Faculty Opinions recommendation of Stoichiometry in an ecological context: testing for links between Daphnia P-content, growth rate and habitat preference.

Abstract Although consumers may use selective feeding to cope with suboptimal resource quality, little work has examined the mechanisms that underlie selective feeding, the efficiency of this behavior or its influence on consumer growth rate. Furthermore, a consumer’s exposure to suboptimal resources may also influence the consumer’s behavior and life history, including growth rate. Here, we studied how the availability of P-rich and P-poor phytoplankton influences the growth and behavior of copepod nauplii. We observed that copepod nauplii preferentially feed on P-rich prey. We also found that even relatively short exposure to P-rich phytoplankton yielded higher nauplii growth rates, whereas the presence of P-poor phytoplankton in a mixture impaired growth. Overall, we observed that swimming speed decreased with increasing phytoplankton P-content, which is a behavioral adjustment that may improve utilization of heterogeneously distributed high-quality food in the field. Based on our results, we propose that the optimal prey C: P ratio for copepod nauplii is very narrow, and that deviations from this optimum have severe negative consequences for growth.

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Genotype-specific relationships among phosphorus use, growth and abundance in Daphnia pulicaria

Royal Society Open Science ◽

10.1098/rsos.170770 ◽

2017 ◽

Vol 4 (12) ◽

pp. 170770 ◽

Cited By ~ 7

Author(s):

Ryan E. Sherman ◽

Priyanka Roy Chowdhury ◽

Kristina D. Baker ◽

Lawrence J. Weider ◽

Punidan D. Jeyasingh

Keyword(s):

Growth Rate ◽

Ecological Stoichiometry ◽

Competitive Ability ◽

Nutrient Content ◽

Nutrient Supply ◽

P Limitation ◽

Poor Predictor ◽

Nutrient Use ◽

P Content ◽

Stoichiometric Models

The framework ecological stoichiometry uses elemental composition of species to make predictions about growth and competitive ability in defined elemental supply conditions. Although intraspecific differences in stoichiometry have been observed, we have yet to understand the mechanisms generating and maintaining such variation. We used variation in phosphorus (P) content within a Daphnia species to test the extent to which %P can explain variation in growth and competition. Further, we measured 33 P kinetics (acquisition, assimilation, incorporation and retention) to understand the extent to which such variables improved predictions. Genotypes showed significant variation in P content, 33 P kinetics and growth rate. P content alone was a poor predictor of growth rate and competitive ability. While most genotypes exhibited the typical growth penalty under P limitation, a few varied little in growth between P diets. These observations indicate that some genotypes can maintain growth under P-limited conditions by altering P use, suggesting that decomposing P content of an individual into physiological components of P kinetics will improve stoichiometric models. More generally, attention to the interplay between nutrient content and nutrient-use is required to make inferences regarding the success of genotypes in defined conditions of nutrient supply.

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Increasing Phosphorus Uptake Efficiency by Phosphorus-Starved Microalgae for Municipal Wastewater Post-Treatment

Microorganisms ◽

10.3390/microorganisms9081598 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1598

Author(s):

Aigars Lavrinovičs ◽

Fredrika Murby ◽

Elīna Zīverte ◽

Linda Mežule ◽

Tālis Juhna

Keyword(s):

Growth Rate ◽

Municipal Wastewater ◽

Removal Rate ◽

Reference Conditions ◽

Phosphorus Uptake ◽

Molar Ratio ◽

Biomass Growth ◽

Activity Increase ◽

Phosphorus Starvation ◽

P Content

Four microalgal species, Chlorella vulgaris, Botryococcus braunii, Ankistrodesmus falcatus, and Tetradesmus obliquus were studied for enhanced phosphorus removal from municipal wastewater after their exposure to phosphorus starvation. Microalgae were exposed to phosphorus starvation conditions for three and five days and then used in a batch experiment to purify an effluent from a small WWTP. After 3-day P-starvation, C. vulgaris biomass growth rate increased by 50% and its PO4 removal rate reached >99% within 7 days. B. braunii maintained good biomass growth rate and nutrient removal regardless of the P-starvation. All species showed 2–5 times higher alkaline phosphatase activity increase for P-starved biomass than at the reference conditions, responding to the decline of PO4 concentration in wastewater and biomass poly-P content. The overall efficiency of biomass P-starvation on enhanced phosphorus uptake was found to be dependent on the species, N/P molar ratio in the wastewater, as well as the biomass P content.

