Benthic diatom communities in streams from zinc mining areas in continental (Canada) and Mediterranean climates (Portugal) Ana T. Luís, Alexa C. Alexander, Salomé F. P. Almeida, Eduardo Ferreira da Silva and Joseph M. Culp ABSTRACT This study compares regional differences in benthic diatom communities exposed to similar stresses in Canada and Portugal. Diatoms were sampled in the Água Forte Stream, Aljustrel (SW Portugal) and in the Little River, New Brunswick (SE Canada), both streams surround the respective zinc mine and are subject to similar metal (e.g. Cd, Cu, Fe, Zn) and acidic (Água Forte pH ¼ 1.9–2.9 vs. Little River pH ¼ 2.2–5.5) stresses. In this kind of extreme environment, diatoms are frequently the main algae group in the streams, widely used as bioindicators. Diatom communities in the Água Forte Stream were dominated mostly by Pinnularia aljustrelica and Eunotia exigua (5% teratological forms), whereas communities in the Little River were more diverse (e.g. Achnanthidium minutissimum, Nitzschia palea, Eunotia sp.). Shannon-Wiener Index (H 0 ) and percentage of taxa relative abundance were used to characterize the diversity and species composition of the diatom communities. Using canonical correspondence analysis (CCA), it was found that regional variation in acceptable in-stream concentrations of metals, conductivity and pH were the primary drivers of benthic diatom community. Mine remediation to decrease metal concentrations and increase pH in streams will increase diatom diversity even in highly impacted streams such as Água Forte. Ana T. Luís (corresponding author) Eduardo Ferreira da Silva GeoBioTec – GeoBioSciences, Geotechnologies and Geoengineering Research Center, Department of Geosciences, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal E-mail: anatluis@ua.pt Ana T. Luís Salomé F. P. Almeida Department of Biology and GeoBioTec – GeoBioSciences, Geotechnologies and Geoengineering Research Center, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal Alexa C. Alexander NSERC Visiting Fellow – Environment Canada at the Canada Centre for Inland Waters, Burlington, Ontario, Canada Alexa C. Alexander Joseph M. Culp Department of Biology at the University of New Brunswick, #10 Bailey Drive, PO Box 4400, Fredericton, New Brunswick, Canada E3B 5A3 Joseph M. Culp Environment Canada, National Water Research Institute, Fredericton, NB, Canada Key words | diatoms, geographically distinct environments, low pH, metals, Portugal and Canada mining areas INTRODUCTION Two geographically and climatically distinct rivers in similar mining areas were studied, one located in Aljustrel, Alentejo (south-west Portugal) and a second in Bathurst, New Bruns- wick (south-east Canada). The mining complex of Aljustrel is located in the Portuguese part of the Iberian Pyrite Belt (IPB). This geological unit corresponds to an area of Devo- nian-Carboniferous volcanic and sedimentary rocks containing massive sulphide deposits, with Zn-Cu being the primary metals extracted. Some ores and sulphides can be deposited as a result of the extraction process. Oxidation of sulphurous ore bodies can result in acid leakages and highly contaminated acid mine drainage (AMD). AMD for- mation is due to the oxidation of thiosalts that are formed by the incomplete oxidation of sulphides which can be further oxidized to form sulphate minerals and hydrogen ions in the water. These processes can mobilize trace 180 © IWA Publishing 2013 Water Quality Research Journal of Canada | 48.2 | 2013 doi: 10.2166/wqrjc.2013.043 Downloaded from https://iwaponline.com/wqrj/article-pdf/48/2/180/379944/180.pdf by guest on 30 May 2020