Periphyton Growth on Artificial Substrates in a Radioactively Contaminated Lake
1967
Neal, Ernest C. | Patten, Bernard C. | DePoe, Charles E.
Periphyton colonization, biomass development and radionuclide accumulation were studied by suspending polyethylene tape vertically for up to 9 weeks in a radioactively contaminated lake. After 2 weeks biomass growth was nearly complete on the upper tape sections, but full development on the deeper sections took longer. Maximum biomass occurred at 25.4—50.8 cm (6—20 in.) depth. Bacterial colonization and slime formation went unobserved. Blue—greens were the initial algal dominants, succeeded by diatoms and filamentous greens. Species succession continued beyond biomass equilibrium, with blue—greens tending to maintain importance in the deeper zones and greens developing best in the upper, lighted regions. Animals were minor constituents. Radioisotope concentrations equilibrated rapidly in both the artificial substrates and the periphyton biomass. Zinc—65 was concentrated highly by the polyethylene tape, Cs¹ ³ ⁷ moderately, and Co⁶ ⁰ and Ru¹ ⁰ ⁶ only slightly or not at all. Ambient concentrations of Zn⁶ ⁵ in water and periphyton were below detection. The other isotopes contributed about equally (ca. 10—20 dpm/mg) to biomass radioactivity. Biomass activity—densities of Ru¹ ⁰ ⁶ and Cs¹ ³ ⁷ increased slightly with depth; this pattern was pronounced for Co⁶ ⁰. Factors considered to account for observed vertical distributions include: different radioisotope concentrations in surface and deep water; a hyperbolic rather than linear relationship between activity—density and biomass; and, in the case of Co⁶ ⁰, concentration by blue—green algae as an essential element, or by microbiota for use in cobalamin synthesis.
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