scholarly journals Seasonal and plant-part isotopic and biochemical variation in Posidonia oceanica

2019 ◽  
Vol 20 (2) ◽  
pp. 357
Author(s):  
PIERRE CRESSON ◽  
CHARLES FRANÇOIS BOUDOURESQUE ◽  
SANDRINE RUITTON ◽  
LAURIE CASALOT ◽  
MARC VERLAQUE ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Isotope Composition ◽  
Posidonia Oceanica ◽  
Plant Part ◽  
Previous Knowledge ◽  
Depth Limit ◽  
Plant Parts ◽  
Carbohydrate Concentration ◽  
High Concentrations ◽  
Lower Depth

Posidonia oceanica is an iconic and highly productive Mediterranean seagrass. As most studies focused on the fate of this production, temporal and plant part-specific variations of isotopic composition and biochemical content were overlooked. Combined seasonal and plant-part stable isotope composition and biochemical concentrations were measured at the lower depth limit of a P. oceanica meadow (~ 25 meter depth), and explained by previous knowledge of the specific metabolic functioning of each part. The predominance of compounds with complex chemical structure was reflected by the high concentrations of insoluble carbohydrates, high C/N ratios, and high δ13C values. Plant parts clustered in 3 groups with similar isotopic or biochemical features and metabolism: rhizomes and juvenile leaves, intermediate and adult leaves, senescent and drifting leaves. This result agrees with the vegetative phenology of the plant. The biochemical composition and the isotopic composition of the plant parts were consistent with previous knowledge about the photosynthetic activity and its seasonal variation. Correlations were found between N-linked descriptors (δ15N and protein content), and between δ13C and insoluble carbohydrate concentration. Epibiont values differed considerably from those of the leaf, as this community is taxonomically diverse and seasonally variable. Biochemical and isotopic composition measured confirmed that the current complex metabolism of P. oceanica results from adaptations to the specific life in a marine oligotrophic environment.

scholarly journals NO<sub>x</sub> cycle and the tropospheric ozone isotope anomaly: an experimental investigation

2014 ◽  
Vol 14 (10) ◽  
pp. 4935-4953 ◽  
Author(s):  
G. Michalski ◽  
S. K. Bhattacharya ◽  
G. Girsch
Keyword(s):  
Steady State ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Dominant Role ◽  
Isotope Effects ◽  
Rate Coefficients ◽  
Atmospheric Conditions ◽  
Exchange Reactions ◽  
Mixing Ratios ◽  
High Concentrations

Abstract. The oxygen isotope composition of nitrogen oxides (NOx) in the atmosphere is a useful tool for understanding the oxidation of NOx into nitric acid / nitrate in the atmosphere. A set of experiments was conducted to examine change in isotopic composition of NOx due to NOx–O2–O3 photochemical cycling. At low NOx / O2 mixing ratios, NOx became progressively and nearly equally enriched in 17O and 18O over time until it reached a steady state with Δ17O values of 39.3 ± 1.9‰ and δ18O values of 84.2 ± 4‰, relative to the isotopic composition of the initial O2 gas. As the mixing ratios were increased, the isotopic enrichments were suppressed by isotopic exchange between O atoms, O2, and NOx. A kinetic model was developed to simulate the observed data and it showed that the isotope effects occurring during O3 formation play a dominant role in controlling NOx isotopes and, in addition, secondary kinetic isotope effects or isotope exchange reactions are also important during NOx cycling. The data and model were consistent with previous studies which showed that the NO + O3 reactions occur mainly via the transfer of the terminal atoms of O3. The model predicts that under tropospheric concentrations of NOx and O3, the timescale of NOx–O3 isotopic equilibrium ranges from hours (for ppbv NOx / O2 mixing ratios) to days (for pptv mixing ratios) and yields steady state Δ17O and δ18O values of 45‰ and 117‰ respectively (relative to Vienna Standard Mean Ocean Water (VSMOW)) in both cases. Under atmospheric conditions when O3 has high concentrations, the equilibrium between NOx and O3 should occur rapidly (h) but this equilibrium cannot be reached during polar winters and/or nights if the NOx conversion to HNO3 is faster. The experimentally derived rate coefficients can be used to model the major NOx–O3 isotopologue reactions at various pressures and in isotope modeling of tropospheric nitrate.

