Dynamics of chlorophyll and photosynthesis in natural phytoplankton associations - II. Seasonal and annual cycles of chlorophyll and phaeopigments, in relation to euphotic depth and their vertical distribution in small Northgerman lakes

In 1981 weekly investigations were made into the relationship between chlorophyll levels and the depth of the euphotic zone and extinction coefficients in the Plußsee. Chlorophyll and phaeopigment production was studied in relation to the algal growth phases, depth, global radiation and temperature. Chlorophyll specific and the non-algal light attenuation were estimated and compared with data from other lakes. In the euphotic zone the mean annual level of chlorophyll-a was about 20mg m-3 or 80mg m-2, over the ranges 1-60mg m-3 or 8*220mg m-2 (1981). Maxima of about 100mg m-3 were observed corresponding to earlier findings. Phaeopigment levels increased from about 15% of chlorophyll-a to about 200 % in metalimnetic layers and during algal decline. The chlorophyll maxima varied over the years of investigation, being highest in 1981. Several algal assemblages with short periods of dominance formed numerous chlorophyll peaks, which together produced 3 major blooms. Chlorophyll maxima could occur at any depth between the surface and 10m. Distinct epilimnetic and metalimnetic chlorophyll maxima were seen in spring and late summer, respectively