Planktonic food chains of a highly humic lake. I: A mesocosm experiment during the spring primary production maximum

The metabolic processes and trophic relationships in plankton from a highly humic lake, Mekkojarvi in Finland, were investigated during the vernal primary production maximal. A mesocosm which excluded the large filter feeders typical of the lake in summer conditions was used. The biomass, production and respiration of the bacterioplankton present showed no strong dependence on the spring maximal of phytoplankton primary production. The utilization of allochthonous organic matter probably explained much of the bacterioplankton growth. Although some nutritional relationships between different species were demonstrated, observed changes in the plankton species composition were not adequately explained. There are 69 references. (see also following abstract).