To Total Phosphorus Research Articles

Critical Sampling Points Methodology: Case Studies of Geographically Diverse Watersheds

Only with a properly designed water quality monitoring network can data be collected that can lead to accurate information extraction. One of the main components of water quality monitoring network design is the allocation of sampling locations. For this purpose, a design methodology, called critical sampling points (CSP), has been developed for the determination of the critical sampling locations in small, rural watersheds with regard to total phosphorus (TP) load pollution. It considers hydrologic, topographic, soil, vegetative, and land use factors. The objective of the monitoring network design in this methodology is to identify the stream locations which receive the greatest TP loads from the upstream portions of a watershed. The CSP methodology has been translated into a model, called water quality monitoring station analysis (WQMSA), which integrates a geographic information system (GIS) for the handling of the spatial aspect of the data, a hydrologic/water quality simulation model for TP load estimation, and fuzzy logic for improved input data representation. In addition, the methodology was purposely designed to be useful in diverse rural watersheds, independent of geographic location. Three watershed case studies in Pennsylvania, Amazonian Ecuador, and central Chile were examined. Each case study offered a different degree of data availability. It was demonstrated that the developed methodology could be successfully used in all three case studies. The case studies suggest that the CSP methodology, in form of the WQMSA model, has potential in applications world-wide.

Responses of periphyton to artificial nutrient enrichment in freshwater kettle ponds of Cape Cod National Seashore

Nutrient enrichment bioassays, in conjunction with sampling and analysis of surface water chemistry, were conducted in freshwater lakes (kettle ponds) of Cape Cod National Seashore (Massachusetts, USA) to ascertain the importance of nitrogen (N) and phosphorus (P) in regulating the growth of periphyton. Arrays of nutrient diffusing substrata (NDS) were suspended 0.5 m below the water surface in a total of 12 ponds in July and August 2005. Algal biomass developing on each NDS after ~3 weeks of exposure in each month was assessed by quantifying chlorophyll a + phaeophyton pigments. In both July and August, strong responses to N + P and N enrichments were observed in the majority of ponds, while P had no stimulatory effect. These responses correspond well with low atomic ratios (1–18) of dissolved inorganic nitrogen (DIN) to total phosphorus (TP) in ambient surface waters. The results suggest that conditions in the kettle ponds develop whereby nitrogen is the primary limiting nutrient to periphyton growth. While this may be a seasonal phenomenon, it has implications for nutrient management in individual ponds and within the larger watershed.

Phosphorus forms and bioavailability of lake sediments in the middle and lower reaches of Yangtze River

Forms of phosphorus in sediments from 25 lakes in the middle and lower reaches of Yangtze River were analyzed by the sequential extraction procedure. Contents and spatial distrubution of algal available phosphorus (AAP) in sediments of Lake Taihu, the third largest freshwater lake of China, were also studied. Relationships between phosphorus forms in sediment and macrophytes coverage in sample sites, as well as phosphorus forms in sediments and chlorophyal contents in lake water were discussed. Exchangeable form of phosphorus (Ex-P) in surface sediments was significantly positive correlative to total phosphorus (TP), dissolved total phosphorus (DTP) and soluble reactive phosphorus (SRP) contents in the lake water. Bioavailable phosphorus (Bio-P) contents in sediments from macrophytes dominant sites were significantly lower than that in no macrophyte sites. In Lake Taihu, Ex-P content in top 3 cm sediment was highest. However, content of ferric fraction phosphorus (Fe-P) was highest in 4–10 cm. Bioavalilble phosphorus (Bio-P) contents in surface sediments positively correlated to Chlorophyll a contents in water of Lake Taihu with significant difference. Therefore, contents of Bio-P and AAP could be acted as the indicators of risks of internal release of phosphorus in the shallow lakes. It was estimated that there were 268.6 ton AAP in top 1 cm sediments in Lake Taihu. Sediment suspension caused by strong wind-induced wave disturbance could carry plenty of AAP into water in large shallow lakes like Lake Taihu.

