scholarly journals Confounding factors in algal phosphorus limitation experiments

2018 ◽  
Author(s):  
Whitney S. Beck ◽  
Ed K. Hall
Keyword(s):  
Algal Biomass ◽  
Field Experiments ◽  
Meta Analysis ◽  
Algal Growth ◽  
Benthic Algae ◽  
Cost Effective ◽  
Phosphorus Limitation ◽  
Significant Inhibition ◽  
Selective Grazing ◽  
Phosphate Salts

AbstractAssessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as nitrogen (N) and phosphorus (P). Unexpectedly, many experiments have also shown decreased algal biomass on NDS P treatments compared to controls. To address whether inhibition of algal growth results from direct P toxicity, NDS preparation artifacts, or environmental covariates, we first quantified the frequency of nutrient inhibition in published experiments. We also conducted a meta-analysis to determine whether heterotrophic microbial competition or selective grazing could explain decreases in algal biomass with P additions. We then deployed field experiments to determine whether P-inhibition of algal growth could be explained by P toxicity, differences in phosphate cation (K vs. Na), differences in phosphate form (monobasic vs. dibasic), or production of H2O2during NDS preparation. We found significant inhibition of algal growth in 12.9% of published NDS P experiments as compared to 4.7% and 3.6% of N and NP experiments. The meta-analysis did not show enhanced heterotrophy on NDS P treatments or selective grazing of P-rich algae. Our field experiments did not show inhibition of autotrophic growth with P additions, but we found significantly lower gross primary productivity (GPP) and biomass-specific GPP of benthic algae on monobasic phosphate salts as compared to dibasic phosphate salts, likely because of reduced pH levels. Additionally, we note that past field experiments and meta-analyses support the plausibility of direct P toxicity or phosphate form (monobasic vs. dibasic) leading to inhibition of algal growth, particularly when other resources such as N or light are limiting. Given that multiple mechanisms may be acting simultaneously, we recommend practical, cost-effective steps to minimize the potential for P-inhibition of algal growth as an artifact of NDS experimental design.

scholarly journals The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate

2014 ◽  
Vol 11 (21) ◽  
pp. 6147-6157 ◽  
Author(s):  
P. K. Swart ◽  
S. Evans ◽  
T. Capo ◽  
M. A. Altabet
Keyword(s):  
Algal Biomass ◽  
Isotope Fractionation ◽  
Algal Growth ◽  
Benthic Algae ◽  
Syringe Pump ◽  
Stable Isotope Fractionation ◽  
Wide Range ◽  
Nitrogen And Oxygen Isotopes ◽  
Fractionation Mechanism ◽  
Residual Solution

Abstract. In order to determine and understand the stable isotope fractionation of 18O and 15N manifested during assimilation of NO3− in marine macro-benthic algae, two species (Ulva sp. and Agardhiella sp.) have been grown in a wide range of NO3− concentrations (2–500 μM). Two types of experiments were performed. The first was one in which the concentration of the NO3− was allowed to drift downward as it was assimilated by the algae, between 24 hour replacements of media. These experiments proceeded for periods of between 7 and 10 days. A second set of experiments maintained the NO3− concentration at a low steady-state value by means of a syringe pump. The effective fractionation during the assimilation of the NO3− was determined by measuring the δ15N of both the (i) new algal growth and (ii) residual NO3− in the free-drift experiments after 0, 12, 24 and 48 h. Modelling these data show that the fractionation during assimilation is dependent upon the concentration of NO3− and is effectively 0 at concentrations of less than ~2 μM. The change in the fractionation with respect to concentration is the greatest at lower concentrations (2–10 μM). The fractionation stablizes between 4 and 6‰ at concentrations of between 50 and 500 μM. Although the δ18O and δ15N values of NO3− in the residual solution were correlated, the slope of relationship also varied with respect to NO3− concentration, with slopes of greater than unity at low concentration. These results suggest shifts in the dominant fractionation mechanism of 15N and 18O between concentrations of 1 and 10 μM NO3−. At higher NO3− concentrations (>10–50 μM), fractionation during assimilation will lead to δ15N values in algal biomass lower than the ambient NO3− and 15N enrichments in the residual NO3−.

