| Title | 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 ¼g 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. |
| Source | Journal of limnology (Testo stamp.) 69(2), pp. 217–224 |
| Keywords | ecotoxicologyreproductiongrowthfertilitycladocerans |
| Journal | Journal of limnology (Testo stamp.) |
| Editor | Istituto per lo Studio degli Ecosistemi., Verbania Pallanza, Italia |
| Year | 2010 |
| Type | Articolo in rivista |
| Authors | Ponti, B., R. Piscia, R. Bettinetti (1) & M. Manca |
| Text | 53164 2010 ecotoxicology reproduction growth fertility cladocerans Long term adaptation of Daphnia to toxic environment in Lake Orta the effects of short term exposure to copper and acidification Ponti, B., R. Piscia, R. Bettinetti 1 M. Manca 1 Department of Chemical and Environmental Sciences, University of Insubria, Via Valleggio 11, 22100 Como 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 ¼g 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. 69 2 Published version Long term adaptation of Daphnia to toxic environment in Lake Orta the effects PONTI_2010.pdf Articolo in rivista Istituto per lo Studio degli Ecosistemi. 1129 5767 Journal of limnology Testo stamp. Journal of limnology Testo stamp. J. limnol. Testo stamp. Journal of limnology. Testo stamp. PONTI BENEDETTA roberta.piscia PISCIA ROBERTA marinamarcella.manca MANCA MARINA MARCELLA TA.P04.016.004 Ecologia teorica e applicata degli ecosistemi acquatici |
