Mean Phosphate Concentrations Research Articles

Assessment of groundwater quality: Physicochemical and bacteriological evidence from boreholes in Sangayan Diriya village, northeast Nigeria

The poor geology of Sangayan Diriya village has barred residents from getting access to water from the groundwater in their homes from time immemorial. This study was aimed at assessing the quality of boreholes sunk in close proximity to River Diriya wherein eight water samples were aseptically collected from the two available boreholes; borehole A (BA1, BA2, BA3 and BA4) and borehole B (BB1, BB2, BB3 and BB4). Standard procedures were employed for determining physicochemical properties, while pour plate method and most probable number (MPN) were used to estimate total viable bacterial counts and coliform count in the water collected, respectively. Results were compared with World Health Organization (WHO) guidelines and Nigerian Standard for Drinking Water Quality (NSDWQ) permissible standards. Results indicated pH, temperature, total hardness, turbidity, electrical conductivity (EC), sulphate, nitrate, alkalinity, calcium, magnesium and nitrate conformed to regulated standards, but mean phosphate concentration (1.79 mg/L) was above WHO allowable limit. However, out of the six heavy metals estimated in the water samples, i.e., Cadmium, Iron, Copper, Arsenic, Lead and Chromium, mean Iron concentration (1.16 mg/L) and mean Arsenic concentration (0.37 mg/L) were above allowable limits. The highest total viable bacterial count (6.3 × 104 CFU/mL) was recorded in BA2. Using the MPN method, BA4 recorded the highest coliform count (14 MPN/100 mL) while BB2 recorded the lowest coliform count (7 MPN/100 mL) each above WHO allowable limit. The findings in this study indicated that the water samples did not meet regulated standards and should be subjected to suitable treatment before drinking.

Nutrient fluxes from an Arctic seabird colony to the adjacent coastal marine ecosystem

Seabirds are important vectors for nutrient transfer across ecosystem boundaries. In this seasonal study, we evaluate the impact of an Arctic colony (Alkhornet, Svalbard) of Black-legged Kittiwakes (Rissa tridactyla) and Brünnich’s Guillemots (Uria lomvia) on stream nutrient concentrations and fluxes, as well as utilization by coastal biota. Water samples from seabird-impacted and control streams were collected regularly throughout the melt season (June–September) for nutrient and organic carbon analysis. Stable carbon and nitrogen isotope analysis (δ13C and δ15N) was used to assess whether seabird-derived nitrogen (N) could be traced into filamentous stream algae and marine algae as well as consumers (amphipods). Concentrations of nitrate (NO3−) and nitrite (NO2−) peaked in July at 9200 µg N L−1 in seabird-impacted streams, 70 times higher than for control streams. Mean concentrations of phosphate (PO43−) in seabird-impacted streams were 21.9 µg P L−1, tenfold higher than in controls. Areal fluxes from seabird-impacted study catchments of NO3− + NO2− and PO43− had estimated ranges of 400–2100 kg N km−2 and 15–70 kg P km−2, respectively. Higher δ15N was found in all biota collected from seabird-impacted sites, indicating utilization of seabird-derived nitrogen. Acrosiphonia sp. from seabird-impacted sites had higher δ15N values (20–23‰ vs. 3–6‰) and lower C:N ratios (10.9 vs. 14.3) than specimens collected from control sites, indicating reliance on seabird-derived nitrogen sources and potentially higher N-availability at seabird-impacted nearshore sites. Our study demonstrates how marine nutrients brought onshore by seabirds also can return to the ocean and be utilized by nearshore primary producers and consumers.

