Influence of different cyanobacterial treatment methods on phosphorus cycle in shallow lake microcosms

Abstract

Cyanobacterial bloom is a pressing issue affecting water supply security and ecosystem health. Phosphorus (P) released from cyanobacterial bloom during recession is one of the most important components involved in the lake P cycle. However, little is known about the consequences and mechanisms of the P cycle in overlying water and sediment due to the anthropogenic treatments of cyanobacterial blooms. In this study, treatment methods using hydrogen peroxide (H₂O₂), polyaluminum chloride (PAC), and the feces of silver carp were investigated for their influence on the P cycle using microcosm experiments. Results showed that H₂O₂ treatment significantly increased the internal cycle of sediment-related P, while PAC treatment showed minor effects. H₂O₂ and PAC treatment suppressed the release of P from sediment before day 10 but promoted the release of P on day 20, while silver carp treatment suppressed the release of P during the whole experiment. The reductive dissolution of iron oxide-hydroxide was the major factor affects the desorption of P. Path analyses further suggested that overlying water properties such as dissolved oxygen (DO) and oxidation-reduction potential (ORP) play critical roles in the treatment-induced sediment P release. Our results quantify the endogenous P diffusion fluxes across the sediment-water interface attributed to cyanobacterial treatments and provide useful guidance for the selection of controlling methods, with silver carp being the most recommended of the three methods studied.

Keywords: Algae bloom control; Cyanobacteria; Diffusive gradients in thin films; Eutrophication; Phosphorus cycle.