Environmental Science › Ecology

Isotope Analysis in Ecology

Works Count: 59136

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Description

This cluster of papers focuses on the application of stable isotopes in trophic ecology, including estimating trophic position, analyzing food webs, conducting isotope analysis for ecological studies, exploring carbon and nitrogen dynamics, and investigating terrestrial-aquatic linkages. The papers cover a wide range of topics such as Bayesian mixing models, diet reconstruction, and ecosystem structure.

Keywords

Stable Isotopes; Trophic Position; Food Web; Isotope Analysis; Ecological Studies; Carbon and Nitrogen; Ecosystem Structure; Bayesian Mixing Models; Diet Reconstruction; Terrestrial-Aquatic Linkages

Fatty acid trophic markers in the pelagic marine environment

2003-01-01

Johanne Dalsgaard , Michael St. John , Gerhard Kattner +2 more

δ13C Measurements as Indicators of Carbon Flow in Marine and Freshwater Ecosystems

1989-01-01

Brian Fry , Evelyn B. Sherr

Principles of isotope geology

1987-06-01

Richard W. Carlson

Comparing isotopic niche widths among and within communities: SIBER - Stable Isotope Bayesian Ellipses in R

2011-03-14

Andrew L. Jackson , Richard Inger , Andrew Parnell +1 more

1. The use of stable isotope data to infer characteristics of community structure and niche width of community members has become increasingly common. Although these developments have provided ecologists with … 1. The use of stable isotope data to infer characteristics of community structure and niche width of community members has become increasingly common. Although these developments have provided ecologists with new perspectives, their full impact has been hampered by an inability to statistically compare individual communities using descriptive metrics. 2. We solve these issues by reformulating the metrics in a Bayesian framework. This reformulation takes account of uncertainty in the sampled data and naturally incorporates error arising from the sampling process, propagating it through to the derived metrics. 3. Furthermore, we develop novel multivariate ellipse-based metrics as an alternative to the currently employed Convex Hull methods when applied to single community members. We show that unlike Convex Hulls, the ellipses are unbiased with respect to sample size, and their estimation via Bayesian inference allows robust comparison to be made among data sets comprising different sample sizes. 4. These new metrics, which we call SIBER (Stable Isotope Bayesian Ellipses in R), open up more avenues for direct comparison of isotopic niches across communities. The computational code to calculate the new metrics is implemented in the free-to-download package Stable Isotope Analysis for the R statistical environment.

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Characterizing aquatic dissolved organic matter.

2003-01-01

Minze Stuiver , Henry Polach

Standards for reporting C-14 age determinations are discussed. All dates should be related either directly or indirectly to the NBS oxalic acid standard. Corrections for isotopic fractionation are also desirable. … Standards for reporting C-14 age determinations are discussed. All dates should be related either directly or indirectly to the NBS oxalic acid standard. Corrections for isotopic fractionation are also desirable. For some materials, particularly marine shell, corrections for reservoir effect are necessary, but these should always be reported separately from the conventional radiocarbon age. The statistical uncertainty (plus or minus one standard deviation) expresses counting errors, inaccuracies in voltage, pressure, temperature, dilution, and should include errors in C-13 ratios. Errors can be significant when isotope ratios are estimated rather than measured directly. The error in the conventional C-14 half life is not included. The article includes tables indicating what data should be reported.

The Influence of Interspecific Competition and Other Factors on the Distribution of the Barnacle Chthamalus Stellatus

1961-10-01

Joseph H. Connell

Sources of variation in consumer-diet ?15N enrichment: a meta-analysis

2003-07-01

Mathew A. Vanderklift , Sergine Ponsard

Approximation of terrestrial lead isotope evolution by a two-stage model

1975-06-01

J. S. Stacey , Jan D. Kramers

On the Isotopic Chemistry of Carbonates and a Paleotemperature Scale

1950-06-01

J. M. McCrea

The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In … The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water.

