PRIMARY PRODUCTIVITY IN A SOUTHERN GREAT PLAINS STREAM1

Abstract

Physico‐chemical conditions and community metabolism in a relatively undisturbed stream in Oklahoma were studied from June 1963 to August 1964. Stream reaches were selected in geological formations outcropping primarily as limestone, granite, and sand. Total alkalinity decreased and carbonate alkalinity increased downstream. Summer chlorophyll concentration was highest on the granite outcrop. High chlorophyll concentrations occurred in upstream reaches on large boulders in the channel bed, and low concentrations occurred downstream on shifting sand. Gross photosynthesis varied from 10.1 g O 2 m −2 day −1 in winter to 48.0 g 02 m −2 day −1 in summer on the granite outcrop and always exceeded respiration. High primary productivity and respiration resulted from large populations of benthic algae and bryophytes growing on the granite formations. Community respiration always exceeded photosynthetic productivity at reaches in limestone and sand formations. Annual primary production varied from 1.1 kg/m 2 on the sand to 7.8 kg/m 2 on the granite. Daily photosynthetic efficiencies ranged from 0.1 to 2.7%. As solar radiation increased during the day, photosynthetic productivity increased, but efficiency of utilization of solar radiation decreased.