Phosphorus dynamics in sediments of a eutrophic lake derived from 31P nuclear magnetic resonance spectroscopy

Abstract

Abstract. The determination of organic phosphorus (P) compounds in lake sediments can provide information on the potential for internal P loading. Settling seston and vertical sediment core samples from highly eutrophic Lake Okaro, New Zealand, were collected during a mixed winter and stratified summer period, representing, respectively, when the water column was well oxygenated and when the bottom waters were anoxic. Samples were analysed with 31 P nuclear magnetic resonance ( 31 P NMR) spectroscopy, which showed that both bottom sediments and settling seston contained orthophosphate, orthophosphate monoesters and diesters, pyrophosphates, polyphosphates and phosphonates. Phosphorus concentration in settling seston increased ,2.5-fold in winter as a result of seasonally induced changes in phytoplankton biomass, with a marked increase in the concentration of orthophosphate. Several potentially bioavailable P compounds in the bottom sediments were identified that were likely to contribute to recycling of P from the sediment to the water column. An 'apparent half-life' was used to quantify the time scales on which these compounds were recycled to the overlying water column. Orthophosphate monoesters that include inositol phosphates were the most persistent P compound. On the basis of half-lives, high internal P loadings may persist for more than 20 years, potentially hindering restoration efforts in Lake Okaro.

Characterization of Organic Phosphorus Form and Bioavailability in Lake Sediments using31P Nuclear Magnetic Resonance and Enzymatic Hydrolysis

“…Large proportions of monoester and diester P compounds have been detected in settling lake seston (Ozkundakci et al, 2014; Reitzel et al, 2012), suggesting that the deposition of algal biomass in July, August, and October 2008 may have contributed to the large proportions of monoesters detected in the surface layer of these cores. In the current study, there were no apparent differences among particulate P species collected in 1‐ and 4‐m depth traps (Table 3, 4).…”

Role of organic phosphorus in sediment in a shallow eutrophic lake

“…In addition to these hypotheses about inorganic P, results with recent advances in analytical techniques, such as 31 P nuclear magnetic resonance analysis, have introduced into the debate the role of organic P in lake sediment [ Ahlgren et al ., ; Reitzel et al ., ; Jørgensen et al ., ]. By using 31 P nuclear magnetic resonance analysis, researchers have found that the concentrations of organic P compounds in the sediment particles (e.g., orthophosphate monoesters and diesters) decrease with increasing depth in the sediment [ Ahlgren et al ., ; Reitzel et al ., ; Özkundakci et al ., ]. These findings suggest that organic P in the sediment particles plays a role as a source of molybdenum unreactive P (MUP, most of which is organic P) in the pore water [ Ahlgren et al ., ; Reitzel et al ., ; Özkundakci et al ., ].…”

“…By using 31 P nuclear magnetic resonance analysis, researchers have found that the concentrations of organic P compounds in the sediment particles (e.g., orthophosphate monoesters and diesters) decrease with increasing depth in the sediment [ Ahlgren et al ., ; Reitzel et al ., ; Özkundakci et al ., ]. These findings suggest that organic P in the sediment particles plays a role as a source of molybdenum unreactive P (MUP, most of which is organic P) in the pore water [ Ahlgren et al ., ; Reitzel et al ., ; Özkundakci et al ., ].…”

Phosphorus and arsenic distributions in a seasonally stratified, iron- and manganese-rich lake: microbiological and geochemical controls

“…Consequently, sedimentary fluxes of P are a major contributor to total P loading in receiving water bodies [11] . Once present in the bottom sediments of quiescent water bodies, such as lakes, sedimentary P and As can be released by the weathering of aluminosilicates such as allophane [12][13][14][15][16][17] , through cycling between organic-P and orthophosphate species [18] , and by desorption from Fe and Mn hydroxide surfaces [19,20] undergoing reductive dissolution [21] . Although the ultimate sources of P within catchments are relatively well known [11,22] , a complete picture of the processes controlling the cycling and bioavailability of P in lakes, including P speciation, remains elusive [11,[23][24][25] , largely due to the complexity of interactions between hydrologic, geochemical and microbiological factors [25] .…”