Biogeochemical Cycling Of Phosphorus Research Articles

Occurrence and ecological implications of pyrophosphate in estuaries

Loading of bioavailable phosphorus, traditionally measured as soluble reactive phosphorus (SRP), contributes to the eutrophication of aquatic ecosystems. However, polyphosphates are also bioavailable but escape detection by the standard method used for measuring SRP. 31P nuclear magnetic resonance spectrometric analysis of sediment extracts and enzymatic assay of surface waters reveal heretofore unreported presence of pyrophosphate (Ppi) in coastal wetlands. We show that the accumulation of Ppi (the smallest chemical form of polyphosphate) in coastal wetlands is related to human impact and can occur in quantities that exceed that of SRP. We further demonstrate that Ppi is readily utilized by microbes in coastal wetland sediments in the presence of nitrogen and carbon and can serve as a reservoir of orthophosphate. Thus, Ppi accumulation in estuaries will subsidize the in situ biogeochemical phosphorus cycle. This has important ecological implications for trophic responses and estuarine productivity.

The biogeochemical cycling of phosphorus in marine systems

The cycling of phosphorus (P) in the ocean has long been viewed from a geological perspective that tends to focus on balancing P sources (riverine and atmospheric) and sinks (sedimentary burial) over long (>1000 years) time scales. There have been substantially fewer treatises, however, that have sought to review current understanding of the processes which effect the distribution of P between these two endpoints. In this paper, a comprehensive review of the biogeochemical cycling of P within the oceans is given, with particular attention focused on the composition and recycling rates of P within the water column.

Effects of Dinitrogen‐Fixing Trees on Phosphorus Biogeochemical Cycling in Contrasting Forests

AbstractPhosphorus availability in soils is controlled by both geochemical and biological reactions. Dinitrogen‐fixing trees differ from non‐N2‐fixing trees in litter production and litter chemistry, and these differences may substantially alter soil P biogeochemistry. We examined the effects of two N2‐fixing tree species on labile P pools and potential P transformation rates and correlated these variables with soil acid phosphatase activity. Experimental treatments include stands of N2‐fixing red alder (Alnus rubra Bong.), conifers, and a mixture of both in Oregon, and plantations of N2‐fixing Albizia falcataria (L.) Fosberg, Eucalyptus saligna Sm., and a mixture of both in Hawaii. Data from Oregon indicated that red alder increased labile organic P (Po) levels and soil phosphatase activity. Soil labile Po concentrations in the red alder and mixed stands were twice those of the conifer stand. Labile inorganic P (Pi) pools and net P solubilization rates in soils under the mixed stand were two‐ to fivefold greater than in pure stands, suggesting that interactions between alder and conifers, rather than alder's effect, triggered changes in P geochemical reactions. In Hawaii, labile Po concentrations in both pure A. falcataria and mixed plantations were higher than in the pure E. saligna plantation. Soil acid phosphatase activity in the pure A. falcataria plantation was twice as high as that in the pure E. saligna plantation. However, labile Pi pools and P transformation rates did not differ among the three Hawaiian plantations. Our results suggest that N2‐fixing trees increase soil labile Po levels and soil phosphatase activities whereas their interactions with non‐N2‐fixing trees vary with species and may result in altering both geochemical and biological P transformations.

Transformation of particle-bound phosphorus at the land-sea interface

The distribution of phosphorus was examined along the salinity gradient of the Chesapeake Bay estuary during spring and summer in 1989 and 1990. Particulate phosphorus (PP) was the dominant form of phosphorus in the estuary accounting for 23–90% of total phosphorus (TP). Particulate phosphorus was highest in the upper estuary (0.42–1.84 μM) and rapidly decreased in concentration in the upper bay with only slight decreases observed down-estuary. Dissolved organic phosphorus (DOP) often comprised a somewhat larger fraction of the TP (8–43%) than did dissolved inorganic phosphorus (DIP; 5–40%) with DOP and DIP concentrations highest in bottom waters during summer anoxia. Both DIP and DOP concentrations were maintained at relatively low levels in surface waters by plankton, especially during the spring phytoplankton bloom. The distribution of particle-bound phosphorus in the suspended matter of the Chesapeake Bay was partitioned by a sequential chemical leaching technique into three major fractions: (1) an organic and loosely-bound fraction (Org-P), (2) an iron-associated fraction extracted with citrate-dithionate-bicarbonate (CDB-P), and (3) a detrital (apatite rich) fraction extracted with hydrochloric acid (HCl-P). The particle-bound phosphorus was associated mainly with Org-P (43–61%), followed by CDB-P (32–46%), with HCl-P generally comprising only a small fraction of the total particle-bound phosphorus (5–13%). The majority of changes in the composition of the particle-bound phosphorus occurred early in the transition from fresh- to saltwater with declines in both iron-associated phosphorus (CDB-P) and apatite-associated phosphorus (HCl-P). The ratios of CDB-Fe to CDB-P in suspended matter were relatively low suggesting that the particulate matter of Chesapeake Bay has a low capacity to absorb additional phosphorus through interactions with iron. Biological processes in the bay were much more important to the biogeochemical cycle of phosphorus than in many other estuaries previously examined for phosphorus biogeochemistry. Although inorganic exchange reactions may occur, they do not have the capacity to ‘buffer’ DIP concentrations throughout the Chesapeake Bay estuary.

