Phosphorus in Aquaculture Ponds: Controlling Technique and its Bioavailability to Cyanobacteria

Abstract

Understanding the loading, speciation, and bioavailability of phosphorus (P) in aquaculture ponds is important for controlling P and harmful algal blooms. This thesis first explored flue-gas desulfurization (FGD) gypsum as a P sorption remediation technique and found that FGD gypsum can effectively remove P from water. The loading and speciation of P on different-sized particles in water collected from aquaculture ponds were then examined by the Hedley extraction method using different reagents. The conditionally bioavailable P extracted by NaOH represented the largest P pool (NaOH-P), followed by bioavailable pools of H2O-P and NaHCO3-P. Small colloids (100–450 nm in size) contained the highest total P (TP) and inorganic P (IP) concentrations, while small nanoparticles (1–50 nm) exhibited the highest organic P (OP) concentration. Bioassay experiments for the cyanobacterium Microcystis aeruginosa with the same TP concentration supplied by different-sized particles showed side-induced growth trends and suggest transformation between IP and OP.