TY - JOUR A1 - Gervais, Frank A1 - Siedel, Ulrike A1 - Heilmann, Britta A1 - Weithoff, Guntram A1 - Heisig-Gunkel, Gabriele A1 - Nicklisch, Andreas T1 - Small-scale vertical distribution of phytoplankton, nutrients and sulphide below the oxicline of a mesotrophic lake N2 - A characteristic vertical sequence of phytoplankton populations was observed below the metalimnetic oxycline of a stratified, mesotrophic lake. Ceratium spp., Closterium acutum and Aphanizomenon flos- aquae were present in the epilimnion but had distinct population maxima in the microaerobic chemocline. Below these populations, Cryptomonas phaseolus, Planktothrix clathrata, Pseudanabaena catenata and Limnothrix sp. followed each other in the transition zone between the chemocline and the sulphide-containing hypolimnion. The dominating populations of P. clathrata and P. catenata caused a deep chlorophyll maximum. Phytoplankton structure was determined by the vertical gradients of sulphide and light. Compared with the epilimnion, nutrient availability was not fundamentally better below the oxycline but the algae might have benefited from reduced grazing pressure in their habitat. Y1 - 2003 UR - http://plankt.oupjournals.org/cgi/content/full/25/3/273 ER -