COMMUNITY METABOLISM IN ECOSYSTEMS RECEIVING OIL REFINERY EFFLUENTS1

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Abstract
The diurnal curve method was used to investigate community metabolism in two oil refinery effluent holding pond systems. Photosynthetic productivity and community respiration, addition of oxygen from the atmosphere, and the effects of light and temperature were studied. Average community respiration was highest in late fall and lowest in early spring. Photosynthetic productivity was higher in spring and fall than in summer and lowest in winter. There was no photosynthetic productivity at Refinery A during winter. Community metabolism in the holding ponds was higher than in most natural communities and lower than in sewage oxidation ponds. Diffusion of oxygen from the atmosphere was a major contributor of oxygen to the system during winter and in the first few ponds of the series. Efficiency of the algae in converting solar energy to chemical energy was greatest during fall and spring, when sunlight was more nearly optimal, and lowest in winter, when sunlight was below optimal. Algae in oil refinery effluent are less efficient than algae in sewage communities or natural climax communities. The direct effect of temperature on the bioactivity of the oil refinery effluent community was small. The community was moving toward a production/respiration (P/R) ratio of about unity at the end of holding time.

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