Direct and Indirect Effects of Consumers on Benthic Algae in Isolated Pools of an Ephemeral Stream

1990 ◽  
Vol 47 (10) ◽  
pp. 2057-2065 ◽  
Author(s):  
Paul V. McCormick
Keyword(s):  
Algal Biomass ◽  
Algal Species ◽  
Algal Growth ◽  
Benthic Algae ◽  
Nitrogen Enrichment ◽  
Direct And Indirect Effects ◽  
Ephemeral Stream ◽  
Positive Effects ◽  
Algal Assemblages ◽  
Trophic Connections

Artificial pools were used to test for interactions among dominant consumer and producer populations that coexist in isolated pools of an ephemeral stream each summer. Nitrogen and/or phosphorus were supplied to one set of pools; herbivorous snails and crayfish and a predaceous centrarchid were added in different combinations to other pools. Algal growth was measured inside and outside wire cages placed in pools to exclude herbivores and/or predators. Algal biomass and the abundance of most algal species were increased by nitrogen enrichment. Algal biomass was also enhanced by addition of consumers. There were few differences in structure between algal assemblages inside and outside cages in any treatment. Under conditions of nitrogen limitation, moderate levels of herbivory can enhance algal growth. Positive effects are greatest at the microsite level and may depend on the ability of algal species to resist digestion by grazers. Predators may affect the algal assemblage indirectly by reducing herbivore survival or activity and directly by converting nutrients stored in herbivore biomass into a form available for algal growth. Because the importance of different trophic connections may vary among ecosystems, experimentation must consider all those that are potentially important.

Meta-analysis and cost effective analysis of portal-superior mesenteric vein resection during pancreatoduodenectomy: Impact on margin status and survival

2017 ◽  
Vol 26 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Richard Bell ◽  
Braden Te Ao ◽  
Natasha Ironside ◽  
Adam Bartlett ◽  
John A. Windsor ◽  
...  
Keyword(s):  
Superior Mesenteric Vein ◽  
Meta Analysis ◽  
Cost Effective ◽  
Margin Status ◽  
Mesenteric Vein ◽  
Vein Resection ◽  
Effective Analysis

scholarly journals Biomass of ryegrass from field experiments: toward a cost-effective and efficient biosourced catalyst for the synthesis of Moclobemide

2020 ◽  
Vol 14 (1) ◽  
pp. 13-20
Author(s):  
Marie Hechelski ◽  
Christophe Waterlot ◽  
Pierrick Dufrénoy ◽  
Brice Louvel ◽  
Adam Daïch ◽  
...  
Keyword(s):  
Field Experiments ◽  
Cost Effective

scholarly journals Incremental Net Monetary Benefit of Bariatric Surgery: Systematic Review and Meta-Analysis of Cost-Effectiveness Evidences

2021 ◽  
Author(s):  
Prapaporn Noparatayaporn ◽  
Montarat Thavorncharoensap ◽  
Usa Chaikledkaew ◽  
Bhavani Shankara Bagepally ◽  
Ammarin Thakkinstian
Keyword(s):  
Systematic Review ◽  
Bariatric Surgery ◽  
Cost Effectiveness ◽  
Evaluation Studies ◽  
Meta Analysis ◽  
Cost Effective ◽  
Diabetes Group ◽  
Lifetime Horizon ◽  
Middle Income ◽  
Full Economic Evaluation

AbstractThis systematic review aimed to comprehensively synthesize cost-effectiveness evidences of bariatric surgery by pooling incremental net monetary benefits (INB). Twenty-eight full economic evaluation studies comparing bariatric surgery with usual care were identified from five databases. In high-income countries (HICs), bariatric surgery was cost-effective among mixed obesity group (i.e., obesity with/without diabetes) over a 10-year time horizon (pooled INB = $53,063.69; 95% CI $42,647.96, $63,479.43) and lifetime horizon (pooled INB = $101,897.96; 95% CI $79,390.93, $124,404.99). All studies conducted among obese with diabetes reported that bariatric surgery was cost-effective. Also, the pooled INB for obesity with diabetes group over lifetime horizon in HICs was $80,826.28 (95% CI $32,500.75, $129,151.81). Nevertheless, no evidence is available in low- and middle-income countries. Graphical abstract

scholarly journals Active Surveillance of Small Renal Masses: A Systematic Review

Kidney Cancer ◽  
2021 ◽  
pp. 1-14
Author(s):  
Elizabeth E. Ellis ◽  
Edward Messing
Keyword(s):  
Active Surveillance ◽  
Meta Analysis ◽  
Cost Effective ◽  
Management Approach ◽  
Small Renal Masses ◽  
Cancer Specific Survival ◽  
Renal Masses ◽  
Review Current ◽  
Delayed Intervention

Background: Our goal is to review current literature regarding active surveillance (AS) of small renal masses (SRMs) and identify trends in survival outcomes, factors that predict the need for further intervention, and quality of life (QOL). Methods: We performed a comprehensive literature search in PubMed and EMBASE and identified 194 articles. A narrative summary was performed in lieu of a meta-analysis due to the heterogeneity of selected studies. Results: Seventeen articles were chosen to be featured in this review. Growth rate (GR) was not an accurate predictor of malignancy, although it was the characteristic most commonly used to trigger delayed intervention (DI). The mean 5-year overall survival (OS) of all studies was 73.6% ±1.7% for AS groups. The combined cancer specific survival (CSS) for AS is 97.1% ±0.6% , compared to 98.6% ±0.4% for the primary intervention (PI) groups, (p = 0.038). Conclusions: Short and intermediate-term data demonstrate that AS with the option for DI is a management approach whose efficacy (in terms of CSS) approaches that of PI at 5 years, is cost effective, and prevents overtreatment, especially in patients with significant comorbidities.

