Showing papers on "Phosphorus published in 1979"

Microdetermination of Phosphorus

Abstract: Several different procedures are recommended for the determination of total phosphorus in biologic samples. The method described here has the greatest sensitivity, being able to demonstrate the presence of 0.10 μg phosphorus per ml. It is based on the reduction of phosphomolybdate complex with ascorbic acid. The procedure described here is essentially identical to the method published by Chen, Toribara and Warner (1956).

Mayan urbanism: impact on a tropical karst environment.

Abstract: From the first millennium B.C. through the 9th-century A.D. Classic Maya collapse, nonurban populations grew exponentially, doubling every 408 years, in the twin-lake (Yaxha-Sacnab) basin that contained the Classic urban center of Yaxha. Pollen data show that forests were essentially cleared by Early Classic time. Sharply accelerated slopewash and colluviation, amplified in the Yaxha subbasin by urban construction, transferred nutrients plus calcareous, silty clay to both lakes. Except for the urban silt, colluvium appearing as lake sediments has a mean total phosphorus concentration close to that of basin soils. From this fact, from abundance and distribution of soil phosphorus, and from continuing post-Maya influxes (80 to 86 milligrams of phosphorus per square meter each year), which have no other apparent source, we conclude that riparian soils are anthrosols and that the mechanism of long-term phosphorus loading in lakes is mass transport of soil. Per capita deliveries of phosphorus match physiological outputs, approximately 0.5 kilogram of phosphorus per capita per year. Smaller apparent deliveries reflect the nonphosphatic composition of urban silt; larger societal outputs, expressing excess phosphorus from deforestation and from food waste and mortuary disposal, are probable but cannot be evaluated from our data. Eutrophication is not demonstrable and was probably impeded, even in less-impacted lakes, by suspended Maya silt. Environmental strain, the product of accelerating agroengineering demand and sequestering of nutrients in colluvium, developed too slowly to act as a servomechanism, damping population growth, at least until Late Classic time.

Nutrient dependence of primary productivity in lakes1

Abstract: An analysis of growing season measurements of daily primary productivity, chlorophyll, water chemistry, and transparency from 58 north temperate lakes shows a strong correlation between volumetric rates of photosynthesis, chlorophyll, and nutrients. Mean daily rates of photosynthesis per unit volume euphotic zone, v, are correlated with mean chlorophyll concentration (r2 = 0.80). The mean daily rate of photosynthesis at optimal depth, Āopt, is highly correlated with mean total P(r2 = 0.95), and with mean total N(r2 = 0.91). In contrast, integral rates of photosynthesis are linked less tightly to nutrient concentration because of their simultaneous dependence on transparency. The Dillon-Rigler phosphorus loading model is extended to predict volumetric rates of photosynthesis (v and Āopt) in lakes where the N:P balance indicates control by phosphorus (N:P ⩾ 13).

Ecosystem Dynamics and a Phosphorus Budget of an Alluvial Cypress Swamp in Southern Illinois

Abstract: Annual patterns in hydrology, phosphorus circulation, and sediment dynamics were studied in a southern Illinois, USA floodplain swamp dominated by bald cypress (Taxodium disti- chum) and swamp tupelo (Nyssa aquatica). The study emphasized the swamp's interactions with the adjacent river. For the year, major inputs of water to the swamp were throughfall (74.3 cm) and runoff (69.4 cm) with minor contributions due to groundwater (21.6 cm). Outflows were by evapo- transpiration (72.3 cm), surface outflow (56.5 cm), and groundwater (21.0 cm), with the latter two draining primarily to the river. A flood occurred during the study period, passing 1.6 x 107 m3 of river water over the swamp and depositing 0.06 cm of sediments. An annual phosphorus budget was developed for the swamp from field measurements. The greatest input of phosphorus to the swamp was 3.6 g P.m-2 yr-1, due to deposition of high-phosphorus sediments during the flood. This was 10 times greater than the outflow of phosphorus to the river, 0.34 g P.m-2 yr-', and 26 times greater than the throughfall input of 0.14 g P.m-2 yr-1. Total tree uptake from sediments was estimated to be 0.87 g P.m-2 yr-t of which 0.77 g P.m-2 yr-t returns as litterfall to the swamp sediments. Duckweed productivity was estimated to take 3.3 g P.m-2 yr-t from the water column and deposit this in the sediments during die-off. For the period 1937-1967, cypress growth, based on tree ring analyses, was closely correlated with several measures of flooding frequency and magnitude, all obtained from past river data. Tree ring data prior to 1937 showed poor correlation with flooding, probably because of logging activity. Cypress growth has decreased dramatically in recent years, corresponding to the rise in water level caused by beaver activity.

