Effect of Chlorination on the Gill Lipids of the Mussel Mytilus edulis (L)

Experiments are described which involve the chlorination of standard solutions of lipids and populations of the mussel, Mytilus edulis (L). The object was to test the hypothesis that chlorine will bind to unsaturated lipids. Evidence is presented that chlorine and aqueous chlorinated species rapidly and readily form addition compounds with unsaturated lipids in vivo as well as in vitro. The relevance of these findings to possible environmental effects of chlorination is discussed.     

Modelling the effect of acidity on mercury uptake by walleye in acidic and circumneutral lakes

An association between acidification of lakes and high mercury concentrations in fishes has been reported. In northern Wisconsin (USA), for example, walleye (Stizostedion vitreum) in naturally acidic lakes have higher mercury concentrations than walleye in circumneutral lakes (Weiner, 1983). In this study a bioenergetic based model for mercury uptake is applied to identify potential causes of higher mercury concentrations in fishes living in acidic lakes. Application of the model to walleye populations in northern Wisconsin indicates that higher mercury concentrations in acidic lakes are most likely a result of both increased concentrations in the water and increased efficiencies of uptake from water. Higher concentrations in the water would result in higher concentrations in the food.     

Ozone uptake by an evergreen forest canopy: temporal variation and possible mechanisms

Patterns of ozone concentration ([O(3)]), O(3) deposition velocity (v(d)) and O(3) flux (F(c)) over an evergreen forest canopy are shown in relation to measuring method, physiological activity of the trees, and time of year. The gradient and eddy correlation methods were compared and showed similar diel v(d) patterns. Daytime F(c) was correlated with CO(2) and water vapour fluxes, while no correlation between [O(3)] in the range 10-70 ppb (nl l(-1)) and F(c) was seen in this study. F(c) was primarily driven by stomatal conductance, reactions with surfaces, particles and gases, and not by [O(3)]. On a monthly basis, [O(3)] was always highest in the afternoon while v(d) was typically higher in the morning, resulting in an equal F(c) over the day. Night-time F(c) was more than half of the daytime O(3) flux. The data reveal the importance of emissions of nitric oxide and terpenes as O(3) removal factors in evergreen forest dominated by Norway spruce.     

Effect of tetracycline residues in pig manure slurry on tetracycline-resistant bacteria and resistance gene tet(M) in soil microcosms

Effects of tetracycline residues from pig manure slurry on the prevalence of tetracycline-resistant bacteria and the tetracycline resistance gene, tet(M), were studied in soil microcosms. Four types of soil microcosms were established for a period of 152 days, supplemented with combinations of pig manure slurry and a tetracycline-resistant Enterococcus faecalis, CG110, containing the tetracycline resistance gene tet(M) (on the conjugative transposon, Tn916). The prevalence of both tetracycline-resistant aerobic bacteria and tetracycline-resistant enterococci declined rapidly until day 45 where no significant differences in the levels of tetracycline-resistant bacteria in any of the four types of microcosms could be detected. tet(M) could be detected in microcosms supplemented with either pig manure slurry and/or E. faecalis CG110 (tet(M)) for the whole period (152 days). tet(M) could be detected longer than tetracycline-resistant enterococci could be isolated (limit of detection 100 CFU/g soil) probably due to viable but not culturable (VBNC) bacteria with tet(M), horizontal gene transfer of tet(M) to indigenous soil bacteria or presence of "free" DNA. The concentration of chlortetracycline and oxytetracycline were almost stable through out the experimental period, but the tetracycline concentrations had no effect on prevalence of tetracycline-resistant bacteria. The presented microcosm approach simulated natural farmland conditions well and supported results from previous field studies.