Showing papers on "Phosphorus published in 2006"

Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere.

Abstract: Terrestrial biosphere–atmosphere carbon dioxide (CO2) exchange is dominated by tropical forests, where photosynthetic carbon (C) uptake is thought to be phosphorus (P)-limited. In P-poor tropical forests, P may also limit organic matter decomposition and soil C losses. We conducted a field-fertilization experiment to show that P fertilization stimulates soil respiration in a lowland tropical rain forest in Costa Rica. In the early wet season, when soluble organic matter inputs to soil are high, P fertilization drove large increases in soil respiration. Although the P-stimulated increase in soil respiration was largely confined to the dry-to-wet season transition, the seasonal increase was sufficient to drive an 18% annual increase in CO2 efflux from the P-fertilized plots. Nitrogen (N) fertilization caused similar responses, and the net increases in soil respiration in response to the additions of N and P approached annual soil C fluxes in mid-latitude forests. Human activities are altering natural patterns of tropical soil N and P availability by land conversion and enhanced atmospheric deposition. Although our data suggest that the mechanisms driving the observed respiratory responses to increased N and P may be different, the large CO2 losses stimulated by N and P fertilization suggest that knowledge of such patterns and their effects on soil CO2 efflux is critical for understanding the role of tropical forests in a rapidly changing global C cycle.

Water Quality Improvement through Bioretention Media: Nitrogen and Phosphorus Removal

Abstract: High nutrient inputs and eutrophication continue to be one of the highest priority water quality problems. Bioretention is a low-impact development technology that has been advocated for use in urban and other developed areas. This work provides an in-depth analysis on removal of nutrients from a synthetic stormwater runoff by bioretention. Results have indicated good removal of phosphorus (70 to 85%) and total Kjeldahl nitrogen (55 to 65%). Nitrate reduction was poor (< 20%) and, in several cases, nitrate production was noted. Variations in flowrate (intensity) and duration had a moderate affect on nutrient removal. Mass balances demonstrate the importance of water attenuation in the facility in reducing mass nutrient loads. Captured nitrogen can be converted to nitrate between storm events and subsequently washed from the system. Analysis on the fate of nutrients in bioretention suggests that accumulation of phosphorus and nitrogen may be controlled by carefully managing growing and harvesting of vegetation.

Dietary phosphorus regulates serum fibroblast growth factor-23 concentrations in healthy men.

Abstract: Context: Fibroblast growth factor 23 (FGF-23) is important in the regulation of phosphorus and vitamin D metabolism. States of excess circulating FGF-23 are associated with renal phosphate wasting and inappropriately low serum 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations. Conversely, states of absent or biologically inactive circulating FGF-23 are associated with increased serum phosphorus and 1,25(OH)2D concentrations. Restriction of the dietary intake of phosphorus increases renal phosphate reabsorption and 1,25(OH)2D production, whereas the opposite occurs when dietary phosphorus is supplemented. Objective: We sought to determine whether serum FGF-23 concentration is regulated by dietary phosphorus and thereby mediates the physiological response of serum 1,25(OH)2D to changes in dietary phosphorus. Design, Setting, and Participants: We studied 13 healthy men as inpatients during a 4-wk dietary phosphorus intervention study. Intervention: Subjects consumed a constant diet that provided 500 mg of ...

Eutrophication and trophic state in rivers and streams

Abstract: Many natural streams are net heterotrophic, so I propose that trophic state be divided into autotrophic and heterotrophic state. This division allows consideration of the influence of external carbon sources as well as nutrients such as nitrogen and phosphorus. Empirical results suggest that phosphorus and nitrogen are the most important nutrients regulating autotrophic state in flowing waters and that benthic algal biomass is positively correlated to gross primary production in streams. Reference (minimally influenced by human activities) nutrient concentrations and correlations of nutrients with algal biomass are used to characterize reference distributions of stream autotrophic state. Only when reference nutrient concentrations are in the upper one third of those expected in the United States, is maximum benthic chlorophyll projected to exceed 100 mg m 22 (a concentration commonly used to indicate nuisance levels) .30% of the time. Average reference nutrient concentrations lead to sestonic chlorophyll concentrations above those considered typical of eutrophic lakes (. 8m g m 23 ) less than half the time. Preliminary analysis suggests that autotrophic state is variable in small pristine streams because it is influenced by canopy cover (light), but heterotrophic state is less variable because it can be based on allochthonous or autochthonous production. Nitrogen and phosphorus enrichment can influence both heterotrophic and autotrophic state, and these effects could cascade to animal communities. Stoichiometry should be considered because carbon, nitrogen, and phosphorus are all involved in trophic state. The proposed definition of trophic state offers a starting conceptual framework for such considerations.

