EVALUATING EFFECTS OF MULTIPLE EXPOSURE BY MEANS OF PALEOLIMNOLOGICALTECHNIQUES

The acidification chronology of Gr. Arbersee (Bavarian Forest, Germany ) was studied by means of subrecent diatom, and chrysophyte as well as metal (Al, Cu, Cd, Mg, Ca) stratigraphies. pH was inferred by diatom assemblages so that the simultaneous effects of acid and accompanying metals on chrysophytes could be evaluated. The occurrence of seven dom inant Mallomonadacean taxa was related to the environmental variables by applying Spearman rank correlation and factor analysis. During the post-glacial period of natural acidification, increases in organic car bon and declining pH favor Mallomonas crassisquama and disfavor M. het erospina and M. caudata. Potentially toxic metals (Al, Cu, Cd) and the two alkaline earth metals (Ca, Mg) impact the occurrence as well. Alt hough acidity appears to be also the major driving force during the re cent acidification period, the occurring Mallomonadacean species may b e differentiated by their tolerance toward Al and heavy metals.