Periphyton production in an Appalachian river

Periphyton primary production was measured by ¹⁴C uptake on natural substrates in two sections of the New River, Virginia, U.S.A. Production ranged from 6.71 ± 0.43 mg C g^-1 h^-1 in summer to 1.47 ± 0.22 mg C g^-1 h^-1 in late autumn in the hardwater reach and from l.90 ± 0.10 mg C g^-1 h^-1 to 0.12 ± 0.08 mg C g^-1 h^-1 in the softwater reach. Production in the hardwater reach was 3-5 times greater than in the softwater reach and significantly correlated with dissolved inorganic carbon (DIC) concentration (r² = 0.506). No significant correlation was found between periphyton production and photosynthetically active radiation (PhAR). Extrapolation of periphyton production to a 135 km reach of the New River yielded an estimated annual input of 2 252 T AFDW from this source. Estimates of allochthonous (excluding upstream contributions) and aquatic macrophyte inputs to this same reach were 64 T AFDW and 2 001 T AFDW, respectively. While periphyton is not a large source of organic matter, its high food quality and digestibility make it an important component of the New River energy dynamics.