The role of sediments and bryophytes in phosphorus dynamics in a headwater stream ecosystem1

Abstract: Streambed sediments and the bryophyte community are sites of retention and processing of dissolved phosphorus (DP) in Bear Brook, an undisturbed headwater stream in the Hubbard Brook Experimental Forest. Sorption of DP by sediments in an equilibrium phosphorus concentration for silty and sandy sediments was equal to the mean ambient DP concentration (2 micrograms P/liter). The buffering capacity of the sediments was at a maximum in the pH range characteristic of Bear Brook. Silty sediments had a higher phosphorus buffering capacity than sandy sediments, and leaf-leachate phosphorus was sorbed less than orthophosphate. Phosphorus sorption increased as sediment particle size decreased and as aluminum and organic matter content increased. The microbial community appears to be a relatively minor component of phosphorus buffering capacity in these sediments.

Functionally distinct classes of complex phosphorus compounds in lake water1

Abstract: Abstmct Complex phosphorus compounds were classified functionally according to the manner by which orthophosphate was released. Filtrable phosphorus compounds in two cutrophic lakes (East and West Twin lakes) and a humic bog (Crazy Eddie Bog) in northeastern Ohio wcrc fractionated by anion-exchange and gel-filtration chromatography. Fractions were analyzed for soluble reactive phosphorus and total dissolved phosphorus; absorbance at 400 nm was used as a measure of filtrable “yellow acids.” The cutrophic lakes contained numerous low molecular weight compounds which were resistant to low-dose ultraviolet irradiation but readily released orthophosphate upon treatment with alkaline phosphatase. Filtrable phosphorus compounds of the humic bog were predominantly high molecular weight, cochromatographed with the yellow acids in each fractionation procedure, and resisted enzyme hydrolysis, but released orthophosphate upon irradiation with low doses of ultraviolet light.

Phosphorus inputs into a stream draining an agricultural watershed: II: Amounts contributed and relative significance of runoff types

Abstract: The amounts of P forms transported in surface, accelerated subsurface, and subsurface runoff, and the stream draining a 20 ha area of a pasture watershed were measured for 3 yr. Stream-bank erosion and resuspension of stream sediment contributed the major proportion of the particulate P (PP), total P, and sediment transported annually in stream flow (86, 77, and 74%, respectively, in 1977). In addition, 29% of the annual dissolved inorganic P (DIP) loading of the stream in 1977 was attributed to the release of P from suspended in situ particulate material. Remarkably similar proportions of water, P forms, and sediment were contributed by the runoff types in each of the 3 yr of study. Subsurface runoff contributed the major proportion (67% in 1977) of stream flow. Although surface runoff contributed only a minor proportion of stream flow (11% in 1977), it contributed the major proportion of both DIP (32% in 1977) and PP loading (90% in 1977) compared with the other runoff types. Differences in the amounts of P forms transported in the three runoff types can be attributed to several factors, one of the most important being the time of contact between soluble P in runoff waters and soil components.

Chemical characteristics of small streams near Haney in southwestern British Columbia

Abstract: The hydrological, thermal, and chemical characteristics of two small streams flowing through relatively undisturbed, low-elevation mountain watersheds in southwestern British Columbia were investigated. All observations and chemical analyses of ecosystems were consistent with the hypothesis that stormflow originated mainly from flow of water through soil macrochannels to groundwater and thence to streams. Water budgets indicated unmeasured groundwater losses. The streams exhibited annual chemical cycles for most parameters, with maximum values in late summer and early autumn and minimum values in winter and early spring. Nitrate concentrations displayed no consistent seasonal variation, whereas potassium and sulphate concentrations were relatively uniform throughout the year. Most chemical parameters decreased with increasing discharge, whereas dissolved oxygen concentrations increased. Potassium concentrations exhibited some increases and some decreases, and chloride, nitrate, and sulphate concentrations were generally not significantly related to discharge. Concentration-discharge relationships were used to infer the origin of stormflow water. Differences in the chemistry of the two very similar streams have important ramifications for the design of watershed nutrient studies. Nutrient budgets were very similar to those of other watersheds in humid temperate regions, with net losses of calcium, sodium, magnesium, potassium, chloride, and sulphur. Nitrogen and phosphorus exports in dissolved or particulate organic form were not measured. Based on dissolved inorganic measurements, nitrogen was accumulated, while any gains or losses of phosphorus were extremely small.

