ABSTRACT
Light effect on cultures of microalgae has been studied mainly on single species cultures. Cyanobacteria have photosynthetic pigments that can capture photons of wavelengths not available to chlorophylls. A native Louisiana microalgae (Chlorella vulgaris) and cyanobacteria (Leptolyngbya sp.) co-culture was used to study the effects of light quality (blue-467 nm, green-522 nm, red-640 nm and white-narrow peak at 450 nm and a broad range with a peak at 550 nm) at two irradiance levels (80 and 400 µmol m-2 s-1) on the growth, species composition, biomass productivity, lipid content and chlorophyll-a production. The co-culture shifted from a microalgae dominant culture to a cyanobacteria culture at 80 µmol m-2 s-1. The highest growth for the cyanobacteria was observed at 80 µmol µmol m-2 s-1 and for the microalgae at 400 µmol m-2 s-1. Red light at 400 µmol m-2 s-1 had the highest growth rate (0.41 d-1), biomass (913 mg L-1) and biomass productivity (95 mg L-1 d-1). Lipid content was similar between all light colors. Green light had the highest chlorophyll-a content (1649 µg/L). These results can be used to control the species composition of mixed cultures while maintaining their productivity.
ABSTRACT
Load duration curves were developed using the Hydrological Simulation Program FORTRAN (HSPF) for dissolved oxygen (DO) for the Amite River in Louisiana, USA. The concept of 'dissolved oxygen reserve', defined as the total quantity of DO, is introduced. The effect of temporal resolution on duration curves of DO reserve was examined using duration curves developed based on daily, weekly, biweekly, and monthly average data. Duration curves for DO exhibited high variability in the load estimated using daily data as compared to those based on biweekly and monthly data. A seasonal analysis revealed the trend in the DO reserve. The daily DO reserve for the Amite River at Port Vincent was 44,049.31 kg when daily summer data were used and 74,255.15 kg for daily annual data. A surplus of 10,691 kg of DO reserve was shown in the monthly data during critical summer months. The coefficient of variation (CV), used to define the temporal scale-induced uncertainty, was found to be linearly and inversely correlated with the logarithm of the time scale. Regression equations were developed to extrapolate near real-time flow and water quality data, greatly simplifying flow and water quality monitoring and reducing the cost involved in flow and water quality monitoring.
