Phosphorus Biogeochemistry and the Impact of Phosphorus Enrichment: Why Is the Everglades so Unique?

The Florida Everglades is extremely oligotrophic and sensitive to small increases in phosphorus (P) concentrations. P enrichment is one of the dominant anthropogenic impacts on the ecosystem and is therefore a main focus of restoration efforts. In this review, we synthesize research on P biogeochemistry and the impact of P enrichment on ecosystem structure and function in the Florida Everglades. There are clear patterns of increased P concentrations and altered structure and processes along nutrient-enrichment gradients in the water, periphyton, soils, macrophytes, and consumers. Periphyton, an assemblage of algae, bacteria, and associated microfauna, is abundant and has a large influence on phosphorus cycling in the Everglades. The oligotrophic Everglades is P-starved, has lower P concentrations and higher nitrogen–phosphorus (N:P) ratios, and has oxidized to only slightly reduced soil profiles compared to other freshwater wetland ecosystems. Possible general causes and indications of P limitation in the Everglades and other wetlands include geology, hydrology, and dominance of oxidative microbial nutrient cycling. The Everglades may be unique with respect to P biogeochemistry because of the multiple causes of P limitation and the resulting high degree of limitation. Received 23 August 2000; Accepted 23 March 2001.     

Phosphorus deficiency increases nodule phytase activity of faba bean–rhizobia symbiosis

The effect of phosphorus deficiency on growth, nodulation and phytase activity was studied in glasshouse for four symbioses involving two faba bean cultivars, namely Aguadulce (AG) and Alfia (AL), and two local rhizobial isolates, namely RhF1 and RhF2. The P deficiency was applied by adding 25 µmol of Pi plant^?1 week^?1 to nutrient solution, whereas the sufficient control received 125 µmol plant^?1 week^?1. At flowering stage, the plants were harvested for assessment of growth and nodulation, P and N contents in organs as well as activities of phytase and phosphatases in nodules. The latter were highly stimulated by P deficiency, particularly for AL–RhF1 symbiosis for which shoot growth and P content were not affected by P deficiency. Using in situ RT-PCR, the expression of a plant histidine acid phytase HAP gene was detected in the nodule cortex under P deficiency. It is concluded that high nodule phytase activity constitutes a mechanism for faba bean plants to adapt their nitrogen fixation to P deficiency.     

Study of the Effect of Phosphorus on Mineral Nutrition of Faba Bean « Vicia fabae L.»

Our study focuses on the study of the phosphorus efficiency on the mineral nutrition of a leguminous plant; to study this efficiency, we tested the effect of increasing doses of phosphorus on the mineral nutrition of faba bean and on the concentration of Nt (total nitrogen), Pi (available phosphorus), KE (exchangeable potassium), C (organic carbon), and the organic matter (OM) rate in the rhizospheric soil after harvest, as well as the concentration of N, P, K, Na, and Ca in the roots, stems, leaves, and seeds of faba bean. The faba bean crop was subjected to four phosphorus doses (P0?=?0 kg/ha; P1?=?70 kg/ha; P2?=?140 kg/ha; P3?=?210 kg/ha). The main results obtained showed that the concentration of the mineral elements in the different faba bean parts reacted differently to the phosphorus treatments. Regarding the dosage of nutrients in the different parts of the faba bean, the results obtained highlight that Pi deficiency in the soil does not only affect phosphate nutrition but can also affect the absorption of other mineral elements, a synergy is recorded between the K concentration in the roots and in the stems with the organic carbon in the soil, and an antagonism between K and Na in the different parts of the plant. All the results obtained in this work show that a phosphate fertilization for doses between 70 kg/ha and 140 kg/ha of P2O5 improves the microbial life of soil microorganisms.

     

Phosphorus concentration in sediment, water and tissues of␣three submerged macrophytes of Myall Lake, Australia