Ecology and Partial Restoration of Daha River for Fish Productivity

Daha river, a threatened water body of polluted nature in the Gopalganj district of Bihar was studied for its degradation and possible restoration. The study reveals high rate of sedimentation and agricultural activities, changes in water quality and biotic community. Agricultural activities have led to high input of nitrogen (N) and phosphate (P) fertilizers along with pesticides being used by the farmers. The positives response of restoration practices was observed with partial improvement in fish-productivity due to hindrance factors acting upon severe fish species.The mean concentration of phosphate, nitrate and ammonia corresponds about 0.60-1.40 mg/l, 1.30-2.50 mg/l and 23-43 mg/l in polluted river, while after restoration declines to 0.20-0.48 mg/l, 0.60-1.10 mg/l and 14-27 mg/l, respectively indicating more suitable towards fish productivity. The observations on other water parameters also showed similar trend during partial restoration of Daha river. The cause of algal bloom and other macrophytic population is inorganic ammonia, however, organic pollution is also in polluted state observed as more quantity of ammonia than nitrate especially at site II and Site III during the study period. The concentration of nitrate is much higher than the critical value in polluted river which causes algal diversity and macrophytic vegetation. Therefore, partial restoration of the river helped to enhance fish productivity concluded from this study.

Severe phosphate limitation on nitrogen fixation in the Bay of Bengal

Several anticyclonic (ACE) and cyclonic (CE) eddies constitute the circulation in the Bay of Bengal (BoB) and are associated with the downwelling and upwelling processes leading to oligotrophic and eutrophic conditions respectively. In this study, the nitrogen (N2) fixation rates and controlling factors are estimated through deck incubation experiments in the BoB using enriched N2 gas dissolution method. We observed measurable concentrations of dissolved inorganic nitrogen (DIN) and phosphate in the CE and close to detection limits in the ACE in the mixed layer. Photic zone integrated N2 fixation rates ranged between 53.3 and 194.1 μmol m−2 d−1 with lower rates in the ACE (91 ± 18 μmol m−2 d−1) than CE (162 ± 28 μmol m−2 d−1) and no eddy regions (NE; 138 ± 27 μmol m−2 d−1). The photic zone integrated N2 fixation rates are linearly correlated with photic zone integrated chlorophyll a and the mean phosphate concentrations in the photic zone suggesting that phosphate is controlling the N2 fixation in the BoB. The observed high N:P ratio (25 ± 3) also indicate that severe phosphate limitation in the BoB. This is further confirmed from increase in N2 fixation rates by 1.2 to 8 times due to artificial increase in phosphate from that rates at in situ phosphate concentrations. This study suggests that though the conditions are conducive for N2 fixation in the BoB, the removal of dissolved phosphate within the estuaries opened to the BoB, provide weaker inputs from subsurface due to stratification and less input from atmospheric dust may limit N2 fixation in the BoB.

The effects of forest clearance for peatland restoration on water quality

Recognition of the importance of peatlands has led to increased efforts to protect and restore these environments but there are concerns about the impact of restoration on water quality, particularly in terms of sediment delivery, nutrient transport and carbon losses. In this study we present the results of almost 10 years of water quality monitoring in 3 catchments at a lowland raised bog that was afforested with conifers in the 1960s and 1970s and cleared over the 2010s.Phosphate concentrations increased after clearfelling with the main peaks seen in the summer after forest clearance; the use of low ground impact harvesting methods, removal of forest residues and especially phased felling tempered phosphate losses. Annual mean phosphate concentrations returned to pre-felling levels 3–5 years after felling finished. Nitrate concentrations increased slightly from baseline levels during and after felling. DOC concentrations increased at two sites with mean annual concentrations still elevated at one site after 4 years; little increase in DOC was recorded with phased felling. Colour levels increased and remain elevated at all sites relative to pre-felling. In only one stream, pH increased improving the WFD water body status from ‘poor’ to ‘high’ in the space of 3 years.Our results show that forest clearance for peatland restoration can impact negatively upon water quality due to phosphate, DOC, colour and suspended sediment releases. The mechanisms by which the releases occur require further investigation but are thought to be driven by nutrient leaching from forest residues, soil disturbance by machine trafficking and indirect effects of forest clearance, such as water table rise following cessation of forest water use. Climatic effects also play a significant role, particularly drying-rewetting cycles and periods of extended drought. To prevent negative impacts, phased felling and less intensive forest harvesting techniques should be employed.

