TP Ratio Research Articles

Calcium:phosphorus ratios and supplemental phytases on broiler performance and bone quality

Summary This study aimed to evaluate 2 phytases, at 2 supplementation doses, in broiler diets with nutritional matrices with reduction in Ca:total P (tP) ratio. One-day-old male chicks (n = 3,960) were distributed in an arrangement of 12 treatments, with 10 replicates each; the experimental unit consisted of a floor pen with 33 birds each. Trial lasted up to 42 D, and birds were given the experimental diets: T1—positive control 1 (high Ca:tP ratio—recommended amount); T2—negative control 1 (reduction of 0.16% Ca and 0.16% available P-AP); T3–T2 + 500 FTU/kg enzyme A; T4–T2 + 500 FTU/kg enzyme B; T5–T2 + 1000 FTU/kg enzyme A; T6–T2 + 1000 FTU/kg enzyme B; T7–positive control 2 (low Ca:tP ratio); T8—negative control 2 (reduction of 0.16% Ca and 0.16% AP); T9–T8 + 500 FTU/kg enzyme A; T10–T8 + 500 FTU/kg enzyme B; T11–T8 + 1000 FTU/kg enzyme A; and T12–T8 + 1000 FTU/kg enzyme B. At 21 and 42 D of age, performance variables were recorded (body weight, body weight gain, feed intake, and feed conversion ratio) and tibial bone composition (Ca and P) and resistance was determined (strength at rupture). Results indicate that enzyme supplementation was efficient, regardless of Ca:tP ratio. The highest phytase dose presented superior results, especially for the 21-D evaluation. Phytase “B,” a bacterial product, showed superior response on performance and bone quality.

Intra‐annual variation of phytoplankton community responses to factorial N, P, and CO2 enrichment in a temperate mesotrophic lake

Abstract Across primary producer communities in different lakes, nitrogen (N) and phosphorus (P) can exhibit many different patterns of limitation. Here, we look at the intra‐annual variability of these patterns in a single lake. Furthermore, we investigate whether a third resource, carbon dioxide (CO2) can have significant effects on phytoplankton biomass and community composition. We performed five in situ lacustrine mesocosm experiments at different times of the year. In each experiment, we had a factorial design with two levels of N, P and CO2 enrichment (no enrichment or double lake concentrations for N and P and atmospheric (400 ppm) and c. 1,000 ppm for CO2) resulting in a total of eight treatments. Mesocosms of c. 1,600 L were suspended in a temperate, mesotrophic lake (Lac Hertel, Canada). Each experiment lasted 2 weeks and chlorophyll a biomass, coarse chemotaxonomic community composition (measured using fluorometry), and several environmental variables were recorded at a minimum of four time points. We found that the limiting, synergistic, and community composition effects of N and P varied between experiments. TN:TP ratios explained, in part, some of this variability, along with insolation and water temperature. Despite relatively high levels of CO2 in the control mesocosms, we found a constant synergistic effect of CO2 with N. In combination with the synergistic effect of P with N found in some experiments, this provides support for CO2 as one of the multiple limiting resources in nutrient‐enriched systems. This finding could have implications for eutrophic lakes exposed to increasing concentrations of CO2. We also found that the effects of CO2 on community composition varied intra‐annually. Thus, we conclude that generalised predictions about the effect of CO2 on community composition at a coarse chemotaxonomic scale are unlikely to hold, but predictions specific to season and system are likely to be reliable.

