Carbon fixation and community dynamics of a phyco-periphyton community

Abstract

The primary productivity of a phyco-periphyton community in a spring fed pond was studied using the carbon-14 method, the oxygen method, and the rate of biomass increase. The contribution of the phyco-periphyton amounted to 79% of the total productivity of the spring, and the contribution remained high during all seasons. The annual mean rate of biomass increase was 108 mg of dry weight/m² of substrate/day and the annual mean rate of productivity was 472 mg C/m² of water surface/day by the oxygen technique, and 320 mg C/m² of water surface/day using the carbon-14 technique. The rate of productivity shows a linear relationship with light and there does not appear to be any photo-inhibition of productivity similar to the surface inhibition phenomenon in phytoplankton. The explanation may be due to "self-shading" and physiological adjustment to intense light. The oxygen method, carbon-14 method, and rate of biomass increase all produced comparable productivity estimates. The rate of biomass increase on glass slides gave best results with short exposures and gravimetric estimates of biomass increase. Intense sunlight lowers the concentration of phytopigments in the phyco-periphyton, particularly when growing on glass slides. The species diversity of the diatom community is less affected by lower light conditions than other algal components of the phyco-periphyton. The bacterial slime stage is not necessary in the succession of the phyco-periphyton in this pond, and the niche may be occupied by the diatoms Frustulia and Eunotia. The succession stages in this biotope were diatoms, followed by desmids, and finally filamentous green and blue green algae.