Determination of phosphate concentration in glaucoma eye drops commercially available in Spain

ObjectivesTo identify and analyze the phosphate concentration in glaucoma eye drops available in Spain. Material and methodsGlaucoma medications containing phosphates were identified according to the 2013 Vademecum and the website of the Spanish Agency for Medicines and Medical Devices. Phosphate concentration was determined in these eye drops using ultraviolet molecular absorption spectrophotometry, and pH was determined using scan image analysis algorithms of pH strips. ResultsA total of 37 phosphate containing glaucoma eye drops were identified. The mean phosphate concentration was 97.72±75.52mM. The group with higher concentration of active substance was timolol (204.85±42.38mM) followed by brimonidine/timolol (200.9mM). No statistically significant difference was found between brand name (95.65±71.11mM) and generic eye drops (99.14±80mM, p=0.892). Although no statistically significant difference was found between products containing preservatives (99.24±76.78mM) and those without preservatives (85.17±72.86mM) (p=0.730), a lower phosphate concentration was observed in the preservative-free Timolol and Latanoprost. Single dose samples showed a lower phosphate concentration than multi-dose ones (102.04±75.39 vs. 22.24±2.98mM, p<0.001). The mean pH was 7.13±0.63. No statistical correlation was found between phosphate concentration and pH (r: 0.07). ConclusionThe phosphate concentration in glaucoma eye drops exceeded the tear film physiological level (1.45mM). No difference was observed between brand names and generic eye drops. Lower phosphate concentration was observed in preservative-free single dose eye drops.

Effect of Cigarette Smoking and Body Mass Index on Salivary Calcium and Phosphate Concentration in Chronic Periodontitis Patients

Background: Periodontitis is a multi-factorial disease related to the formation of dental plaque. Saliva composition plays a role in plaque formation and in the development of periodontal disease. Objectives: This study was designed to compare the salivary concentrations of calcium and phosphate between patients with chronic periodontitis (CP) and healthy individuals and to assess the effect of smoking status in this regard. Patients and Methods: This case control study was conducted on 50 healthy subjects and 56 patients with CP. The two groups were matched in terms of age, sex, and smoking status. After obtaining written informed consents from the subjects, periodontal parameters such as calculus index (CI), plaque index (PI), bleeding index (BI) and clinical attachment loss (CAL) as well as body mass index (BMI) were calculated and recorded. Non-stimulated saliva was collected by the spitting method, and the concentration of calcium and phosphate was measured by spectrophotometry. Data were analyzed using independent t-test. Pearson correlation was utilized to correlate the periodontal parameters with the salivary concentrations of calcium and phosphate in the CP group. Confidence interval and P value were set to 95% and ≤ 0.05, respectively. Results: The mean concentration of phosphate in the saliva of CP patients was significantly higher than that in healthy individuals (P = 0.008). No significant difference was found between the two groups in the mean concentration of calcium in the saliva (P = 0.145). The mean concentrations of calcium and phosphate were not significantly different between non-smoker CP patients and healthy subjects. However, the concentrations of calcium and phosphate in the saliva of smoker CP patients were significantly lower and higher, respectively, than the corresponding values in the healthy smoker group (P = 0.016 and P = 0.037, respectively). In subjects with BMI < 25, the mean concentration of salivary phosphate in CP patients was significantly higher than that in healthy individuals (P = 0.005). Among the periodontal parameters, only CI had a significant correlation with the concentration of phosphate in the saliva of patients with CP (P = 0.029). Conclusions: Cigarette smoking and BMI are two main confounding factors affecting the correlation of calcium and phosphate concentrations in the saliva and periodontal status.