Phosphorus content in sediment, water and tissues of three macrophyte species growing in Myall Lake, Australia were studied from January to November, 2004. The sites investigated were North–West (NW), North–East (NE), South–West (SW) bays and Central deep area of the lake (CL). The objective of this study was to investigate how total phosphorus (TP) in plant tissues relate to phosphorus pools and the role played by the aquatic macrophyte species under investigation in phosphorus recycling in the lake. Of the four investigated sites of the lake, TP in plant tissues were significantly higher in North–West and South–West bays compared to the rest. Najas marina had significantly higher TP content (e.g., 1.55 and 1.44 mg/g dw.; P < 0.05) for NW and SW respectively, than the other two species. N. marina is a rooted macrophyte while charophytes (C. fibrosa and Nitella hyalina) are pseudo-rooted macrophytes. Total phosphorus in the sediment and water column were significantly higher in Central deep area of the lake compared to the other three bays (P < 0.05, n 5). Soluble reactive phosphorus (SRP) and total dissolved phosphorus (TDP) in sediment pore water correlated significantly with phosphorus content in the tissue of N. marina ( ; ) as well as TP in sediment (␣ and ). Using the two-compartmental uptake model, it was observed that, sediment was the main compartment through which Ni. hyalina obtained phosphorus while for the other two species, water column was the uptake route for the phosphorus. These correlations suggest that, water column and sediments are important pathways for phosphorus uptake in plants.     

DETERMINING THE SITE OF BRAIN TUMORS—The Use of Radioactive Iodine and Phosphorus

By tests using radioactive iodine combined with diiodofluorescein, the site of tumors was correctly determined in 61 per cent of 39 cases of tumors of the cerebral hemispheres. In 19 cases where the focal radioactivity was increased 24 per cent or more over that of the surrounding area, there were no errors in localization. Fifteen patients with expanding intracranial lesions were tested at operation with radioactive phosphorus and 14 lesions were correctly localized. This procedure in which the needle probe was used was found of great value in rapidly locating and outlining the area of involvement.     

Phosphorus in sediments — speciation and analysis

Characterization of sediment phosphorus is commonly based on sequential chemical extractions, in which phosphorus is supposed to be selectively removed from different compounds in the sediments. The first extraction schemes were designed to quantify discrete chemical or mineralogical compounds. As extraction schemes have been tested on different sediments, several systematic errors have been detected and the schemes have been modified and simplified accordingly. Other chemical extractions or treatments have attempted to determine phosphorus bound to particles with a certain strength or binding energy, the purpose being to determine the labile, loosely bound, exchangeable, mobile or algal-available fraction of sediment phosphorus. All extraction procedures yield operationally defined fractions and cannot be used for identification of discrete phosphorus compounds. The many methodological modifications make it necessary to be cautious when comparing results from the literature in this field.     

Identification and Characterization of Phosphorus Use Efficiency in a Doubled Haploid Population of Chinese Spring×Lovrin No.10

It is reported that chromosome 1R of rye (Secale cereale L.) convey phosphorus use efficient gene (s), and 1RS/1BL translocation genotype Lovrin No.10 is P use efficient. So we hypothesized whether P efficient gene(s) locate on 1RS, and the high P efficiency of Lovrin No.10 is from 1RS? To test this hypothesis, we investigated the P use efficiency (PUE) of a doubled haploid (DH) population with 61 lines derived from anther culture of F₁ hybrid between Lovrin No.10 and phosphorus uptake inefficient genotype Chinese Spring to see whether PUE differs between DH line with and without 1RS/1BL translocation. Acidic polyacrylamide-gel electrophoresis (A-PAGE) of gliadin and genomic DNA in situ hybridization (GISH) were employed to discriminate 1RS/1BL translocation DH lines from the normal 1B DH lines. Among the 61 DH lines investigated, A-PAGE analysis showed that 34 lines contained the 1RS/1BL translocation chromosome, which was characterized by the presence of a 1RS-specific Sec-1 marker bands. Further verification with GISH proved that 33 in the 34 lines contained a pair of homozygous 1RS/1BL translocation chromosomes, only one line was a 1RS/1BL monosomic line. A field experiment was carried out on P deficient soil to investigate grain yield, biomass, numbers of spikes per plant (SPP), P uptake efficiency (PUpE), and P utilization efficiency (PUtE) of the DH lines and their parents under -P (nil P applied) and +P (60 kg P/hm² applied) at maturity. Results showed soil P deficiency decreased the values of the first four traits in Lovrin No.10, but were more severe for Chinese Spring. Lovrin No.10 had higher values of all the above tested traits at both -P and +P than Chinese Spring did, but had similar PUtE with Chinese Spring. These five traits segregated, and differed greatly among DH lines under both -P and +P conditions. Although the variations among DH lines exceeded the difference between the two parents, the average values of the DH lines were between the two parents. The average of the above five traits, and P deficiency tolerance (PDT) (measured by relative grain yield of -P/+P) were not different between the DH lines with and without 1RS/1BL translocation. This indicated that there was no association between 1RS and PUE and PDT in Lovrin No.10, and 1RS may not have P efficient gene(s). Therefore, in the offspring of Lovrin No.10, it is possible to combine high PUE and PDT with good quality without the negative effect of 1RS on flour quality.     

