Primary production and potential availability of autochthonous carbon in southern Ontario streams

Abstract

Primary production was measured in forested and open streams in southern Ontario to identify the main factors influencing algal growth, and to test the assumption that autochthonous inputs are negligible in forested headwater streams. In low order streams in southern Ontario, primary production is related primarily to light, temperature, and substrate, and appears to be largely independent of location on the river continuum. Net primary production on rock averaged 2.24 and 0.098 g Cm−2 day−1 during the summer at meadow and forested sites, respectively, showing peaks in the spring and fall at the forested sites. Net primary production on sediment was significant, averaging 20% (range of 6 to 82%) of net primary production on rock. When adjusted for assumed invertebrate assimilation efficiency, autochthonous production in riffles at forested sites could provide an estimated 30% of total carbon inputs potentially available to aquatic invertebrates.