Two Sources of Error in the Oxygen Light and Dark Bottle Method1

Abstract

Rates of oxygen uptake per bacterial cell in dark bottles containing bacteria but no phytoplankton were applied to the bacterial population of the dark bottle in two‐day light and dark bottle experiments and showed that, in the temperature range 11–21°C, bacteria were responsible for 42.5% to 62.5% of the total respiration customarily attributed to the phytoplankton. Failure to correct for bacterial respiration results in “net photosynthesis” values that are erroneously low by the same amount.Large changes commonly occur in the bottled populations during a two‐day light and dark bottle experiment: in 22 routine experiments diatoms in the light bottle increased an average of 264%/day and the total population increased 72%/day, while in the dark bottle flagellates and the total population usually decreased slightly. Respiration and net and gross photosynthesis per unit volume of water are therefore probably not the same inside and outside the bottles. The rapid multiplication of diatoms in the light bottle is due to an accelerated regeneration of nutrients by the bacteria attached to the bottle walls, as shown by comparison of diatom growth in water previously conditioned by bacteria with growth in water not so conditioned.