Showing papers on "Phosphorus published in 1998"

Phosphorus Uptake by Plants: From Soil to Cell

Abstract: P is an important plant macronutrient, making up about 0.2% of a plant's dry weight. It is a component of key molecules such as nucleic acids, phospholipids, and ATP, and, consequently, plants cannot grow without a reliable supply of this nutrient. Pi is also involved in controlling key enzyme

The role of phosphorus in the eutrophication of receiving waters: a review

Abstract: Phosphorus (P) is an essential element for all life forms, It is a mineral nutrient Orthophosphate is the only form of P that autotrophs can assimilate Extracellular enzymes hydrolyze organic forms of P to phosphate Eutrophication is the overenrichment of receiving waters with mineral nutrients The results are excessive production of autotrophs, especially algae and cyanobacteria This high productivity leads to high bacterial populations and high respiration rates, leading to hypoxia or anoxia in poorly mixed hottom waters and at night in surface waters during calm, warm conditions Low dissolved oxygen causes the loss of aquatic animals and release of many materials normally hound to hottom sediments including various forms of P This release of P reinforces the eutrophication Excessive concentrations of P is the most common cause of eutrophication in freshwater lakes, reservoirs streams, and headwaters of estuarine systems In the ocean, N becomes the key mineral nutrient controlling primary production Estuaries and continental shelf waters are a transition zone, where excessive P and N create prohlems It is best to measure and regulate total P inputs to whole aquatic ecosystems, but for an easy assay it is hest to measure total P concentrations, induding particulate P, in surface waters or NIP atomic ratios in phytoplankton

Effects of plant composition and diversity on nutrient cycling

Abstract: We evaluated the effects of plant functional group richness on seasonal patterns of soil nitrogen and phosphorus cycling, using serpentine grassland in south San Jose, California. We established experimental plots with four functional types of plants: early-season annual forbs (E), late-season annual forbs (L), nitrogen-fixers (N), and perennial bunchgrasses (P). These groups differ in several traits relevant to nutrient cycling, including phenology, rooting depth, root:shoot ratio, size, and leaf C:N content. Two or three species of each group were planted in single functional group (SFG) treatments, and in two-, three-, and four-way combinations of functional groups. We analyzed available nutrient pool sizes, microbial biomass nitrogen and phosphorus, microbial nitrogen immobilization, nitrification rates, and leaching losses. We used an index of “relative resource use” that incorporates the effects of plants on pool sizes of several depletable soil resources: inorganic nitrogen in all seasons, availabl...

Influence of iron availability on nutrient consumption ratio of diatoms in oceanic waters

Abstract: The major nutrients (nitrate, phosphate and silicate) needed for phytoplankton growth are abundant in the surface waters of the subarctic Pacific, equatorial Pacific and Southern oceans, but this growth is limited by the availability of iron1,2,3,4,5. Under iron-deficient conditions, phytoplankton exhibit reduced uptake of nitrate6 and lower cellular levels of carbon, nitrogen and phosphorus7. Here I describe seawater and culture experiments which show that iron limitation can also affect the ratio of consumed silicate to nitrate and phosphate. In iron-limited waters from all three of the aforementioned environments, addition of iron to phytoplankton assemblages in incubation bottles halved the silicate:nitrate and silicate:phosphate consumption ratios, in spite of the preferential growth of diatoms (silica-shelled phytoplankton). The nutrient consumption ratios of the phytoplankton assemblage from the Southern Ocean were similar to those of an iron-deficient laboratory culture of Antarctic diatoms, which exhibit increased cellular silicon or decreased cellular nitrogen and phosphorus in response to iron limitation. Iron limitation therefore increases the export of biogenic silicon, relative to nitrogen and phosphorus, from the surface to deeper waters. These findings suggest how the sedimentary records of carbon and silicon deposition in the glacial Southern Ocean8 can be consistent with the idea that changes in productivity, and thus in drawdown of atmospheric CO2, during the last glaciation were stimulated by changes in iron inputs from atmospheric dust.