Preservation of elemental and isotopic source identification of sedimentary organic matter

1994-06-01

Philip A. Meyers

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Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals

1984-04-01

Margaret J. Schoeninger , Michael J. DeNiro

How a century of ammonia synthesis changed the world

2008-09-28

Jan Willem Erisman , Mark A. Sutton , James N. Galloway +2 more

Measurement of the Oxygen Isotopic Composition of Nitrate in Seawater and Freshwater Using the Denitrifier Method

2002-09-07

Karen L. Casciotti , Daniel M. Sigman , Meredith G. Hastings +2 more

We report a novel method for measurement of the oxygen isotopic composition (18O/16O) of nitrate (NO3-) from both seawater and freshwater. The denitrifier method, based on the isotope ratio analysis … We report a novel method for measurement of the oxygen isotopic composition (18O/16O) of nitrate (NO3-) from both seawater and freshwater. The denitrifier method, based on the isotope ratio analysis of nitrous oxide generated from sample nitrate by cultured denitrifying bacteria, has been described elsewhere for its use in nitrogen isotope ratio (15N/14N) analysis of nitrate.1 Here, we address the additional issues associated with 18O/16O analysis of nitrate by this approach, which include (1) the oxygen isotopic difference between the nitrate sample and the N2O analyte due to isotopic fractionation associated with the loss of oxygen atoms from nitrate and (2) the exchange of oxygen atoms with water during the conversion of nitrate to N2O. Experiments with 18O-labeled water indicate that water exchange contributes less than 10%, and frequently less than 3%, of the oxygen atoms in the N2O product for Pseudomonas aureofaciens. In addition, both oxygen isotope fractionation and oxygen atom exchange are consistent within a given batch of analyses. The analysis of appropriate isotopic reference materials can thus be used to correct the measured 18O/16O ratios of samples for both effects. This is the first method tested for 18O/16O analysis of nitrate in seawater. Benefits of this method, relative to published freshwater methods, include higher sensitivity (tested down to 10 nmol and 1 μM NO3-), lack of interference by other solutes, and ease of sample preparation.

A Bacterial Method for the Nitrogen Isotopic Analysis of Nitrate in Seawater and Freshwater

2001-07-27

Daniel M. Sigman , Karen L. Casciotti , M. Andréani +3 more

We report a new method for measurement of the isotopic composition of nitrate (NO3-) at the natural-abundance level in both seawater and freshwater. The method is based on the isotopic … We report a new method for measurement of the isotopic composition of nitrate (NO3-) at the natural-abundance level in both seawater and freshwater. The method is based on the isotopic analysis of nitrous oxide (N2O) generated from nitrate by denitrifying bacteria that lack N2O-reductase activity. The isotopic composition of both nitrogen and oxygen from nitrate are accessible in this way. In this first of two companion manuscripts, we describe the basic protocol and results for the nitrogen isotopes. The precision of the method is better than 0.2‰ (1 SD) at concentrations of nitrate down to 1 μM, and the nitrogen isotopic differences among various standards and samples are accurately reproduced. For samples with 1 μM nitrate or more, the blank of the method is less than 10% of the signal size, and various approaches may reduce it further.

The Niche Exploitation Pattern of the Blue‐Gray Gnatcatcher

1967-09-01

Richard B. Root

Tracing origins and migration of wildlife using stable isotopes: a review

1999-08-20

Keith A. Hobson

Food Web Complexity and Species Diversity

1966-01-01

Robert T. Paine

It is suggested that local animal species diversity is related to the number of predators in the system and their efficiency in preventing single species from monopolizing some important, limiting, … It is suggested that local animal species diversity is related to the number of predators in the system and their efficiency in preventing single species from monopolizing some important, limiting, requisite. In the marine rocky intertidal this requisite usually is space. Where predators capable of preventing monopolies are missing, or are experimentally removed, the systems become less diverse. On a local scale, no relationship between latitude (10⚬ to 49⚬ N.) and diversity was found. On a geographic scale, an increased stability of annual production may lead to an increased capacity for systems to support higher-level carnivores. Hence tropical, or other, ecosystems are more diverse, and are characterized by disproportionately more carnivores.