Posidonia oceanica lower depth limits along a latitudinal gradient in the eastern Adriatic Sea

2020 ◽  
Vol 63 (3) ◽  
pp. 209-214
Author(s):  
Ivana Zubak ◽  
Hrvoje Cizmek ◽  
Melita Mokos
Keyword(s):  
Latitudinal Gradient ◽  
Depth Distribution ◽  
Adriatic Sea ◽  
Environmental Changes ◽  
Marine Species ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
Eastern Coast ◽  
Depth Limit ◽  
Lower Depth

AbstractAlthough extensive studies have been made on Posidonia oceanica ecosystems, in terms of their phenological characteristics, shoot density, biomass, and associated faunal assemblages, little attention has been given to the depth distribution of this species in the Adriatic Sea. The depth limits of the Mediterranean endemic seagrass P. oceanica growing along the eastern coast of the Croatian Adriatic Sea were examined by the use of SCUBA diving. Fifty-two independent measurements show that the lower depth limit of P. oceanica in the Croatian Adriatic Sea ranges from 24 m in the north to 36 m in the south, with a strong latitudinal gradient. The information on maximum depth distribution is an important asset when the increased human pressure and rapid environmental changes pose a threat to the survival of this slow-growing marine species.

Factors affecting 13C/12C ratios of inland halophytes. I. Controlled studies on growth and isotopic composition of Puccinellia nuttalliana

1986 ◽  
Vol 64 (11) ◽  
pp. 2693-2699 ◽  
Author(s):  
Robert D. Guy ◽  
David M. Reid ◽  
H. Roy Krouse
Keyword(s):  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Isotope Analysis ◽  
Research Problem ◽  
Carbon Isotope Composition ◽  
Stable Carbon ◽  
Factors Affecting ◽  
Plant Parts ◽  
High Level ◽  
Puccinellia Nuttalliana

Studies on various factors affecting the growth and stable carbon isotope composition of the graminaceous C3 halophyte Puccinellia nuttalliana (Schultes) Hitch. were initiated as a step towards interpreting δ13C variations in nature. For isotope analysis, combustion at 900 °C resulted in higher CO2 yield than at 550 °C but did not affect δ13C values. Differences in δ13C between leaves of different insertion level were unimportant, but roots were about 1‰ more positive than shoots. Trends in δ13C with salinity were the same in all plant parts. Depressions of growth by NaCl or Na2SO4 were similar, but plants grown in Na2SO4 displayed a greater shift in δ13C relative to controls. Growth rates were affected more by salinity than were previously reported photosynthetic rates. At typical salinities, δ13C changed linearly with salinity. The supply of nitrate to stressed and unstressed plants had no important influence on δ13C. Growth in polyethylene glycol produced δ13C values consistent with a high level of stress. After a salinity step-up, changes in δ13C were complete within 10 days. During winter, data were found to be heavily influenced by unintentional, human-respired CO2 enrichment. This represents a potentially serious research problem in laboratories of temperate climes.

scholarly journals Seasonal variations in nitrate isotope composition of three rivers draining into the North Sea

2010 ◽  
Vol 7 (4) ◽  
pp. 6051-6088 ◽  
Author(s):  
A. Deek ◽  
K. Emeis ◽  
U. Struck
Keyword(s):  
Isotopic Composition ◽  
North Sea ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Isotope Effects ◽  
Nitrate Sources ◽  
Particulate Nitrogen ◽  
Soil Nitrification ◽  
Mean Values ◽  
Δ 15N