P limitation of heterotrophic bacteria and phytoplankton in the northwest Mediterranean

Abstract: Surface-water microbial populations were investigated in the northwest Mediterranean for possible indicators of phosphate deficiency and limitation. Low phosphorus availability was suggested by short turnover time (min. observed 0.68 h), high-alkaline phosphatase activity (V,,,,, = 28 nM hydrolyzed h-l), subsaturation of phosphate uptake (2.6-9% of V,,,), and high-pulse uptake capacity of added orthophosphate. Based on high pulse uptake capacity and subsaturated uptake in both the >l-pm and in the 0.2-l-pm size fractions, P deficiency is suggested for both phytoplankton and heterotrophic bacteria. P limitation of heterotrophic bacteria was also supported by fast positive responses after phosphate addition in both thymidine incorporation in whole-water samples and increased bacterial cell numbers in predator-free water. No effects were found after addition of carbon or nitrogen sources alone. Combined with other published evidence, we suggest that the growth rates of not only phytoplankton, but also of heterotrophic bacteria, are P limited in this environment in summer. The finding has important implications for the dynamics of accumulation of dissolved organic carbon in the photic zone and thus for the carbon cycle of oceans. The generally oligotrophic state of the Mediterranean Sea has traditionally been explained as a consequence of its antiestuarine circulation; the net evaporation from the Mediterranean produces an inflow of low-nutrient surface water through the Gibraltar and an eastward surface current in the Mediterranean (Redfield et al. 1963). If one combines an assumption of nitrogen-limited growth in the inflowing Atlantic water with the usual assumption of a faster recycling of phosphorus than of nitrogen, one might expect a strong nitrogen limitation in the upper photic zone during Mediterranean summer stratification. Contrary to such an expectation, accumulated experimental data seem to indicate that parts of the Mediterranean are characterized by a nitrate : phosphate ratio below Redfield (Krom et al. 1991). This seems to be particularly prominent in the eastern parts of the Mediterranean (Krom et al. 1991) and in the Adriatic Sea (Vukadin and Stojanski 1976). In an investigation of orthophosphate uptake in surface water from Villefranche Bay on the French Mediterranean coast, Dolan et al. (1995) found relatively short turnover times (down to 1.6 h). Estimates of bioavailable orthophosphate concentrations in this area (Thingstad et al. 1995) are also very low (0.8 nM), indicating, but not proving, that P may be the limiting nutrient also in this part of the western Mediterranean. The underlying biogeochemical mechanisms behind such an apparent shift toward P deficiency seem still to be unknown,

Marine phosphorus is selectively remineralized

Abstract: Phosphorus is a vital nutrient of the world's oceans1,2, where in vast regions it is associated with dissolved organic matter (DOM) in surface waters3,4. We have characterized the major compound classes of high-molecular-weight marine dissolved organic phosphorus, phosphorus esters and phosphonates, by using tangential-flow ultrafiltration and phosphorus-31 nuclear magnetic resonance (31P NMR). We find that the composition and abundance of organic phosphorus in DOM differ significantly from the values in fresh organic matter, indicating that dissolved organic phosphorus (DOP) is preferentially remineralized from DOM.

Forms of phosphorus transfer in hydrological pathways from soil under grazed grassland

Abstract: Phosphorus (P) from soil can impair the water quality of streams and lakes. We have studied the forms and pathways of its movement from soil to water using 1-ha plot lysimeters, managed as grazed grassland for 12 months in temperate South-west England. The water flow through three pathways, namely (i) surface plus interflow to 30 cm (on undrained soil), (ii) surface plus interflow to 30 cm (on a mole and tile drained soil), and (iii) mole and tile drains (to 85 cm), were gauged. Samples of water from each path were treated with various combinations of 0.45-mu m filtration and sulphuric acid-persulphate digestion and molybdate reaction, to determine the different forms of P. The total P (TP) concentration was greatest in the surface plus interflow to 30 cm paths (means 232 and 152 mu g l(-1)), whereas the mean concentration in the drainage to 85 cm was 132 mu g l(-1). This reflects the substantial enrichment of the Olsen-P extracts from the surface horizons, as extracts from the 0-2 cm layer were 10-fold more than below 45 cm. In all paths, the dissolved P comprised the greatest proportion of the P transferred, with dissolved reactive P being the dominant form. Draining land reduced the transfer of TP by about 30% (approximate to 1 kg(-1) ha(-1) year(-1)), because it can be sorbed as it flows through soil to drains. All these concentrations could cause eutrophication in surface waters.

