The thermal, oxygen and light regimes in isolated columns of water in a turbid impoundment

SUMMARY. Temperature, oxygen and secchi disc transparency were measured in 5-m diameter isolation columns positioned in water approximately 4 m deep. In general the difference in thermal conditions between the adjacent open water and columns was slight. Oxygen levels in bottom waters in the enriched columns were often slightly lower than in the open water but never dropped below 50% saturation. It seems unlikely that sufficient depletion occurred to markedly increase release of phosphorus from the sediment. Light penetration in the columns was more varied than in the open water but was seldom sufficient to permit the development of large stands of benthic algae.