Informational uncertainties of risk assessment about accidents of chemicals

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Enhanced photo--catalytic activity of gold ion and gold modified

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Nitrate-reductase activity and in vivo nitrate-reduction rate in Ulva rigida illuminated by blue light

In the marine green alga Ulva rigida C. Agardh, nitrate reductase (NR) is synergetically induced by blue light and nitrate. The present study examines the effect of blue light and a large NO ₃ ^– pulse (0.3 mM) on relevant variables of NO ₃ ^– -assimilation such as NO ₃ ^– -uptake, intracellular NO ₃ ^– -storage, NR activity, in vivo NO ₃ ^– -reduction rate and NO ₂ ^– and NH ₄ ⁺ -accumulation. Nitrate uptake started immediately upon addition of NO ₃ ^– , suggesting the presence of a constitutive carrier, however in the first 1.5 to 2 h, periods of net NO ₃ ^– efflux were frequent. After this time, NO ₃ ^– -uptake and intracellular NO ₃ ^– -accumulation proceeded linearly with time, suggesting the existence of a different NO ₃ ^– -uptake mechanism, which seems to be inducible. Our results indicate that in vivo NO ₃ ^– -reduction is not exclusively dependent on the potential NR activity. In U. rigida, during the first 2 h after a NO ₃ ^– pulse (300 M) there were clear indications that the induction state of the NO ₃ ^– -carrier limits the reduction rate of NO ₃ ^– . Once the induction of the NO ₃ ^– -transporter had been completed (1.5 to 2 h), the NO ₃ ^– -assimilation pathway reached a steady state, NO ₃ ^– -uptake rate, NO ₃ ^– -reduction rate and NO ₂ ^– and NH ₄ ⁺ -accumulation being linear with time. Since the reduction of NO ₃ ^– leads mainly to the accumulation of NH ₄ ⁺ , we conclude that, after the NO ₃ ^– -reduction itself, NH ₄ ⁺ -fixation into carbon skeletons is the limiting step in the assimilation of NO ₃ ^– by U. rigida under blue light.     

UV induces reactive oxygen species,damages sperm,and impairs fertilisation in the sea urchin <Emphasis Type="Italic">Anthocidaris crassispina</Emphasis>

We demonstrated that environmentally relevant levels of UVA and UVB can reduce sperm motility (UVA: by 38–58%; UVB: by 42–85%; P < 0.05) and subsequently fertilisation success (UVA: by 38–72%; UVB: by 91–98%; P < 0.05) of urchins (Anthocidaris crassispina) in a dose-dependent manner, implicating that recruitment of urchin populations might be reduced by UVR (ultraviolet radiation) prevailing in their natural habitats. Concomitantly, reactive oxygen species (ROS) production was enhanced by UVA and UVB in a dose-dependent manner (UVA: by 1.3-fold; UVB: by 6.6–7.3-fold; P < 0.05), and the increase in ROS resulted in an increase in lipid peroxidation (LPO) in urchin sperm (UVA: by 4.2–7.2-fold; UVB: by 2.3–2.7-fold; P < 0.05). This study demonstrated that ROS production and oxidative damages enhanced by UVR may account for the observed declines in sperm motility and fertilisation, and suggests that levels of UVR prevailing in the environment may pose a significant threat to the reproductive success of natural populations of urchins spawning in shallow waters.     

Low levels of genetic variation in mtDNA sequences over the western Mediterranean and Atlantic range of the sponge<Emphasis Type="Italic"> Crambe crambe</Emphasis> (Poecilosclerida)

Crambe crambe is a common encrusting sponge found in the Mediterranean and Atlantic littoral. An analysis of a partial sequence (535 bp) of the mitochondrial DNA (mtDNA) gene cytochrome oxidase subunit I (COI) was conducted in an attempt to determine population structure in this species. This is the first study of population genetics using this kind of marker in the phylum. Samples (N=86) were taken in eight populations separated by distances from 20 to 3,000 km, spanning from the western Mediterranean to the Atlantic. Low variability of this gene was found, as only two haplotypes were identified, along with low nucleotide diversity (=0.0006). However, the different frequencies found among populations revealed genetic structure and low gene flow between close populations, as expected from the dispersal biology of the species. The low variability found in sponges is in agreement with reports on cnidarians and points to a high conservation of mtDNA in diploblastic phyla.     

Short-term effects of data-loggers on Cory’s shearwater (<Emphasis Type="Italic">Calonectris diomedea</Emphasis>)

We investigated the possible effects of a 12-g data-logger attached to a darvic ring on the performance of Corys shearwater (Calonectris diomedea, 600–850 g) from two different colonies in the western Mediterranean Sea. We compared return rates, current breeding success and body condition between equipped and unequipped birds. Effects on feeding ecology during winter and breeding period was also evaluated through the measurement of stable isotopes of carbon (¹³C) and nitrogen (¹⁵N) in one of the colonies. We found no evidence of negative effects of loggers on demographic parameters analysed or in feeding ecology. Power analyses suggested a high power to detect medium effect size, but a low power to detect small changes. Despite the non-significant results we could only exclude medium to strong effects of the devices on one of these parameters. We detected some short-term negative effects on body condition for the equipped birds, but these were unlikely to have had important consequences. Results suggest that the use of loggers is an adequate methodology to obtain information from seabirds at sea, but data should be carefully interpreted with regard to potential biases during severe environmental conditions.Communicated by S.A. Poulet, Roscoff     

Simultaneous nitrification, denitrification, and phosphorus removal in single-tank low-dissolved-oxygen systems under cyclic aeration.