Burial efficiency of phosphorus and the geochemistry of iron in continental margin sediments

Abstract: We have examined the distributions of phosphorus and iron in sediments from well-oxygenated environments on the Atlantic Canadian and the Portuguese continental margins and from the anoxic region of the Chesapeake Bay. The measurements include total, citrate-dithionite-bicarbonate (CDB) extractable, ascorbate extractable, and dissolved P and Fe; acid volatile sulfide; and pyrite. A surface layer (varying in thickness between 2 and 4 cm) enriched in P and Fe was revealed by both the CDB and the ascorbate extractions in all sediments except those from the Chesapeake Bay. The amount of phosphate extracted by the two reagents was similar, but more iron was extracted by the CDB reagent, probably because of its ability to dissolve crystalline iron oxides. Within the Feand P-enriched surface layer, the Fe : P ratio in the ascorbate extract varied within a narrow range (6-14), as did the soluble-reactive phosphate (SRP) concentration (5-16 PM), suggesting that SRP is in sorption equilibrium with the solid phase. Our data are consistent with a dynamic cycling of P and strong interactions between the cycles of P, Fe, and sulfur in many marine environments. The reductive dissolution of amorphous Fe during burial and the formation of pyrite diminish the capacity of the sediment to sequester P, and only a portion of the P that arrives at the sediment-water interface actually gets buried with the sediment.

Nitrogen- versus phosphorus-limited growth and sources of nutrients for coral reef macroalgae

Abstract: Recent investigations of nutrient-limited productivity in coral reef macroalgae have led to the conclusion that phosphorus, rather than nitrogen, is the primary limiting nutrient. In this study, comparison of the dissolved inorganic nitrogen:phosphorus ratio in the water column of Kaneohe Bay, Hawaii, with tissue nitrogen:phosphorus ratios in macroalgae from Kaneohe Bay suggested that nitrogen, rather than phosphorus, generally limits productivity in this system. Results of nutrient-enrichment experiments in a flow-through culture system indicated that inorganic nitrogen limited the growth rates of 8 out of 9 macroalgae species tested. In 6 of the species tested, specific growth rates of thalli cultured in unenriched seawater from the Kaneohe Bay water column were zero or negative after 12 d. These results suggest that, in order to persist in low-nutrient coral reef systems, some macroalgae require high rates of nutrient advection or access to benthic nutrient sources in addition to nutrients in the overlying water column. Nutrient concentrations in water samples collected from the microenvironments inhabited or created by macroalgae were compared to nutrient concentrations in the overlying water column. On protected reef flats, inorganic nitrogen concentrations within dense mats of Gracilaria salicornia and Kappaphycus alvarezii, and inorganic nitrogen and phosphate concentrations in sediment porewater near the rhizophytic algae Caulerpa racemosa and C. sertularioides were significantly higher than in the water column. The sediments associated with these mat-forming and rhizophytic species appear to function as localized nutrient sources, making sustained growth possible despite the oligotrophic water column. In wave-exposed habitats such as the Kaneohe Bay Barrier Reef flat, water motion is higher than at protected sites, sediment nutrient concentrations are low, and zones of high nutrient concentrations do not develop near or beneath macroalgae, including dense Sargassum echinocarpum canopies. Under these conditions, macroalgae evidently depend on rapid advection of low-nutrient water from the water column, rather than benthic nutrient sources, to sustain growth.

Pre-polymerised inorganic coagulants and phosphorus removal by coagulation - A review

Abstract: This paper reviews the use of pre-polymerised inorganic coagulants in water and waste-water treatment, and discusses the remova l of phosphorus by chemical precipitation and coagulation. Commonly used inorganic coagulants are aluminium or iron (III) based salts, but a range of hydrolysed Al/Fe species, and not the Al/Fe salt itself, are responsible for the removal of impurities fr om water. By the development and use of polymeric inorganic coagulants, the coagulation performance can be improved significantly in some cases. Chemical precipitation and coagulation in phosphorus removal are two different processes, with the former related t o the compound solubility and the latter depending on the destabilisation-adsorption mechanism. Presently, there is uncertainty concerning the mechanisms and overall performance of phosphorus removal by pre-polymerised metal coagulants.