Determination of phosphate concentration and pH in artificial tear drops

ObjectiveTo determine phosphate concentration and pH in artificial tear eye drops commercially available in Spain. Materials and methodsA total of 71 examples of artificial tear preparations were identified in a search of Vademecum 2014 and the Spanish Medicines Agency website. In the 24 artificial tear products containing phosphates, quantification of these was performed by ultraviolet molecular absorption spectrophotometry, and the determination of pH was performed using scan image analysis algorithms of pH strips. ResultsOf the 71 artificial tears tested, 24 contained phosphate among their excipients in the data sheet, three of which had a concentration level below detection limit (<0.1mM). The mean phosphate concentration was 17.91±23.87mM. The artificial tear sample containing a higher concentration was Colircusi Humectante (87.1mM). Lubricants based on hypromellose showed the highest phosphate concentration (41.59±32.1mM), showing statistically significant differences compared to povidone (p=0.0196) and hyaluronate (p=0.0067). Statistically significant differences were found between products containing preservatives (32.39±20.91mM), and preservative free ones (8.49±11.98mM) (p=0.0498). However, no difference was found between multidose (20.21±26.91mM) and unidose (9.31±14.39mM) samples, or between brand name (15.44±23.3mM) and generic eye drops (20.81mM). The mean pH was 6.93±0.26 (6.2–7.22). No statistical correlation was detected between phosphate concentration and pH (Spearman's Rho −0.1089 and p=0.6125). ConclusionA total of 24 (33.8%) of the 71 artificial tears contained phosphate. We believe identifying the phosphate concentration of artificial tears is useful information in order to avoid complications in high-risk patients.

Determinación de la concentración de fosfatos en los colirios antiglaucomatosos comercializados en España

ObjectivesTo identify and analyze the phosphate concentration in glaucoma eye drops available in Spain. Material and methodsGlaucoma medications containing phosphates were identified according to the 2013 Vademecum and the website of the Spanish Agency for Medicines and Medical Devices. Phosphate concentration was determined in these eye drops using ultraviolet molecular absorption spectrophotometry, and pH was determined using scan image analysis algorithms of pH strips. ResultsA total of 37 phosphate containing glaucoma eye drops were identified. The mean phosphate concentration was 97.72±75.52mM. The group with higher concentration of active substance was timolol (204.85±42.38mM) followed by brimonidine/timolol (200.9mM). No statistically significant difference was found between brand name (95.65±71.11mM) and generic eye drops (99.14±80mM, P=.892). Although no statistically significant difference was found between products containing preservatives (99.24±76.78mM) and those without preservatives (85.17±72.86mM) (P=.730), a lower phosphate concentration was observed in the preservative-free Timolol and Latanoprost. Single dose samples showed a lower phosphate concentration than multi-dose ones (102.04±75.39 vs. 22.24±2.98mM, P<.001). The mean pH was 7.13±0.63. No statistical correlation was found between phosphate concentration and pH (r: 0.07). ConclusionThe phosphate concentration in glaucoma eye drops exceeded the tear film physiological level (1.45mM). No difference was observed between brand names and generic eye drops. Lower phosphate concentration was observed in preservative-free single dose eye drops.

Determinación de la concentración de fosfatos y pH en los colirios de lágrima artificial

ObjectiveTo determine phosphate concentration and pH in artificial tear eye drops commercially available in Spain. Materials and methodsA total of 71 examples of artificial tear preparations were identified in a search of Vademecum 2014 and the Spanish Medicines Agency website. In the 24 artificial tear products containing phosphates, quantification of these was performed by ultraviolet molecular absorption spectrophotometry, and the determination of pH was performed using scan image analysis algorithms of pH strips. ResultsOf the 71 artificial tears tested, 24 contained phosphate among their excipients in the data sheet, three of which had a concentration level below detection limit (<0.1mM). The mean phosphate concentration was 17.91±23.87mM. The artificial tear sample containing a higher concentration was Colircusi Humectante (87.1mM). Lubricants based on hypromellose showed the highest phosphate concentration (41.59±32.1mM), showing statistically significant differences compared to povidone (P=.0196) and hyaluronate (P=.0067). Statistically significant differences were found between products containing preservatives (32.39±20.91mM), and preservative free ones (8.49±11.98mM) (P=.0498). However, no difference was found between multidose (20.21±26.91mM) and unidose (9.31±14.39mM) samples, or between brand name (15.44±23.3mM) and generic eye drops (20.81mM). The mean pH was 6.93±0.26 (6.2-7.22). No statistical correlation was detected between phosphate concentration and pH (Spearman's Rho −0.1089 and P=.6125). ConclusionA total of 24 (33.8%) of the 71 artificial tears contained phosphate. We believe identifying the phosphate concentration of artificial tears is useful information in order to avoid complications in high-risk patients.

