Discharge and the response of biofilms to metal exposure in Mediterranean rivers |
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Authors: | Helena Guasch Güluzar Atli Berta Bonet Natàlia Corcoll Manel Leira Alexandra Serra |
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Institution: | 1.Institute of Aquatic Ecology,Universitat de Girona,Girona,Spain;2.Department of Biology, Faculty of Sciences and Letters,University of ?ukurova,Adana,Turkey;3.Faculty of Sciences,University of A Coru?a,A Coru?a,Spain |
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Abstract: | The expected response of fluvial biofilms to the environment and metal pollution prevailing under different discharge conditions
was investigated. The relationship between inter-annual hydrological variability and metal concentration in water and sediments
was explored in Mediterranean rivers (Catalonia, NE Spain) affected by low but chronic metal pollution, using monitoring data
provided by the Catalan Water Agency (ACA). During the period investigated (2000–2006), metal pollution was characterized
by low water concentrations and high concentrations in sediments. The most consistent pattern was observed for sediment cadmium
(Cd) concentrations, showing a positive relationship with annual discharge, reaching values of environmental concern (above
ecotoxicological benchmarks). A different pattern was observed for Cu, Zn, and As increasing with flow in some sites and decreasing
in others. While Cd seems to proceed from diffuse sources being washed by surface runoff, Zn, Pb, and As may proceed from
either diffuse or point-sources in the different river sites investigated. The relevance of diffuse metal pollution in the
area of study indicates that polluted landfills runoff might be an important source of metals causing repetitive pulses of
high metal concentration in the receiving water courses. The experimental results presented demonstrate that metal effects
in fluvial biofilms may be accumulative, increasing the toxicity after repetitive pulse exposures. Since draughts and extreme
rain events are expected to increase at higher latitudes due to global change, the sources of metal pollution, its final concentration
and potential effects on the fluvial ecosystem may also change following the patterns expected for human-impacted Mediterranean
rivers. |
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