Laboratory Development of Permeable Reactive Mixtures for the Removal of Phosphorus from Onsite Wastewater Disposal Systems

Abstract: Laboratory batch and column studies were conducted to develop permeable reactive mixtures to remove phosphorus from the effluent of onsite wastewater disposal systems. Mixtures can be placed in situ, as horizontal or vertical reactive barriers in sediments receiving wastewater discharge, or can be used in single pass, self-contained treatment modules in alternative treatment systems. Reactive mixtures composed of silica sand, high calcium crushed limestone, and readily available metal oxides were tested to evaluate phosphorus attenuation. Iron/calcium oxides, produced from steel manufacturing, and fine-grained activated aluminum oxide outperformed other oxides tested during batch experiments. These materials removed greater than 99% of PO4 from a 10 mg/L PO4−P solution within 1 h of contact. Long-term attenuation capacities of the mixtures were assessed by continually loading bench-scale columns with a 3.3 mg/L PO4−P solution, at representative groundwater flow rates. A column containing 50 wt % silica sa...

Effect of buffering on the phosphate-solubilizing ability of microorganisms

Abstract: Native microflora present in the alkaline vertisols and two phosphate-solubilizing bacteria (PSB) isolated from soil using conventional screening media could not release phosphorus from alkaline Indian vertisol soils supplemented with carbon and nitrogen sources. The two PSBs could solubilize both rock phosphate and di-calcium phosphate in unbuffered media but failed to solubilize rock phosphate in buffered media. The organic acids secreted by these PSBs were 20-50 times less than that required to solubilize phosphorus from alkaline soil.

Soil-plant interactions in a neotropical mangrove forest: iron, phosphorus and sulfur dynamics.

Abstract: We examined soil porewater concentrations of sulfate, alkalinity, phosphorus, nitrogen, and dissolved organic carbon and solid phase concentrations of pyrite in relation to mangrove species distributions along a 3.1-km-long transect that traversed a 47.1-km2 mangrove forest in the Dominican Republic. Iron, phosphorus, and sulfur dynamics are closely coupled to the activity of sulfate-reducing bacteria, the primary decomposers in anoxic soils of mangrove ecosystems. Patterns in the chemistry data suggested that sulfate reduction rates and storage of reduced sulfur were greater in the inland basin forest dominated by Laguncularia racemosa than the Rhizophora mangle dominated forest of the lower tidal region. The distribution of Laguncularia was significantly correlated with concentrations of total phosphorus (r= 0.99) and dissolved organic carbon (r= 0.86), alkalinity (r= 0.60), and the extent of sulfate depletion (r= 0.77) in the soil porewater and soil pyrite concentrations (r= 0.72) across the tidal gradient. Leaf tissue chemistry of Laguncularia was characterized by lower C:N and C:P ratios that could fuel the higher rates of decomposition in the Laguncularia-dominated forest. We suggest that a plant-soil-microbial feedback contributes to the spatial patterning of vegetation and soil variables across the intertidal zone of many mangrove forest communities.

Mechanisms for internal loading of phosphorus in lakes

Abstract: Lake sediments play an important role in the phosphorus metabolism in lakes. The impact depends on the tendencies to retain and to release phosphorus.The internal loading will often determine the eutrophication status of the lake and the time lag for recovery after reduction of the external loading. Internal loading is most important during the summer. The potential source of phosphorus in the surficial sediments is very large in comparison to the pools in the water column. This means that even if only a very small amount is released, it will have significant impact on the phosphorus concentration in the lake water. The distribution of phosphorus forms in sediments have been investigated since the 1950s. Generally, vertical profiles of sediment phosphorus content, expressed on dry weight basis, show an increasing total content towards the sediment surface. The vertical profile continues up into the water when looking at the particulate matter. A number of environmental factors are important in the mobilisation processes. Most studies indicate that sediment bacteria have a significant role in uptake, storage and release of phosphorus including anaerobic release of iron-bound phosphorus. Several phytoplankton species have resting stages overwintering on the sediment. When growth is induced, they leave their habitat in order to shift their life-form to a pelagic one. In Lake Erken the cyanobacteria Gloeotrichia echinulata has been shown to contribute significantly to the internal loading of phosphorus during the summer.

