Effects of cyanobacterial growth and decline on dissolved organic matter and endogenous nutrients release at the sediment–water interface

Abstract Understanding the interactions between dissolved organic matter (DOM) and nutrient behavior during cyanobacterial events has important implications for water management. Therefore, we constructed a simulated cyanobacterial growth and decline experiment, measured the changes in the DOM and the nitrogen and phosphorus fluxes at the sediment–water interface (SWI), and examined the effects of cyanobacterial growth and decline on DOM components and nitrogen and phosphorus release. Results of 3D fluorescence spectroscopy showed that the fluorescent components of DOM in the sediment and overlying water comprised microbially derived humic-like C1, terrestrially derived humic-like C2, tyrosine-like C3, and tryptophan-like C4. From initial cyanobacterial growth to the blooms phase, C3 and C4 in overlying water increased due to the formation and release of extracellular algal-derived organic matter. During the cyanobacterial growth and decline, protein-like C3 and C4 in sediment increased from the settling of algae. The rapid increase in phosphorus fluxes during the blooms stage indicated that cyanobacterial growth promoted the release of phosphorus from sediments through organic phosphorus mineralization and Fe/Al-P transformation. High ammonium fluxes occurred at the initial cyanobacterial growth mainly due to the mineralization of organic matter in sediments. Redundancy analysis showed that changes in the sediment DOM were primarily associated with the loss on ignition and cyanobacterial blooms promoted the release of DOM into the water. This study provides fresh perspectives on the associations between DOM and nutrient behavior during cyanobacterial growth and decline and has strong implications for internal pollution management. Graphical Abstract