Consuming toxins produced by algal species in running waters and freshwater bodies can have deleterious effects on fish and other aquatic organisms. These toxins are produced by harmful algal blooms (HAB) of cyanobacteria in water. These blooms can be caused by several factors including light, temperature, carbon dioxide, phosphorous and nitrogen.
The effects of different concentrations of phosphorous on stimulating and inhibiting growth in cyanobacterial species Jaaginema sp. was studied in this paper. Pure cultures of Jaaginemasp. were cultured in two culture media (Z8 and BG11) using two different concentrations of phosphorous. Four replicates were run for each experimental group and one control group with normal concentration of phosphorous was also studied. Water temperature was 25 ± 1°C and light intensity was 2200 lux. Observations were made once every 48 h. This species appeared yellow in the BG11 medium and green in the Z8 medium. Counting was made using a hemocytometer and the microscopic observations were made under a light microscope. Results obtained were analyzed using computer based software like SPSS and Excel. Growth rates in the cyanobacterium species were significantly higher in the treatment with phosphorous concentrations of two times the original concentration. Higher concentrations of phosphorous resulted in inhibiting growth in this species. It is evident from the results obtained that phosphorous can be considered a growth inhibiting factor for cyanobacteria and thus influence the occurrence of blooms and release of toxins into water bodies.