Relationships Between Bacterial Populations and Oxygen Levels in the Central Basin of Lake Erie

Studies were made to ascertain the relationships between bacteria and particulate organic carbon, particulate nitrogen, and the depletion of oxygen from the hypolimnetic waters of the central basin of Lake Erie. Heterotrophic bacterial populations, dissolved oxygen, particulate organic carbon, and total particulate nitrogen were determined during May, August, and September. Data indicate 1) a relationship between heterotroph populations and dissolved oxygen; 2) epilimnion oxygen concentrations of 9 mg/L were associated with bacterial levels of ?4 × 10³ colonies per mL; 3) bacterial densities started to increase from the thermocline downward; 4) hypolimnion oxygen levels of ?l mg/L were associated with bacterial densities of approximately three times the epilimnion values; 5) bacterial oxygen uptake rate in the hypolimnion varied from 1.5 to 7.4 × 10^?10 mg/L/hr; 6) particulate organic carbon and bacteria showed similar distribution patterns in the water column; 7) particulate nitrogen remained unchanged at 0.1 mg/L in the water column showing no relationship to the other parameters measured.