PHYTOPLANKTON COMMUNITIES OF WESTERN LAKE ERIE AND THE CO2 AND O2 CHANGES ASSOCIATED WITH THEM

Abstract

Phytoplankton studies using samples concentrated by settling revealed population densities several times higher than those reported previously, based on centrifuge and bolting cloth concentrates. Clear and dark bottle experiments employing natural population densities revealed photosynthetic yields averaging 1.6 µmoles of CO2 absorbed per microliter of plant volume per hour. This yield is three times higher than previously reported yields based on artificially concentrated populations. Comparison of daily photosynthetic yields per square meter of water as computed from bottle data with yields measured under completely natural conditions indicated an additional twofold discrepancy, with the natural condition yielding the higher value. The reduction of turbulence in bottles may be operating to reduce the photosynthetic yield. Eddy diffusivity in western Lake Erie, computed from pH change in the dysphotic zone, and vertical pH gradients, is about 25 cm2/sec. Simultaneous determinations of CO2 and O2 changes showed that O2 changes usually were lower than CO2 changes, suggesting that processes other than photosynthesis are influencing the CO2 and O2 budgets.