One measure of microbiological respiration is the biochemical
oxygen demand (BOD), which measures the oxygen consumed in a
specified time period per unit volume of water, in the absence of
photosynthesis. Briefly, samples of pond effluent initially are
saturated with DO and maintained in sealed, dark bottles in a stable
laboratory environment, and measurements of DO in the samples are
performed at regular intervals. Samples are re-aerated periodically, as
necessary, to maintain DO concentrations above 2 mg L
−1
(Clesceri et
1998).