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

Phytoplankton studies using samples concentrated by settling revealed population dcnsitics several timcs higher than those rcportcd previously, based on centrifuge and bolting cloth concentrates. Clear and dark bottle experiments employing natural population densities rcvcaled photosynthetic yields averaging 1.6 ~molcs of CO2 absorbed per microlitcr of plant volume per hour. This yield is three times higher than previously reported yields based on artificially conccntratcd populations. Colnparison 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 highcr value. The reduction of turhulcncc in bottles may be operating to reduce the photosynthetic yield. Ecldy diffusivity in western I,akc Eric, computed from pFI change in the dysphotic zone, and vertical pH gradients, is about 25 cnP/sec. Simultaneous detcrminations of CO2 and 02 changes showed that 0~ changes usually were lower than CO2 changes, suggesting that proccsscs other than photosynthesis arc influencing the CO2 and O2 budgets. During the past 30 years the aquatic communities of western Lake Erie have received rather intensive study. Until 1956, however, the phytoplankton studies utilized centrifuge and bolting cloth to concentrate the organisms before counting, and average standing crops observed were less than one microliter of plant matter per liter (Verduin 1951, 1954). In the summer of 1956 Davis (1958) used a direct count method which avoided the losses inherent in centrifuge and bolting cloth methods. His average standing crop for the summer amounted to 6 PI/L which is similar to the maxima1 crops reported during the previous 30 years, and is 10 times the previous averages. Much of the previous research in photosynthesis was also based on concentrated samples (Verduin 1956a). The present paper presents the results of a research program using natural population densities. During the period June, 1957, to September, 1958, the National Science Foundation subsidized a study of phytoplankton at Put-in-Bay, Ohio, in western Lake Erie (G3836). Th c work was intensive in the summer months. Miss E. E. Whitwer, ASSOciatc Professor of Biology at Bowling Green State University, conducted photosynthesis investigations (clear and dark bottle) during both summers, Phytoplankton abundance was determined by Frances Piasecki Kramer during the summer of 1957, and by Mr. Fred Keefcr during the summer of 1958. Mr. Bruce Cowcll studied photosynthesis under completely natural conditions during the summer of 1958. Mrs. Kramer and Mr. Cowell were undergraduate students at Bowling Green State University, and Mr. Kecfer at Thicl College, Greenville, Pennsylvania. One of the significant discoveries in this study was that an intelligent undergraduate student can bc trained in a few days to take charge of a portion of this type of research program and carry it satisfactorily. The facilities of the F. T. Stone Laboratory (The Ohio State University, Natural Resources Institute), Put-in-Bay, Ohio, were used in this study.