Nutrient conversions by photosynthetic bacteria in a concentrated animal feeding operation lagoon system

A diurnal examination was conducted to determine the effect of photosynthet ic bacteria on nutrient conversions in a two-stage concentrated animal feed ing operation (CAFO) lagoon system in west-central Oklahoma. Changes in nut rients, microbial populations, and physical parameters were examined at thr ee depths (0, 1.5, and 3.0 m) every 3 h over a 36-h period. The south lagoo n (SL) was anaerobic (dissolved oxygen [DO] = 0.09 +/- 0.12 mg/L) while the north lagoon (NL) was facultative (DO ranged from 4.0-0.1 mg/L over 36-h p eriod). Negative sulfide-sulfate (-0.85) and bacteriochlorophyll a (bchl a) sulfate (-0.83) correlations, as well as positive bchl a-sulfide (0.87) and light intensity (I)-bchl a (0.89) correlations revealed that the SL was do minated by sulfur conversions driven by the photosynthetic purple sulfur ba cteria (PSB). The correlation data was supported by diurnal trends for sulf ate, sulfide, and bchl a. Both nitrogen and sulfur conversions played a rol e in the NL; however, nitrogen conversions appeared to dominate this system because of the activity of cyanobacteria. This was shown by positive chlor ophyll a (chl a)-I (0.91) and chi a-nitrate (0.98) correlations and the neg ative correlation between ammonium and nitrite (-0.88). Correlation data wa s further supported by diurnal trends observed for chi a, DO, and ammonium. For both lagoons, the dominant photosynthetic microbial species determined which nutrient conversion processes were most important.