Variation in δ15N and δ13C trophic fractionation: Implications for aquatic food web studies

2001-11-01

M. Jake Vander Zanden , Joseph B. Rasmussen

Use of stable isotope techniques to quantify food web relationships requires a priori estimates of the enrichment or depletion in δ 15 N and δ 13 C values between prey … Use of stable isotope techniques to quantify food web relationships requires a priori estimates of the enrichment or depletion in δ 15 N and δ 13 C values between prey and predator (known as trophic fractionation; hereafter Δδ 15 N and Δδ 13 C). We conducted a broad‐scale analysis of Δδ 15 N and Δδ 13 C from aquatic systems, including three new field estimates. Carnivores had significantly higher Δδ 15 N values than herbivores. Furthermore, carnivores, invertebrates, and lab‐derived estimates were significantly more variable than their counterparts ( f‐test, p < 0.00001). Δδ 13 C was higher for carnivores than for herbivores ( p = 0.001), while variances did not differ significantly. Excluding herbivores, the average Δδ 15 N and Δδ 13 C were 3.4‰ and 0.8‰, respectively. But even with unbiased fractionation estimates, there is variation in isotopic fractionation that contributes to error in quantitative isotope model outputs. We simulated the error variance in δ 15 N‐based estimates of trophic position and two‐source δ 13 C diet mixing models, explicitly considering the observed variation in Δδ 15 N and Δδ 13 C, along with the other potential error sources. The resultant error in trophic position and mixing model outputs was generally minor, provided that primary consumers were used as baseline indicators for estimating trophic position and that end member d13C values in dietary mixing models were sufficiently distinct.

Isotopic standards for carbon and oxygen and correction factors for mass-spectrometric analysis of carbon dioxide

1957-01-01

Harmon Craig

Carbon Isotopes in Photosynthesis

1988-05-01

Marion H. O’Leary

Journal Article Carbon Isotopes in Photosynthesis: Fractionation techniques may reveal new aspects of carbon dynamics in plants Get access Marion H. O'Leary Marion H. O'Leary Search for other works by … Journal Article Carbon Isotopes in Photosynthesis: Fractionation techniques may reveal new aspects of carbon dynamics in plants Get access Marion H. O'Leary Marion H. O'Leary Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 38, Issue 5, May 1988, Pages 328–336, https://doi.org/10.2307/1310735 Published: 01 May 1988

CAN STABLE ISOTOPE RATIOS PROVIDE FOR COMMUNITY-WIDE MEASURES OF TROPHIC STRUCTURE?

2007-01-01

Craig A. Layman , D. Albrey Arrington , Carmen G. Montaña +1 more

Stable isotope ratios (typically of carbon and nitrogen) provide one representation of an organism's trophic niche and are widely used to examine aspects of food web structure. Yet stable isotopes … Stable isotope ratios (typically of carbon and nitrogen) provide one representation of an organism's trophic niche and are widely used to examine aspects of food web structure. Yet stable isotopes have not been applied to quantitatively characterize community-wide aspects of trophic structure (i.e., at the level of an entire food web). We propose quantitative metrics that can be used to this end, drawing on similar approaches from ecomorphology research. For example, the convex hull area occupied by species in δ13C–δ15N niche space is a representation of the total extent of trophic diversity within a food web, whereas mean nearest neighbor distance among all species pairs is a measure of species packing within trophic niche space. To facilitate discussion of opportunities and limitations of the metrics, we provide empirical and conceptual examples drawn from Bahamian tidal creek food webs. These examples illustrate how this methodology can be used to quantify trophic diversity and trophic redundancy in food webs, as well as to link individual species to characteristics of the food web in which they are embedded. Building from extensive applications of stable isotope ratios by ecologists, the community-wide metrics may provide a new perspective on food web structure, function, and dynamics.

