradation of ethinyl estradiol by nitrifying activated sludge

Degradation of ethinyl estradiol (EE2) by nitrifying activated sludge was studied with micro-organisms grown in a reactor with feedback of sludge fed with only a mineral salts medium containing ammonium as the sole energy source. Ammonium was oxidised by this sludge at a rate of 50 mg NH4+ g(-1) DW h(-1). This activated sludge was also capable of degrading EE2 at a maximum rate of 1 microg g(-1) DW h(-1). Using sludge with an insignificant nitrifying capacity of 1 mg NH4+ g(-1) DW h(-1), no degradation of EE2 was detected. Oxidation of EE2 by nitrifying sludge resulted in the formation of hydrophilic compounds, which were not further identified. Most probably degradation by nitrifying sludge results in a loss of estrogenic activity, as hydroxylated derivatives of EE2 are known to have a substantially lower pharmacological activity than EE2.     

Removal of ammonia by biofilters: a study with flow-modified system and kinetics

The characteristics of ammonia removal by two types of biofilter (a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow) were investigated. A mixture of organic materials such as compost, bark, and peat was used as the biofilter media based on the small-scale column test for media selection. Complete removal capacity, defined as the maximum inlet load of ammonia that was completely removed, was obtained. The modified biofilter showed complete removal up to 1.0 g N/kg dry material/day. However, the removal capacity of the standard biofilter started to deviate from complete removal around 0.4 g N/kg dry material/day, indicating that the modified biofilter system has higher removal efficiency than the standard upflow one. In kinetic analysis of the biological removal of ammonia in each biofilter system, the maximum removal rate, Vm, was 0.93 g N/kg dry material/day and the saturation constant, Ks, was 32.55 ppm in the standard biofilter. On the other hand, the values of Vm and Ks were 1.66 g N/kg dry material/day and 74.25 ppm, respectively, in the modified biofilter system.