Atmospheric nitrogen deposition has caused nitrogen enrichment and eutrophication of lakes in the northern hemisphere

Abstract: Atmospheric nitrogen deposition has caused nitrogen enrichment and eutrophication of lakes in the northern hemisphere

Responses of estuarine and coastal marine phytoplankton to nitrogen and phosphorus enrichment

Abstract: A cross-ecosystem comparison of data obtained from 92 coastal zone ecosystems worldwide revealed a strong positive response of marine phytoplankton biomass to nutrient enrichment that is highly consistent with the general patterns reported previously in the limnological literature for freshwater lakes and reservoirs. Average concentrations of chlorophyll a in estuarine and coastal marine systems were strongly dependent on the mean concentrations of total nitrogen and total phosphorus in the water column. Moreover, as is true of freshwater ecosystems, the identity of the primary growth-limiting nutrient for marine phytoplankton appeared to be generally predictable from watercolumn total nitrogen : total phosphorus (TN : TP) ratios. This similarity in physiological response to nutrients likely derives from the shared evolutionary histories of marine and freshwater phytoplankton.

Arbuscular mycorrhizal fungi contribute to phosphorus uptake by wheat grown in a phosphorus‐fixing soil even in the absence of positive growth responses

Abstract: Summary • We used 32P to quantify the contribution of an arbuscular mycorrhizal (AM) fungus (Glomus intraradices) to phosphorus (P) uptake by wheat (Triticum aestivum), grown in compartmented pots. The soil was from a major cereal-growing area, the Eyre Peninsula, South Australia; it was highly calcareous and P-fixing. Fertilizer P was added to soil at 20 mg kg−1, as solid or liquid. Two extraction methods were used to estimate plant-available P. • Fungal colonization was well established at harvest (36 d). Application of P decreased both colonization and hyphal length density in soil, with small differences between different P fertilizers. • Plants showed large positive responses in terms of growth or total P uptake to all P additions, and showed no positive (or even negative) responses to AM colonization, regardless of P application. • 32P was detected only in AM plants, and we calculated that over 50% of P uptake by plants was absorbed via AM fungi, even when P was added. The results add to the growing body of knowledge that ‘nonresponsive’ AM plants have a functional AM pathway for P transfer to the plant; it should not be ignored in breeding plants for root traits designed to improve P uptake.

Iron Reduction and Soil Phosphorus Solubilization in Humid Tropical Forests Soils: The Roles of Labile Carbon Pools and an Electron Shuttle Compound

Abstract: The affinity of iron oxides and hydroxides for phosphorus is thought to contribute to phosphorus limitation to net primary productivity in humid tropical forests on acidic, highly weathered soils. Perennially warm, humid conditions and high biological activity in these soils can result in fluctuating redox potential that in turn leads to considerable iron reduction in the presence of labile carbon and humic substances. We investigated the effects of reducing conditions in combination with the addition of labile carbon substrates (glucose and acetate) and an electron shuttle compound on iron reduction and phosphorus release in a humid tropical forest soil. Glucose or acetate was added to soils as a single dose at the beginning of the experiment, and as pulsed inputs over time, which more closely mimics patterns in labile carbon availability. Iron reduction and phosphorus mobilization were weakly stimulated by a single low level addition of carbon, and the addition of the electron shuttle compound with or without added carbon. Pulsed labile carbon additions produced a significant increase in soil pH, soluble iron, and phosphorus concentrations. Pulsed labile carbon inputs also promoted the precipitation of ferrous hydroxide complexes which could increase the capacity for P sorption, although our results suggest that rates of P solubilization exceeded re-adsorption. Plant and microbial P demand are also likely to serve as an important sinks for released P, limiting the role of P re-adsorption. Our results suggest that reducing conditions coupled with periodic carbon inputs can stimulate iron reduction and a corresponding increase in soil phosphorus mobilization, which may provide a source of phosphorus to plants and microorganisms previously undocumented in these ecosystems.

