River Periphyton Research Articles

The effect of flow patterns on uptake of phosphorus by river periphyton

The effect of various flow patterns on the uptake of 32P by river periphyton was examined in a laboratory flume. In general, water movement increased 32P uptake, except where the phosphorus demand of the microorganisms was presumably satisfied by molecular diffusion at high phosphorus concentrations (105 µg·liter−1 PO4‐P). However, there was little difference in 32P uptake between the several distinct flow regimes produced by increasing or decreasing velocity and turbulence associated with a hump and hydraulic jump. It appears that the threshold limit for water movement, after which no further stimulation occurs, is ⩽5.4 cm·s−1, the lowest velocity tested. A reduction in 32P uptake by formaldehyde‐killed films of periphyton indicated that 50–75% of the uptake of the untreated films was due to biological activity.

A method for the spectrophotometric measurement of chlorophyll a and pheophytin a in benthic microalgae1

A method is described that allows the measurement of river periphyton chlorophyll a and pheophytin a both on rocks and in soft sediments. The method involves successive extractions directly from frozen samples with boiling methanol. Pigments are estimated by optical density measurements before and after acidification. Methanol is superior to acetone for the distinction of chlorophyll a and pheophytin a by this means.