Phosphorus-31 MR Spectroscopy in Pediatric Liver Transplant Recipients: A Noninvasive Assessment of Graft Status with Correlation with Liver Function Tests and Liver Biopsy

Noninvasive in vivo hepatic phosphorus-31 MR spectroscopy has recently been shown to provide information about hepatic functional status. We sought to show the correlation of phosphorus-31 MR spectroscopy with blood biochemistry and liver biopsy results in pediatric patients after liver transplantation. Eleven pediatric transplant recipients (eight with good graft function, two with chronic hepatitis, and one with acute rejection) and four healthy control subjects were studied with in vivo 31P MR spectroscopy. Ratios of phosphomonoesters (PME) to total phosphorus (TP), phosphodiester (PDE) to TP, nucleotide triphosphates (NTP), inorganic phosphate (Pi), and intracellular acid-base status (pH) were measured. Liver function test (n = 11) and biopsy (n = 3) results were obtained for correlation with spectroscopic findings. The eight patients with good graft function displayed spectral profiles similar to those of the healthy subjects, and no significant difference in the metabolic ratios of these patients compared with the control subjects was detected. Three patients with abnormal liver function and biopsy-proven hepatic complications showed elevated PME/TP ratios when compared with those of both the control subjects and the group with good graft function. Phosphorus-31 MR spectroscopy is a feasible technique for the noninvasive assessment of host-related complications in pediatric patients after liver transplantation. Our preliminary data suggest that the technique may be integrated with MRI for the investigation of impaired liver function in transplant recipients when neither a biliary complication nor a vascular complication is identified.

Planktonic Primary Production in the Offshore Waters of Dreissenid-infested Lake Erie in 1997

Phosphorus and chlorophyll a (Chl a) concentrations in 1997 decreased from the west basin, which receives most of the lake's nutrient loading, to the central and eastern basins. By contrast, average areal primary production varied little between basins, because higher Chl a concentrations in the west basin were offset by poorer light penetration. Sub-epilimnetic production in the deeper central and east basins, which might be favored by trends to greater water clarity over recent decades, was a minor contributor to total primary production. With additional data from the literature, it was shown that pre-dreissenid Lake Erie produced significantly less Chl a relative to total phosphorus (TP) than did other Great Lakes or smaller inland lakes. Chl a:TP ratios did not change significantly consequent to dreissenid colonization. Despite the continued low yield of Chl a, Lake Erie in post-dreissenid years had areal primary production relative to TP as high as other, dreissenid-free, Great Lake locations and much higher than comparably oligotrophic inland lakes. Absolute concentrations of TP and Chl a have decreased over the decades of nutrient controls and, in the west basin, in parallel with dreissenid colonization. The lake nonetheless remained highly efficient at translating TP into primary production up to 1997, revealing little or none of the depression associated with dreissenid impacts in shallower systems.

Environmental and algal forcing of Daphnia production dynamics

Recent studies of lakes suggest that the relative availability of light and phosphorus in the mixed layer helps determine the quality of phytoplankton consumed by herbivorous zooplankton. In turn, increases in algal quality positively affect zooplankton growth and reproductive rates. However, these studies have concentrated on explaining variation among lakes over relatively short time periods and have not evaluated the temporal dynamics in the physical‐chemical forcing on zooplankton production. We investigated whether there were seasonal changes in the relationship between Daphnia fecundity and the physical‐chemical environment, algal community characteristics, and Daphnia length using dynamic linear models (DLM) to analyze a high‐resolution, 16‐yr time series from Lake Washington. We used two metrics to describe algal quality: the percentage of blue‐green algae and the light to total phosphorus (TP) ratio as an indirect metric for algal C: P. Chlorophyll a (Chl a) concentration and algal biovolume served as measures of algal quantity. As expected, both the light :TP ratio and the percentage of blue‐green algae had negative effects on Daphnia fecundity, and Chl a concentration and biovolume had positive effects on fecundity. However, we found a comparatively stronger effect of Daphnia length on fecundity, although it was negative and therefore opposite to expectation. In all cases, we observed strong seasonal differences in environmental effects, but no temporal change in the fundamental relationships between our indices of algal quantity and quality, allometry, and Daphnia reproduction. Our results support a hypothesis of physical‐chemical coupling to algal quality and zooplankton production but highlight the importance of temporal variation in this forcing.

