Bioavailability of different phosphorus forms in freshwater systems

Abstract

The recent literature on the bioavailability of different forms of P in freshwater systems is reviewed. Bioavailable P is defined as the sum of immediately available P and the P that can be transformed into an available form by naturally occurring processes. Methods used to estimate the bioavailable P pool, which vary between studies largely depending on the time perspective applied, are critically evaluated. Most studies on particulate P aim to determine the potentially available P pool. Potential bioavailability of particulate P is normally analysed in bioassays with algal yield determinations and the available P fraction is characterized from interpretations of results of sequential chemical extractions. NaOHextractable P is in most studies the most algal-available P fraction. For soil samples and 'tributary water particulate matter, NaOH-P has often been found to be equal to algal extractable P. In other studies depletions of NaOH-P have accounted for the algal P uptake, but only a minor proportion of the fraction has been utilized. Organic P in lake water particulate matter and bed sediments of eutrophic lakes can also be algal-available to a significant extent.Studies on the bioavailability of dissolved P have often been concerned with immediate availability, or the minimum amount of available P. Such studies need other types of experimental design and normally assays with radiotracers are used. Immediately available P is frequently found to be less than P chemically assessed as dissolved reactive P (DRP) at low (< 10 pg DRP * l-') concentrations. However, immediate availability may also approach or exceed DRP concentrations, especially at higher concentrations. Potential bioavailability, assayed as for particulate P, may generally render higher bioavailability than P assayed as immediately available. Large fractions of dissolved P remain unutilized and are primarily found in the high molecular weight fraction of dissolved P. Introductionthe total P load on lakes will be available to the lake biota for production of organic matter. In Empirical relations between phosphorus loading, recent years increased attention has therefore phosphorus concentrations and algal biomasses been paid to determinations of the bioavailable or in lakes are normally based on total phosphorus, algal-available proportion of P from different cf. the OECD report on eutrophication of waters sources, with the aim of improving understanding (OECD, 1982). However, it is well known, and of P cycling in lakes, refining empirical models or also stated in the OCED report, than only part of improving lake management strategies.

The role of periphyton in phosphorus retention in shallow lakes with different trophic status, China

“…The actual bioavailability of Fe-P was greater in the two lakes containing higher nutrient levels, Nanhu (59%) and Donghu (46%), than in the ones containing lower nutrient levels, Niuchaohu (44%) and Liangzihu (38%), and Fe-P was the dominant form of phosphorus in all lakes. This finding agreed with a previous study which reported that Fe-P was the most algaeavailable phosphorus fraction (Bostrom et al, 1988). Zhou et al (2001) suggested that Fe-P can be used to estimate the amounts of phosphorus available both in the short term and over the long term (from sediments).…”

“…OP made a relatively minor contribution to total sedimentary phosphorus, compared with that of Fe-P. OP in the superficial sediment only slightly decreased during the experimental period, which suggested that the mineralization process during the entire sampling period was slow (Amirbahman et al, 2013). Several studies have revealed low availability of OP to periphyton (Bostrom et al, 1988). About 60% of the extractable OP was mobile (Rydin, 2000).…”

“…1). Fe-P is an important contributor to TP and is the most bioavailable phosphorus fraction for algae (Bostrom et al, 1988). It can be digested by periphyton directly, delaying the process of eutrophication (Hisashi, 1983;Jensen and Thamdrup, 1993;Tuominen et al, 1999;Ruban et al, 2001a,b;Heisler et al, 2008;Yuan et al, 2014).…”

Iron colloids reduce the bioavailability of phosphorus to the green alga Raphidocelis subcapitata

“…For practical purposes, the bioavailable P is often 54 measured by colorimetric methods and reported as soluble reactive phosphorus (SRP) or 55 dissolved reactive phosphorus (DRP), an approach followed in water quality monitoring 56 programmes worldwide. However, it has been shown that SRP often overestimates the 57 bioavailable P fraction (Boström et al, 1988;Reynolds and Davies, 2001;Rigler, 1968). 58…”

Limnological variations of a deep reservoir in periods with distinct rainfall patterns

“…Indeed, in 2007Indeed, in /2008Indeed, in and in 2008Indeed, in /2009 precipitation values were below the mean and TP concentrations did not increase significantly and were substantially lower than those observed in 2000/2001 and 2001/2002. Despite the lack of data concerning the intensity of those processes in Azibo reservoir, it is plausible that those changes are the result of the balance between the sedimentation rates, nutrient loads and biotic recycling processes (Boström et al, 1988;Catalan and Fee, 1994;Barbosa and Hvitved-Jacobsen, 1999;Rybak, 2000). It should be stressed that Azibo's tributaries are temporary streams and they were almost dried during 2007/2008 and 2008/2009.…”