DIATOM-TEMPERATURE TRANSFER-FUNCTIONS BASED ON THE ALTITUDINAL ZONATION OF DIATOM ASSEMBLAGES IN PAPUA-NEW-GUINEA - A POSSIBLE TOOL IN THE RECONSTRUCTION OF REGIONAL PALEOCLIMATIC CHANGES

Indirect and direct gradient ordination techniques were used to study the relationship between present-day benthic and periphytic diatom ass emblages and environmental factors along an altitudinal gradient in Pa pua New Guinea. Both within the screened initial data-set and a narrow ly-defined subset of soft-water lakes, shifts in diatom assemblages ar e clearly related to altitudinal differences. This relation is used to construct transfer functions for inferring altitude (and hence averag e water temperature) from the diatom records. Calibration by canonical correspondence analysis (CCA) and simple weighted averaging calibrati on proved to be superior to models using WA with tolerance downweighti ng and toa a simple WA model based on a selection of 52 indicator taxa . From the calibration models and the linear relationship between alti tude and epilimnetic water temperature, the average lake water tempera ture can be predicted with an accuracy of 3.2 degrees C. After further refinement, a transfer function for palaeotemperature based on diatom s would be of potential value for climatic reconstructions in tropical regions.