Regulation of Phosphate Accumulation in the Unicellular Cyanobacterium Synechococcus

Abstract: The phosphorus contents of acid-soluble pools, lipid, ribonucleic acid, and acid-insoluble polyphosphate were lowered in Synechococcus in proportion to the reduction in growth rate in phosphate-limited but not in nitrate-limited continuous culture. Phosphorus in these cell fractions was lost proportionately during progressive phosphate starvation of batch cultures. Acid-insoluble polyphosphate was always present in all cultural conditions to about 10% of total cell phosphorus and did not turn over during balanced exponential growth. Extensive polyphosphate formation occurred transiently when phosphate was given to cells which had been phosphate limited. This material was broken down after 8 h even in the presence of excess external orthophosphate, and its phosphorus was transferred into other cell fractions, notably ribonucleic acid. Phosphate uptake kinetics indicated an invariant apparent Km of about 0.5 μM, but Vmax was 40 to 50 times greater in cells from phosphate-limited cultures than in cells from nitrate-limited or balanced batch cultures. Over 90% of the phosphate taken up within the first 30 s at 15°C was recovered as orthophosphate. The uptake process is highly specific, since neither phosphate entry nor growth was affected by a 100-fold excess of arsenate. The activity of polyphosphate synthetase in cell extracts increased at least 20-fold during phosphate starvation or in phosphate-restricted growth, but polyphosphatase activity was little changed by different growth conditions. The findings suggest that derepression of the phosphate transport and polyphosphate-synthesizing systems as well as alkaline phosphatase occurs in phosphate shortage, but that the breakdown of polyphosphate in this organism is regulated by modulation of existing enzyme activity.

Effects of nutrients and temperature on decomposition of Myriophyllum spicatum L. in a hard‐water eutrophic lake1

Abstract: Temperature, phosphorus, and nitrogen were investigated as possible factors influencing decay of Myriophyllum spicatum shoots. In laboratory experiments, nitrogen enrichment significantly increased decay rates while phosphorus enrichment did not. Similar increases in decay rate per unit of added nitrogen occurred whether nitrogen was provided as nitrate or was present as additional tissue nitrogen. Exponential decay coefficients depended on temperature with a Q10 of about 3. Predictions of decay rates during litter bag experiments were based on laboratory responses of decay rate to temperature and initial nitrogen concentration of the shoots. Observed decay rates correlated closely with predictions, demonstrating the usefulness of temperature and shoot nitrogen content in explaining variations in decay rates in Lake Wingra. However, predictions underestimated decay rates. Possible explanations for the discrepancies include slow establishment of the detrital microflora, lower nitrogen availability, and absence of animals in the laboratory incubations.

Chironomid influence on phosphorus release in sediment-water microcosms'

Abstract: Microcosms of Lake Mendota, Wisconsin, USA sediment and oxygenated water, maintained in darkness, were used to evaluate phosphorus increments in the overlying water as influenced by 2 species of chironomids, chironomid density and chironomid-temperature interactions. Similar systems were held in light and tested with algae present to determine if the presence of chironomids enhances algal growth. Both species, Chironomous riparius and Chironomus tentans, cause increases in phosphorus content of overlying water, with the larger C. tentans producing the greater effect. Release of total phosphorus at 20?C increased approximately linearly from 0.3-9.4 mg m-2 d-1 over a range of 6 densities from 0-6585 larvae/M2. Increasing temperature from 1O-20'C had little effect on phosphorus release rates in microcosms without chironomids, but in systems with C. tentans increased temper- ature resulted in a -10-fold increase in total phosphorus release rates. Most phosphorus released to the overlying water was soluble reactive phosphorus (SRP) which was quickly taken up by algae in lighted microcosms. Lighted controls had little total phosphorus in the overlying water or on glass substrates (wall growth), while microcosms with C. tentans contained significantly more total phos- phorus in the overlying water and on glass substrates. Excretion by chironomids, rather than translocation of phosphorus from the interstitial waters of the sediment, could explain the observed data. Regardless of the mechanism, chironomids enhance phosphorus release and where abundant in the aerobic regions of lake sediments, their activities may be expected to result in a significant source of phosphorus to the epilimnetic region.