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Juvenile tree growth correlates with photosynthesis and leaf phosphorus content in central Amazonia

Revista CERES ◽

10.1590/0034-737x201562020007 ◽

2015 ◽

Vol 62 (2) ◽

pp. 175-183 ◽

Cited By ~ 1

Author(s):

Ricardo Antonio Marenco ◽

Nilvanda dos Santos Magalhães ◽

Paula Romenya dos Santos Gouvêa ◽

Saul Alfredo Antezana-Vera

Keyword(s):

Growth Rate ◽

Soil Water ◽

Nutrient Content ◽

Gas Exchange Parameters ◽

P Content ◽

Rainfall Seasonality ◽

Central Amazonia ◽

Sapling Growth ◽

Leaf P ◽

Exchange Parameters

Light and soil water availability may limit carbon uptake of trees in tropical rainforests. The objective of this work was to determine how photosynthetic traits of juvenile trees respond to variations in rainfall seasonality, leaf nutrient content, and opening of the forest canopy. The correlation between leaf nutrient content and annual growth rate of saplings was also assessed. In a terra firme rainforest of the central Amazon, leaf nutrient content and gas exchange parameters were measured in five sapling tree species in the dry and rainy season of 2008. Sapling growth was measured in 2008 and 2009. Rainfall seasonality led to variations in soil water content, but it did not affect leaf gas exchange parameters. Subtle changes in the canopy opening affected CO2 saturated photosynthesis (A pot, p = 0.04). Although A pot was affected by leaf nutrient content (as follows: P > Mg > Ca > N > K), the relative growth rate of saplings correlated solely with leaf P content (r = 0.52, p = 0.003). At present, reduction in soil water content during the dry season does not seem to be strong enough to cause any effect on photosynthesis of saplings in central Amazonia. This study shows that leaf P content is positively correlated with sapling growth in the central Amazon. Therefore, the positive effect of atmospheric CO2 fertilization on long-term tree growth will depend on the ability of trees to absorb additional amount of P

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Ontogenetic changes in the elemental composition and stoichiometry of marine copepods with different life history strategies

Journal of Plankton Research ◽

10.1093/plankt/fbaa018 ◽

2020 ◽

Vol 42 (3) ◽

pp. 320-333 ◽

Cited By ~ 1

Author(s):

Enric Saiz ◽

Kaiene Griffell ◽

Albert Calbet

Keyword(s):

Growth Rate ◽

Life History ◽

Elemental Composition ◽

Growth Rates ◽

Stoichiometric Composition ◽

Maximum Growth ◽

Life History Strategies ◽

Ontogenetic Variation ◽

Ontogenetic Changes ◽

P Content

Abstract We describe the ontogenetic variation in elemental and stoichiometric composition of two copepod species with very contrasted life history patterns, the calanoid Paracartia grani and the cyclopoid Oithona davisae. The first species is a broadcasting, highly productive copepod, whereas the latter is an egg-carrying copepod, much less productive. We reared cultures of both species under conditions of excess food and analyzed their C, N and P composition, and their molar ratios, along development. Both species differed on their specific P content, whereas the specific C and N content were similar. As expected, the specific P content of P. grani was higher, resulting in lower C:P and N:P ratios. Furthermore, we compared our elemental composition data with previously reported stage-specific (nauplii and adult female) maximum growth rates of these two species. We found that for O. davisae, the ontogenetic variation in specific P content agreed with the reported differences in growth rate along development; however, in the case of P. grani, in which juvenile and adult maximum growth rates are similar, the variations in specific P content along development did not reflect the growth rate pattern.

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Associations between DNA methylation and telomere length during early life: insight from wild zebra finches (Taeniopygia guttata)

10.22541/au.161715129.96880077/v1 ◽

2021 ◽

Author(s):

Elizabeth Sheldon ◽

Riccardo Ton ◽

Winnie Boner ◽

Pat Monaghan ◽

Shirley Raveh ◽

...

Keyword(s):

Dna Methylation ◽

Growth Rate ◽

Telomere Length ◽

Early Life ◽

Life History Traits ◽

Zebra Finches ◽

Ecological Context ◽

Life Conditions ◽

Early Life Conditions ◽

Length Changes

Telomere length and DNA methylation (DNAm) are two promising biomarkers of biological age. Environmental factors and life history traits are known to affect variation in both these biomarkers, especially during early life, yet surprisingly little is known about their reciprocal association. Here, we present the first study on a natural population to explore how variation in DNAm, growth rate and early-life conditions are associated with telomere length changes during development. We tested these associations by collecting data from wild, nestling zebra finches in the Australian desert. We found that increases in the level of DNAm were negatively correlated with telomere length changes across early life. We also confirm previously documented effects of post hatch growth rate and clutch size on telomere length in a natural ecological context for a species that has been extensively studied in the laboratory. However, we did not detect any effect of ambient temperature during developmental on telomere dynamics. We also found that the absolute telomere length of wild zebra finches, measured using the in-gel TRF method, was similar to that of captive birds. Our findings highlight exciting new opportunities to link and disentangle potential relationships between environmental, epigenetic and telomere length dynamics during early life.

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The threshold energy for atom displacement in fcc metals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100175788 ◽

1990 ◽

Vol 48 (4) ◽

pp. 530-531

Author(s):

Wilfried Sigle ◽

Matthias Hohenstein ◽

Alfred Seeger

Keyword(s):

Growth Rate ◽

Elevated Temperatures ◽

Threshold Energy ◽

Dislocation Loops ◽

Absolute Minimum ◽

Voltage Electron ◽

Atom Displacement ◽

Electron Microscopes ◽

Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

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