Chironomids, temperature and numerical models: a reply to Seppala

We reply to comments by Seppala (2001) concerning the suitability of the su rface-water temperature measurements and mean July air temperature estimate s used by Olander et al. (1999) to derive quantitative chironomid-temperatu re transfer functions. We use new data for water temperatures based on two- hourly recordings from thermistors installed in 32 lakes and air-temperatur e data from an automatic weather station at one lake to refute Seppalas acc usations that our field data are unsatisfactory. We also respond to Seppala 's suggestions about factors influencing chironomid distribution and abunda nce and suggest that there is a serious confusion of temporal and spatial s cales between Seppala's ideas and the Olander et al. study. We attempt to e xplain the underlying logic behind empirical transfer functions that form a major part of Holocene quantitative environmental reconstructions and the major assumptions behind such transfer functions as Seppala appears not to understand the basis or the assumptions of such widely used numerical model s in palaeolimnology. We respond to Seppala's comments that lakewater pH an d distance beyond tree-line have been inadequately measured and answer his erroneous understanding that a helicopter was used to facilitate lake sampl ing. We briefly consider Seppala's suggestion that a helicopter can totally mix the surface water of a lake for many hours.