Responses of nitrogen stable isotopes in fish to phosphorus limitation in freshwater wetlands

Human-induced eutrophication has altered ecological processes in aquatic ecosystems. Detection of ecological changes is a prerequisite for protecting ecosystems from degradation. In this study, nitrogen stable isotopes (δ15N) in fish are evaluated as indicators of environmental changes in south Florida wetlands. Stable nitrogen isotope (δ15N) data of select fish species and water quality collected from the Florida Everglades between the 1990s and 2000s were used to assess the relationship between total phosphorus concentrations and δ15N ratios. The δ15N ratios in nine of ten select fish species increase significantly as total phosphorus concentration in the surface water increases. There were significant relationships between total nitrogen concentration in the surface water and δ15N ratios in several fish species. The pattern of changes in δ15N ratios along nutrient gradients suggests that increased eutrophication is recorded as the δ15N ratios in fish. The lack of human wastewater loading, the dominance in agricultural runoff and the high TN:TP ratio suggest that phosphorus is the limiting factor driving ecosystem productivity and the changes of δ15N ratios in fish. Results from this analysis demonstrate that δ15N ratios in fish integrate biotic responses to eutrophic process over time and could be a robust indicator for early ecological changes.

Comparison of formulation costs for poultry feeds based on crude protein versus the digestible lysine to protein ratio

Abstract The objective of this study was to determine the influence of using dLys:TP instead of crude protein recommendations of commercial poultry breeding companies to meet the chicken’s need for dietary essential and non-essential amino acids. The ingredient composition matrix used in the feed formulation was compiled from Feedstuffs Magazine. The rations were formulated using a linear feed formulation program to meet the minimum cost, with crude protein or dLys: TP of 5.58%. Using the dLys to TP ratio versus CP minimums for the model diets chosen, formula costs were changed from +$10.96 to -$4.26 per ton of feed. The magnitude of the changes was dependent on the imbalance present in the feeds from using the breeder management guide recommendations and ingredient prices. Through the use of dLys: TP, it is possible to improve the feed formulation process, assuring the birds get adequate EAA and NEAA without being wasteful and reducing environmental pollution.

Decadal variations of total organic carbon production in the inner-shelf of the South China Sea and East China Sea

Abstract Organic carbon content is one of the major proxies of aquatic primary production and implication of environmental changes. However, there is a scarcity of information regarding the decadal variation of organic carbon production in inner-shelf of South China Sea (SCS) and East China Sea (ECS). To bridge this gap of information two sediment cores were collected from the inner shelf of SCS (Leizhou Peninsula) and ECS. Then, Total Organic Carbon (TOC), Total Inorganic Carbon (TIC) and Total Nitrogen (TN) content were examined. The TOC content in the Leizhou Peninsula averaged 0.56% and varied from 0.35% to 0.81%. At decadal time scale, the TOC content of Leizhou Peninsula erratically increased in the last century, and it distinctly peaked after 1990’s. This is related to increased primary production due to the increased input of anthropogenic nutrients and rainfall level. The TOC content of the inner shelf of ECS averaged 0.5% and varied narrowly from 0.46% to 0.53%. The TOC:TN ratio of ECS averaged 5.65 and varied from 4.42 to 7.85, indicating there is high degree of organic matter degradations. The TN:TP ratios were below 10 for the periods before late-1990’s, indicating that there had been a potential nitrogen limitation in the inner shelf of ECS. Generally, this study showed that the TOC and TIC of ECS and SCS inner-shelf had undergone substantial changes in the last century.

Drivers and ecological consequences of dominance in periurban phytoplankton communities using networks approaches