Effects of arsenic speciation and phosphate concentration on arsenic inhibition of skeletonema costatum bacillariophyceae

Abstract: Arsenate is taken up readily by Skeletonema costatum (Greville) Cleve due to its chemical similarity to phosphate, and it inhibits primary productivity at concentrations as low as 67 nM when the phosphate concentration is low. A phosphate enrichment of greater than 0.3 ..mu..M alleviates this inhibition; however, the arsenate stress causes an increase in the cell's requirement for phosphorus. Arsenite is also toxic to Skeletonema at similar concentrations. Methylated species, such as dimethylarsinic acid, did not affect cell productivity at the levels examined. Thus, the reduction and methylation of arsenate to dimithylarsinic acid by the cell produces a stable, non-toxic compound.

Effect of surface-casting earthworms on the transport of phosphorus and nitrogen in surface runoff from pasture

Abstract: Treatment of a soil under permanent pasture with carbaryl (a broad spectrum carbamate biocide) resulted in a 2-fold increase in the volume of surface runoff. This was attributed to a 3-fold reduction in infiltration rate as a result of litter accumulation at the soil surface in the absence of surface-casting earthworm activity. The amounts of dissolved inorganic P (DIP), NH+4-N, and NO−3-N in surface runoff from pasture treated with carbaryl (1.18, 9.53 and 4.25 kg ha−1 yr−1, respectively) were appreciably greater than those from untreated pasture (0.31, 1.63 and 0.52 kg ha−1 yr−1). This was attributed to the large amounts of DIP, NH+4-N, and NO−13-N released from decomposing litter. Following incubation at 4°C for 18 days the release of DIP, NH+4-N and NO−3-N from litter was 160, 1600 and 950 μg g−1, respectively. Losses of particulate P and sediment in surface runoff were lower in the absence (0.31 and 290 kg ha−1 yr−1, respectively) than in the presence (0.56 and 1120 kg ha− yr−1) of surface casts, pointing to the importance of surface casts as a source of sediment. Surface casts accounted for 45 and 75%, respectively, of the annual loading of particulate P and sediment in surface runoff. Nevertheless, the total loss in surface runoff of P and N forms was increased substantially when the production of earthworm casts was eliminated

A bioassay for comparing phosphorus availability in soils

Abstract: (1) A bioassay method, based on the uptake of 32P from 5 x 10-6 M phosphate solution during a 15 min period, was used to detect phosphorus deficiency in plants. (2) The method was tested using birch (Betuld verrucosa Ehrh.) and sycamore (Acerpseudoplatanus L.) seedlings grown in (a) sand culture supplied with 1-100 Pg P ml 1, (b) phosphorus deficient soils either unfertilized or fertilized (0.1 g P Kg-1 soil), and (c) a range of twenty-five soils varying from extremely deficient to adequate in available P content. (3) There was a negative exponential relationship (r =-0-95) between phosphorus uptake by birch from the test solution and the concentration of phosphorus previously supplied in sand culture solution. (4) Birch seedlings grown in fertilized soils took up less 32P from the bioassay solution than did those from unfertilized soils. Birch seedlings grown for 2 years in phosphate-deficient soils took up greater amounts of 32P from the bioassay solution than did those grown in soils with adequate phosphorus. Eighty-two per cent of the variation in phosphorous uptake by birch seedlings was accounted for by the extractable P content, the isotopically exchangeable P, the total P content and the phosphatase activity of the soils on which they were previously grown. Ninety-three per cent of the variation was accounted for if the plant phosphorus content and the mycorrhizal development on rootsystems were also included in the regression. The corresponding amounts of variation for sycamore seedlings, grown on the same soils, were 58 and 83% respectively. (5) The 32P uptake from the bioassay solution, by both sycamore and birch, was markedly inhibited by 5 x 10-3 M KCN in the bioassay solution, indicating that uptake was metabolically mediated. (6) The results are discussed in relation to the study of phosphorus deficiency in plants, and phosphorus availability in soils.