Release of Bacterial DNA by Marine Nanoflagellates, an Intermediate Step in Phosphorus Regeneration

The concentrations of dissolved DNA and nanoflagellates were found to covary during a study of diel dynamics of the microbial food web in the Adriatic Sea. This observation was further investigated in a continuous seawater culture when nanoflagellates were fed bacteria grown in filtered seawater. Analysis of dissolved organic phosphorus and dissolved DNA showed a sixfold increase of dissolved DNA in the presence of the nanoflagellates (Ochromonas sp.). The amount of DNA released suggested that the majority of the consumed bacterial DNA was ejected. Phagotrophic nanoflagellates thus represent an important source of origin for dissolved DNA. The rate of breakdown of dissolved DNA and release of inorganic phosphorus in the pelagic ecosystem is suggested to be dependent on the ambient phosphate pool. In the P-limited northern Adriatic Sea, rapid degradation of the labelled DNA could be demonstrated, whereas the N-limited southern California bight water showed a much lower rate. Phosphorus originating from dissolved DNA was shown to be transferred mainly to organisms in the <3-mum-size fractions. On the basis of the C/P ratios, we suggest that a significant fraction of the phosphorus demand by the autotrophs may be sustained by the released DNA during stratified conditions. Thus, the nucleic acid-rich bacterial biomass grazed by protozoa plays an important role in the biogeochemical cycling of phosphorus in the marine environment.

Fluorine-induced chemiluminescence detection of phosphine, alkyl phosphines and monophosphinate esters

Phosphine, alkylated phosphines and monophosphinate esters are detected with high sensitivity in capillary gas chromatography (GC) by their chemiluminescent reactions with molecular fluorine. Detection limits are estimated to be 1.3 pg, 0.5 pg, 8 pg, and 17 pg for phosphine, trimethyl phosphine, trimethyl phosphinate ester, and triethyl phosphine, respectively. As found earlier with alkylated sulfur, selenium and tellurium compounds, the detector exhibits a linear response. For triethyl phosphine, a linear range of greater than three orders of magnitude was demonstrated. Emission spectra were obtained for the trimethyl phosphine and triethyl phosphine systems. Chemiluminescence emitters include electronically excited HCF, vibrationally excited HF, and an unknown species in the trimethyl phosphine system. Banded emission from vibrationally excited HF and a broad continuum were observed for both trimethyl phosphine and triethyl phosphine; however, HCF emission was observed only for TMP. Under the conditions employed, the principal emitter is HCF for trimethyl phosphine and HF and the unknown emitter for triethyl phosphine. This detector may have important applications in investigations of the biogeochemical cycling of phosphorus.

A model of biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in the ocean: One step toward a global climate model

An ocean model has been developed which, for prescribed physics, deals with interrelationships between chemical distributions, biogeochemical sinks and sources, chemical reactions at redox fronts, and transports across the air‐sea and sediment‐water interfaces. In its first application here, the model focuses on biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in an ocean forced by river input of nutrients. This is a natural starting point for a global climate model since ocean circulation and biology determine atmospheric CO2 concentrations for a given inventory of inorganic C and oceanic production is controlled mainly by the availability of inorganic P and/or N. A general approach is taken to look at oxic versus anoxic conditions, P versus N limitation of primary production, with or without inorganic removal of phosphate to the sediments. As demanded by this approach, the model is nonlinear and continuous in a vertical coordinate. To focus on the biogeochemical aspects, ocean physics are kept as simple as possible. Cold, oxygen‐rich water sinks at high latitudes and is upwelled with a constant velocity. Turbulent mixing is parameterized with a constant, vertical diffusion coefficient. The biogeochemical processes considered are new production, burial, nitrogen fixation, phosphorite formation, and three types of organic decomposition: oxidation with O2, denitrification, and sulphate reduction. Organic matter is taken to consist of a high‐ and a low‐reactive fraction. The chemical species considered explicitly are PO43−‐P, NO3−‐N, O2, NH4+‐N and H2S‐S. Results indicate that a change from oxic to weakly anoxic conditions at middepths in a P‐limited ocean would lead to strong local denitrification and low nitrate concentrations throughout the water column. New production would also become dominated by nitrogen fixers. Geological evidence implies that anoxic conditions in the water column have been rare in the Phanerozoic ocean. Both phosphorite formation (for P limitation) and denitrification (for N limitation) can strongly constrain primary production and the development of anoxia. N limitation, i.e., negligable nitrogen fixation, practically precludes anoxia but is unlikely for very long times scales. For P limitation and no phosphorite formation the model indicates that the redox state of the ocean may be most sensitive to changes in ocean biology followed by changes in ocean circulation and mixing and finally by changes in ocean temperature.

Diversity and phosphate solubilization by bacteria isolated from Laki Island coastal ecosystem

Widawati S. (2011). Diversity and phosphate solubilization by bacteria isolated from Laki Island coastal ecosystem. Biodiversitas 12: 1721. Soil, water, sand, and plant rhizosphere samples collected from coastal ecosystem of Laki Island, Jakarta, Indonesia were screened for phosphate solubilizing bacteria (PSB). While the population was dependent on the cultivation media and the sample type, the highest bacterial population was observed in the rhizosphere of Ipomoea aquatica. The PSB strains isolated from the sample registered 18.59 g-1 L-1. 18.31 g-1 L-1, and 5.68 g-1 L-1 of calcium phosphate (Ca-P), Al-P and rock phosphate solubilization after 7-days. Phosphate solubilizing capacity was the highest in the Ca-P medium. Two strains, 13 and 14, registered highest phosphomonoesterase activities (2.01 µgNP.g-1.h-1 and 1.85NP µg.g-1.h-1) were identified as Serratia marcescens, and Pseudomonas fluorescens, respectively. Both strains were isolated from the crops of Amaranthus hybridus and I. aquatica, respectively, which are commonly observed in coastal ecosystems. The presence of phosphate solubilizing microorganisms and their ability to solubilize various types of phosphate species are indicative of the important role of both species of bacteria in the biogeochemical cycle of phosphorus and the plant growth in coastal ecosystems.