Evaluating the causes and consequences of dominance by a limited number of taxa in phytoplankton communities is of huge importance in the current context of increasing anthropogenic pressures on natural ecosystems. This is of particular concern in densely populated urban areas where usages and impacts of human populations on water ecosystems are strongly interconnected. Microbial biodiversity is commonly used as a bioindicator of environmental quality and ecosystem functioning, but there are few studies at the regional scale that integrate the drivers of dominance in phytoplankton communities and their consequences on the structure and functioning of these communities. Here, we studied the causes and consequences of phytoplankton dominance in 50 environmentally contrasted waterbodies, sampled over four summer campaigns in the highly-populated Île-de-France region (IDF). Phytoplankton dominance was observed in 32–52% of the communities and most cases were attributed to Chlorophyta (35.5–40.6% of cases) and Cyanobacteria (30.3–36.5%). The best predictors of dominance were identified using multinomial logistic regression and included waterbody features (surface, depth and connection to the hydrological network) and water column characteristics (total N, TN:TP ratio, water temperature and stratification). The consequences of dominance were dependent on the identity of the dominant organisms and included modifications of biological attributes (richness, cohesion) and functioning (biomass, RUE) of phytoplankton communities. We constructed co-occurrence networks using high resolution phytoplankton biomass and demonstrated that networks under dominance by Chlorophyta and Cyanobacteria exhibited significantly different structure compared with networks without dominance. Furthermore, dominance by Cyanobacteria was associated with more profound network modifications (e.g. cohesion, size, density, efficiency and proportion of negative links), suggesting a stronger disruption of the structure and functioning of phytoplankton communities in the conditions in which this group dominates. Finally, we provide a synthesis on the relationships between environmental drivers, dominance status, community attributes and network structure.

Hypolimnetic oxygenation 3: an engineered switch from eutrophic to a meso-/oligotrophic state in a California reservoir

Horne AJ, Beutel M. 2019. Hypolimnetic oxygenation 3: an engineered switch from eutrophic to a meso-/oligotrophic state in a California reservoir. Lake Reserv Manage. 35:338–353. A long-term improvement in water quality due to a hypolimnetic oxygenation system (HOS) used without other management actions was shown for Camanche Reservoir in California (volume = 514 million m3). Prior to oxygenation, the reservoir was eutrophic with low water clarity, high chlorophyll a (Chl-a), and blooms of cyanobacteria primarily caused by internal nutrient loading from anoxic sediments. All 4 trophic state indicators showed major improvement, most pointing to a new oligotrophic state. Days after HOS startup in July 1993, hypolimnion soluble phosphate and ammonium concentrations declined and, unexpectedly, nitrate remained low. This report covers pre-HOS (1988 to mid-1993) and 12 yr of post-HOS measurements (mid-1993 to mid-2005). For surface waters during the growth season (Apr–Oct) after HOS, average Chl-a decreased 79% (14.6–3.1 μg/L) and peak Chl-a decreased sixfold (from 49 to 8 μg/L). Average Secchi depth increased 10-fold (0.47 to 4.9 m) and peak Secchi depth doubled (4.2–8 m). Cyanobacteria (Aphanizomenon and Dolichospermum, formerly Anabaena) decreased >95% while the previously absent Merismopedia, an indicator of clean water, appeared. The large colonial diatom Fragilaria also decreased by >90%. Zooplankton (rotifers and crustaceans) appeared unchanged. After HOS, late winter surface nutrients prior to the next spring bloom were much reduced (total phosphorus, TP, by 58%, total inorganic nitrogen, TIN, by 88%). The TIN:TP ratio dropped from 6 to 1.6. In 2004, the last full year of measurements, further declines were found for nitrate nitrogen (42–3 μg/L) and Chl-a (3.1–2.8 μg/L) while TP was unchanged (14 μg/L).

Using algal biomass-phosphorus (P) relationships and nutrient limitation theory to evaluate the adequacy of P water quality criteria for regulated monsoon rivers and reservoirs

ABSTRACTDifferent P criteria have been set for lotic and lentic waters where the latter had stricter criteria than the former. The binary P criteria have been developed due to differences in limnological features and this helps avoid unneeded costs with stricter criteria for flowing waters that normally have lower potential of algal blooms. However, if different criteria are warranted, the responses of Chl a to TP and TN:TP ratio should vary distinctively between rivers and reservoirs. Contrary to these predictions, inconsistent and statistically indistinguishable variations have been observed between the two types of waterbody in Chl a yield per unit TP. Additionally, there was no significant difference in the strength of relationship between Chl a and TN:TP ratio between waterbody types, although the mass ratio of TN to TP was significantly higher in reservoirs than in rivers. Hence, the data suggest that there is no scientifically defensible reason that lotic and lentic waters require different TP standards and specifically that lentic waters do not necessarily require stricter P criteria. A more holistic and nuanced approach would aid in developing revised or new TP criteria in which water quality issues can be addressed scientifically as well as pragmatically.