Phosphorus retention in calcareous soils and the effect of organic matter on its mobility

Abstract: A survey of the interactions between phosphorus (P) species and the components of calcareous soils shows that both surface reactions and precipitation take place, especially in the presence of calcite and limestone. The principal products of these reactions are dicalcium phosphate and octacalcium phosphate, which may interconvert after formation. The role of calcium carbonate in P retention by calcareous soils is, however, significant only at relatively high P concentrations – non-carbonate clays play a more important part at lower concentrations. In the presence of iron oxide particles, occlusion of P frequently occurs in these bodies, especially with forms of the element that are pedogenic in origin. Progressive mineralization and immobilization, often biological in nature, are generally observed when P is added as a fertilizer. Manure serves both as a source of subsurface P and an effective mobilizing agent. Blockage of P sorption sites by organic acids, as well as complexation of exchangeable Al and Fe in the soil, are potential causes of this mobilization. Swine and chicken manure are especially rich P sources, largely due the practice of adding the element to the feed of nonruminants. Humic materials, both native and added, appear to increase recovery of Olsen P. In the presence of metal cations, strong complexes between inorganic P and humates are formed. The influence of humic soil amendments on P mobility warrants further investigation.

Long-term effect of fertilizer and manure application on soil-carbon sequestration and soil fertility under the wheat–wheat–maize cropping system in northwest China

Abstract: Maintenance of soil organic carbon (SOC) is important for the long-term productivity of agroecosystems. An investigation was conducted to study the effects of long-term application of inorganic fertilizers and farmyard manure (FYM) on soil organic carbon (SOC), nitrogen, phosphorus, and potassium nutrient content, water-stable aggregate distribution, and aggregate-associated carbon in a field experiment started in 1982 in an arid region of northwest China. Application of inorganic fertilizer alone (N, NP, or NPK treatments) did not increase SOC concentrations compared with no application of fertilizers (CK) and SOC concentration was significantly reduced, by 18% on average, compared with the initial value at the beginning of the experiment. Application of imbalanced inorganic fertilizer (N and NP), especially, resulted in a significant decrease in available phosphorus and potassium nutrients at a depth of 20 cm. This indicates that long-term application of inorganic fertilizers were inadequate to maintain levels of SOC and nutrients under conventional management with no aboveground crop residues returning to the soil. Long-term application of FYM alone or combined with inorganic fertilizers (M (FYM), MN, MNPK, or MNPK treatments), however, improved SOC and total nitrogen concentrations from initial values of 12.1 and 0.76 g kg−1, respectively, to 15.46 and 1.28 g kg−1, on average, and also enhanced available nitrogen, phosphorus, and potassium concentrations by 47, 50, and 68%, respectively, during the 23-year period. Treatment with FYM resulted in a 0.48 mm greater average mean weight diameter (MWD) of aggregates and a higher percentage of macro-aggregates (>2 mm) and small macro-aggregates (2–0.25 mm) than treatment without FYM. The MWD increased with increasing SOC concentration (R 2=0.75). The SOC concentration was highest in small macro-aggregates, intermediate in macro-aggregates, and lowest in micro-aggregates (0.25–0.05 mm). Approximately 54–60% of total SOC was stored in micro-aggregates (0.25–0.05 mm) and sand+silt fractions ( 0.25 mm) after treatment with FYM. MNPK treatment had the greatest effect on improving the levels of SOC and NPK nutrients and in enhancing the formation and stability of macro-aggregates.

Plant- and microbial-based mechanisms to improve the agronomic effectiveness of phosphate rock: a review

Abstract: Deficiency in plant-available phosphorus is considered to be a major limiting factor to food production in many agricultural soils. Mineral resources are necessary to restore soil phosphorus content. In regions where conventional fertilizers are not used due to cost limitations or to mitigate adverse environmental effects, local sources of phosphate rock are being increasingly recognized for potential use as alternative phosphorus fertilizers. The main obstacle associated with using directly applied ground phosphate rock is that the phosphate released is often unable to supply sufficient plant-available phosphorus for crop uptake. Plantand microbial-based mechanisms are low-cost, appropriate technologies to enhance the solubilization and increase the agronomic effectiveness of phosphate rock. Common mechanisms of phosphate rock dissolution including proton and organic acid production will be reviewed for both plants and microorganisms. This review will also address possibilities for future research directions and applications to agriculture, as well as highlight ongoing research at the University of Guelph, Guelph, Canada.

Air- and moisture-stable secondary phosphine oxides as preligands in catalysis

Abstract: The application of secondary phosphine oxides to catalysis is reviewed. A survey of the literature up to summer 2005 is provided, covering the use of these air- and moisture-stable preligands in transformations catalyzed by transition-metal complexes and their use as precatalysts in nucleophilic catalysis.

Removal of Dissolved Nitrogen, Phosphorus and Carbon from Stormwater by Biofiltration Mesocosms

Abstract: Biofiltration systems are becoming a popular stormwater treatment device in water sensitive urban design for the removal of fine particulate and dissolved pollutants from stormwater. However, there is limited published data on the effectiveness of these systems for nutrient removal. We constructed biofiltration mesocosms to assess nutrient removal (nitrogen, phosphorus and carbon) under experimental conditions. Different types of media were compared (gravel, sand, and sandyloam) in vegetated and non-vegetated mesocosms (six treatments in total). Five plant species were used. Vegetated sand and vegetated sandy-loam provided the best overall treatment. Vegetated mesocosms were very effective in removing nitrogen (63-77% removal) and phosphorus (85-94% removal) from synthetic stormwater, and removed substantially more nutrients than the non-vegetated treatments. All treatments removed a substantial portion of the carbon from the stormwater (28-66%). Wben flushed with tap water, nitrogen and phosphorus were retained by the vegetated mesocosms, but leached from the non-vegetated mesocosms. Plant growth was most vigorous in the sandy-loam media, indicating that this is a good growth media, even without the addition of organic matter.

Occurrence and functioning of phosphate solubilizing microorganisms from oil palm tree (Elaeis guineensis) rhizosphere in Cameroon

Abstract: Phosphorus replenishment, particularly in smallholder agriculture, remains a challenge as it is mainly fertilizer dependent. While the use of soluble mineral phosphate fertilizers is the obvious best means to combat phosphate deficiency in Cameroon, their use is limited by their high cost and availability at farmer’s level. This study was aimed at maintaining the fertility of Cameroon soils by biological means, in order to improve agricultural production, using low inputs technology. Isolates were obtained from oil palm tree (Elaeis guineensis) root fragments and rhizospheric soils and their activity in mobilizing phosphate from insoluble sources was evaluated on agar plates and liquid culture media containing sparingly soluble phosphates. At the end of incubation time, it appeared that, phosphate solubilization resulted from a combined effect of pH decrease of the media and organic acids production. Furthermore, each of the tested isolates was able to produce at least one of the most important organic acids such as citrate, malate and tartrate. Among the ten isolates tested, three were identified as Pseudomonas fluorescens and would be considered as potential biofertilizers.

Genome-based approaches to understanding phosphorus deprivation responses and PSR1 control in Chlamydomonas reinhardtii.

Abstract: The Chlamydomonas reinhardtii transcription factor PSR1 is required for the control of activities involved in scavenging phosphate from the environment during periods of phosphorus limitation. Increased scavenging activity reflects the development of high-affinity phosphate transport and the expression of extracellular phosphatases that can cleave phosphate from organic compounds in the environment. A comparison of gene expression patterns using microarray analyses and quantitative PCRs with wild-type and psr1 mutant cells deprived of phosphorus has revealed that PSR1 also controls genes encoding proteins with potential “electron valve” functions—these proteins can serve as alternative electron acceptors that help prevent photodamage caused by overexcitation of the photosynthetic electron transport system. In accordance with this finding, phosphorus-starved psr1 mutants die when subjected to elevated light intensities; at these intensities, the wild-type cells still exhibit rapid growth. Acclimation to phosphorus deprivation also involves a reduction in the levels of transcripts encoding proteins involved in photosynthesis and both cytoplasmic and chloroplast translation as well as an increase in the levels of transcripts encoding stress-associated chaperones and proteases. Surprisingly, phosphorus-deficient psr1 cells (but not wild-type cells) also display expression patterns associated with specific responses to sulfur deprivation, suggesting a hitherto unsuspected link between the signal transduction pathways involved in controlling phosphorus and sulfur starvation responses. Together, these results demonstrate that PSR1 is critical for the survival of cells under conditions of suboptimal phosphorus availability and that it plays a key role in controlling both scavenging responses and the ability of the cell to manage excess absorbed excitation energy. While phosphorus (P) is an abundant element in the Earth’s crust, its availability can limit the growth of organisms present in both aquatic and terrestrial environments. P is essential for many fundamental processes that sustain life, including nucleic acid synthesis, membrane synthesis, energy metabolism, signaling, redox reactions, and modification of protein activities. The major form of P readily assimilated and utilized by most or

Atmospheric inputs of phosphorus and nitrogen to the southwest Mediterranean region: Biogeochemical responses of high mountain lakes

Abstract: We quantified dry and wet deposition of dust, nitrogen, and phosphorus over the southwest Mediterranean region (Sierra Nevada, Spain) and assessed its effects on the nutrient status and the chlorophyll a (Chl a) concentration in two high mountain lakes. Atmospheric deposition of particulate matter (PM) and total phosphorus (TP) were mainly associated with dryfall and showed a seasonal pattern similar to that reported for Saharan dust export toward the Mediterranean region, with maxima during spring and summer. In contrast, total nitrogen (TN) deposition was related to rainfall and did not follow the pattern observed for PM and TP. The molar TN : TP ratio was significantly lower (i.e., phosphorus-enriched) in dry deposition (TN vs. TP slope 5 11.2) than in wet deposition (TN vs. TP slope 5 95.5). In the study lakes, the molar TN : TP ratios and the Chl a concentrations were significantly influenced by the molar TN : TP ratio and the TP content of atmospheric deposition, respectively. Lake responses were more pronounced in the more phosphorous-limited system. These results establish a direct connection between atmospheric deposition and lake nutrient status and Chl a, making evident that in the Mediterranean region these inputs are an important source of phosphorous affecting biogeochemistry of oligotrophic systems.

Detection of quantitative trait loci for seminal root traits in maize ( Zea mays L.) seedlings grown under differential phosphorus levels

Abstract: Suboptimal phosphorus availability is a primary constraint for terrestrial plant growth Seminal roots play an important role in acquisition of nutrients by plant seedlings The length and number of seminal roots may be particularly important in acquisition of immobile nutrients such as phosphorus by increasing soil exploration The objective of this study was to identify quantitative trait loci (QTL) controlling seminal root growth in response to phosphorus stress in maize, and to characterize epistatic interactions among QTL Seminal root length and number were evaluated in 162 recombinant inbred lines derived from a cross between B73 and Mo17 in seedlings grown in a controlled environment B73 and Mo17 significantly differed for seminal root length under low phosphorus, but not under adequate phosphorus conditions Seminal root length of the population grown under low phosphorus ranged from 0 to 792 cm with a mean of 323 cm; while seminal root length of plants grown under high phosphorus ranged from 067 to 590 cm with a mean of 234 cm Under low phosphorus, one main-effect QTL was associated with seminal root length and three QTL with seminal root number; under high phosphorus, two QTL with seminal root length and three QTL for seminal root number These accounted for 11, 254, 228, and 241% of the phenotypic variations for seminal root length and number at low phosphorus, and seminal root length and number at high phosphorus, respectively Di-genic epistatic loci were detected for seminal root length at low phosphorus (two pairs) seminal root number at low phosphorus (eight pairs), seminal root length at high phosphorus (four pairs), and seminal root number at high phosphorus (two pairs), which accounted for 232, 506, 322, and 203% of the total variations, respectively Seminal root traits observed here were positively yet weakly correlated with shoot biomass in the field under low phosphorus, although no coincident QTL were detected These results suggest that epistatic interactions are important in controlling genotypic variation associated with seedling seminal root traits

QTL Analysis of Adventitious Root Formation in Common Bean under Contrasting Phosphorus Availability

Abstract: Low phosphorus availability is a primary constraint to crop production in developing countries. Adventitious roots play an important role in phosphorus acquisition, as they are localized near the soil surface where phosphorus is relatively abundant A population of recombinant inbred lines of Phaseolus vulgaris L. (G2333/G19839) was screened under high- and low-phosphorus conditions in the greenhouse and field. We observed phenotypic variation and transgressive segregation for adventitious root traits in both environments. Allomctric analysis revealed that although the taproot and basal roots are closely linked to shoot growth, recombinant inbred line (RILs) differ substantially in biomass allocation for adventitious roots. A linkage map with 149 genetic markers and a total cumulative map length of 1175 cM was used to identify a total of 19 QTL across 8 of the 11 linkage groups. Together these quantitative trait lod (QTL) accounted for 19 to 61% of the total phenotypic variation for adventitious root traits in the field and 18 to 39% under greenhouse conditions. Two major QTL for adventitious rooting under low phosphorus conditions in the field were observed on linkage groups B2 and B9 that together accounted for 61% of the observed phenotypic variation. We conclude that adventitious rooting under low phosphorus is a feasible target for bean breeding.