Non-Algal Seston, Light, Nutrients and Chlorophyll in Missouri Reservoirs

ABSTRACT Limnological measurements were performed at five or six Missouri reservoirs in June-September 1992–1995 to examine the relation of light conditions and non-algal seston (NAS) to chlorophyll (CHL) and dissolved nutrient concentrations. NAS was estimated as the sum of non-volatile suspended solids and filterable (Whatman 934AH filter) suspended solids. Mean mixed layer irradiance (I mix ) varied ≈20 fold among observations, largely due to variation in light attenuation by NAS. In 42% of the observations, I mix was less than 7 E·m−2 d−1, a range where light limitation is likely. NAS comprised 15–96% (mean= 58%) of total seston and accounted for 89% of the temporal and inter-site variation in I mix . NAS was strongly correlated to total phosphorus (TP) and soluble reactive phosphorus (SRP) concentrations (r= 0.91 and r=0.84, respectively, p<0.0001). When NAS > 5 mg·L−1 or I mix was < 5 E m−2 d−1, SRP and dissolved inorganic N (DIN) were usually at concentrations capable of saturating algal nutrient uptake (SRP >3 μg·L−1, DIN >50 μg·L−1), suggesting light limitation replaced nutrient limitation under those conditions. Light limitation resulting from NAS in turbid lakes may alter the relationship of phytoplankton to phosphorus, yielding a CHL-TP relationship that is dome-shaped rather than asymptotic. Variation in the relation of NAS to TP will affect how CHL responds to nutrients in individual waterbodies.

Patterns of Algal Biomass in Dominant Odd‐ vs. Even‐Link Lake Ecosystems

Foodchain models predict strong positive response of algal biomass to total phosphorus (TP) in odd—link ecosystem where grazers are controlled by planktivores and no significant response of algal biomass in even—link ecosystem where grazers are released from planktivore predation. On the other hand, resource— or ratio—dependent models predict proportional increase in algal biomass with increasing TP. These predictions were tested with field data from a large number of north temperature lake ecosystems exhibiting a wide range of TP. Instead of using the traditional approach of the number of trophic links present in an ecosystem, I used the presence vs. absence or near absence of large Daphnia and planktivorous fish to indicate the function dominance of odd vs. even links. Results showed that algal biomass response to TP is stronger in dominant odd—link ecosystems than in dominant even—link ecosystems, which is consistent with the predictions of foodchain models. The significant positive slope of the relationship of algal biomass to total phosphorus for dominant even—link ecosystems is not consistent with foodchain models. In addition, a nonlinear response pattern of algal biomass to total phosphorus appears to be inconsistent with both foodchain and ratio—dependent models. Results also showed that even—link ecosystems produce proportionately lower algal biomass, demonstrating that grazers can modify ratio dependence of algal biomass. Overall, algal biomass appears to be both predator and ratio dependent because grazers are capable of modifying algal response to nutrients, and algae show positive response to nutrients even in the presence of larger grazers.

Phosphorus–Chlorophyll Relationships under Contrasting Zooplankton Community Structure: Potential Mechanisms

Data from experimental enclosures and natural and manipulated lakes were used to test whether the variable chlorophyll a (Chl) yields to total phosphorus (TP) can be explained by the variable contributions of dissolved (TDP) and zooplankton phosphorus (ZP; P &gt; 200 μm) to TP. Results indicate that low Chl yields to TP in systems with abundant large Daphnia are closely related to greater contributions of TDP and ZP to TP. An opposite pattern is produced by systems lacking large Daphnia. These patterns seem to be consistent among mesoeutrophic to hypereutrophic systems; Chl yields to TP decline with increasing contributions of TDP to TP. In the large-Daphnia-dominated systems, both high grazing and reduced phosphate demand allow a greater sequestering of P into zooplankton and dissolved pools rather than in algae, which generate a lower observed Chl yields to TP. Conversely, lack of large Daphnia and low grazing rates allow proliferation of small algae, and an associated intense phosphate demand allows greater sequestering of P into small algae rather than into zooplankton and dissolved pools, and consequently, a higher Chl yield to TP is produced.

