1. Department of Environmental Science, Stockholm University, SE-106 91 Stockholm, Sweden
2. Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
3. Umeå Marine Sciences Centre, Umeå University, SE-910 20 Hörnefors, Sweden
4. Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden
5. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden