Dissolved Organic P Research Articles

Mersin Körfezi-Erdemli Kıta Sahanlığı Yüzey ve Dip Sularında İnorganik ve Organik Fosfor Formlarının Zaman ve Mekan Ölçekli Değişimleri

The aim of this study was to understand spatial and temporal variations of inorganic and organic forms of phosphorus in the surface and deep waters of Erdemli shelf zone of the Mersin Bay. For this goal, time- series hydrographical and phosphorus data were obtained monthly at the three selected stations between December 2001 and December 2003. The present results have shown that the concentrations of different fractions of total phosphorus displayed a decreasing trend from nearshore to shelfbreak zone of the bay. Total phosphorus (dissolved+particulate) in the shelf water was dominated by dissolved-P fraction (TDP:56-97%) and dissolved organic-P (DOP) was principally the major constituent of the TDP in the shelf water. Similarly, particulate organic-P (POP) dominates the particulate-P (PP) pool; however, the contribution of particulate inorganic-P (PIP) to PP pool was more pronounced in the nearshore zone fed by riverine inputs.

Current Wet Persulfate Digestion Method Considerably Underestimates Total Phosphorus Content in Natural Waters

T phosphorus (TP) in river and lake water is an important environmental variable that can be used as an indicator of nutrient status and water quality. TP was recently selected as an environmental stressor and numeric criteria have been developed based on its background concentration in a given environment. To minimize the eutrophication risk in aquatic ecosystems, U.S. Environmental Protection Agency water quality criteria require that TP is not exceed 10−128 μg/L for river and streams. Following EPA method 365.1, TP in surface waters is routinely determined on unfiltered water samples that are digested by autoclave in the presence of persulfate. Recent studies, however, indicated this method suffers low recovery of particulate phosphorus (PP) and we suggest reliable high temperature combustion method be used for PP determination. Raw water samples contain both suspended particles and dissolved constituents. In EPA TP method 365.1, unfiltered water sample is used for persulfate digestion but no attention was given on how to keep sample homogeneous and representative to the field condition. Due to rapid settling of large particles in water sample containers, it is difficult to keep sample homogeneous during subsampling and analysis. For example, it is practically impossible to avoid particle settling when samples are seating in an autosampler during automated online digestion and analysis. TP consists of particulate phosphorus and total dissolved phosphorus (TP = PP + TDP). Because most TP resides in particulate phase loss of particles during sampling and analysis can result in a significantly underestimated TP. To obtain representative particulate samples, filtration through 0.45 μm pore size filters has been used to separate PP from TDP (it might require a large volume of water if water turbidity is low). Particles collected on the filters are used to determine the PP. The filtrates are used to determine dissolved inorganic phosphorus (DIP) and TDP. The difference between TDP and DIP is operationally defined as dissolved organic P (DOP). The sum of PP and TDP can provide an accurate estimate of TP in natural waters. DOP and PP are usually converted to DIP which can then be measured by the molybdenum blue method. Wet persulfate digestion has been widely used for digesting TDP samples with variable conversion efficiency for different DOP compounds, ranging from 66% for inositol phosphate to 100% for ADP. On the other hand, high temperature combustion is needed for PP determination. High temperature combustion at above 550 °C can decompose all organic matters and inorganic minerals to simple inorganic compounds. With commercial CHN elemental analyzer available, it has become a conventional technique for measuring carbon, hydrogen and nitrogen content of particulate samples. In PP determination, high temperature combustion in the presence of oxidizing reagent Mg(NO3)2 was followed by acid extraction to recover DIP. This method has been used for analysis of PP in sediment and TDP in water samples and achieved a close to 100% conversion efficiency. However, no commercial P elemental analyzer is available and manual analysis of PP by high temperature combustion remains time-consuming and labor-intensive. It is worth to note that the first persulfate digestion method developed by Menzel and Corwin in 1965 was for measuring seawater TP. In that study, only a few DOP compounds were tested for recovery. A dried zooplankton tissue was suspended in distilled water and then the filtrate from the suspension was analyzed by persulfate digestion method. This extracted, filtered sample contained only DOP and no PP sample was tested. Ironically, this seawater method become obsolete in marine community has since been widely adapted for TP measurement in freshwater where particulate matter, dominated by clay minerals, is much more abundant than oceanic waters. Recently, Suzumura pointed out the limitation of this method for determination of TP in natural waters. He compared wet persulfate digestion with high temperature combustion on sediment, plankton and mineral samples. While

Diverted Mississippi River sediment as a potential phosphorus source affecting coastal Louisiana water quality

Mississippi River water and associated sediment are seasonally diverted into Louisiana coastal basins to restore historic hydrologic and salinity regimes and to slow or reverse the widespread wetland loss. More river diversions are planned; however, very little research has been conducted on the potential source of phosphorous (P) of these sediments transported by the Mississippi River into the coastal areas through these diversions. In addition, the sediments have the potential to undergo changes in redox status when these significant flooding events occur. Therefore, we examined the effect of sediment redox condition on P release from newly deposited Mississippi River sediment. Sediment was collected from Big Mar Lake, the receiving water body of the Caernarvon diversion structure, through which river water is diverted into the Breton sound estuary. Sediment suspensions were incubated in the laboratory under reducing conditions, and the relation of redox conditions to P release was determined. Soluble reactive P (SRP), dissolved organic P (DOP), Fe, and Mn concentrations increased with decreasing sediment redox potential. The SRP and DOP concentrations increased 32 - and 8-fold during 20 days of anaerobic conditions. The increase in SRP and DOP availability was significantly correlated to an increase in ferrous iron with no significant relationship with Al, Ca, or Mg. While the vast majority of studies on nutrients associated with the Mississippi River diversions have focused on excess inorganic nitrogen forms (primarily NO3) in the river water, this study is one of the first to demonstrate that upon reduction associated with prolonged flooding, the diverted Mississippi River suspended sediment can be a significant source of available P to the coastal basin.

Temporal and Spatial Patterns of Internal Phosphorus Recycling in a South Florida (USA) Stormwater Treatment Area

Large constructed wetlands, known as stormwater treatment areas (STAs), have been deployed to remove phosphorus (P) in drainage waters before discharge into the Everglades in South Florida, USA. Their P removal performance depends on internal P cycling under typically hydrated, but with occasionally desiccated, conditions. We examined the spatial and temporal P removal capacity under different hydrologic conditions along a STA flow path. While inflow soils are P enriched, the outflow region of the wetland contained P-unsaturated soils with minimal net recycling of bound soil P to the water column as plant-available P. The outflow-region soils were characterized by low porewater soluble reactive P (SRP) (≤40 μg L) and high total sulfide (TS) (2-9 mg L) concentrations, and total ammoniacal nitrogen (TAN) and SRP flux rates that averaged 1.51 and 0.002 mg m d, respectively. Pronounced increases in porewater and surface-water concentrations of SRP, dissolved organic P (DOP), and TAN were observed immediately after rehydration of the cell after an extended drought. Elevated total P concentrations persisted at the outfall of the cell for several months thereafter, resulting in an annual outflow total P concentration nearly threefold higher than the long-term mean. Relative to processes that can occur during extended periods of inundation, such as sulfate-enhanced P release from organic matter mineralization or iron sulfide formation, aerobic oxidation of organic matter during prolonged dryout periods is a more significant biogeochemical process in compromising soil P retention in STAs.

Effects of Lime and Phosphorus Application on Phosphorus Runoff Risk

Lime was investigated as a soil amendment to decrease phosphorus (P) loss in runoff from two Delaware sandy loam soils, one high and one low in P. Soils were limed at three rates (control and target pH values of 6 and 6.8, respectively), packed into runoff boxes (2,000 cm2) and received simulated rainfall (80 mm h−1 for 30 min). Lime showed potential to decrease P loss in runoff, but its effectiveness was soil specific and dependant on other management factors also. Lime decreased dissolved reactive P (DRP) and dissolved organic P (DOP) loss by 20–25 and 52–93 %, respectively, for the high-P soil and particulate P (PP) by 13 % for the low-P soil. The majority of P lost in runoff was DOP (3–29 %) or PP (64–96 %). Lime increased PP losses from the finer-textured soil following P application, indicating that increased P sorption can lead to increased losses if P is sorbed to more erodable particles. Initial soil P status was more important than liming in determining P loss. While amendments may decrease P losses in the short term, addressing nutrient imbalances at the field scale is clearly necessary in the long term. Losses increased significantly following inorganic P application. Although P was sorbed rapidly, with less than 2 % of added P removed in runoff, mean concentrations in excess of 700 μg l−1 DRP, 2,500 μg l−1 OP and 6,500 μg l−1 PP were recorded for both soils immediately following P application.

The distribution and chemical speciation of dissolved and particulate phosphorus in the Bering Sea and the Chukchi–Beaufort Seas

Water samples were collected from the Bering Sea and the Chukchi–Beaufort Seas during the 4th Chinese Arctic Research Expedition in summer 2010 to examine the abundance, spatial distribution and phase partitioning of phosphorus (P) between dissolved and particulate, inorganic and organic phases. Measurements of P species included dissolved inorganic P (DIP), dissolved organic P (DOP) and five particulate P species operationally defined by sequential extraction techniques. Inorganic P was generally the predominant form of both dissolved and particulate P, comprising on average up to 91±13% of the dissolved phase and 72±23% of the particulate phase in the study area. Concentrations of DIP in the water column of the Chukchi Sea and Bering Sea were considerably higher than those in the Beaufort Sea (>3μM vs. ∼1μM), showing a strong influence of North Pacific inflow waters. The percentage of DOP in the dissolved P pool was generally higher in surface waters than deeper waters, and higher in the Chukchi Sea than in the Bering Sea, consistent with their difference in primary productivity and reflecting sources of DOP from the surface waters. Within the particulate P pool, the labile P and ferric bound P were the two predominant species, especially in the upper water column (<1000m), while authigenic or CaCO3 bound P and detrital P were the two least abundant particulate P species. A positive correlation between labile particulate P and particulate organic carbon (POC) or particulate nitrogen (PN) was observed, where labile P concentrations decreased with increasing DIP concentrations and decreasing biological activity in the upper water column, indicating the contribution of labile particulate P from biological production. Labile P was an active component in regeneration of particulate P in the water column. The authigenic P was relatively abundant in deeper waters, especially in the Bering Sea, suggesting an active transformation between labile-P and authigenic P and a possible sink for P as authigenic particulate P in the deeper water column. In contrast to labile P, authigenic P, and organic P, the distributions of ferric-bound P and detrital P were mostly regulated by physicochemical processes, such as lateral transport and sediment resuspension. Therefore, different particulate P species could play a distinct role in biogeochemical cycling of P in the water column and understanding the detailed chemical and phase speciation of P should provide a better understanding of the dynamic cycling of P in the marine environment.

Speciation and transformation of phosphorus and its mixing behavior in the Bay of St. Louis estuary in the northern Gulf of Mexico

Water samples were collected for measurements of dissolved, colloidal, and particulate inorganic and organic phosphorus (P) from the Bay of St. Louis estuary in the northern Gulf of Mexico during August 2008 and October 2009. Laboratory mixing experiments were also carried out using end-member river water and seawater to examine key processes and mechanisms controlling the behavior of P during estuarine mixing. Dissolved organic P (DOP) was the dominant species in the total dissolved P (TDP) pool in both lower (S<10) and higher salinity (S>25) regions, while dissolved inorganic P (DIP) predominated in mid-salinity regions (S of 10∼20) comprising up to 75% of the TDP. Both DIP and DOP behaved non-conservatively during estuarine mixing showing dramatic changes and transformation between different P species. The total particulate phosphorus (TPP) accounted for up to 85% of total phosphorus (TP=TDP+TPP) in the low-salinity areas but fell to about 38% in higher salinity regions. The quasi-negative correlation between TDP and TPP and the similarity in mixing behavior between field observations and laboratory experiments supported our hypothesis that physicochemical processes, such as dynamic repartitioning between water and particles or adsorption/desorption, are the predominant mechanisms controlling the biogeochemical cycling of P species in the Bay of St. Louis. River export fluxes of DIP could be significantly underestimated without the quantification of particulate P species, especially in more pristine river basins. The value of the distribution coefficient (in terms of logKd) ranged from 4.4 to 5.6 and decreased with increasing suspended particulate matter concentration and salinity, indicating that P is highly particle reactive and the presence of colloidal P may play an important role in the cycling of P in estuarine environments. Colloidal inorganic P (CIP) and colloidal organic P (COP), as quantified by an ultrafiltration permeation model, comprised 0–62% of the DIP and 34–93% of the DOP with the highest values in the river mouth area, suggesting a river source for colloidal P. The % CIP dropped to below the detection limit as salinity increased, whereas % COP first decreased but increased again with increasing salinity, reflecting different sources for CIP and COP in the lower estuary. The DOC/DOP ratio decreased rapidly with increasing salinity indicating a diagenetically older dissolved organic matter pool from the river and a dynamic change in sources and chemical speciation of P in the estuary.

Carbon, nitrogen and phosphorus resource supply and utilisation for coastal planktonic heterotrophic bacteria in a gradient of nutrient loading

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 447:55-75 (2012) - DOI: https://doi.org/10.3354/meps09473 Carbon, nitrogen and phosphorus resource supply and utilisation for coastal planktonic heterotrophic bacteria in a gradient of nutrient loading Olav Vadstein1,*, Tom Andersen2, Helge R. Reinertsen3, Yngvar Olsen3 1Department of Biotechnology, and 3Department of Biology, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway 2University of Oslo, Department of Biology, PO Box 1066 Blindern, 0316 Oslo, Norway *Email: olav.vadstein@biotech.ntnu.no ABSTRACT: Data from 7 mesocosms with a gradient in daily nutrient loading rate (LN) and inverse modelling were used to estimate all C, N and P flows in an idealised food web. The gradient in LN created autotrophic production (AP) of 7 to 314 µg C l−1 d−1 (mean values over 18 d). The production of dissolved organic C (DOC) decreased from 240 to 40% of AP, and was dominated by heterotrophs (80 to 58%), with heterotrophic bacteria (BAC) producing 48 ± 8% (means ± SD) by excretion or lysis. The consumption of DOC by BAC was 133 to 86% of AP, and DOC accumulated when experimental LN ≥ natural LN. C of BAC origin constituted 5.5 to 0.2% of the C consumed by copepods. The production of dissolved N and P was mainly by heterotrophs (92 ± 2% of DN, 92 ± 4% DP), but autotrophs produced 26 ± 7% of dissolved organic N (DON) and 21 ± 8% of dissolved organic P (DOP). For the production of inorganic N and P (DIN and DIP, respectively), BAC predators ­produced >50% of DIN and >70% of DIP at low or moderate LN (averages 37 ± 16% of DIN and 66 ± 14% of DIP). The contribution by BAC was low for DIN (12 ± 6%) and zero for DIP. For the re-mineralisation of N and P, the significance of BAC was as N and P rich food particles. DOP accumulated more than DOC, despite the high demand for P. Turnover time of dissolved organic matter (DOM) decreased from around 80 to 12 d with increasing LN. These data provide new insights into the role of various functional groups of organisms for the cycling of DOM, and to the differences in C, N and P cycling. KEY WORDS: DOM production · DOM utilisation · Heterotrophic bacteria · ­Community ­interactions · DOC accumulation · Re-mineralisation · Inverse modelling ∙ Full text in pdf format PreviousNextCite this article as: Vadstein O, Andersen T, Reinertsen HR, Olsen Y (2012) Carbon, nitrogen and phosphorus resource supply and utilisation for coastal planktonic heterotrophic bacteria in a gradient of nutrient loading. Mar Ecol Prog Ser 447:55-75. https://doi.org/10.3354/meps09473 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 447. Online publication date: February 13, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Characterization of the rate and temperature sensitivities of bacterial remineralization of dissolved organic phosphorus compounds by natural populations.

Production, transformation, and degradation are the principal components of the cycling of dissolved organic matter (DOM) in marine systems. Heterotrophic Bacteria (and Archaea) play a large part in this cycling via enzymatic decomposition and intracellular transformations of organic material to inorganic carbon (C), nitrogen (N), and phosphorus (P). The rate and magnitude of inorganic nutrient regeneration from DOM is related to the elemental composition and lability of DOM substrates as well as the nutritional needs of the mediating organisms. While many previous efforts have focused on C and N cycling of DOM, less is known in regards to the controls of organic P utilization and remineralization by natural populations of bacteria. In order to constrain the relative time scales and degradation of select dissolved organic P (DOP) compounds we have conducted a series of experiments focused on (1) assessment of the short-term lability of a range of DOP compounds, (2) characterization of labile DOP remineralization rates, and (3) examination of temperature sensitivities of labile DOP remineralization for varying bacterial populations. Results reinforce previous findings of monoester and polyphosphate lability and the relative recalcitrance of a model phosphonate: 2-aminoethylphosphonate. High resolution time-series of P-monoester remineralization indicates decay constants on the order of 0.67–7.04 day−1 for bacterial populations isolated from coastal and open ocean surface waters. The variability of these rates is predictably related to incubation temperature and initial concentrations of heterotrophic bacteria. Additional controls on DOP hydrolysis included seasonal shifts in bacterial populations and the physiological state of bacteria at the initiation of DOP addition experiments. Composite results indicate that bacterial hydrolysis of P-monoesters exceeds bacterial P demand and thus DOP remineralization efficiency may control P availability to autotrophs.

Dissolved phosphorus pools and alkaline phosphatase activity in the euphotic zone of the Western north pacific ocean.

We measured pools of dissolved phosphorus (P), including dissolved inorganic P (DIP), dissolved organic P (DOP) and alkaline phosphatase (AP)-hydrolyzable labile DOP (L-DOP), and kinetic parameters of AP activity (APA) in the euphotic zone in the western North Pacific Ocean. Samples were collected from one coastal station in Sagami Bay, Japan, and three offshore stations between the North Pacific subtropical gyre (NPSG) and the Kuroshio region. Although DIP concentrations in the euphotic zone at all stations were equally low, around the nominal method detection limit of 20 nmol L-1, chlorophyll a (Chl a) concentrations were one order of magnitude greater at the coastal station. DOP was the dominant P pool, comprising 62–92% of total dissolved P at and above the Chl a maximum layer (CML). L-DOP represented 22–39% of the total DOP at the offshore stations, whereas it accounted for a much higher proportion (about 85%) in the coastal surface layers. Significant correlations between maximum potential AP hydrolysis rates and DIP concentrations or bacterial cell abundance in the offshore euphotic zone suggest that major APA in the oligotrophic surface ocean is from bacterial activity and regulated largely by DIP availability. Although the range of maximum potential APA was comparable among the environmental conditions, the in situ hydrolysis rate of L-DOP in the coastal station was 10 times those in the offshore stations. L-DOP turnover time at the CML ranged from 4.5 days at the coastal station to 84.4 days in the NPSG. The ratio of the APA half-saturation constant to the ambient L-DOP concentration decreased markedly from the NPSG to the coastal station. There were substantial differences in the rate and efficiency of DOP remineralization and its contribution as the potential P source between the low-phosphate/high-biomass coastal ecosystem and the low-phosphate/low biomass oligotrophic ocean.

Intra- and inter-annual trends in phosphorus loads and comparison with nitrogen loads to Rehoboth Bay, Delaware (USA)

Monthly phosphorus loads from uplands, atmospheric deposition, and wastewater to Rehoboth Bay (Delaware) were determined from October 1998 to April 2002 to evaluate the relative importance of these three sources of P to the Bay. Loads from a representative subwatershed were determined and used in an areal extrapolation to estimate the upland load from the entire watershed. Soluble reactive phosphorus (SRP) and dissolved organic P (DOP) are the predominant forms of P in baseflow and P loads from the watershed are highest during the summer months. Particulate phosphorus (PP) becomes more significant in stormflow and during periods with more frequent or larger storms. Atmospheric deposition of P is only a minor source of P to Rehoboth Bay. During the period of 1998–2002, wastewater was the dominant external source of P to Rehoboth Bay, often exceeding all other P sources combined. Since 2002, however, due to technical improvements to the sole wastewater plant discharging directly to the Bay, the wastewater contribution of P has been significantly reduced and upland waters are now the principal source of P on an annualized basis. Based on comparison of N and P loads, primary productivity and biomass carrying capacity in Rehoboth Bay should be limited by P availability. However, due to the contrasting spatial and temporal patterns of N and P loading and perhaps internal cycling within the ecosystem, spatial and temporal variations in N and P-limitation within Rehoboth Bay are likely.

Manure Composition and Incorporation Effects on Phosphorus in Runoff Following Corn Biomass Removal

Greater demand for corn ( L.) stover for bioenergy use may lead to increased corn production acreage with minimal surface residue cover, resulting in greater risk for soil erosion and phosphorus (P) losses in runoff. A rainfall simulation study was conducted to determine the effects of spring-applied dairy cow () manure (none, in-barn composted, and exterior walled-enclosure pit) with >200 g kg organic solids content following fall corn biomass removal with and without incorporation (chisel plow [CP] and no-till [NT]) on sediment and P in runoff. Runoff was collected from a 0.83-m area for 60 min following the onset of rainfall simulation (76 mm h), once in spring and once in fall. Runoff dissolved reactive P (DRP) and dissolved organic P (DOP) concentrations were positively correlated with manure P rate and were higher in NT compared with CP. Conversely, sediment and particulate P (PP) concentrations in runoff were inversely correlated with manure P rate (and manure solids) and were higher in CP compared with NT. Runoff volume where no manure was applied was higher in NT than in CP in spring but similar in fall. The addition of manure reduced runoff volumes by an average of 82% in NT and 42% in CP over spring and fall. Results from this study indicate that surface application of dairy manure with relatively high solids content may reduce sediment and PP losses in runoff without increasing the risk of increased DRP and DOP losses in the year of application where corn biomass is harvested.

Seasonal phosphorus depletion and microbial responses to the change in phosphorus availability in a subarctic coastal environment

Temporal variations of phosphorus (P) pools (soluble reactive P (SRP), dissolved organic P (DOP), and particulate P (PP)), alkaline phosphatase activity (APA), and orthophosphate uptake were measured in Funka Bay to describe the annual P cycle in the bay and determine the phytoplankton and bacterial responses to the change in P availability. Observations over 4 years demonstrated that SRP concentrations in the surface waters decreased from the winter maximum of 1.0 μmol L −1 to 0.3 μmol L −1 at the end of the spring phytoplankton bloom, and then to under the detection limit by around August. The DOP concentration was relatively constant at 0.1 μmol L −1 throughout the year with higher concentrations up to 0.3 μmol L −1 just after the peak of the spring bloom. PP concentrations varied around 0.1 μmol L −1 with higher concentrations up to 0.6 μmol L −1 during the high chlorophyll a concentration period. SRP comprised 85% of the total P pool prior to the spring bloom, but the contribution decreased to less than 30% in the post-bloom period and DOP dominated the P pool in the surface. Most of the measured APA was less than 0.1 nmol L −1 min −1 in the whole water column, but exceptionally high values up to 1.4 nmol L −1 min −1 were observed in low SRP surface waters during summer. When SRP decreased from 0.3 μmol L −1 in spring to under the detection limit in summer, turnover time for orthophosphate at 10 m depth decreased from 61 days to 4.2 h. The high APA and short turnover time for orthophosphate suggested that microbes in the surface mixed layer experienced severe P stress in summer. Under severely P stressed conditions, APA was detected mostly in the > 10 μm fraction, suggesting that large phytoplankton would acquire P from DOP to overcome the P stress. This was supported by the result that large phytoplankton were outcompeted by the 0.2–1 μm sized microbes for orthophosphate uptake.

Characterization of alkaline phosphatase activity in the North and South Pacific Subtropical Gyres: Implications for phosphorus cycling

We characterized alkaline phosphatase (AP) activity (APA) and report AP kinetic parameters in the North and South Pacific Subtropical Gyres (NPSG and SPSG, respectively) to evaluate the relative importance of APA in dissolved organic P (DOP) remineralization. APA potential hydrolysis rates were low but measurable (0.10 ± 0.06 nmol L−1 h−1, n = 12, and 0.13 ± 0.08 nmol L−1 h−1, n = 6) in surface samples from the NPSG and central SPSG, respectively. When compared to dissolved inorganic P (DIP) uptake rates, the potential utilization of DOP by APA may be important for microbial communities in these oligotrophic habitats. Assuming an upper (80%) and a lower (10%) fraction of the DOP to be AP‐hydrolyzable, APA could represent 25% ± 18% (n = 11) and 4% ± 3% (n = 11) of the DIP uptake, respectively, in surface waters of the NPSG and 147% ± 86% (n = 6) and 20% ± 12% (n = 6), respectively, in surface waters of the central SPSG. The ratio of APA to DIP uptake was significantly larger in the SPSG compared to the NPSG despite having higher DIP and lower DOP. The half‐saturation constant (Km) was in the range of DOP concentrations measured in the two gyres, meaning that microorganisms can adjust their DOP utilization according to DOP availability. Dissolved APA was a large fraction of total APA in the NPSG, contributing between 12% and 100% (41 ± 23%, n = 23) of total APA at Sta. ALOHA. Utilization of the AP‐hydrolyzable fraction of the DOP probably contributes to production in the extensive Pacific oligotrophic gyres.

Treatability and fate of various phosphorus fractions in different wastewater treatment processes

The increasingly more stringent phosphorus (P) discharge limits, which are below the concentrations reliably achievable with currently available technologies, demand for better understanding of phosphorus removal mechanisms. This study investigated the compositional fractions of phosphorus (P) in various effluents as well as the efficacy of different levels of treatment processes for removing different fractions of P in wastewater. The results showed that BNR can effectively remove most fractions of P, with relatively higher efficiencies (>93%) towards bioavailable forms of P including soluble reactive P (sRP), particulate reactive P (pRP) portion and particulate acid hydrolysable P (pAHP) and, it showed relatively lower efficiency (78%) towards organic P. Soluble acid hydrolysable P (sAHP) was not effectively removed (<40%). Chemical P removal process was more effective for elimination of sRP, sAHP and particulate organic P (pOP), but was not as effective for removing pAHP and, it exhibited nearly no removal of dissolved organic P (DOP). We found that chemical P removal process led to a significant increase in the concentration of pRP by up to 255%, indicating that these pRP (presumably as chemically bounded P) are likely formed through chemical precipitation/co-adsorption. Only 22% and 64% of the pRP was removed through tertiary clarifier and filtration, respectively. This implies that chemical addition converts sRP into particulate-associated P, mostly as pRP that was not easily removed by sedimentation and filtration, therefore, the efficacy of chemical P removal highly depends on the effectiveness of solid and liquid separation process. As more sRP and particulate P were removed through the series of treatment processes, the percentage contribution from organic P increases with the level of treatment due to its recalcitrant nature. Our results indicated that in order to achieve extremely low effluent P levels, technologies and processes that can enhance pRP and DOP removal will be required.

Phosphorus in humped and hollowed soils of the Inchbonnie catchment, West Coast, New Zealand: II. Accounting for losses by different pathways

Phosphorus (P) is the limiting nutrient for the eutrophication of Lake Brunner, West Coast, New Zealand. In a previous study, the top 7.5 cm of soil in grazed dairy pastures in the Inchbonnie catch‐ment which drains into Lake Brunner was estimated to lose about 20 kg P ha‐1 year‐1. Only some of this goes into waterways and the lake, but how much and in what chemical form is unclear. Hence, my aim was to account for P losses within the farm and estimate potential losses to waterways according to a number of source treatments typical for a dairy pasture. Soil turves and lysimeters were collected, treatments imposed (control, dung equivalent to that deposited during a 24‐h grazing period, superphosphate at 30 kg P ha‐1, and dung plus superphosphate) and subjected to 330 mm of simulated rainfall over a period of 30 days, equivalent to 1 month's rainfall. Total runoff (overland now and subsurface now—shallow leachate in this study—combined) was collected and analysed for dissolved reactive P (DRP), dissolved organic P (DOP), particulate P and total P. More P was lost from the dung + fertiliser treatment than the sum of dung and fertiliser treatments. Dung and fertiliser treatments lost significantly more P than the control. More P was lost via overland flow than leaching. The loss of DOP was more important in leachate than overland flow due to the poorer sorp‐tion of DOP compared to DRP (largely comprised of orthophosphate). When aggregated to a year, P losses were estimated to be 6.6–9.7 kg ha‐1 year‐1 of which 1.6–2.2 kg ha‐1 year‐1 was via leaching. In accounting for P lost from the 0–7.5 cm soil layer of a grazed diary pasture, it was estimated that 7 kg P ha‐1 year‐1 was transferred to the effluent block, while 0.6 kg Pha‐1 year‐1 was estimated as lost via lanes and stream crossings, leaving 2.7–5.8 kg P ha‐1 year‐1 unaccounted for. This was thought to be associated with Plost from, or transferred to, deeper soil layers, effluent ponds or stand‐off or feedpads, but needs to be further investigated. Management practices to mitigate P losses in overland flow and leachate from humped and hollowed paddocks include: maintaining soil Olsen P concentrations at as low a concentration as economically optimal, using low water solubility P fertilisers and keeping cows off wet paddocks as often as practically possible.

Speciation, phase association and potential bioavailability of phosphorus on a Svalbard glacier

Glacier surfaces are known to harbour abundant and active microbial communities. Phosphorus has been shown to be deficient in glacial environments, and thus is one of the limits on microbial growth and activity. We quantified the phosphorus pool in cryoconite debris and the concentration of dissolved phosphorus in supraglacial water on Werenskioldbreen, a Svalbard glacier. The mean total P content of the cryoconite debris was ~2.2 mg g−1, which is significantly more than would be expected in rock debris from local sources. 57% of this P was present in the fraction defined as organic P. It may account for the P in excess of the rock debris, and could be explained by allochthonous input of organic matter. The concentration of total dissolved P in supraglacial water was very low (5.2–8.5 μg l−1), which was probably caused by efficient flushing and re-adsorption onto mineral surfaces. Dissolved organic P (DOP) was a very important component of the dissolved phosphorus pool on Werenskioldbreen, as concentrations of DOP typically exceeded those of dissolved inorganic P (or SRP) by more than four times in all the glacial water types. It is very difficult to assess whether P was limiting in this environment solely on the basis of the N:P ratios in the debris or biomass. There may be some degree of biological control over the C:N:P ratios in the debris, but the phosphorus cycling in the supraglacial environment on this glacier seems to be mainly controlled by physical and geochemical processes.