Long-term effects of nutrient changes on rotifer communities in a subtropical lake

External nutrient loading has a major influence on the abundance, composition and diversity of zooplankton communities. To clarify how the reduction of nutrient loading during lake restoration interacts with other abiotic and biotic factors and how the interactive factors affect long-term changes in rotifer communities, we analyzed the relationships between the rotifer communities and environmental factors using a 17-year dataset. After the reduction of nutrients, both the abundance and biomass of rotifers declined, and the dominant rotifers changed from eutrophic-tolerant species to less tolerant ones. The lower TN:TP ratio that was caused by the imbalanced decrease in TN and TP after restoration promoted cyanobacteria, which negatively related to the resource-use efficiency of rotifers. Moreover, seasonal differences in the Shannon–Wiener index–TN relationships and the decrease in the Pielou index with the increase in water temperature implied there were interactive effects of water temperature and nutrients on species diversity. The study concluded that changes in rotifer abundance and community composition were mainly related to TN, but the changes in species diversity were mainly related to the interactive effects of the TN:TP ratio, water temperature and food quality. Our findings highlighted the effects caused by imbalanced nutrient changes on species diversity.

Physical, biogeochemical, and meteorological factors responsible for interannual changes in cyanobacterial community composition and biovolume over two decades in a eutrophic lake

This study used a 20-year dataset (1995–2014) to identify factors affecting cyanobacterial community composition (CCC) and abundance in a eutrophic lake. We hypothesized that differences in thermal structure, nutrients, and meteorology drive interannual variability in CCC and abundance. Cluster analysis differentiated dominant cyanobacteria into rare, low abundance, or sporadically occurring taxa. The bloom-forming genera were Microcystis and Aphanizomenon, accounting for ~ 70% of total cyanobacterial biovolume (BV) on average, whereas unusually high abundance of Planktothrix, Synechococcus, and Oscillatoria were clear outliers in three of the years. Variability in CCC was significantly correlated (P 0.3) with ice duration, Kjeldahl nitrogen (TKN), and spring nitrite + nitrate (NO2+3); ice duration and TKN were associated with the occurrence of primarily non-bloom-forming genera. Pairwise correlations tested linear, exponential, and polynomial correlates of absolute and relative total Cyanophyta, Microcystis, or Aphanizomenon BV. TKN, total nitrogen (TN) and phosphorus (TP), TN:TP ratio, Schmidt stability, and rainfall correlated with total Cyanophyta, Microcystis, and Aphanizomenon BV, whereas ice cover, NO2+3, and TKN correlated with relative Microcystis and Aphanizomenon BV. Despite increasing TN:TP ratio over two decades, cyanobacterial abundance had not changed significantly. These data suggest differing responses of cyanobacterial genera to important environmental factors over two decades.

Decreased nitrogen loading controls summer cyanobacterial blooms without promoting nitrogen‐fixing taxa: Long‐term response of a shallow lake

AbstractThe effectiveness of controlling nitrogen (N) to manage lake eutrophication is debated. Long‐term, whole‐lake case studies are required to determine whether diazotrophic cyanobacteria can fix sufficient N to offset a reduction of N‐inputs. We document the recovery of shallow, productive Lake Müggelsee (Germany) over 37 yr (sampling interval 1–2 weeks) during a decrease of N and phosphorus (P) loading of 79% and 69%, respectively. Nitrogen concentrations in the lake responded immediately to loading reduction whereas P concentrations remained elevated for about 20 yr. Total nitrogen (TN) in the lake was always lower than TN in the inflow. Accordingly, estimated denitrification and N‐burial rates substantially exceeded N2 fixation rates in the long term. Phosphorus was growth limiting in spring whereas N was clearly limiting in summer due to high sediment P‐release. TN : TP ratios, normalized to phytoplankton biovolume by regression, were 25.5 (weight) in spring and 3.3 in summer. During the study period, dissolved inorganic N (DIN) concentrations in summer decreased and the duration of low DIN concentrations increased by ca. 100 d. The biovolume of cyanobacteria and total phytoplankton decreased by 89% and 76%, respectively. The proportion of N2‐fixing cyanobacteria during summer decreased from 36% to 14% of the total phytoplankton biovolume. The total concentration of heterocysts and estimated total N2 fixation did not change over time. In the long term, decreasing N‐inputs effectively controlled summer cyanobacteria including N2‐fixing taxa, which did not compensate for the N‐deficit. A P‐only control strategy would not have been as successful.