Supporting Informal Caregivers of People With Dementia in Cost-Effective Ways: A Systematic Review and Meta-Analysis

2021 ◽  
Author(s):  
Zhaohua Huo ◽  
Joyce Y.C. Chan ◽  
Jiaer Lin ◽  
Baker K.K. Bat ◽  
Tak Kit Chan ◽  
...  
Keyword(s):  
Systematic Review ◽  
Meta Analysis ◽  
Informal Caregivers ◽  
Cost Effective ◽  
People With Dementia

scholarly journals Very-low-dose aspirin and surveillance colonoscopy is cost-effective in secondary prevention of colorectal cancer in individuals with advanced adenomas: network meta-analysis and cost-effectiveness analysis

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Sajesh K. Veettil ◽  
Siang Tong Kew ◽  
Kean Ghee Lim ◽  
Pochamana Phisalprapa ◽  
Suresh Kumar ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Cost Effectiveness ◽  
Secondary Prevention ◽  
Low Dose ◽  
Meta Analysis ◽  
Cost Effective ◽  
Cost Effectiveness Analysis ◽  
Surveillance Colonoscopy ◽  
Combination Strategy ◽  
Effectiveness Analysis

Abstract Background Individuals with advanced colorectal adenomas (ACAs) are at high risk for colorectal cancer (CRC), and it is unclear which chemopreventive agent (CPA) is safe and cost-effective for secondary prevention. We aimed to determine, firstly, the most suitable CPA using network meta-analysis (NMA) and secondly, cost-effectiveness of CPA with or without surveillance colonoscopy (SC). Methods Systematic review and NMA of randomised controlled trials were performed, and the most suitable CPA was chosen based on efficacy and the most favourable risk–benefit profile. The economic benefits of CPA alone, 3 yearly SC alone, and a combination of CPA and SC were determined using the cost-effectiveness analysis (CEA) in the Malaysian health-care perspective. Outcomes were reported as incremental cost-effectiveness ratios (ICERs) in 2018 US Dollars ($) per quality-adjusted life-year (QALY), and life-years (LYs) gained. Results According to NMA, the risk–benefit profile favours the use of aspirin at very-low-dose (ASAVLD, ≤ 100 mg/day) for secondary prevention in individuals with previous ACAs. Celecoxib is the most effective CPA but the cardiovascular adverse events are of concern. According to CEA, the combination strategy (ASAVLD with 3-yearly SC) was cost-saving and dominates its competitors as the best buy option. The probability of being cost-effective for ASAVLD alone, 3-yearly SC alone, and combination strategy were 22%, 26%, and 53%, respectively. Extending the SC interval to five years in combination strategy was more cost-effective when compared to 3-yearly SC alone (ICER of $484/LY gain and $1875/QALY). However, extending to ten years in combination strategy was not cost-effective. Conclusion ASAVLD combined with 3-yearly SC in individuals with ACAs may be a cost-effective strategy for CRC prevention. An extension of SC intervals to five years can be considered in resource-limited countries.

Response of Lake Michigan Benthic Algae to in situ Enrichment with Si, N, and P

1988 ◽  
Vol 45 (2) ◽  
pp. 271-279 ◽  
Author(s):  
Hunter J. Carrick ◽  
Rex L. Lowe
Keyword(s):  
Chlorophyll A ◽  
Algal Biomass ◽  
Lake Michigan ◽  
Benthic Algae ◽  
Benthic Diatoms ◽  
Nearshore Area

The possibility that benthic algae in the nearshore area of Lake Michigan might be growth limited by Si was tested using nutrient-releasing substrata. Nutrient treatments were Si, N + P, Si + N + P, and controls (CONT) and were sampled after 7, 14, and 31 d of exposure. Addition of Si alone had little stimulatory effect on algal biomass, while enrichment with Si + N + P led to the greatest increase in chlorophyll a, particulate Si, total biovolume, and diatom biovolume after 14 d of incubation (P < 0.0001). By day 31, communities on CONT and Si substrata exhibited little change in biomass and remained dominated by diatoms (98% of total biovolume), while algal biomass on both N + P and Si + N + P substrata increased more than eightfold (P < 0.0001) and consisted mainly of Stigeoclonium tenue (Chlorophyta) and Schizothrix calcicolas (Cyanophyta). These results indicate that benthic diatoms in Lake Michigan are not currently limited by Si, but may become Si limited following enrichment with N + P.

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