Development and application of dissolved oxygen ( DO ) and biological oxygen demand ( BOD ) model for P anshet and U jjani R eservoirs, M aharashtra, I ndia

A model of dissolved oxygen (DO) and biological oxygen demand (BOD) was developed to assess the water quality of Panshet and Ujjani Reservoir in Maharashtra, India, to ascertain if their water was suitable for various beneficial and designated uses. The model was calibrated with observed data from these two reservoirs. Seasonal water quality variations were studied during 2010–2011 The pH of Panshet Reservoir water is almost neutral, whereas Ujjani Reservoir is marginally alkaline. A rapid decrease in DO with depth during the summer appeared to be a common phenomenon for both reservoirs. Although the mean phosphate concentrations of both reservoirs were comparable, biological growth was much higher in Ujjani Reservoir, being attributed to a higher dissolved salt concentration in Ujjani Reservoir. The nitrate (NO3−) concentrations in both reservoirs remained within a range close to the global average for unpolluted freshwater. Sewage contamination appears to be a major problem for Ujjani Reservoir, especially as it relates to domestic water uses. A two-layer, two-dimensional mathematical model also was developed to assess reservoir water quality. An explicit, second-order-accuracy finite-volume technique was used to solve two-dimensional shallow water equations. The governing equations were solved with a Mac Cormack predictor–corrector scheme. The Reynolds turbulence terms were modelled with a sub-grid-scale (SGS) model, using a large eddy simulation (LES) approach. An empirical relationship developed by Street and Phelps describing liquid–air phase demand and natural re-aeration was used to determine water quality parameters. The model was validated with numerical results from the literature. The field investigations were satisfactorily applied for the simulation of hydrodynamics and the prediction of DO and BOD in Panshet and Ujjani Reservoir.

Effectiveness of a single fixed dose of rasburicase 3 mg in the management of tumour lysis syndrome

Effectiveness of a single fixed dose of rasburicase 3 <scp>mg</scp> in the management of tumour lysis syndrome

Improvement of Hyperphosphatemia following Patient Education

Background: Patient adherence to a phosphate binder treatment regimen is crucial in the management of hyperphosphatemia. Nonadherence may be due to a lack of patient knowledge of the nature and treatment of the illness. Objective: To investigate the effectiveness of pharmacist-provided education regarding phosphate binders and hyperphosphatemia on serum phosphate concentration and calcium x phosphorous product in hemodialysis patients. Methods: A total of 398 hemodialysis patients who were prescribed phosphate binders participated in a pharmacist-run, education-based intervention session regarding phosphate binders and hyperphosphatemia. Each session was individualized on the basis of patient knowledge, assessed via a questionnaire. Particular attention was given to correcting patient misconceptions. Patients with elevated serum phosphate received additional education. Mean serum concentrations of phosphate and calcium, averaged from 4 measurements obtained at both baseline and postintervention, were compared to evaluate the efficacy of the intervention. Results: Postintervention, patients with the highest baseline serum phosphate concentrations (≥7.0 mg/dL) showed a significant decrease in mean ± SD serum concentrations of phosphate and calcium-phosphate product (7.4 ± 0.4 mg/dL and 72.6 ± 6.4 mg2/dL2 to 6.5 ± 0.8 mg/dL and 63.1 ± 8.4 mg2/dL2, respectively; p &lt; 0.001). Likewise, patients with serum phosphate concentrations ranging from 6.0–6.9 mg/dL showed a significant decrease in both parameters after educational intervention (p &lt; 0.05 and p &lt; 0.005, respectively). Conclusions: An education session regarding phosphate binders and hyperphosphatemia, provided by pharmacists for hemodialysis patients, appeared effective in reducing serum phosphate concentrations and calcium x phosphorus product, thus contributing to improved patient prognoses.

