NITROGEN FIXATION IN LAKE ERKEN1

Publisher Website
Google Scholar
Abstract
In situ fixation of molecular nitrogen was measured in 1970 in the pelagial of Lake Erken by the acetylene reduction technique every 2 weeks during a period of 5 months. The diurnal cycles and vertical distribution of algae were also investigated.Fixation was correlated with the presence of heterocystous blue‐green algae, especially Aphanizomenon, in the phytoplankton, and was light dependent, though appreciable dark fixation also occurred, owing to endogenous utilization of photosynthetic products formed during previous light periods. The annual contribution of nitrogen fixation in the pelagial was of the order 0.5 g N/m2. The highest values were obtained before mass development of Aphanizomenon and maximal primary production. The algae showed highest nitrogenase activity in the first period of algal development.Lake Erken is moderately eutrophic and unpolluted. The contribution of easily available combined nitrogen by pelagic nitrogen fixation increases the annual loading of combined nitrogen by 40% and must therefore be considered quite important.

This publication has 0 references indexed in Scilit: