Real-time monitoring and automatic density control of large-scale microalgal cultures using near infrared (NIR) optical density sensors

Signals from near infrared (NIR) light transmittance sensors were used for both real-time monitoring of algal biomass density in growing mass cultures (200l tubular biofences), and also as feedback in a system that controlled the density of the culture by automatic injection of fresh growth medium. When operated in a semi-continuous production mode between predefined density values, diurnal growth patterns were recorded on-line that provided information on the dynamics of the microalgal cultures with respect to environmental conditions. The bioreactor system was also programmed to operate in constant biomass density mode, thereby maintaining the culture at the optimal population density (OPD), and sustaining high biomass production levels. The system has potential for operating a dynamic density set point for microalgal cultures where the optimal population density varies as a function of ambient growing conditions.

Assessment of ammonia toxicity in tests with the microalga, Nephroselmis pyriformis, Chlorophyta

Previous studies of an industrial effluent have indicated toxic effects by the ammonium/water system in tests with the unicellular green alga, Nephroselmis pyriformis. This investigation was undertaken to determine the toxicity of ammonia to this alga, and to identify the dominant toxicant in an industrial process effluent. The algal standard test was modified to improve the pH control, i.e. by testing at shorter exposure time and in the presence of a buffering agent, 3 mM HEPES. Ammonia was found to be the predominant toxic form in the dissociating ammonium/water system and the specific toxicity of ammonia (EC50, 24 h exposure) was 2.34 microM (32.8 microg ammonia nitrogen/L). Due to the dissociation, the toxicity is strongly pH dependent. Joint toxicity with additive effects of ammonia and ammonium ions was indicated, but the toxicity of ammonium ions was almost a factor 100 less (EC50, 24 h exposure, 224 microM or 3140 microg ammonium-nitrogen/L). According to the results the EC50 for effect on growth rate of N. pyriformis in seawater of pH 8.0 is 71 microM total ammonium. Hence, this alga appears to be more sensitive to ammonia than other studied marine plankton algae. Ammonia was found to be the dominant toxicant in the industrial effluent, using N. pyriformis as test organism.

Effects of three fungicides alone and in combination on glutathione S-transferase activity (GST) and cytochrome P-450 (CYP 1A1) in the liver and gill of brown trout (Salmo trutta)

In order to evaluate the gill glutathione S-transferase (GST) activity as a biomarker of effect of fungicide exposure in juvenile brown trout (Salmo trutta), the fungicides propiconazole [(R,S)-1-[2-(2,4-diclophenyl)-4-propyl-1,3-dioolan-2-ylmetyl]-1H-1,2,4-triazole] and fenpropimorph [(+/-)-cis-4-[3-(4-tert-butylphenyl)-2-metyl propyl]-2,6 dimetylmorfolinc] were administrated in the water separately and together in a static system (80 microg/l for each pesticide) for 5 days. The combined fungicides gave a significant decrease in gill GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB), whilst hepatic GST-activity was not significantly changed. Furthermore, continuous exposure to 540 ug/l thiabendazole[2-(thiazol-4'-yl)benzimidazole] in a flow-through system for 4 days significantly increased the gill glutathione S-transferase (GST) activity towards CDNB, whilst hepatic GST and cytochrome P450 (CYP 1A) activities were not increased by the treatment.

Comparative toxicity of acrylic acid to marine and freshwater microalgae and the significance for environmental effects assessments

In this study, we compared the sensitivity of freshwater and marine organisms to two structurally similar substances, acrylic acid and methacrylic acid. Reported acute toxicity data (L(E)C50-values) for freshwater organisms range from 0.1 to 222 mg/l and 85 to >130 mg/l for acrylic acid and methacrylic acid, respectively. The large variation in toxicity data for acrylic acid is due to a specific toxicity to certain species of freshwater microalgae, with algae EC50-values being two to three orders of magnitude lower than L(E)C50-values reported for fish and invertebrates. To evaluate the sensitivity of marine organisms, ecotoxicity data was generated for ten species of microalgae, one invertebrate species and one fish species. For methacrylic acid, we found a marine acute toxicity that ranged from 110 to >1260 mg/l, which is comparable to reported data on freshwater organisms. In strong contrast, the resulting L(E)C50-values for acrylic acid ranged from 50 to >1000 mg/l, and there was no specific sensitivity of marine algae when compared to marine invertebrates and fish. For acrylic acid, therefore, use of the available freshwater toxicity data for an effects assessment for the marine environment is likely to overestimate the hazard and risk from this substance. Overall, the results of the study suggest that ecotoxicity data generated on freshwater species may not always be appropriate for the effects assessments of organic chemicals in the marine environment, thus emphasising the importance of using ecologically relevant data to assess environmental risk.

Environmental risk assessment of acrylamide and methylolacrylamide from a grouting agent used in the tunnel construction of Romeriksporten, Norway

Increased focus on the possible evironmental risk associated with large-scale use of grouting agents has revealed that leakage of chemicals from grouting activities may cause harm to the environment. Chemical grouting agents are used to reduce water leakages in e.g. tunnel constructions. The present study focuses on monitoring results and environmental risk caused by releases of non-polymerised monomers during use of the acrylamide-based grouting agent Rhoca-Gil (Siprogel). Drainage water from the tunnel Romeriksporten was monitored with respect to acrylamide and methylolacrylamide, as leakage of these substances was observed earlier in connection with similar constructions where Rhoca-Gil was used. Concentrations of acrylamide and methylolacrylamide in the draining water showed that these substances leaked out both in connection with the injection of Rhoca-Gil and in connection with after-injection using other grouting agents. Gel formation studies with Rhoca-Gil showed that a low degree of polymerisation (and hence, large leakages of monomers) can be expected if the product is diluted with water. Results from investigation of the environmental fate of methylolacrylamide showed that this substance is chemically transformed at the high-pH conditions of the tunnel. Ecotoxicological testing of the substances and an environmental effects assessment for the receiving water (River Alna and the Oslofjord) showed that the discharge of acrylamide and methylolacrylamide may have caused effects on the aquatic life in the river and in a limited area of the fjord.

Some effects of the fungicide propiconazole on cytochrome P450 and glutathione S-transferase in brown trout (Salmo trutta)

The fungicide propiconazole (1-(2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl) -1H-1,2,4-triazole) induced the hepatic cytochrome P4501A (CYP1A) activity towards ethoxyresorufin-O-deethylase (EROD), the content of CYP1A protein as quantified by enzyme-linked immunosorbent assay (ELISA) and the glutathione S-transferase (GST) activity towards the three commonly used substrates CDNB(1-chloro-2,4-dinitrobenzene), cumene hydroperoxide (CU) and ethachrynic acid (EA) in brown trout (Salmo trutta) depending on dose and body weight. An exponential dose response relationship existed between propiconazole exposure and CYP1A activity. A 2. order polynomial regression of the propiconazole concentration (square root transformed) on the data for CDNB, EU and CU revealed a bell-shaped pattern of the GST induction. Reverse-phase HPLC of the GSH-affinity chromatography purified GST isozymes in trout exposed to respectively 8.3, 23, 93, 313 and 606 microg l(-1) propiconazole in the water indicated that the propiconazole treatment may lead to changes in the composition of the subunits compared to the controls. Thus, propiconazole exposure through the water changed the properties of the brown trout hepatic CYP1A and GST, and these changes may be used as a bioindicator on the molecular level of exposure and effect of propiconazole in controlled experiments. The use in monitoring of propiconazole exposure under natural field conditions is possible, however needs further investigation.