Paleoindication of acidification in Kleiner Arbersee (Federal Republic of Germany,Bavarian Forest) by chydorids,chrysophytes, and diatoms

In a sediment core of Lake Kleiner Arbersee, located in the Bavarian Forest on gneiss bedrock and with spodosolic soils in the catchment, acidification was reconstructed using assemblages of chydorids, scaled chrysophytes, and diatoms as paleoindicators. All paleoindicators demonstrated acidification of Kleiner Arbersee. There were marked differences, however, in the extent of the indicated acidification: In lower layers, where scaled chrysophytes and chydorids clearly indicate beginning acidification, pH-decline inferred by diatoms lies within the standard deviation, and is statistically not significant until the 7 cm layer. We conclude that mallomonadaceans reflect the acidification of the water body and strongly respond to the lowest seasonal pH, as their indicated rate of acidification is higher than that of diatoms, which appear to more closely indicate the pH of the sediment/water interface, especially when the pH of the water column has dropped below ca. 5.5. Chydorids may additionally be influenced by proton release of dense Sphagnum-stands, which cover the littoral of Kleiner Arbersee completely.We dedicate this paper to Prof. Dipl.-Ing. L. Strobel, who encouraged new perspectives in limnological water management, on the occasion of his 65^th anniversary.