Primary hypoparathyroidism in dogs: a retrospective study of 17 cases

To evaluate the clinico-pathological findings, response to treatment and prevalence of complications in dogs with primary hypoparathyroidism. Retrospective study of 17 dogs presenting to the University of Melbourne Veterinary Clinical Centre and Murdoch University Veterinary Hospital over a 15 year period (1990 to 2004). Case records were evaluated for signalment, body weight, diet type, historical and clinical findings, serum total calcium, phosphate, albumin and parathyroid hormone concentrations, urinary fractional excretion ratios of calcium and phosphate, electrocardiogram (ECG) results, treatments administered, outcome and period of follow-up. The most common breeds identified were St Bernard (three dogs), Chihuahua (two dogs), German Shepherd (two dogs) and Jack Russell Terrier (two dogs). Three dogs were cross bred. Seizures, muscle tremors and fasciculations, stiff gait, tetany, muscle cramping, behavioural change and hyperventilation were the most common clinical signs. Vomiting, inappetence, diarrhoea, abdominal pain, hyperthermia, facial pruritus, ataxia, weakness, cataracts, and circling also occurred with less frequency. The mean duration of observed clinical signs preceding diagnosis was 33 days (median 13 days, range 1 to 173 days). All dogs had marked hypocalcaemia with normal or mildly increased serum albumin concentrations. Mean phosphate concentrations were significantly higher in inappetent dogs (P = 0.049). Mean serum calcium concentrations were significantly lower in dogs with cataracts compared to those without (P = 0.046). There were no other significant relationships between serum calcium or phosphate concentrations and the clinical presentation or outcome. No significant correlations were identified between the presence of a particular clinical sign and the duration of clinical signs. ECGs were obtained in four dogs and all exhibited QT interval prolongation due to a ST-segment prolongation. Sixteen of 17 dogs were treated successfully for hypocalcaemia and discharged from hospital. Acute management included parenteral calcium gluconate (10 dogs) and intravenous anticonvulsants (five dogs). Chronic therapy included oral vitamin D analogues and calcium supplementation. Treatment complications occurred in two dogs and included acute renal failure (one dog) and iatrogenic tissue necrosis following subcutaneous calcium administration (one dog). The mean follow-up period was 14.5 months (median 13 months, range 0 to 39 months). Twelve dogs were alive at the last follow up and two dogs were euthanased for unrelated reasons. The type of vitamin D analogue used was not associated with outcome. Primary hypoparathyroidism was an uncommon diagnosis in dogs. Saint Bernards, cross bred dogs, German Shepherd dogs and Terrier breeds were most commonly affected. Neurological signs were the most common presenting clinical signs, although alimentary signs may have been more common than previously reported. Dogs with primary hypoparathyroidism appeared to have a good prognosis following initiation of calcium supplementation and vitamin D therapy. Complications of treatment were uncommon and could be minimised with regular monitoring.

Calcium-enriched bread for treatment of uremic hyperphosphatemia

Objective To assess phosphate-binding efficacy of a new food product, bread with unusually high calcium content (Ca-bread). Design and setting A randomized parallel group trial in the university hospital outpatient dialysis unit. Patients Fifty-three randomly selected uremic patients who met the following inclusion criteria: (1) required maintenance hemodialysis treatment, (2) were not to receive vitamin D throughout the study, (3) were nondiabetic, and (4) were diagnosed with hyperphosphatemia. Intervention Fifty-three patients were randomized into 2 groups: control group (n = 26), which received calcium acetate as a phosphate binder throughout the study, and Ca-bread group (n = 27), which, after a 2-week washout period, received Ca-bread containing 2.5% of elemental calcium (by weight), which served as a phosphate binder. Bread was made using wheat flour, calcium carbonate, and fermented buttermilk. The amount of elemental calcium used as a phosphate binder was similar in both groups. Observation of both groups lasted 14 weeks. Results Mean serum phosphate concentration at randomization was 2.11 ± 0.14 mmol/L in the control group and 2.20 ± 0.13 mmol/L in the Ca-bread group. Mean serum calcium concentration at randomization was 2.12 ± 0.21 mmol/L in the control group and 2.14 ± 0.11 mmol/L in the Ca-bread group. The Ca-bread group patients’ predialysis phosphate concentration decreased to a mean of 1.67 ± 0.18 mmol/L ( P < .05), and their mean calcium concentration increased to 2.27 ± 0.11 mmol/L ( P = NS). In the control group, neither value changed significantly from the original readings. After the hemodialysis session, the mean serum calcium concentration in the control group and the Ca-bread group increased by 7.5% and 7.9%, respectively ( P = NS). Mean phosphate concentration simultaneously decreased to nearly 1/2 its original predialysis value in both groups. Ca-bread group patients saw a decrease in the mean phosphate concentration (from predialysis to postdialysis values) that was 13.8% greater than that of the control group ( P = NS). Conclusion A new form of calcium-containing phosphate binder was developed: Ca-bread with an elemental calcium content of 2.5%. Ca-bread allows for effective amelioration of hyperphosphatemia without inducing hypercalcemia. Furthermore, patient compliance may increase if hyperphosphatemia can be treated by consuming bread with an elevated calcium content.