DIATOM ASSEMBLAGES AS INDICATORS OF LAKE TROPHIC STATUS IN SOUTHEASTERN ONTARIO LAKES1

ABSTRACTCanonical correspondence analysis (CCA) was used to explore the relationship between measured environmental variables and surficial diatom (Bacillariophyceae) assemblages in alkaline lakes from southeastern Ontario. Total nitrogen (TN), watershed area, alkalinity, and maximum depth each explain significant (P ≤ 0.05) directions of variance in the distribution of diatom taxa.TN was highly correlated to total phosphorus (TP) (r = 0.92), chlorophyll a (r = 0.86), and Secchi depth (r =0.77). When a series of CCAs were run with the first axis constrained to each of these variables in turn, the ratio of the eigenvalue of the first axis to that of the second axis (λ1/λ2) was highest for TN, indicating that TN best explained the distribution of the diatom assemblages in this set of lakes. Furthermore, results of Monte Carlo permutation tests indicated that these four variables did not act independently on the diatom assemblages. Therefore, TN was selected to represent these four closely related variables to infer lake trophic status.Weighted‐averaging regression and calibration (with classical deshrinking) were used to develop transfer functions to infer TN from the relative abundances of 83 diatom taxa recovered from the surficial sediments of 51 lakes. There was a good correlation between diatom‐inferred TN concentrations and measured TN concentrations (r2= 0.75, n = 51).The weighted‐averaging regression and calibration model was used to infer lake trophic status (represented by TN) from diatom assemblages presented in the sediments from Little Round Lake, Ontario. These data were used in conjunction with historical land‐use data in order to quantify the sequence and extent of nutrient enrichment related to human activity in the watershed area.

Light, Nutrients, and Water Temperature as Determinants of Phytoplankton Production in Two Saline, Prairie Lakes with High Sulphate Concentrations

Our data support empirical models indicating that algal productivity is low relative to total phosphorus (TP) levels in prairie lakes with high sulphate concentrations. Mean chlorophyll accounted for 91.1% of the variance in euphotic zone primary production (ΣA) in Humboldt Lake (total dissolved solids (TDS) = 3.3 g∙L−1; Zmax = 6 m), while TP, total dissolved phosphorus, and water temperature accounted for 82.7% of ΣA variance in Redberry Lake (TDS = 20.9 g∙L−1; Zmax = 17 m). The relative importance of these variables to ΣA resulted from biological, chemical, and physical differences of these lakes. Light usually penetrated to the bottom of Redberry Lake due to a mean euphotic zone (Zeu) chlorophyll of 1.7 mg∙m−3, while Humboldt Lake's mean Zeu was 3.4 m with a mean chlorophyll concentration of 62.6 mg∙m−3. Chlorophyll was the dominant factor correlated with light penetration in Humboldt Lake (r2 = 0.65) but not in Redberry Lake. Photosynthetic capacity was correlated (r2 = 0.72) with water temperature only in Redberry Lake. The mean ΣA was 57.1 and 230.2 mg C∙m−2∙h−1 for Redberry and Humboldt lakes, respectively.

Evaluation of indicators of nitrogen limitation in deep prairie lakes with laboratory bioassays and limnocorrals

The deep lakes in central Alberta are characterized by relatively high total nitrogen (TN) to total phosphorus (TP) ratios (33 to 64, by weight) and high TP (10 to 100 µg 1−1) in the euphotic zone in summer. These same lakes show indications of nitrogen limitation: (1) blue-green algae are relatively important in summer (7 to 88% of total biomass) and a large proportion of the filaments contain heterocysts and (2) inorganic nitrogen levels are extremely low in the surface waters (NOinf2sup−+ NOinf3sup−+ NHinf4sup+− N < 10 µg 1−1). In 1985 and 1986 inorganic nitrogen (25 to 1200 µg 1−1 − N) and/or phosphorus (12 to 100 µg 1−1 − P) was added to water in 31 m3 limnocorrals or 21 bottles from four deep prairie lakes. In most cases, phytoplankton biomass (estimated as chlorophyll a) was stimulated only by phosphorus additions. However, for a short period (8 d) after an unusual storm, phytoplankton biomass was stimulated by nitrogen additions. After this storm, TP increased by up to 75% in the epilimnion of the study lakes whereas TN did not increase. The algae which increased in these experiments tended to be the dominant algae in the control vessels, which varied with the experiment and the lake. Thus, a large proportion of blue-green algae and low inorganic nitrogen levels are not indicative per se of nitrogen limitation in lakes.