Phosphorus in acidified lakes: The example of Lake Gårdsjön,Sweden

Supply and turnover of phosphorus was studied in an acidified lake ecosystem, Lake Gårdsjön, located in southwestern Sweden. This study included transport and budget calculations combined with field and laboratory experimental work on abiotic phosphorus chemistry and biological utilization of phosphorus. The main conclusions presented in this paper are:

- The acidification process in inland waters resulting from acid atmospheric deposition is accompanied by ‘oligotrophication’ because of reduced input of phosphorus from the drainage area, possibly due to efficient fixation of phosphorus to aluminium complexes in the B-horizon of podzol soils

- Primary productivity in acidified lakes is limited mainly by low phosphorus supply

- Algal utilization of phosphorus in acidified lakes is impaired, yielding lower biomass than could be expected from ambient phosphorus concentrations. One possible reason for this could be that enzymatic recycling of organic phosphates is prevented by high levels of aluminium in lake water.

     

Phosphorus: a limiting nutrient for humanity?

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Highlights? P is essential to build key molecules, such as RNA needed for rapid growth. ? P is often limiting to productivity in ecosystems, including to crops. ? Large amounts of P are mined annually to make fertilizer to produce food. ? Current P use is unsustainable owing to ecosystem impacts and uncertainties about fertilizer production. ? A food system redesign to combine P-efficient crops with P recycling is needed.     

Effects of Phosphorus Nutrient on the Hydraulic Conductivity of Sorghum （Sorghum vulgare Pers.） Seedling Roots Under Water Deficiency

Hydroponic experiments were conducted in a growth chamber and changes in the hydraulic conductivity of sorghum (Sorghum vulgare Pers.) roots (Lpr) at the three-leaf stage were measured using the pressure chamber method. Water deficiency was imposed with polyethylene glycol (PEG) 6000 and the phosphorus (P) levels were controlled by complete Hoagland solution with and without P nutrient. The objective of this study was to investigate the effect of P nutrition on root Lpr under water deficiency. The results showed that the Lpr in P deficiency treatments decreased markedly, but the Lpr recovered to the same value as that of control when sufficient P was supplied for 4-24 h. Water deficiency decreased Lpr, but the hydraulic conductivity of the roots with sufficient P supply was still higher than that of plants without P supply. When resuming water supply, the Lpr of the water-deficient plants under P supply recovered faster than that of plants without P supply, which indicates that plants with sufficient P nutrient are more drought tolerant and have a greater ability to recover after drought. The treatment of HgCl2 indicated that P nutrient could regulate the Lpr by affecting the activity and the expression levels of aquaporins.     

Phosphorus fractions in montane forest soils of the Cordillera de Piuchué, Chile: biogeochemical implications

The Hedley fractionation procedure as modified by Tiessen and Moir (1993) was used to evaluate the amounts of P in several soil chemical pools in an old, unglaciated landscape at 600 m elevation in the Cordillera de Piuchué, Chile (42° 30′ S. 74° W). This is an area of primary forests which have escaped disturbance from forest harvesting, land clearing and the deposition of anthropogenic chemicals. Two study watersheds are conifer-dominated with moorland on wind-exposed ridgetops. In a third study watershed, vegetation is dominated by evergreen broadleaf trees. Soils are thin (ca. 40 cm) and have a high organic matter content. Across all communities, most of the soil P is in non-labile forms in organic combinations or in combination with secondary soil minerals. Little P was present in primary minerals. The remainder (ca. 20%) was in labile forms extractable with anion exchange resin or bicarbonate solution. From litterfall and allometric relationships, we estimated the annual P requirement of growing vegetation to be <1 kg ha^-1 in the moorland and < 3 kg ha^-1 in the conifer and mixed forests. This is substantially less than the standing pool of resin-extractable P (ca. 20 kg ha^-1), which is considered to be P fraction most readily available to plants. Resin-extractable P was strongly correlated with soil carbon content ( R² =0.72 − 0.87, p < 0.001) suggesting that soil organic matter is the likely proximate source of plant-available P. On a kg ha^-1 basis, the most labile forms of P did not differ significantly across 3 of the 4 community types despite dramatic differences in species, live biomass and annual P requirement, suggesting little control of available P pools by forest vegetation type. On a more detailed level, resin-extractable P was strongly correlated with HCO₃-extractable organic (and inorganic) P. This is consistent with other findings of P behavior in acid soils high in organic matter in which microbial transformations are key in regulating pools of plant-available P. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of β1 →4 Linked Galactooligosaccharides on Use of Magnesium and Calcification of the Kidney and Heart in Rats Fed Excess Dietary Phosphorus and Calcium