Anthropogenic regulation of the phosphorus balance in the Thau catchment–coastal lagoon system (Mediterraean Sea, France) over 24 years

In the Thau lagoon, despite there being no phosphate limitation policy, the annual mean phosphate concentrations decreased by 90% between 1971 and 1994. The present study indicates a relationship between the decrease of phosphate concentrations and changes in urban, industrial and agricultural activities within the catchment generating phosphorus (P) inputs; and shellfish farming leading to phosphorus storage and export. The relationship (tonnes of P) is: P–PO 4 3− in the lagoon waters=1.0124 anthropogenic phosphorus balance––47.62 ( r 2=0.824, p<0.000). As population growth is expected in coastal zones, sustainable development requires the need for addressing the role played by human activities and the multi-scale regulation of them. As an element of integrated coastal zone management, the present study provides a regional scale analysis of these aspects.

Seasonal changes of dissolved nutrients within and around Port Foster Deception Island, Antarctica

Abstract Temporal and spatial distribution of dissolved macronutrients (ammonia, nitrate, phosphate and silica) and productivity were investigated within and around Port Foster, the flooded 160-m-deep caldera of Deception Island, Antarctica. This study was part of the Erupt Project, which included five seasonal cruises over a complete annual cycle during 1999–2000. Seawater samples were collected and physical properties were monitored from seven stations within Port Foster and 12 stations in the adjacent Bransfield Strait. In addition, shallow-water and beach interstitial-water samples were collected along the shorelines of the peripheral coves. Port Foster macronutrient/depth profiles were typical for a normal shallow seawater column in a polar region. The water column in early austral spring was well mixed and changed to a stratified water column with a weak thermocline during the summer. By early winter, the thickness of the well-mixed surface layer increased until the entire water column returned to well-mixed conditions. This early winter transition from stratified conditions to well-mixed conditions occurred in June and appeared to be abrupt. During the seasons of light limitation and low-primary productivity, local currents were effective at redistributing dissolved biochemical components throughout the bay. During the summer season, the dissolved nutrient and oxygen distributions reflected consumption of nutrients by primary producers. The mid-depth maximum observed in the ammonia profiles implies the excretion of metabolites from resident animal populations. Residence time of dissolved ammonia must have been shorter than the circulation time within Port Foster because ammonia is not as uniformly distributed during the summer months as it was during the winter and spring. Dissolved nitrate concentrations in the Bransfield Strait during this study were similar to those measured in previous studies. The mean concentrations of phosphate, nitrate, and silica in the beach interstitial samples were significantly higher (2.8–9.5 times) than in the shore, offshore and CTD samples. Possible sources for the high phosphate, nitrate, and ammonia concentrations in the beach interstitial and shore waters include decaying organic matter and bird and mammal excrement. Elevated silica concentrations appear to be associated with hydrothermal heating of beach and near-shore waters. However, the elevated macronutrient concentrations measured in the beach interstitial water were not traceable beyond 5 m of the shoreline. Phytoplankton biomass in Port Foster exhibited temporal variability similar to other coastal and continental shelf zones (CCZ) of the Antarctic Peninsula. Blooms in February and November 2000 were dominated by the centric diatoms Thalassiosira spp. and Rhizosolenia spp. Chlorophyll a (chl a ) values of 15 and 19 mg m −3 in Port Foster during these blooms were comparable to maximum-recorded levels in western Antarctic Peninsula CCZ (30–40 mg chl a m −3 ), while chl a values from November 1999 and June 2000 (non-bloom conditions) corresponded to historical monthly chl a averages of western Antarctic Peninsula CCZ ( −3 ). During blooms, phytoplankton standing stock could account for about 15 μM nitrate, which corresponds to the observed surface nitrate depletion.