Simultaneous nitrification and denitrification (SND or SNdN) may occur at low dissolved oxygen concentrations. In this study, bench-scale (approximately 6 L) bioreactors treating a continuous feed of synthetic wastewater were used to evaluate the effects of solids retention time and low dissolved oxygen concentration, under cyclic aeration, on the removal of organics, nitrogen, and phosphorus. The cyclic aeration was carried out with repeated cycles of 1 hour at a higher dissolved oxygen concentration (HDO) and 30 minutes at a lower (or zero) dissolved oxygen concentration (LDO). Compared with aeration at constant dissolved oxygen concentrations, the cyclic aeration, when operated with proper combinations of HDO and LDO, produced better-settling sludge and more complete nitrogen and phosphorus removal. For nitrogen removal, the advantage resulted from the more readily available nitrate and nitrite (generated by nitrification during the HDO period) for denitrification (during the LDO period). For phosphorus removal, the advantage of cyclic aeration came from the development of a higher population of polyphosphate-accumulating organisms, as indicated by the higher phosphorus contents in the sludge solids of the cyclically aerated systems. Nitrite shunt was also observed to occur in the LDO systems. Higher ratios of nitrite to nitrate were found in the systems of lower HDO (and, to less dependency, higher LDO), suggesting that the nitrite shunt took place mainly because of the disrupted nitrification at lower HDO. The study results indicated that the HDO used should be kept reasonably high (approximately 0.8 mg/L) or the HDO period prolonged, to promote adequate nitrification, and the LDO kept low (< or =0.2 mg/L), to achieve more complete denitrification and higher phosphorus removal. The above findings in the laboratory systems find strong support from the results obtained in full-scale plant implementation. Two plant case studies using the cyclic low-dissolved-oxygen aeration for creating and maintaining SND are also presented.     

Fungal laccase-catalyzed degradation of hydroxy polychlorinated biphenyls

Hydroxy polychlorinated biphenyls (hydroxy PCBs) are toxic metabolites of PCBs. Their toxicity such as strong endocrine disruption demands effective remediation methods. Laccases from Trametes versicolor and Pleurotus ostreatus were tested to degrade hydroxy PCBs. Optimum pHs for both enzymes were around 4.0. Laccase from T. versicolor degrades hydroxy PCBs more rapidly than that from P. ostreatus. The enzymatic activities remained little changes in up to 10% organic solvents, but decreased rapidly in more than 10% acetone, acetonitrile or DMSO. Degradation rate constants decreased with increase of chlorination and no degradation was observed with tetra-, penta- and hexa-chloro hydroxy PCBs in non-mediated reactions. However, the tetra- to hexa-chloro hydroxy PCBs were degraded by laccase from T. versicolor in the presence of the mediator 2,2,6,6-tetramethylpiperidine-N-oxy radical. The other mediators, 4-ethyl-2-methoxyphenol, 2,2'-azino-bis(3-ethylbenzthiazoline sulfonic acid) diammonium salt and 1-hydroxybenzotriazole and humic acid, also enhanced degradation of all the hydroxy PCBs except 4-hydroxy-2',3,3',4',5,5'-hexachlorobiphenyl. The results showed that 3-hydroxy biphenyl was more resistant to laccase degradation than 2- or 4-hydroxy analogues. Significant linear-correlations (coefficient of determination, r2 = 0.9097 and 0.8186 for laccases from P. ostreatus and T. versicolor, respectively) were found between the ionization potentials and the removal rate constants of hydroxy PCBs.     

Effects of pre-exposure to ultraviolet-B radiation on responses of tomato (Lycopersicon esculentum cv. New Yorker) to ozone in ambient and elevated carbon dioxide

Patterns of environmental change in the biosphere include concurrent and sequential combinations of increasing ultraviolet (UV-B) and ozone (O(3)) at increasing carbon dioxide (CO(2)) levels; long-term changes are resulting mainly from stratospheric O(3) depletion, greater tropospheric O(3) photochemical synthesis, and increasing CO(2) emissions. Effects of selected combinations were evaluated in tomato (Lycopersicon esculentum cv. New Yorker) seedlings using sequential exposures to enhanced UV-B radiation and O(3) in differential CO(2) concentrations. Ambient (7.2 kJ m(-2 )day(-1)) or enhanced (13.1 kJ m(-2) day(-1)) UV-B fluences and ambient (380 microl l(-1)) or elevated (600 microl l(-1)) CO(2) were imposed for 19 days before exposure to 3-day simulated O(3) episodes with peak concentrations of 0.00, 0.08, 0.16 or 0.24 microl l(-1) O(3) in ambient or elevated CO(2). CO(2) enrichment increased dry mass, leaf area, specific leaf weight, chlorophyll concentration and UV-absorbing compounds per unit leaf area. Exposure to enhanced UV-B increased leaf chlorophyll and UV-absorbing compounds but decreased leaf area and root/shoot ratio. O(3) exposure generally inhibited growth and leaf photosynthesis and did not affect UV-absorbing compounds. The highest dose of O(3) eliminated the stimulating effect of CO(2) enrichment after ambient UV-B pre-exposure on leaf photosynthesis. Pre-exposure to enhanced UV-B mitigated O(3) damage to leaf photosynthesis at elevated CO(2).