1. School of Chemical and Life Sciences, University of Greenwich, Woolwich Campus, Wellington Street, Woolwich SE18 6PF, U.K., Department of Biological and Chemical Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K., and Bayrisches Geoinstitut, Universität Bayreuth, D-955440 Bayreuth, Germany