Seasonal cycle of phosphate in the open ocean

The seasonal cycle of phosphate in the world ocean is described using all historical data (over 170,000 profiles) held at the U.S. National Oceanographic Data Center and World Data Center-A for Oceanography. Generally, phosphate concentrations are depressed in the season of highest primary production, in conformance with phosphate's role as a major nutrient. Mean phosphate concentration in the North Pacific are twice those in the North Atlantic. The largest seasonal differences occur in the sub-polar North Atlantic and Pacific, where changes in concentration are as large as a factor of two. Temperate and equatorial regions exhibit less seasonal variability. High latitudes, upwelling areas, and river mouths exhibit a notable seasonal signal in phosphate. Enrichment of phosphate from the Amazon and Orinoco rivers appears to dominate the seasonal signal in the tropical Atlantic. In fact, the extent of the rivers’ effects extend so far north into the North Atlantic gyre that it obscures the normal pattern of summer depletion occurring elsewhere in the basin. The seasonal signal in the tropical Pacific Ocean is a function of seasonal variability in the winds, which affect the strength of coastal upwelling.

Release of mineral ions in dental plaque following acid production

The release of appreciable amounts of calcium, phosphate and fluoride found in whole plaque into the plaque-fluid phase, following bacterial acid production, can potentially reduce the driving force for tooth demineralization. However, limited information is available on this topic, particularly on the release of fluoride. This study sought to determine the change in calcium, phosphate and fluoride concentrations in plaque fluid after sucrose exposure. 48 h overnight-fasted supragingival plaque samples were collected from all tooth surfaces (with the exception of the lower lingual anterior teeth) of one half of an individual mouth, following a 1 min water rinse. Plaque samples were then collected from the other half of the same mouth, following a 292 mM sucrose rinse. Plaque fluid was isolated by centrifugation and analysed for total calcium and phosphate (ion chromatography) and for free fluoride (ion-specific electrode). Samples were collected from seven individuals. Following sucrose exposure, plaque-fluid pH decreased significantly from 6.5±0.3 to 5.4±0.2; calcium concentrations (mmol/l) also increased significantly ( p<0.01) from 1.9±0.5 to 5.0±2.1. Fluoride and phosphate concentrations in plaque fluid, however, did not increase significantly after sucrose exposure: mean concentrations (mmol/l) of fluoride after the water and sucrose rinses were 0.006±0.003 and 0.005±0.002, respectively, and mean phosphate concentrations (mmol/l) were 11.0±2.0 and 12.0±3.0, respectively. When results were expressed per wet plaque weight, phosphate concentrations were also found to increase significantly. The same trends were observed when additional plaque samples were treated in vitro with sucrose: fluoride-ion activity did not increase in plaque under in vivo-like conditions.

Effects of drought on nutrient and ABA transport in Ricinus communis

ABSTRACTWe studied the effects of variations of water flux through the plant, of diurnal variation of water flux, and of variation of vapour pressure deficit at the leaf on compensation pressure in the Passioura‐type pressure chamber, the composition of the xylem sap and leaf conductance in Ricinus communis. The diurnal pattern of compensation pressure showed stress relaxation during the night hours, while stress increased during the day, when water limitation increased. Thus compensation pressure was a good measure of the momentary water status of the root throughout the day and during drought. The bulk soil water content at which predawn compensation pressure and abscisic acid concentration in the xylem sap increased and leaf conductance decreased, was high when the water usage of the plant was high. For all xylem sap constituents analysed, variations in concentrations during the day were larger than changes in mean concentrations with drought. Mean concentrations of phosphate and the pH of the xylem sap declined with drought, while nitrate concentration remained constant. When the measurement leaf was exposed to a different VPD from the rest of the plant, leaf conductance declined by 400mmol m−2 s−1 when compensation pressure increased by 1 MPa in all treatments. The compensation pressure needed to keep the shoot turgid, leaf conductance and the abscisic acid concentration in the xylem were linearly related. This was also the case when the highly dynamic development of stress was taken into account.