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−.

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

2014 ◽  
Vol 11 (5) ◽  
pp. 6909-6943 ◽  
Author(s):  
P. K. Swart ◽  
S. Evans ◽  
T. Capo ◽  
M. A. Altabet
Keyword(s):  
Isotope Fractionation ◽  
Algal Growth ◽  
Benthic Algae ◽  
Syringe Pump ◽  
Stable Isotope Fractionation ◽  
Wide Range ◽  
Algal Material ◽  
The Relationship ◽  
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 h replacements of media. These experiments proceeded for periods of between seven and ten 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. Fitting models to these data show that the fractionation during assimilation is dependent upon the concentration of NO3− and is effectively zero at concentrations of less than 1 μM. The change in the fractionation with respect to concentration is the greatest at lower concentrations (1–10 μM). The fractionation determined using the δ15N of the NO3− or the solid algal material provided statistically the same result. Therefore, at typical marine concentrations of NO3−, fractionation during assimilation can probably be considered to be negligible. Although the δ18O and δ15N of NO3− in the residual solution were correlated, the slope of the relationship varied with NO3− concentration, with slopes of greater than unity at low concentration. These results suggest shifts in the dominant fractionation mechanism between 1 and 10 μM NO3−. At typical marine concentrations of NO3−, fractionation during assimilation can be considered to be negligible. However, at higher concentrations, fractionation during assimilation will lead to both δ15N values for algal biomass lower than the NO3− source, but also 15N enrichments in the residual NO3−.

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.

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.

scholarly journals Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

2021 ◽  
Author(s):  
Andrea Watzinger ◽  
Melanie Hager ◽  
Thomas Reichenauer ◽  
Gerhard Soja ◽  
Paul Kinner
Keyword(s):  
Stable Isotope ◽  
Constructed Wetlands ◽  
Hydrogen Isotope ◽  
Petroleum Hydrocarbon ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Filter Material ◽  
Hydrocarbon Biodegradation ◽  
Stable Isotope Fractionation ◽  
Filter Materials

AbstractMaintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g−1 day−1) than in the expanded clay (1.0 µg CO2 g−1 day−1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day−1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

Effects of food quality, starvation and life stage on stable isotope fractionation in Collembola

Pedobiologia ◽  
2005 ◽  
Vol 49 (3) ◽  
pp. 229-237 ◽  
Author(s):  
Dominique Haubert ◽  
Reinhard Langel ◽  
Stefan Scheu ◽  
Liliane Ruess
Keyword(s):  
Stable Isotope ◽  
Food Quality ◽  
Isotope Fractionation ◽  
Life Stage ◽  
Stable Isotope Fractionation

Magnesium stable isotope fractionation in marine biogenic calcite and aragonite

2011 ◽  
Vol 75 (19) ◽  
pp. 5797-5818 ◽  
Author(s):  
F. Wombacher ◽  
A. Eisenhauer ◽  
F. Böhm ◽  
N. Gussone ◽  
M. Regenberg ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Stable Isotope Fractionation

Compound-Specific Stable Isotope Fractionation of Pesticides and Pharmaceuticals in a Mesoscale Aquifer Model

2016 ◽  
Vol 50 (11) ◽  
pp. 5729-5739 ◽  
Author(s):  
Heide K. V. Schürner ◽  
Michael P. Maier ◽  
Dominik Eckert ◽  
Ramona Brejcha ◽  
Claudia-Constanze Neumann ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Stable Isotope Fractionation

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.

Stable isotope fractionation by Clostridium pasteurianum. 5. Effect of SeO42− on the physiology and associated sulfur isotope fractionation during SO32− and SO42− reductions

1982 ◽  
Vol 28 (3) ◽  
pp. 325-333 ◽  
Author(s):  
G. I. Harrison ◽  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Stationary Phase ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Reductase Activity ◽  
Clostridium Pasteurianum ◽  
Elemental Selenium ◽  
Whole Cells ◽  
Stable Isotope Fractionation ◽  
Sulfur Isotope Fractionation ◽  
Inverse Isotope Effect

The addition of 1 mM SeO42− significantly affected the physiology and metabolism of Clostridium pasteurianum growing on SO42− in the following ways: (1) the generation time was increased, essentially producing a biphasic growth curve, (2) cells became elongated and chains formed, (3) no H2S was liberated during the stationary phase, (4) assimilatory SO32− reductase activity was decreased, (5) ferredoxin levels decreased by a factor of 4. The effects of 1 mM SeO42− on Clostridium pasteurianum growing on SO32− were comparatively minor.H2S evolution in the stationary phase decreased by a factor of 2 and the δ34S maximum in the inverse isotope effect pattern occurred at a slightly lower percent H2S evolution. The deleterious effects of SeO42− addition were less pronounced than those associated with SeO32− addition. SeO32− but not SeO42− was reduced to elemental selenium by both whole cells and crude extracts.

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