Nutrient limitations and their implications on the effects of atmospheric deposition in coastal dunes; lime-poor and lime-rich sites in the Netherlands

Abstract: 1 A survey of plant and soil parameters was carried out in dry dune grasslands along the Dutch coast in the lime- and iron-poor Wadden district and initially lime- and iron-rich Renodunaal district, in order to detect differences in nutrient availability related to soil characteristics and potential sensitivity to atmospheric deposition of nitrogen. 2 Plant biomass and phosphorus pools in the shoot were higher in the Wadden district. The low foliar nitrogen concentrations and nitrogen/phosphorus ratios in the Wadden district suggested nitrogen-limitation, while in the Renodunaal district there appeared to be a balanced supply of both nitrogen and phosphorus. 3 Soil pH, soil organic matter, soil nitrogen and phosphorus concentrations and total amounts were generally higher in the Renodunaal district. In both districts mineral phosphorus decreased with acidification and phosphorus oxalate (iron and aluminium bound) increased. 4 In the Wadden district iron is present primarily in iron–organic matter complexes, which leads to reversible binding of phosphorus. In the Renodunaal district large amounts of iron (hydr)oxides occur and at high pH may contribute to reversible phosphorus-sorption, but at low pH this probably leads to immobilization of phosphorus. 5 While pools of soil phosphorus are low in the Wadden district, the phosphorus availability may be relatively high due to the comparatively loose nature of phosphorus-sorption. As a result the area may be nitrogen-limited and grass-encroachment may thus have resulted from atmospheric deposition of nitrogen. 6 In the Renodunaal district, atmospheric deposition probably only accelerates grass-encroachment, because deposition of acid and nitrogen increases the availability of both nitrogen and phosphorus and maintains the ‘co-limitation’.

Application of a novel method for phosphorus determinations in the oligotrophic North Pacific Ocean

Abstract: Phosphorus (P) is an essential macronutrient and is present in seawater as both dissolved inorganic (primarily orthophosphate, Pi) and organic compounds. Current analytical techniques measure soluble reactive phosphorus (SRP) as a surrogate for Pi and soluble nonreactive phosphorus as a surrogate for dissolved organic phosphorus (DOP). A new method provides a measure of Pi concentrations directly and eliminates interference from other reactive P compounds. The same method can also be used to make direct measurements of non-Pi phosphorus (NPiP) concentrations (i.e., [total dissolved P] — [Pi]) with greater precision and accuracy limits than current methods provide. With this new method, Pi concentrations in North Pacific surface waters were found to be lower, by up to 50% or more, than SRP concentrations measured with standard autoanalyzer techniques. Mean (±SD) N-PiP concentrations in the deep (>1,000 m) North Pacific were determined to be 16.2 ± 12.5 nM. These results have significant implications for turnover and residence times of dissolved P pools and for utilization of DOP in the deep sea. This new method for Pi and N-PiP measurements has numerous potential applications in marine and freshwater research.

Calcium, iron, potassium, phosphorus and vitamin C content of organic and hydroponic tomatoes

Abstract: Two tomato (Lycopersicon esculentum Mill.) cultivars were grown in two organic and two inorganic media to evaluate the effects upon the levels of Ca, Fe, K, P, and vitamin C in the fruit. 'Platense' tomato was grown in a glasshouse, on sand or peat-perlite (hydroponic substrates) irrigated with a complete solution of macro and microelements, or on 100% vermicompost or 50% vermicompost-50% soil (organic substrates) irrigated with water. Fruit were harvested at physiological maturity, and levels of P, K, Ca, Fe, and vitamin C were determined. Fruit grown on organic substrates contained significantly more Ca and vitamin C and less Fe than did fruit grown on hydroponic media. Phosphorus and K content did not differ between fruit from organic and hydroponic substrates.