Abstract. Nitrate loading of coastal ecosystems by rivers that drain industrialised catchments continues to be a problem in the South Eastern North Sea, in spite of significant mitigation efforts over the last 2 decades. To identify nitrate sources, sinks, and turnover in three German rivers that discharge into the German Bight, we determined δ 15N-NO3- and δ18O- NO3- in nitrate and δ 15N of particulate nitrogen for the period 2006–2009 (biweekly samples). The nitrate loads of Rhine, Weser and Ems varied seasonally in magnitude and δ 15N-NO3- (6.5–21‰), whereas the δ 18O-NO3- (-0.3–5.9‰) and δ 15N-PN (4–14‰) were less variable. Overall temporal patterns in nitrate mass fluxes and isotopic composition suggest that a combination of nitrate delivery from nitrification of soil ammonia in the catchment and assimilation of nitrate in the rivers control the isotopic composition of nitrate. Nitrification in soils as a source is indicated by low δ 18O-NO3- in winter, which traces the δ 18O of river water. Mean values of δ 18O-H2O were between –9.4‰ and –7.3‰; combined in a ratio of 2:1 with the atmospheric oxygen δ 18O of 23.5‰ agrees with the found δ 18O of nitrate in the rivers. Parallel variations of δ 15N-NO3- and δ 18O-NO3- within each individual river are caused by isotope effects associated with nitrate assimilation in the water column, the extent of which is determined by residence time in the river. Assimilation is furthermore to some extent mirrored both by the δ 15N of nitrate and particulate N. Although δ 15-NO3- observed in Rhine, Weser and Ems are reflected in high average δ 15N-PN (between 6‰ and 9‰, both are uncorrelated in the time series due to lateral and temporal mixing of PN. That a larger enrichment was consistently seen in δ 15N-NO3- relative to δ 18O-NO3- is attributed to constant additional diffuse nitrate inputs deriving from soil nitrification in the catchment area. A statistically significant inverse correlation exists between increasing δ 15N-NO3- values and decreasing NO3- concentrations. This inverse relationship – observed in each seasonal cycle – together with a robust relationship between human dominated land use and δ 15N-NO3- values demonstrates a strong influence of human activities and riverine nitrate consumption efficiency on the isotopic composition of riverine nitrate.

scholarly journals The “good, the bad and the double-sword” effects of exposure to MPs and their organic additives on N2-fixing bacteria

2020 ◽  
Author(s):  
Víctor Fernández-Juárez ◽  
Xabier López-Alforja ◽  
Aida Frank-Comas ◽  
Pedro Echeveste ◽  
Antoni Bennasar-Figueras ◽  
...  
Keyword(s):  
Posidonia Oceanica ◽  
Dioctyl Phthalate ◽  
Benthic Organisms ◽  
Protein Overexpression ◽  
Organic Additives ◽  
Physical Interactions ◽  
High Concentrations ◽  
Species Specific ◽  
Micro Organisms ◽  
First Time

AbstractThe accumulation of microplastics (MPs) pollution at depths suggests the susceptibility of benthic organisms (e.g. seagrasses and their associated macro- and micro-organisms) to the effects of these pollutants. Little is known about the direct effects of MPs and their organic additives on marine bacteria, e.g. in one of the most ecologically significant groups, the diazotrophs or N2-fixing bacteria. To fill this gap of knowledge, we exposed marine diazotrophs found in association with the endemic Mediterranean seagrass Posidonia oceanica to pure MPs which differ in physical properties (e.g. density, hydrophobicity and/or size), namely, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS) and to their most abundant associated organic additives (e.g. fluoranthene, 1,2,5,6,9,10-hexabromocyclododecane [HBCD] and dioctyl-phthalate [DEHP]). Growth, protein overexpression, direct physical interactions between MPs and bacteria, phosphorus (P) acquisition mechanisms and N2-fixation rates were evaluated. Our results show species-specific responses of the autotrophic and heterotrophic N2-fixing bacteria tested and the responses were dependent on the type and concentration of MPs and additives. N2-fixing cyanobacteria were positively affected by environmental and high concentrations of MPs (e.g. PVC), as opposed to heterotrophic strains, that were only positively affected with high concentrations of ∼120 µm-size MPs (detecting the overexpression of proteins related to plastic degradation and C-transport), and negatively affected by 1 µm-size PS beads. Generally, the organic additives (e.g. fluoranthene) had a deleterious effect in both autotrophic and heterotrophic N2-fixing bacteria and the magnitude of the effect is suggested to be dependent on bacterial size. We did not find evidences that specific N2-fixation rates were significantly affected by exposure to MPs, albeit changes in bacterial abundance can affect the bulk N2-fixation rates. In summary, we reported for the first time, the beneficial (the “good”), deleterious (the “bad”) and/or both (the “double-sword”) effects of exposure to MPs and their organic additives on diazotrophs found in association with seagrasses.