Magnesium deficiency was induced in male Wistar rats by adding an excess of phosphorus and calcium to the diet (1.195 g of phosphorus and 1.04g of calcium/100g of diet). Feeding of these animals with a diet containing β1→4 linked galactooligosaccharides (4′-GOS) (5g of 4′-GOS/100g of diet) increased the apparent magnesium absorption ratios and the concentrations of magnesium in the serum and femur, and reduced accumulation of calcium in the kidney and heart. We speculate that the use of magnesium increased by feeding 4′-GOS to a limited extent prevented the lower magnesium status and the severity of calcification of the kidney and heart caused by excess dietary phosphorus and calcium.     

Can Hydrodynamics Change Phosphorus Strategies of Diatoms?—Nutrient Levels and Diatom Blooms in Lotic and Lentic Ecosystems

Diatom blooms occur in many water bodies worldwide, causing significant ecological and social concerns. In order to understand the mechanisms of diatom blooms formation, the effects of varying phosphorus (P) concentration and hydrodynamics on the growth of diatoms were studied by combining results from field observations and laboratory experiments. The field investigation showed that spring diatom blooms (Cyclotella meneghiniana and Stephanodiscus hantzschii) occurred in Lake Taihu and Hanjiang River with similar environmental factors such as water temperature, pH, and dissolved oxygen in 2008. Concentrations of total phosphorus (TP), total nitrogen, and ammonia nitrogen (NH₄-N) in Lake Taihu were significantly higher than the concentrations in the Hanjiang River. Laboratory experiments were conducted to evaluate growth and physiological responses of four lotic diatoms (Cyclotella atomus, Fragilaria crotonensis, Nitzschia palea, and S. hantzschii, isolated from the Hanjiang River) and three lentic diatoms (C. meneghiniana, Melosira varians, and Stephanodiscus minutulus, isolated from Lake Taihu, Lake Donghu, and Guanqiao Pond, respectively) to various P concentrations under small-scale turbulent and standing conditions. Our results showed that, with turbulence, lotic diatoms C. atomus, F. crotonensis, N. palea, and S. hantzschii demonstrated a significant increase in affinity for P compared with lentic diatoms C. meneghiniana, M. varians, and S. minutulus. Moreover, lotic diatoms C. atomus, F. crotonensis, and N. palea had higher growth rates and photosynthetic efficiencies with small-scale turbulence than with standing conditions both in P-limited and P-replete conditions. Lotic species S. hantzschii and three lentic diatoms (C. meneghiniana, M. varians, and S. minutulus) grew well under standing conditions. Our results may explain our field observation that the occurrence of diatom blooms in lakes is often associated with higher TP concentrations whereas in rivers, diatom blooms occur at a wide range of TP concentrations under flows. Therefore, different hydrodynamics and nutrient concentrations determined the dominant diatom species, according to their habitat-dependent physiological characteristics.     

Root Cluster Formation and Citrate Exudation of White Lupin （Lupinus albus L.） as Related to Phosphorus Availability

A split-root system was used to investigate whether the external or internal P concentration controls root cluster formation and citrate exudation in white lupin (Lupinus albus L.) grown under controlled conditions. In spite of low P concentrations in the shoots and roots of the -P plant, its dry weight was not reduced compared with the P plant. Supplying external P (0.25 mmol/L) to one root half resulted in an increase in P concentration not only in the shoot, but also in the P-deprived root half, indicating P cycling within the plants. Omitting P from both split-root pots stimulated root cluster formation in both root halves,whereas P supply to one root half stimulated root cluster formation at the beginning of the treatment. Neither P supply to just one root half continuously nor resupply of P to one root half after 19 d of P starvation inhibited root cluster formation on the P-deprived side, although the concentration of P in this root half and shoot increased markedly. The results indicate that root cluster formation in L. albus is controlled by both shoot and root P concentrations. The rates of citrate exudation by both root halves with P deficiency were higher than those of the one root half supplied with P only. In the treatment with one root half supplied with P, the rates of citrate exudation by either the P-supplied or -deprived root halves were almost the same,regardless of P concentration in the roots. The results suggest that internal P concentration controls root cluster formation and citrate exudation in white lupin, but these processes may be regulated by different mechanisms.     