Influence of Water Temperature and Nitrogen to Phosphorus Ratios on the Dominance of Blue-Green Algae in Lake St. George, Ontario

Data collected at Lake St. George, Ontario, over five summers spanning a period of 13 yr showed that there was no correlation between percent blue-green algal composition and the ratio of total nitrogen (TN) to total phosphorus (TP), However, percent blue-green algae was positively correlated with temperature and negatively correlated with nitrate nitrogen (NO3-N), total inorganic nitrogen (TIN), and the ratio of NO3-N:TP. Multiple correlations involving percent blue-green algae (dependent variable) with respect to temperature, in combination with one of NO3-N, TIN, NO3-N:TP, or TIN:TP, were also significant. In all cases, temperature effects accounted for most of the explained variation. The strongest correlation was found for the multiple regression involving percent blue-green algae versus temperature and the NO3-N: TP ratio. The pattern that emerged from the Lake St. George data set was that when temperature exceeded 21 °C and the ratio of NO3-N:TP was below 5:1, the likelihood of a blue-green algal bloom was high. When temperature was below 21 °C and NO3-N:TP exceeded 5:1, blue-green blooms never occurred.

A re-assessment of phosphorus inputs to Loch Leven (Kinross, Scotland): rationale and an overview of results on instantaneous loadings with special reference to runoff

ABSTRACTConcern over the effects of eutrophication of Loch Leven led to an assessment of the phosphorus (P) loading and the contributions from runoff (from a catchment area of 145 km2), rain on the loch, roosting wildfowl, treated sewage effluent and P-rich industrial waste. Integrated programmes of flow gauging and nutrient analyses on twelve stream systems were carried out at eight-day intervals from January 1985 to February 1986. The paper concentrates on runoff and is restricted largely to total phosphorus (TP) loadings estimated from instantaneous flow and concentration data. The potential for deriving continuous loadings is discussed; examination of instantaneous and continuous discharge figures for a major inflow suggests that the present sampling regime has characterised its hydrological behaviour well. Nearly 90% of the water enters the loch in four streams of 0·1–1·0 m3 s−1 mean flow. The total input of water was high in 1985–134·4 × 106 m3 which is equivalent to a flushing rate of 2·6 (loch volumes); the effect on the loading results of the unusually wet study period is discussed.Inflow concentrations of TP ranged from &lt;10μg 1−1 to c. 4 mg 1−1; they generally increased with increasing flow but co-efficients of determination (r2 values) were only ≦0·57. Rating curves based on log load/log flow gave, for most waters, r2 values of 0·85, suggesting that load-flow, rather than concentration-flow models, will prove more favourable for predicting loads on non-sampling dates.The total TP loading in runoff in 1985 was 9·4 tonnes, 38% of which was in soluble reactive form (SRP). Losses of P varied between sub-catchments, with 0·41–1·67 kg TP ha−1 yr−1 and typically &lt;0·25 kg SRP ha−1 yr−1—representing only 5% of the annual agricultural applications of P. Initial calculations of inputs from sewage treatment works and industry suggest that these point-sources together contribute at least as much TP as in runoff, and twice the SRP in runoff. The significance of these findings for P control is discussed.

Evaluation of Factors Related to the Unusually Low Chlorophyll Levels in Prairie Saline Lakes

Prairie saline lakes in Canada have remarkably low chlorophyll a (Chl a) levels relative to total phosphorus (TP) and total nitrogen (TN) levels. To evaluate factors related to low Chl a levels, three Alberta saline lakes (total dissolved solids &gt; 5 g∙L−1) were studied in 1983 and 1984. Mean summer phytoplankton Chl a ranged from 3 to 10 μg∙L−1, mean summer periphyton Chl a was less than 70 mg∙m−2, while mean summer TP and TN ranged from 2 to 13 and from 4 to 11 mg∙L−1, respectively. Chl a and phytoplankton primary production were extremely low relative to predictions from measured TP and TN levels and empirical models for freshwaters. Bioassays indicated that inorganic phosphorus was not limiting, whereas inorganic nitrogen was limiting algal growth. Bacterial densities and zooplankton dry weight were high (&gt; 107 cells∙mL−1 and &gt; 1.0 mg∙L−1, respectively) relative to predictions from Chl a and empirical models for freshwaters. Phytoplankton biomass was insufficient to maintain the zooplankton populations; bacteria and detritus were likely a major food source for zooplankton. This study suggests that freshwater models are not applicable to prairie saline lakes.