Periphyton production in fort River, Massachusetts

The primary production and general ecology of a periphyton community of a New England, lowland stream were studied over a seventeen‐month period. Temperature, light, periphyton chlorophyll‐α, and community structure were monitored regularly. Seasonally distinct chlorophyll peaks coincided with the light maximum in early May, just prior to the appearance of leaves of riparian trees, and again in autumn after terrestrial leaf fall. During midwinter, despite low light and temperature levels and high stream discharge, mean chlorophyll concentrations remained similar to summer values. A mathematical expression relating periphyton photosynthesis per unit chlorophyll‐α to temperature, light and periphyton density was established with submersible light‐dark chambers in situ. Survey data collected over the study period were employed in the empirical equation to estimate seasonal variations in periphyton primary production. Weekly mean daily estimates of periphyton gross production ranged from < 0.1 g O2 m−2, during midwinter, to 6.5 g O2 m−2 during early May. Estimated annual periphyton gross production and respiration were 0.58 and 1.27 kg O2 m−2, respectively. Factors influencing seasonal variations of Fort River periphyton standing crop are discussed.