Factor productivity trends in a rice–wheat cropping system under long-term use of chemical fertilizers

Abstract: A long-term fertilizer experiment was conducted on the rice-wheat cropping system at four locations in India. Trends in partial factor productivity of applied nitrogen, benefit:cost ratio of fertilizer application, grain yield, changes in soil organic carbon, and available nitrogen (N), phosphorus (P) and potassium (K) were studied in control (N 0 P 0 K 0 ), N (N 120 P 0 K 0 ), NP (N 120 P 80 K 0 ), NK (N 120 P 0 K 40 ) and NPK (N 120 P 80 K 40 ) fertilizer treatments. On average at all locations, continuous rice-wheat cropping for 16 years decreased the yield of rice by 57% in unfertilized plots and by 32% in plots receiving nitrogen and phosphorus fertilizers. Over the same period wheat yields only declined in unfertilized plots by 18%; in plots receiving nitrogen, phosphorus and potassium yields increased by 18% and they increased by 33.6% in plots receiving nitrogen and phosphorus fertilizer. Partial factor productivity of applied nitrogen (the ratio of output value to the cost of a specific input) exhibited similar trends. Profit from fertilizer application, however, increased over the 16-year cycle by 130% in rice and by 262% in wheat in the treatment given nitrogen and phosphorus fertilizers. The long-term rice-wheat cropping system became depleted in soil organic carbon and available nitrogen and phosphorus at two locations but increased in organic carbon, available nitrogen and potassium at the third location. The available phosphorus and potassium content of the soil also increased at the fourth location.

Effect of RenaGel, a non-absorbed, calcium- and aluminium-free phosphate binder, on serum phosphorus, calcium, and intact parathyroid hormone in end-stage renal disease patients.

Abstract: Background. Control of dietary phosphate absorption in end-stage renal disease patients is essential to prevent the deleterious sequelae of phosphorus retention. Efficacy of currently available calcium- and aluminium-containing phosphate binders is constrained by the side-effects associated with the absorption of calcium and aluminium. The current study examined the efficacy of RenaGel, a calcium- and aluminium-free, polymeric phosphate binder, in end-stage renal disease patients. Methods. Administration of calcium- or aluminium-containing phosphate binders ceased during a 2-week washout period. RenaGel, at starting doses of one, two, or three 500-mg capsules three times per day with meals, was administered for 8 weeks. RenaGel dose was titrated up 1 capsule per meal at the end of each 2-week period if necessary to achieve phosphorus control. A second 2-week washout period followed the end of RenaGel treatment. Results. Mean serum phosphorus rose from a pre-washout level of 6.9 mg/dl (2.23 mmol/l) to 8.1 mg/dl (2.62 mmol/l) at the end of the initial 2-week washout. With RenaGel treatment, serum phosphorus declined and returned to pre-washout levels after 4 weeks. Serum phosphorus reached a nadir of 6.5 mg/dl (2.10 mmol/l) after 7 weeks of RenaGel treatment. Serum phosphorus rose to 8.2 mg/dl (2.65 mmol/l) 2 weeks after cessation of RenaGel treatment. As anticipated, calcium declined during the initial washout period when calcium-based phosphate binders were stopped for the majority of patients. The rise in serum phosphorus and decline in serum calcium during washout resulted in an increase in median intact parathyroid hormone (iPTH) levels from 292 pg/ml to 395 pg/ml. iPTH fell to 283 pg/ml after 6 weeks of RenaGel treatment despite a persistently lower serum calcium. RenaGel treatment also reduced serum total and LDL cholesterol by 25 mg/dl (0.65 mmol/l) and 23 mg/dl (0.59 mmol/l) respectively. Conclusions. RenaGel appears to be an effective phosphate binder free of calcium and aluminium. Phosphorus control with two to four RenaGel capsules per meal appears to result in comparable phosphorus lowering seen with calcium- or aluminium-based phosphate binders. RenaGel may offer an alternative for the control of phosphorus retention in end-stage renal disease patients.