Phosphorus released from sediment of Dianchi Lake and its effect on growth of Microcystis aeruginosa

Abstract

Phosphorus stored in lake sediments is an inner nutrient source and can be released into overlying water to exacerbate algal blooms. A simulated microcosm of Dianchi Lake was built to investigate phosphorus release from sediments to overlying water and its effect on the growth of Microcystis aeruginosa. The sediments of Dianchi Lake had a total phosphorus (TP) content of 1.7-1.8 mg g(-1) with Ca bound phosphorus (Ca-P, 50-54 %) and organic phosphorus (Org-P, 28-32 %) as the main fractions. The sediments released 8 % of TP into the overlying water with Fe/Al bound phosphorus (Fe/Al-P, 26 %) and Org-P (65 %) being the main fractions released. The phosphorus concentration of the overlying water increased from 0.14-0.16 to 0.28-0.33 mg L(-1). The biomass density of M. aeruginosa was positively correlated (R (2) = 0.825) with the concentration of orthophosphate, which was the predominant bioavailable phosphorus fraction for algal growth. Org-P can be partly utilized by M. aeruginosa but will not cause a bloom. A good understanding of the geochemical cycles of phosphorus is needed for regulating phosphorus release from sediments and thereby reducing the risk of cyanobacterial blooms.

Periphyton: an important regulator in optimizing soil phosphorus bioavailability in paddy fields

“…4). Ca-P is usually regarded as the most thermodynamically stable mineral-bound P form (Liu et al 2016b). Normally, Ca-P cannot be considered as exchangeable P fraction unless there is a dramatic change in sediment pH accompanied by dissolution of metal oxides (Rzepecki 2010).…”

“…However, P is the major contributor to eutrophication and is directly responsible for nuisance and harmful algal blooms in surface waters (Smith and Schindler 2009). Accordingly, P discharge into natural waterways must be controlled (Liu et al 2016b), but is usually hard to control from the nonpoint sources, such as agricultural runoff. Consequently, a substantial amount of P is brought from cropland into surrounding aquatic ecosystems such as lakes, streams, and rivers (Ulén et al 2007).…”

Mechanisms of enhanced inorganic phosphorus accumulation by periphyton in paddy fields as affected by calcium and ferrous ions

“…Therefore, periphyton could accumulate P i through bio-sorption, including assimilation, entrapment, and adsorption as mentioned above, even when no Ca(II) was added ( Fig. 2A) (Liu et al, 2016a(Liu et al, , 2016bDodds, 2003;Lu et al 2014Lu et al , 2016b. Photosynthetic-driven changes in pH are likely the driver for P i uptake under light conditions.…”

“…Moreover, periphyton can induce oxidation of Fe(II) generated in paddy soils under low redox conditions to Fe(III), thereby inducing abiotic accumulation of P i as Fe(III) phosphate or phosphate adsorbed on newly formed ferric hydroxides. These forms of P i are generally regarded as bioavailable through desorption, ligand exchange, or reductive dissolution (Liu et al, 2016b). Fortunately, P i accumulation induced by 1.2 mM Ca(II) and 0.2 mM Fe(II) were comparable, and thus the capacity of enhanced abiotic P i accumulation induced by Fe(II) was much more efficient than that of Ca(II).…”

“…Abiotic P i accumulation by periphyton can be enhanced by Ca(II) addition, apparently via Ca-phosphate precipitation and co-precipitation with carbonate at pH N 8. These Ca-phosphates are thermodynamically stable (Liu et al, 2016b) and non-bioavailable until the pH of the periphyton micro-environments decreases, for example during respiration or oxidation of Fe(II) (Rzepecki, 2010). Moreover, periphyton can induce oxidation of Fe(II) generated in paddy soils under low redox conditions to Fe(III), thereby inducing abiotic accumulation of P i as Fe(III) phosphate or phosphate adsorbed on newly formed ferric hydroxides.…”