Browsing by Subject "biokertyvyys"

This work was carried out to find out, in what manner exposure to or the avoidance of sun's ultraviolet radiation (UV) affects the reproduction of water fleas (Daphnia magna) at different copper (Cu) concentrations. A 21-day long reproduction test containing two stress factors was performed adapting the OECD chemical testing standard number 211 ”Daphnia magna Reproduction Test” from the year 1998. Using an element contents analysis (ICP MS) that was done of the water fleas which have participated in the reproduction test, it was studied whether the UV affects Cu accumulation in Daphnia magna. UVB radiation has been reported being harmful to many aquatic organisms directly by harmful biological effects as well as indirectly due to the radiation interacting with chemicals occurring in the environment so that the toxicity of chemicals will increase. Thus UV is an environmental factor that may cause effects to be taken into account when assessing the effects of emissions of chemicals. Copper levels were 3, 9, 30, 90 and 300 µg Cu increment per liter of Elendt M7 growth medium, which contains 1.6 µg Cu / l as a nutrient. UV exposure was carried out using solar radiation so that half of the test units (+UV) was placed under UV-permeable polyethylene film and the other half (−UV) under UV-protection foil (Wipa-foil clear SR). At the beginning of the test, there were ten parallel individual water fleas in each UV and Cu treatment combination and 14 parallel Cu blanks at both UV levels. To test run the experimental apparatus, that had been built in Viikki Helsinki under a plexiglas canopy absorbing 40 % of UV, a shorter pre-test was made in the midsummer. The actual reproduction test was performed in July–August. One important element of the experimental part of this study was to examine the test apparatus according to the demands of the testing standard. Because of methodological problems, amount of the feeding (0.027 ± 0.006 mg C / Daphnia / day) was only 13–27 % of the requirements of the standard. Reproduction of the control water fleas remained at only about a third of the minimum requirement of the standard, so the test wasn't valid. The response variable was the average cumulative number of living offspring produced per surviving parent animal at the end of the test. The NOEC and LOEC values for reproduction were 30 µg Cu / l and 90 µg Cu / l expressed in the Cu spiking levels (Tukey, p < 0.001). They were inaccurate, because they were based on too few concentrations chosen from too large a range. Already the Cu spiking 90 µg / l was extremely high on the grounds of survival, because among the −UV test units the mortality was 70 % and in the +UV test units 60 %. In the lower spikings than 90 µg / l there was no mortality caused by the test factors. Copper bioaccumulation assay suffered from contamination. The UV exposure without Cu spikings did not affect statistically significantly cumulative offspring production (t-test, p = 0.87, df = 26). On the average, the UV factor had a significant increasing effect (ANOVA, p < 0.01) on the production over all the Cu levels: the average cumulative number of offspring produced (± SD) was in the −UV level 22.8 ± 6.3 (n = 45) and in the +UV level 24.4 ± 5.2 (n = 48). Interaction was perceived between UV and Cu spiking at extended risk level (ANOVA, 0.05 < p < 0.1) so that the UV exposure trend-wise dampened the decrease of production in the spiking level of 90 µg / l. Statistically significant (p < 0.01) interaction effect of UV and spiking to offspring production was found after fitting a non-linear model for the data set using a second degree polynome for the Cu spiking and performing a regression analysis. This unexpected interaction requires further examination using the same flow-through growth medium for both of the UV levels. In such flow-through test design the changes in growth media possibly caused by the UV do not affect the results. In order to avoid exposing the −UV water fleas to radiation pulses during the daily examination, they must be only handled in UV protected space, unlike was done in this work.