Effect of Early Mycorrhizal Infection on Nodulation and Nitrogen Fixation in Trifolium subterraneum L.

Abstract: Three experiments are described. Rapid establishment of vesicular-arbuscular mycorrhizas in roots of T. subterraneum cv. Mt Barker, using natural soil inoculum, was associated with improved nodulation, increased nitrogenase activity per plant (nmol C2H2 reduced per plant per hour) and increased nodule efficiency on the basis of nodule volume (nmol C2H2 reduced per mm³ nodule per hour). In two experiments (on soil low in nutrients), this increase occurred before any positive growth response to mycorrhizal infection was apparent. In all experiments, mycorrhizal roots had a higher phosphorus concentration (%P) than did non-mycorrhizal roots. This difference, which was evident before any differences in total plant phosphorus were detected, was not accompanied by an increase in nodule phosphorus concentration, so that differences in nodule efficiency could not be attributed to differences in this parameter. In the third experiment (on soil with higher nutrient levels), establishment of mycorrhizas was also accompanied by increased growth, phosphorus and nitrogen contents within a 35-day experimental period. Phosphorus inflow into roots (moles P per cm root per second) was higher in mycorrhizal plants. Delay in formation of mycorrhizas (by reduction in the amount of inoculum in soil) was accompanied by lower inflow, and delay in both the establishment of high root phosphorus concentration and in the onset of enhanced nodulation and nitrogenase activity.

The influence of chironomus plumosus larvae on the exchange of dissolved substances between sediment and water

Abstract: 4th instar Chironomus plumosus larvae (about 1000·m−2) were added to tubes containing sediment and overlying water. At a temperature of 20°C the larvae greatly increased the trasnport of silica, phosphorus and iron from the sediment to the water. Oxygen concentrations did not influence the exchange of silica. For two non-calcareous sediments the exchange of phosphorus and iron was much higher under anaerobic than under aerobic conditions while the difference was small for sediment from a hardwater lake. Exchange of inorganic nitrogen was little influenced by added chironomid larvae.

Phosphorus and nitrogen

Abstract: Hydrochemical investigations on Neusiedlersee have been made over a great number of years. However, at the beginning of this investigation in 1970 there were no published data on nutrient conditions of the lake.

Evaluation of soil phosphate buffering indices

Abstract: Seven phosphate buffering indices were evaluated by determining the additional variance accounted for when each index was added to a regression of plant phosphorus uptake on labile soil phosphate. The study was done on two groups of soils: one relatively homogeneous group of 24 soils all formed on the same parent material, and a heterogeneous group of 30 soils formed on a variety of parent materials. A separate pot experiment was done on each group, ryegrass being grown on the homogeneous soils and white clover on the heterogeneous soils. Only two indices did not account for a large and significant increase in variance in phosphate uptake. The extra variance accounted for was much greater in the heterogeneous group than in the homogeneous group, although the total variance accounted for by both variables was greater in the homogeneous group. The much smaller volume of soil used in the ryegrass experiment may explain the smaller buffering effect in the homogeneous soils. The three most effective and consistent indices were a simple index of the maximum buffer capacity, determined from the Langmuir isotherm over a standard range of equilibrium solution concentrations, the slope of the isotherm at the natural solution concentration, and the amount of adsorption at a standard equilibrium concentration of 0.3 pg phosphorus/ml.

The effect of flow patterns on uptake of phosphorus by river periphyton

Abstract: The effect of various flow patterns on the uptake of /sup 32/P by river periphyton was examined in a laboratory flume. In general, water movement increased /sup 32/P uptake, except where the phosphorus demand of the microorganisms was presumably satisfied by molecular diffusion at high phosphorus concentrations (105 ..mu..g.liter/sup -1/ PO/sub 4/-P). However, there was little difference in /sup 32/P uptake between the several distinct flow regimes produced by increasing or decreasing velocity and turbulence associated with a hump and hydraulic jump. It appears that the threshold limit for water movement after which no further stimulation occurs, is less than or equal to 5.4 cm.s/sup -1/, the lowest velocity tested. A reduction in /sup 32/P uptake by formaldehyde-killed films of pheriphyton indicated that 50 to 75% of the uptake of the untreated films was due to biological activity.