PRIMARY PRODUCTIVITY AND ENERGY RELATIONSHIPS IN ARTIFICIAL STREAMS1

Abstract

The productivity of algal communities was investigated in two recirculating artificial streams. Emphasis was placed on a study of the effects of various factors on energy flow and on the characterization of artificial streams as a research tool. Productivity was measured by pH and carbon dioxide changes, upstream‐downstream oxygen changes, and the biomass of algae collected on artificial substrata.A temperature increase caused a small, but insignificant, increase in net productivity, while increased light intensity caused an increase in net productivity. A higher current velocity caused an increase in net productivity, significant as shown by riffle vs. pool communities, but not significant between a fast and a slow stream. A shorter, but more frequent photoperiod did not change the rate of production significantly. High chelate concentration caused a reduction in net productivity.Estimates of net productivity by the carbon dioxide and oxygen methods were in agreement for two out of five studies, while estimates by the biomass of algae on substrata were consistently lower than estimates by the gas methods. Net production varied from 2,815 to 5,565 cal m−2 day−1, resulting in efficiencies from 3.8 to 9.8%. Efficiencies of gross productivity varied from 6.4 to 16.1%.