Architectural Tradeoffs between Adventitious and Basal Roots for Phosphorus Acquisition

Abstract: Adventitious rooting contributes to efficient phosphorus acquisition by enhancing topsoil foraging. However, metabolic investment in adventitious roots may retard the development of other root classes such as basal roots, which are also important for phosphorus acquisition. In this study we quantitatively assessed the potential effects of adventitious rooting on basal root growth and whole plant phosphorus acquisition in young bean plants. The geometric simulation model SimRoot was used to dynamically model root systems with varying architecture and C availability growing for 21 days at 3 planting depths in 3 soil types with contrasting nutrient mobility. Simulated root architectures, tradeoffs between adventitious and basal root growth, and phosphorus acquisition were validated with empirical measurements. Phosphorus acquisition and phosphorus acquisition efficiency (defined as mol phosphorus acquired per mol C allocated to roots) were estimated for plants growing in soil in which phosphorus availability was uniform with depth or was greatest in the topsoil, as occurs in most natural soils. Phosphorus acquisition and acquisition efficiency increased with increasing allocation to adventitious roots in stratified soil, due to increased phosphorus depletion of surface soil. In uniform soil, increased adventitious rooting decreased phosphorus acquisition by reducing the growth of lateral roots arising from the tap root and basal roots. The benefit of adventitious roots for phosphorus acquisition was dependent on the specific respiration rate of adventitious roots as well as on whether overall C allocation to root growth was increased, as occurs in plants under phosphorus stress, or was lower, as observed in unstressed plants. In stratified soil, adventitious rooting reduced the growth of tap and basal lateral roots, yet phosphorus acquisition increased by up to 10% when total C allocation to roots was high and adventitious root respiration was similar to that in basal roots. With C allocation to roots decreased by 38%, adventitious roots still increased phosphorus acquisition by 5%. Allocation to adventitious roots enhanced phosphorus acquisition and efficiency as long as the specific respiration of adventitious roots was similar to that of basal roots and less than twice that of tap roots. When adventitious roots were assigned greater specific respiration rates, increased adventitious rooting reduced phosphorus acquisition and efficiency by diverting carbohydrate from other root types. Varying the phosphorus diffusion coefficient to reflect varying mobilities in different soil types had little effect on the value of adventitious rooting for phosphorus acquisition. Adventitious roots benefited plants regardless of basal root growth angle. Seed planting depth only affected phosphorus uptake and efficiency when seed was planted below the high phosphorus surface stratum. Our results confirm the importance of root respiration in nutrient foraging strategies, and demonstrate functional tradeoffs among distinct components of the root system. These results will be useful in developing ideotypes for more nutrient efficient crops.

Phosphorus scavenging in the unicellular marine diazotroph Crocosphaera watsonii.

Abstract: Through the fixation of atmospheric nitrogen and photosynthesis, marine diazotrophs play a critical role in the global cycling of nitrogen and carbon. Crocosphaera watsonii is a recently described unicellular diazotroph that may significantly contribute to marine nitrogen fixation in tropical environments. One of the many factors that can constrain the growth and nitrogen fixation rates of marine diazotrophs is phosphorus bioavailability. Using genomic and physiological approaches, we examined phosphorus scavenging mechanisms in strains of C. watsonii from both the Atlantic and the Pacific. Observations from the C. watsonii WH8501 genome suggest that this organism has the capacity for high-affinity phosphate transport (e.g., homologs of pstSCAB) in low-phosphate, oligotrophic systems. The pstS gene (high-affinity phosphate binding) is present in strains isolated from both the Atlantic and the Pacific, and its expression was regulated by the exogenous phosphate supply in strain WH8501. Genomic observation also indicated a broad capacity for phosphomonoester hydrolysis (e.g., a putative alkaline phosphatase). In contrast, no clear homologs of genes for phosphonate transport and hydrolysis could be identified. Consistent with these genomic observations, C. watsonii WH8501 is able to grow on phosphomonoesters as a sole source of added phosphorus but not on the phosphonates tested to date. Taken together these data suggest that C. watsonii has a robust capacity for scavenging phosphorus in oligotrophic systems, although this capacity differs from that of other marine cyanobacterial genera, such as Synechococcus, Prochlorococcus, and Trichodesmium.