Nutrient enrichment and its effects on growth and metabolism of chlorella vulgaris and phormidium laminosum

ABSTRACT

In this study, the dry weight and chlorophyll a content of Chlorella vulgaris and Phormidium laminosum progressively increased with elevation of phosphate and nitrate doses supplemented to the culture media. The accumulation of total carbohydrates in both organisms were suppressed at all phosphate levels, but in Phormidium, it was stimulated under nitrate treatments. Both salts singly caused a drop in nitrate uptake which was associated by decrease in protein and total nitrogen contents. All phosphate levels stimulated the phosphorus absorption from the media and the phosphorus contents of both organisms while, the nitrate effect showed no constant trend. Irrespective of some fluctuations there was a clear trend for the mixture effects which are expressed by increase in dry weight, chlorophyll a, total carbohydrate accumulation, nitrate uptake, phosphorus uptake and contents in both algae. Total nitrogen and protein accumulation were adversely affected in most mixture treatments. Lowering the concentration of either phosphate or nitrate in both algal cultures below control levels suppressed the growth and inactivate the physiological processes. The N/P uptake ratios were generally decreased following limitation and/or enrichment with nitrate and phosphate