Diel Oxygen Changes in Closed Ecological Systems: Predictive of Lake Metabolism?

The net oxygen change over a 24-hour day/night cycle in a laboratory study showed strong consistent patterns of (1) gain, when nutrients and light were available; (2) maintain, with daytime gains being matched by nighttime losses; and (3) loss, over brief periods of time during intense zooplankton grazing on previously grown phytoplankton or over long durations without an external source of nutrients. These were simplified aquatic communities closed to the atmosphere, Closed Ecological Systems (CES). Natural lakes are much more complex. While temperate lakes, having a winter accumulation of nutrients followed by sequential algal and zooplankton blooms, may show similar patterns, tropical and flood lakes may exhibit different patterns. Examination of archived lake metabolic studies could yield new insights while looking for these patterns by examining net ecosystem production (NEP), often measured as changes in oxygen concentrations.