Status-quo of carbonate cadmium isotope compositions as a paleo-productivity proxy

2021 ◽  
Author(s):  
Simon V. Hohl
Keyword(s):  
Isotopic Composition ◽  
Isotope Composition ◽  
Status Quo ◽  
Ambient Seawater ◽  
Isotopic Compositions ◽  
Marine Carbonates ◽  
The Status ◽  
State Changes ◽  
Underlying Processes ◽  
Isotope Systematics

&lt;p&gt;Cadmium (Cd) and isotope systematics are emerging tools for studying the biogeochemical cycling of micronutrients in the oceans, and sedimentary archives, as Cd concentrations in seawater show a nutrient-like behaviour, with surface depletion and deep water enrichments. However, the underlying processes are yet to be fully understood. The Cd concentration and isotopic composition of seawater are set by the balance of Cd inputs (and their isotopic composition) and the fractionation on removal to sedimentary sinks. The most favoured explanation is the Cd utilisation by marine phototrophic biomass, causing the surface water&amp;#8217;s dissolved Cd pool depletion creating a depth gradient of increasing Cd concentrations and lighter isotopic compositions. Under incomplete oxidative recycling, organic matter may act as an effective Cd sink and authigenic minerals may store the ambient seawater&amp;#8217;s Cd isotope composition.&lt;/p&gt;&lt;p&gt;Consequently, stable Cd isotope compositions in marine carbonates show broad variations linked to paleo-productivity and redox state changes. Additional fractionation processes govern the Cd isotopic compositions of marine sediments. Besides biological utilisation, experimental Cd partitioning into authigenic calcites or sulphides under variable redox and salinity conditions has been shown. &amp;#160;Therefore, when applying Cd isotopes in carbonates, other geochemical proxies must be evaluated very carefully to understand the involved Cd fractionation processes. This presentation aims to present the status quo of research done on authigenic and biologic carbonates and carbonate leachates in carbonatic shales to show the strengths and pitfalls of this new emerging bio-geoscience isotope proxy and its use for paleoenvironmental reconstructions on Earth and beyond.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Laboratory Assessment of Molluscicidal and Cercaricidal Activities of Balanites aegyptiaca against Vectors of Schistosomiasis (Biomphalaria pfeifferi)

2021 ◽  
Vol 8 (5) ◽  
pp. 479-486
Author(s):  
Muhammad Isa
Keyword(s):  
Plant Part ◽  
Snail Species ◽  
Phytochemical Screening ◽  
Biomphalaria Pfeifferi ◽  
Laboratory Assessment ◽  
Balanites Aegyptiaca ◽  
Standard Methods ◽  
Plant Parts ◽  
Activity Test

Studies were conducted on assessment of molluscicidal and cercaricidal activities of leaves, fruits and endocarp of Balanite aegyptiaca Del against adult vectors of schistosomiasis (Biomphlaria Pfeifeferi) using standard methods. Preliminary phytochemical screening was conducted, where alkaloids, saponins, flavonoids were found present in leaves, fruits, and endocarp. Molluscicidal and cercaricidal activity test were also conducted. Snail mortalities were compared between each plant part and snail specie as well as LC50 of the plant parts were also recorded. The result obtained revealed that leaves extract was more susceptible to the death of the snail species. Comparing LC50, the leaves extract shows 0.0726 considered as the highest cercaricidal while fruits and endocarp showed highest LC50of 0.0531 and 0.0426 respectively. Keywords: Balanites Aegyptiaca, Molluscicidal, Cercaricidal Activities, Schistosomiasis (Biomphalaria pfeifferi).

scholarly journals Unique and highly specific cyanogenic glycoside localization in stigmatic cells and pollen in the genus Lomatia (Proteaceae)

