To measure the seasonal changes in the diatom community from epilithic
biofilms, 3-4 small stones were collected every time at depths of ~20-30 cm from Jun
2004 to Jun 2005 at two places, which were 50 m apart from each other from the
littoral zone of Lake Constance, Germany (47°41´N, 9°11´E). In the laboratory,
adhering biofilms were scraped off from the stones and pooled for each collection
site. Pore water was removed by centrifugation at 5000 rpm for 10 minutes and was
stored at -20 °C. The resulting pellets were further divided into three parts. One part
was used for the identification and documentation of diatom frustules (described
below). One part was used for determination of chlorophyll a according to the method
of Jeffrey & Humphrey (1975), and one part was used for the analysis of EPS (as
described below)