Phosphorus Cycling in Montreal’s Food and Urban Agriculture Systems

Cities are a key system in anthropogenic phosphorus (P) cycling because they concentrate both P demand and waste production. Urban agriculture (UA) has been proposed as a means to improve P management by recycling cities’ P-rich waste back into local food production. However, we have a limited understanding of the role UA currently plays in the P cycle of cities or its potential to recycle local P waste. Using existing data combined with surveys of local UA practitioners, we quantified the role of UA in the P cycle of Montreal, Canada to explore the potential for UA to recycle local P waste. We also used existing data to complete a substance flow analysis of P flows in the overall food system of Montreal. In 2012, Montreal imported 3.5 Gg of P in food, of which 2.63 Gg ultimately accumulated in landfills, 0.36 Gg were discharged to local waters, and only 0.09 Gg were recycled through composting. We found that UA is only a small sub-system in the overall P cycle of the city, contributing just 0.44% of the P consumed as food in the city. However, within the UA system, the rate of recycling is high: 73% of inputs applied to soil were from recycled sources. While a Quebec mandate to recycle 100% of all organic waste by 2020 might increase the role of UA in P recycling, the area of land in UA is too small to accommodate all P waste produced on the island. UA may, however, be a valuable pathway to improve urban P sustainability by acting as an activity that changes residents’ relationship to, and understanding of, the food system and increases their acceptance of composting.     

Phosphorus dynamics and bioavailability in sediments of the Penzé Estuary (NW France): in relation to annual P-fluxes and occurrences of Alexandrium Minutum

The macrotidal estuary of Penzé (Brittany, Western part of the Channel, France) has been subjected to recurrent annual toxic blooms of Alexandrium minutum since 1988. This study aims to specify the phosphorus dynamics and bioavailability in sediments in order to improve our understanding of Alexandrium occurrences. Sediment-P pools and diffusive phosphate fluxes were studied under similar hydrodynamic conditions, in the intermediate estuary in May, June and July 2003 and along the salinity gradient from August 2004 to June 2005. The results highlight a decrease in bioavailable phosphorus (iron and organic bound) from the inner part of the estuary seaward. The ratio of iron-bound phosphorus to iron-oxyhydroxides is lower in the inner and intermediate estuaries (5–8) than in the outer site (15), suggesting a saturation of sorption sites and greater phosphorus bioavailability in this area. Pools of bioavailable phosphorus in surficial sediments are about eight times higher than the annual net-export of P (7 ton year⁻¹). Phosphate releases from sediments are always lower than 5 μmol m⁻² d⁻¹ in March. The highest supplies occur in June and August in the intermediate area (up to 400 μmol m⁻² d⁻¹) where they represent up to 50% of river loadings. These results further suggest that phosphate pulses coincide with occurrences of Alexandrium reported in June.     

Atmospheric Phosphorus Deposition in Ashiu, Central Japan – Source Apportionment for the Estimation of True Input to a Terrestrial Ecosystem

Atmospheric bulk depositions of soluble reactive phosphorus (SRP), soluble unreactive phosphorus (SUP), particulate inorganic phosphorus (PIP), particulate organic phosphorus (POP), total phosphorus (TP) and some other dissolved and particulate components were monitored for 3 years in Ashiu, Central Japan. The mean bulk depositions of SRP, SUP, PIP, POP, TP, dissolved components (Na, Mg, nss-Ca, K, V, Mo, nss-SO₄) and particulate components (Al, Fe, Ti, Ca, Mg, Mn, Ba, Sr, Zn) were 175, 76, 136, 397, 783, 156,000, 10,900, 7450, 5470, 10.3, 1.52, 40,100, 13,200, 3590, 2630, 576, 624, 42.3, 30.2, 17.4, 8.2 μmol m⁻² year⁻¹, respectively. The value for TP deposition was in the lower range of previous literature. The low P deposition probably reflected the method applied to reduce the contribution of local particles, including (1) placement of samplers off the ground surface, (2) installation of multiple samplers, and (3) rejection of contaminated samples. Al data suggested that 15 ± 5% of TP was brought by lithogenic dust from East Eurasia. Nss-SO₄ and Mo data and air-mass backward trajectories suggested that 39 ± 4% of TP was derived from coal combustion in China. It was speculated that the rest (47 ± 6%) of the TP deposition might be predominantly attributed to the contribution of local biogenic particles. Net atmospheric TP input (lithogenic dust and fossil fuel combustion) was almost equal to the TP outflow from Japanese forests on granitic soils.