Showing papers by "Roberta Bettinetti published in 2010"

The role of zooplankton in DDT biomagnification in a pelagic food web of Lake Maggiore (Northern Italy)

Abstract: Background In the present study, we report the analytical results of ppDDT, ppDDE and ppDDD determination in lake water, plankton and zooplanktivorous fish of Lake Maggiore (Northern Italy), rather recently polluted by DDT of industrial origin, in order to understand the bottom-up pollution transfer among the abiotic and biotic components of the lake ecosystem. Materials and methods Fourteen water sampling cam- paigns were carried out from March 2003 to January 2009 in the water column of the deepest point (Ghiffa) of Lake Maggiore. Suspended and dissolved pollutants were deter- mined separately. Three sampling campaigns were carried out from July 2008 to January 2009 for zooplankton and pelagic fish, and DDT residues were analysed by HRGC coupled with ECD and MS. Moreover, food items were detected in fish stomachs. Results and discussion Starting from 2007, the DDT contamination along the water column became rather homogeneous, probably because no flooding or other relevant hydrological events occurred; although steady- state condition should be expected, lipid normalised concentrations of ppDDE and ppDDD in zooplankton exceeded the levels of the same compounds in zooplank- tivorous fishes. Conclusion As this finding represents a thermodynamic paradox since bioaccumulative pollutant concentrations are expected to increase along the trophic chain, it was supposed that the abiotic and biotic lake components were not in a steady-state condition in Lake Maggiore.

Long-term adaptation of Daphnia to toxic environment in Lake Orta: the effects of short-term exposure to copper and acidification

Abstract: Because of its 80-year history of heavy pollution and re-colonization, Lake Orta provides a good opportunity for investigating the response of zooplankton organisms to heavy metals and acidification as well as the mechanisms involved. After the recent establishment of Daphnia galeata Sars, and the detection of an extremely low clonal diversity of Lake Orta population, we carried out a study to investigate the lethal tolerance to ionic copper, as well as to acidity, and the impact of newborn Daphnia exposure to sublethal concentrations of copper for their later development and reproduction. We conducted acute toxicity tests to estimate the EC50 for ionic copper and tolerance to low pH, as well as life table experiments. Tolerance to ionic copper was high, three times that reported in literature. An increased mortality soon after exposure to low pH confirmed a high sensitivity to acidity and explained the success of the species in Lake Orta only after pH recovery. An analysis of reproductive and demographic parameters revealed that D. galeata Sars was stressed at concentrations of ionic copper only twice higher than those presently recorded in the lake (i.e., ca 3 µg L -1 ). An increased cumulative number of eggs produced by each female were in fact counterbalanced by an increasing abortion rate, which resulted in an unaltered or lower intrinsic rate of population increase. Our results are likely due to the strong selective pressure, more than physiological processes (acclimation), in a polluted area in which only specific adapted clones are able to grow, confirming the results previously obtained on Lake Orta's D. obtusa Kurz population. The reproductive response and the relatively low within treatment variability suggest that clone specificity, rather than physiological acclimation, was the driving force. The low variability confirmed results previously obtained from life tables experiments on Lake Orta's D. obtusa clone. Overall, our results suggest that, despite the chemical recovery, Lake Orta may be regarded as highly vulnerable to biodiversity loss.