The Phosphorus Status of Eutrophic Lake Sediments as Related to Changes in Limnological Conditions—Phosphorus Mineral Components

Abstract

Studies of the relationship between limnological factors and changes in the P status of noncalcareous sediments of a eutrophic lake previously indicated that changes in sediment inorganic P were directly related to the biological productivity of the surface waters. This relationship was particularly pronounced in a shallow bay where sediment P decreased with lake phytoplankton growth and increased with their decline. The present studies were undertaken to identify the inorganic P components responsible for these changes using chemical techniques for characterization of P in sediments where changes occurred.Release of P from sediments during periods of maximal biological productivity in the shallow bay waters was due primarily to reductions in inorganic P mineral components soluble in NaOH (0.1M) and citrate‐dithionite, suggesting that P associated with hydrated Fe oxides was the principal source of P to the overlying waters and to the biota. Increases in sediment inorganic P, which occurred when phytoplankton growth diminished, were due principally to increases in P mineral components soluble in NH4F, indicating that resorbed P was F‐exchangeable and/or associated with crystalline and amorphous Al‐P components. Changes in the form of sediment P which occurred in the lake and in laboratory equilibrium studies, indicated that conversion of resorbed NH4F soluble‐P to NaOH (0.1M) and citrate‐dithionite soluble‐P, must be a relatively long term (>2 years) process. Taken together, the NH4F, NaOH (0.1M), and citrate‐dithionite fractions accounted for approximately 85% of the seasonal variance in total inorganic P which occurred at all sampling locations in the lake system.

Phosphorus Retention in Streams and Wetlands: A Review

“…Depending on the strength of the extracting solution and the fractionation method, bioavailable P has been estimated from such extracts as: 1 M NH 4 Cl (Hieltjes and Lijklema, 1980;van Eck, 1982), 1 M KCl (Reddy et al, 1995a), 0.1 M NaOH (Wildung et al, 1977;Hieltjes and Lijklema, 1980;Ostrofsky, 1987), citrate-bicarbonate-dithionite , and nitrolotriacetic acid (NTA) (Golterman et al, 1969;Gunatilaka et al, 1988). The Ca-bound P (HCl-RP) such as apatite was found to be unavailable (Pettersson, 1986;Gunatilaka, 1988), while the redox-sensitive Fe-bound P may become available under anaerobic conditions (Wildung et al, 1977;Furumai and Ohgaki, 1982;Hosomi et al, 1981).…”

Forms and distribution of inorganic phosphorus in sediments of two shallow eutrophic lakes in Florida

“…Phosphorus removed by the first one or two extracting solutions in a sequential fractionation method is usually considered readily available (Gunatilaka, 1988 ;Psenner et al, 1988) . Depending on strength of extracting solution and fractionation method, readily available P has been estimated from such extracts as : 1 M NH4C1 (Hieltjes & Lijklema, 1980 ;van Eck, 1982), 0 .1 M NaOH (Wildung et al, 1977 ;Hieltjes & Lijklema, 1980 ;Ostrofsky, 1987), citrate-bicarbonatedithionite (Williams et al, 1971), and nitrolotriacetic acid (NTA) (Golterman et al, 1969 ;Gunatilaka et al, 1988) . The Ca-bound P (HCl-P) such as apatite was found to be unavailable (Pettersson, 1986 ;Gunatilaka, 1988), while the redox-sensitive Fe-bound P (NaOH-P) may become available under anaerobic conditions (Wildung et al, 1977 ;Furumai & Ohgaki, 1982 ;Hosomi et al, 1981) .…”

“…Chemical characterization of sediment P in eutrophic lakes provides information on the distribution of various P forms and their potential mobility and bioavailability under prevailing redox potential (Eh) and pH. Lake systems dominated by Fe-bound P, for example, are predicted to release P under anaerobic conditions (Wildung et al, 1977 ;Hosomi et al, 1981) . Similarly, P solubility in lake systems dominated by Ca-bound P are sensitive to changes in pH .…”

Effect of growth and subsequent decomposition of cyanobacteria on the transformation of phosphorus in submerged soils

“…In a similar study with lake sediment, Nalewajko and Lean (1978) observed that during early exponential growth of algae the influx of P from different sources might be less than total P uptake. Wildung et al (1977) also observed such a change in different forms of sediment-P which could be related to P uptake by expanding algal communities. The results, therefore, indicate that cyanobacteria might be able to solubilize P from these difficulty available forms in soils (Brady, 1990) and assimilate it during their growth.…”

“…Growth of cyanobacteria caused a small decrease, which is controversial in view of the fact that growth of cyanobacteria provides a more aerobic environment in soil due to release of photosynthetic 0 2. Wildung et al (1977) observed a decrease in citrate-bicarbonate-dithionite (CBD)-extractable P (considered to be reductant-soluble Fe-P) in lake sediments and suggested such phosphates to be an important source of P for algae, while Lee et al (1980) were of the opinion that P adsorbed onto hydrated oxides of Fe was unavailable for supporting algal growth.…”