2020 ◽  
Vol 126 (3) ◽  
pp. 387-400
Author(s):  
Edita Ritmejerytė ◽  
Berin A Boughton ◽  
Michael J Bayly ◽  
Rebecca E Miller
Keyword(s):  
Mass Spectrometry Imaging ◽  
Chemical Defence ◽  
Ionization Mass ◽  
Congeneric Species ◽  
Substantial Variation ◽  
Plant Parts ◽  
High Concentrations ◽  
Strategic Allocation ◽  
Defence Strategies ◽  
Constitutive Defence

Abstract Background and Aims Floral chemical defence strategies remain understudied despite the significance of flowers to plant fitness, and the fact that many flowers contain secondary metabolites that confer resistance to herbivores. Optimal defence and apparency theories predict that the most apparent plant parts and/or those most important to fitness should be most defended. To test whether within-flower distributions of chemical defence are consistent with these theories we used cyanogenic glycosides (CNglycs), which are constitutive defence metabolites that deter herbivores by releasing hydrogen cyanide upon hydrolysis. Methods We used cyanogenic florets of the genus Lomatia to investigate at what scale there may be strategic allocation of CNglycs in flowers, what their localization reveals about function, and whether levels of floral CNglycs differ between eight congeneric species across a climatic gradient. Within-flower distributions of CNglycs during development were quantified, CNglycs were identified and their localization was visualized in cryosectioned florets using matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Key Results Florets of all congeneric species studied were cyanogenic, and concentrations differed between species. Within florets there was substantial variation in CNglyc concentrations, with extremely high concentrations (up to 14.6 mg CN g−1 d. wt) in pollen and loose, specialized surface cells on the pollen presenter, among the highest concentrations reported in plant tissues. Two tyrosine-derived CNglycs, the monoglycoside dhurrin and diglycoside proteacin, were identified. MALDI-MSI revealed their varying ratios in different floral tissues; proteacin was primarily localized to anthers and ovules, and dhurrin to specialized cells on the pollen presenter. The mix of transient specialized cells and pollen of L. fraxinifolia was ~11 % dhurrin and ~1.1 % proteacin by mass. Conclusions Tissue-specific distributions of two CNglycs and substantial variation in their concentrations within florets suggests their allocation is under strong selection. Localized, high CNglyc concentrations in transient cells challenge the predictions of defence theories, and highlight the importance of fine-scale metabolite visualization, and the need for further investigation into the ecological and metabolic roles of CNglycs in floral tissues.

Stable isotopes reveal post-release trophodynamic and ontogenetic changes in a released finfish, mulloway (Argyrosomus japonicus)

2010 ◽  
Vol 61 (3) ◽  
pp. 302 ◽  
Author(s):  
Matthew D. Taylor ◽  
Debashish Mazumder
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Turnover Rate ◽  
Isotope Composition ◽  
Wild Fish ◽  
Ontogenetic Changes ◽  
Nitrogen Stable Isotope ◽  
Δ13c And Δ15n ◽  
Carbon And Nitrogen ◽  
Nitrogen Isotopic Composition

Carbon and nitrogen stable isotope ratios were analysed for hatchery-reared, recaptured and wild mulloway, Argyrosomus japonicus, to investigate temporal and growth-related changes in isotopic composition for stocked fish after release, and to evaluate changes in isotopic composition in terms of ontogenetic dietary switches. δ13C and δ15N values decreased and increased, respectively, after release. The isotope composition of released fish was distinct from wild fish until 200 days after release, but after 200 days post-release fish did not differ significantly from wild fish of similar or greater sizes. Abrupt dietary transitions from crustaceans to teleost fish (>50 cm total length (TL)) were evident in a rapid δ13C and δ15N change in wild mulloway, and δ15N was significantly greater in wild fish >65 cm TL compared with wild fish <50 cm TL. Multivariate carbon and nitrogen isotopic data were suitable for separating stocked and wild fish for up to 200 days after release, but did not separate wild fish grouped according to dietary composition. Carbon and nitrogen isotopic composition closely reflected dietary transitions and rapid adaptation by stocked mulloway to wild diets, which was evident in a high tissue turnover rate of up to 0.017 day–1. Stable isotopes are a useful tool for examining the integration of released fish into stocked ecosystems and can be used to describe convergence in the diets of wild and released fish.

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