Changes in Total Protein Concentration Due to Fluid Removal During and Shortly after Hemodialysis

Background: Changes in plasma volume during hemodialysis are complex and have been shown to depend on the rate of fluid removal and the degree of fluid overload. We examined changes in total protein concentration during and shortly after a dialysis treatment in archived data from the HEMO study. Methods: During follow-up months 4 and 36 of the HEMO study, additional blood samples were obtained during a typical dialysis session at 30 and 60 min after dialysis. In 315 studies from 282 patients where complete data were available, we calculated the concentration change in total protein and compared it to the modeled change in both total body water and extracellular fluid space as derived from 2-pool urea kinetic modeling. Results: The mean postdialysis modeled urea volume (V) was 31.1 ± 6.18 L. Mean fluid removal was 2.76 ± 1.27 kg, over a session length of 207 ± 28 min. The ratio of predialysis V to postdialysis V averaged 1.090 ± 0.040. The mean TP ratios (post/pre) at 0, 30, and 60 min postdialysis averaged 1.121 ± 0.070 (SD), 1.091 ± 0.090, and 1.091 ± 0.086. The dialysate to serum sodium gradient, studied in a different group of treatments where this information was available, had no impact on these findings, nor did the length of the interdialytic interval. Conclusions: On average, after equilibration, the change in plasma volume due to fluid removal is similar to the modeled change in total body water (urea space), irrespective of dialysate to serum sodium gradient. This supports previous observations that during dialysis with ultrafiltration, plasma volume contracts to a lesser degree than the interstitial volume and that some fluid may be removed from spaces other than the extracellular fluid.

A Comparative Examination of Recent Changes in Nutrients and Lower Food Web Structure in Lake Michigan and Lake Huron.

The lower food webs of Lake Huron and Lake Michigan have experienced similar reductions in the spring phytoplankton bloom and summer populations of Diporeia and cladocerans since the early 2000s. At the same time phosphorus concentrations have decreased and water clarity and silica concentrations have increased. Key periods of change, identified by using a method based on sequential t-tests, were 2003-2005 (Huron) and 2004-2006 (Michigan). Estimated filtration capacity suggests that dreissenid grazing would have been insufficient to directly impact phytoplankton in the deeper waters of either lake by this time (mid 2000s). Despite some evidence of decreased chlorophyll:TP ratios, consistent with grazing limitation of phytoplankton, the main impact of dreissenids on the offshore waters was probably remote, e.g., through interception of nutrients by nearshore populations. A mass balance model indicates that decreased phosphorus loading could not account for observed in-lake phosphorus declines. However, model-inferred internal phosphorus dynamics were strongly correlated between the lakes, with periods of increased internal loading in the 1990s, and increased phosphorus loss starting in 2000 in Lake Michigan and 2003 in Lake Huron, prior to dreissenid expansion into deep water of both lakes. This suggests a limited role for deep populations of dreissenids in the initial phosphorus declines in the lakes, and also suggests a role for meteorological influence on phosphorus dynamics. The high synchrony in lower trophic level changes between Lake Michigan and Lake Huron suggests that both lakes should be considered when investigating underlying causal factors of these changes.

SMOOTHNESS INDEX OF CENTRAL BLOOD PRESSURE AND PARAMETERS FOR VASCULAR STIFFNESS AFTER 20 WEEK TREATMENT WITH LOSARTAN PLUS AMLODIPINE VS. THIAZIDE RANDOMIZED TRIAL

Objective: With limitation of clinic and brachial BP, central BP and vascular parameters have known to be better to probe efficacy of antihypertensive drug. Because vascular parameters are measured at resting state, role of ambulatory central BP and vascular parameters to explain the difference in clinical efficacy between renin angiotensin system inhibitor in combination with amlodipine versus hydrochlorthiazide was uncertain. Design and method: As sub-study of multicenter randomized double blinded, losartan based therapy combined with amlodipine (LA) versus hydrochlorthiazide (LH), 143 patient (LH:73, LH:70) out of 220 patients with 80% or more valid readings in 24 hour ambulatory monitoring using Mobile-O-graph which provide ambulatory central BP and vascular stiffness data were analyzed. Smoothness index (SI) of SBP, central SBP(ACSBP), pulse pressure amplification(APPA), augmentation index([email protected]), and carotid femoral pulse wave velocity(AcfPWV). APPA was calculated by the ratio of SBP to ACSBP. Results: Age was 58.9 ± 12.3 years and female was 25.9%. Prevalence of drinking and current smoking were 51.5% and 21.7%, respectively. Diabetes mellitus was noted in 14.7%. Clinic BPs were 153.8 ± 10.2/92.4 ± 8.5 mmHg. Ambulatory 24 hour SBP and ACSBP were 136.5 ± 11.7 mmHg and 126.6 ± 11.0 mmHg. Changes in office BP was not different (LH:-15.2 ± 15.0/-7.8 ± 8.0 vs. LA:-14.9 ± 13.7/-9.2 ± 7.5 mmHg). Reductions of 24 hour SBP were greater in LA than LH (-10.3 ± 12.6 vs. -6.6 ± 10.2 mmHg, p = 0.0478). Only nocturnal ACSBP reduction was significant (LH:4.1 ± 12.2 vs. LA:9.4 ± 12.2, p = 0.01). And only nocturnal AcfPWV reduction was significant (LH:0.09 ± 0.41 vs LA: 0.26 ± 0.44 m/sec, p = 0.023). Intra-individual SIs for SBP and ACSBP were higher in LA than LH(SBP:-0.57 ± 0.78 vs. -0.39 ± 0.57, p = 0.0196; ACSBP:-0.57 ± 0.74 vs. -0.40 ± 0.57, p = 0.022). Intra-individual SI for AcfPWV were marginally significant (LH:0.31 ± 0.58 vs. LA:0.54 ± 0.77, p = 0.053). SIs for APPA and AAIx75 were not different. Intra-individual TP ratios were higher in LA than LH group but the differences are not significant for both SBP(0.30[95%CI, -0.07∼1.30] and ACSBP(0.24[95% CI, -0.51∼3.80]). Conclusions: LA combination seems to be superior to LH combination in reduction of ambulatory SBP. But for the reduction of ACSBP or AcfPWV was significant only in nighttime. Difference in intra-individual SI was significant both in SBP and ACSBP but not in AcfPWV. Further larger sample size studies are need

Temporal and spatial distribution of phytoplankton functional groups and role of environment factors in a deep subtropical reservoir

Phytoplankton and environment factors were investigated in 2015 and phytoplankton functional groups were used to understand their temporal and spatial distribution and their driving factors in Wanfeng Reservoir. Seventeen functional groups (B, D, E, F, G, J, Lo, MP, P, S1, T, W1, W2, X1, X2, Xph, Y) were identified based on 34 species. The dominant groups were: J/B/P/D in dry season, X1/J/Xph/G/T in normal season and J in flood season. Phytoplankton abundance ranged from 5.33×104 cells/L to 3.65×107 cells/L, with the highest value occurring in flood season and lowest in dry season. The vertical profile of dominant groups showed little differentiation except for P, which dominated surface layers over 20 m as a result of mixing water masses and higher transparency during dry season. However, the surface waters presented higher values of phytoplankton abundance than other layers, possibly because of greater irradiance. The significant explaining variables and their ability to describe the spatial distribution of the phytoplankton community in RDA differed seasonally as follows: dry season, NH4-N, NO3-N, NO2-N, TN:TP ratio and transparency (SD); normal season, temperature (WT), water depth, TN, NH4-N and NO3-N; flood season, WT, water depth, NO3-N and NO2-N. Furthermore, nitrogen, water temperature, SD and water depth were significant variables explaining the variance of phytoplankton communities when datasets included all samples. The results indicated that water physical conditions and hydrology were important in phytoplankton community dynamics, and nitrogen was more important than phosphorus in modifying phytoplankton communities. Seasonal differences in the relationship between the environment and phytoplankton community should be considered in water quality management.

Forms and subannual variability of nitrogen and phosphorus loading to global river networks over the 20th century

Abstract Nitrogen (N) and phosphorus (P) play a major role in the biogeochemical functioning of aquatic systems. N and P transfer to surface freshwaters has amplified during the 20th century, which has led to widespread eutrophication problems. The contribution of different sources, natural and anthropogenic, to total N and P loading to river networks has recently been estimated yearly using the Integrated Model to Assess the Global Environment - Global Nutrient Model (IMAGE-GNM). However, eutrophic events generally result from a combination of physicochemical conditions governed by hydrological dynamics and the availability of specific nutrient forms that vary at subyearly timescales. In the present study, we define for each simulated nutrient source: i) its speciation, and ii) its subannual temporal pattern. Thereby, we simulate the monthly loads of different N (ammonium, nitrate + nitrite, and organic N) and P forms (dissolved and particulate inorganic P, and organic P) to global river networks over the whole 20th century at a half-degree spatial resolution. Results indicate that, together with an increase in the delivery of all nutrient forms to global rivers, the proportion of inorganic forms in total N and P inputs has risen from 30 to 43% and from 56 to 65%, respectively. The high loads originating from fertilized agricultural lands and the increasing proportion of sewage inputs have led to a greater proportion of DIN forms (ammonium and nitrate), that are usually more bioavailable. Soil loss from agricultural lands, which delivers large amounts of particle-bound inorganic P to surface freshwaters, has become the dominant P source, which is likely to lead to an increased accumulation of legacy P in slow flowing areas (e.g., lakes and reservoirs). While the TN:TP ratio of the loads has remained quite stable, the DIN:DIP molar ratio, which is likely to affect algal development the most, has increased from 18 to 27 globally. Human activities have also affected the timing of nutrient delivery to surface freshwaters. Increasing wastewater emissions in growing urban areas induces constant local pressure on the quality of aquatic systems by delivering generally highly bioavailable nutrient forms, even in periods of low runoff.

Quantifying thermal decomposition regimes of textile dyeing sludge, pomelo peel, and their blends

Abstract Thermal decomposition behaviors of textile dyeing sludge (TDS), pomelo peel (PP), and their blends (TP) were detected using TG-FTIR. The blend ratios of TDS to PP ranged from 10 to 40 wt% and were subjected to heat above room temperature up to 1000 °C under four heating rates. Our results pointed to four stages for TDS combustion and three stages for PP combustion. The interactions between TDS and PP exerted inhibitive effects during the co-combustion process. Releases of CO2 and light organics occurred less with a TP ratio of 70%–30% (TP73) than with the individual fuels. Apparent activation energy (Ea) was obtained using Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. The FWO-based Ea estimates were in the range of 59.7–122.2 kJ·mol−1 for TDS, 84.4–243.5 kJ·mol−1 for PP, and 94.3–142.1 kJ·mol−1 for TP73.