Spatial contributions of diffuse inputs and within-channel processes to the form of stream water phosphorus over storm events

Summary Concentrations of suspended particulate matter (SPM), NO 3 -N and P fractions: PO 4 -P, dissolved organic P (DOP), particulate P (PP) and bioavailable exchangeable P were examined over 5 storm events in two nested agricultural catchments in NE Scotland: a (51 km 2 ) catchment and its headwater (4 km 2 ). NO 3 -N showed anticlockwise hysteresis for all storms in both catchments. In contrast, the headwater showed strong clockwise hysteresis of SPM, dissolved and particulate P concentrations, but which weakened through summer to spring. Less pronounced hysteresis of P forms in the larger catchment was attributed to a combination of factors: a less energetic system, nutrient leaching from the floodplain, a point source of a small sewage treatment works and the occurrence of coarser soil and sediment parent materials with less P adsorption and transport capacity. The headwater exhibited a strong ‘first flush’ effect of sediment and dissolved P, particularly following dry conditions, received a significant transfer of readily-solubilized organic P from the surrounding soils in late summer and after manure applications in winter, and was the likely cause of large sediment associated P signals observed in the 51 km 2 catchment. Our results suggest that steeper gradient headwaters should be targeted for riparian improvements to mitigate soil erosion from headwater fields. The efficiency of riparian erosion controls is also dependant on the size of the store of fine sediment material within the stream channel and this may be large.

Dredging effects on P status and phytoplankton density and composition during winter and spring in Lake Taihu, China

Phytoplankton density and composition, together with phosphorus (P) concentrations and size-fractionated alkaline phosphatase activity (APA), were investigated in dredged and undredged zones in Lake Taihu from January to April 2004. P concentrations were also determined in the corresponding interstitial water. Enzyme Labeled Fluorescence (ELF) was used for localizing extracellular phosphatase on phytoplankton cell membranes in April. The increase in phytoplankton density was paralleled by a significant increase in soluble reactive P (SRP) concentrations in the water column and interstitial water at all sites from January to April, with chlorophyte gradually becoming dominant. In February, at the undredged site, more algae dominated by chlorophyte occurred in overlying water, rather than in the surface, coinciding with higher SRP concentrations in overlying and interstitial water. Therefore, P status in the bottom is important to phytoplankton development in terms of density and composition. Undredged sites had higher SRP concentrations in interstitial water than dredged sites. Furthermore, Higher APA was observed, accompanied by higher dissolved organic P (DOP) and lower total P at the undredged site in February. Enzymatic hydrolysis of DOP may have been an additional source of P for phytoplankton. In April, Schroederia sp. was ELF labeled in surface water at the dredged site, which showed markedly lower SRP concentration, but not at the undredged site with higher SRP concentration. Thus, the dredging might regulate algal density and composition in water column by reducing P bioavailability.

Distribution and partitioning of nitrogen and phosphorus in a fringing reef lagoon of Ishigaki Island, northwestern Pacific

Concentration of dissolved and particulate carbon (C), nitrogen (N), and phosphorus (P) were measured daily and seasonally in the water column of a coral reef lagoon at Ishigaki Island. Concentrations of dissolved inorganic N and P (DIN, DIP), dissolved organic C and N (DOC, DON), particulate organic C, and particulate N and P (POC, PN, PP) were usually higher in the lagoon than at offshore stations, while dissolved organic P (DOP) was higher at the offshore stations than in the lagoon. Concentration ratios of DIN:DIP and PN:PP were near 16:1 in winter and >20:1 in summer. DON:DOP was always ≥30. Total P (DIP + DOP + PP) was fairly constant around 0.177 ± 0.025 μmol l–1 (mean ± SD), suggesting conservative behavior of water-column P around this reef. DIP and PP seemed to be produced at the expense of DOP, and PP rather than DIP increased when gross primary production (GPP) was high. In contrast, total N (DIN + DON + PN) showed large spatial and seasonal variation from 4.3 to 12.4 μmol l–1. DON and PN increased when GPP and DIN:DIP were high, which suggests that export production of organic N by the lagoon biota was enhanced by primary production and the availability of N relative to P. Estimation of C, N, and P exchange fluxes between the lagoon and the outer ocean using a simple hydrodynamic model showed that the lagoon ecosystem released N (especially DIN) but not P to the surrounding ocean. Oceanic DOP could be the major source for the P budget of the lagoon. While the lagoon was a net source of organic C to the outer ocean, the net export was only a minor fraction (<5%) of gross exchange of organic C between these 2 ecosystems.