Diel dynamics of vertical changes of chlorophyll and bacteriochlorophyll in small humic lakes

The diel variability of algal and bacterial chlorophyll and the physicochemical parameters (temperature, pH, dissolved oxygen, conductivity, transparency) in the vertical profile of three mid-forest humic lakes in Drawa National Park (northwest Poland) were analyzed in summer. The euphotic zone consisted of the smaller part of the water column in poly- and mesohumic lakes but almost the whole water column of the oligohumic lake. The 24-hour dynamics of chlorophyll a and bacteriochlorophyll d+e in poly- and mesohumic lake was significantly smaller than that in the polyhumic lake. The maximum concentrations of chlorophyll a and bacteriochlorophyll d+e were observed near the bottom border or below the euphotic zone in waters with oxygen deficits and containing sulfur hydrogen. The main producers of chlorophyll in meso- and oligohumic lake were green anaerobic sulphuric bacteria.