Disentangling natural and anthropogenic influences on Patagonian pond water quality

The water quality of wetlands is governed not only by natural variability in hydrology and other factors, but also by anthropogenic activities. Patagonia is a vast sparsely-populated in which ponds are a key component of rural and urban landscapes because they provide several ecosystem services such as habitat for wildlife and watering for livestock. Integrating field-based and geospatial data of 109 ponds sampled across the region, we identified spatial trends and assessed the effects of anthropogenic and natural factors in pond water quality. The studied ponds were generally shallow, well oxygenated, with maximum nutrient values reported in sites used for livestock breeding. TN:TP ratio values were lower than 14 in >90% of the ponds, indicating nitrogen limitation. Water conductivity decreased from de east to the west, meanwhile pH and dissolved oxygen varied associated with the latitude. To assess Patagonian ponds water status we recommend the measure of total suspended solids and total nitrogen in the water, and evaluate the mallín (wetland vegetation) coverage in a 100m radius from the pond, since those features were significantly influenced by livestock land use. To evaluate the relative importance of natural variability and anthropogenic influences as driving factors of water quality we performed three generalized linear models (GLM) that encompassed the hydrology, hydroperiod and biome (to represent natural influences), and land use (to represent anthropogenic influences) as fixed effects. Our results revealed that at the Patagonian scale, ponds water quality would be strongly dependent on natural gradients. We synthetized spatial patterns of Patagonian pond water quality, and disentangled natural and anthropic factors finding that the dominant environmental influence is rainfall gradient.

Macrophyte-induced thermal stratification in a shallow urban lake promotes conditions suitable for nitrogen-fixing cyanobacteria

Densely vegetated shallow lakes often experience low water column nutrient levels and reduced phytoplankton growth, but in some cases a high phytoplankton biomass can co-exist with submerged macrophytes. The conditions that favour phytoplankton blooms within areas colonized by submerged macrophytes remain largely unexplored. We investigated changes in water quality variables and phytoplankton community composition data in relation to macrophyte-induced thermal stratification in a shallow urban lake. The results indicate that submerged macrophytes may favour internal loadings of phosphorus and low DIN:TP ratios, in periods when macrophyte-induced thermal stratification of the water column is common. Blooms of nitrogen-fixing cyanobacteria occurred under the strongly stratified conditions triggered by the high macrophyte biomass and elevated canopy, even though nitrogen limitation was apparent during the whole growing season. These findings suggest that submerged macrophytes can promote blooms of nitrogen-fixing cyanobacteria once they are sufficiently tall and dense to induce stable water column conditions.

High-Frequency Ultrasound: Description of Sacral Tissue Characteristics in Healthy Adults.

The purpose of this study was to describe selected sacral tissue characteristics in a convenience sample of healthy volunteer subjects. Descriptive. Fifty healthy volunteers in a clinical learning center in a school of nursing. Sacral scans were obtained using a 20-MHz ultrasound scanning system in 3 positions: prone and 60° and 90° side-lying from the back. The images were analyzed by software in the ultrasound program using quantitative parameters of dermal thickness and density (dermal median intensity and derived number of low-echogenic pixels to total pixels [LEP:TP] ratio). In general, average values were as follows: dermal thickness between 2.32 and 2.65 mm; median pixel intensity between 102 and 112; and the LEP:TP ratio between 0.39 and 0.56. There were significant differences in sacral tissue characteristics between measures of thickness and dermal density (median intensity and LEP:TP ratio) by subject side-lying position (60° and 90°) versus prone position, with all P values less than .0001. Overall, the ranges were consistent across measures of thickness and dermal density except for systematic differences between side-lying and prone positions. When comparing thickness, median intensity, or LEP:TP ratio, it is important to report subject position. To best recognize tissue inflammation indicative of pressure injuries before surface changes are seen, it is useful to understand healthy high-frequency ultrasound sacral tissue characteristics. It is anticipated that quantitative assessment of dermal thickness, density, and LEP:TP ratio could help identify individuals with incipient pressure injury.