Source Partitioning Using Stable Isotopes: Coping with Too Much Variation

2010-03-11

Andrew Parnell , Richard Inger , Stuart Bearhop +1 more

Stable isotope analysis is increasingly being utilised across broad areas of ecology and biology. Key to much of this work is the use of mixing models to estimate the proportion … Stable isotope analysis is increasingly being utilised across broad areas of ecology and biology. Key to much of this work is the use of mixing models to estimate the proportion of sources contributing to a mixture such as in diet estimation.By accurately reflecting natural variation and uncertainty to generate robust probability estimates of source proportions, the application of Bayesian methods to stable isotope mixing models promises to enable researchers to address an array of new questions, and approach current questions with greater insight and honesty.We outline a framework that builds on recently published Bayesian isotopic mixing models and present a new open source R package, SIAR. The formulation in R will allow for continued and rapid development of this core model into an all-encompassing single analysis suite for stable isotope research.

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Carbon isotope fractionation in plants

1981-01-01

Marion H. O’Leary

Stepwise enrichment of 15N along food chains: Further evidence and the relation between δ15N and animal age

1984-05-01

Masao Minagawa , Eitaro Wada

Stable isotope geochemistry

1973-12-01

Jochen Hoefs

Fractionation and turnover of stable carbon isotopes in animal tissues: Implications for ?13C analysis of diet

1983-03-01

Larry L. Tieszen , Thomas W. Boutton , K. G. Tesdahl +1 more

Tansley Review No. 9515N natural abundance in soil‐plant systems

1997-10-01

Peter Högberg

summary Equilibrium and kinetic isotope fractionations during incomplete reactions result in minute differences in the ratio between the two stable X isotopes, 15 N and 14 N, in various N … summary Equilibrium and kinetic isotope fractionations during incomplete reactions result in minute differences in the ratio between the two stable X isotopes, 15 N and 14 N, in various N pools. In ecosystems such variations (usually expressed in per mil [δ 15 N] deviations from the standard atmospheric N 2 ) depend on isotopic signatures of inputs and outputs, the input‐output balance, N transformations and their specific isotope effects, and compartmentation of N within the system. Products along a sequence of reactions, e.g. the N mineralization‐N uptake pathway, should, if fractionation factors were equal for the different reactions, become progressively depleted. However, fractionation factors van. For example, because nitrification discriminates against 15 N in the substrate more than does N mineralization, NH 4 + can become isotopically heavier than the organic N from which it is derived. Levels of isotopic enrichment depend dynamically on the stoichiometry of reactions, as well as on specific abiotic and biotic conditions. Thus, the δ 15 N of a specific N pool is not a constant, and 15 N of a N compound added to the system is not a conservative, unchanging tracer. This fact, together with analytical problems of measuring 15 N in small and dynamic pools of N in the soil‐plant system, and the complexity of the X cycle itself (for instance the abundance of reversible reactions), limit the possibilities of making inferences based on observations of 15 N abundance in one or a few pools of N in a system. Nevertheless, measurements of δ 15 N might offer the advantage of giving insights into the N cycle without disturbing the system by adding 15 N tracer. Such attempts require, however, that the complex factors affecting 15 N in plants be taken into account, viz. (i) the source(s) of N (soil, precipitation, NO X , NH 3 , N 2 ‐fixation), (ii) the depth(s) in soil from which N is taken up, (iii) the form(s) of soil‐N used (organic N, NH 4 + , NO 3 − ), (iv) influences of mycorrhizal symbioses and fractionations during and after N uptake by plants, and (v) interactions between these factors and plant phenology. Because of this complexity, data on δ 15 N can only be used alone when certain requirements are met, e.g. when a clearly discrete N source in terms of amount and isotopic signature is studied. For example, it is recommended that N in non‐N 2 ‐fixing species should differ more than 5% from N derived by N 2 ‐fixation, and that several non‐N 2 ‐fixing references are used, when data on δ 15 N are used to estimate N a ‐fixation in poorly described ecosystems. As well as giving information on N source effects, δ 15 N can give insights into N cycle rates. For example, high levels of N deposition onto previously N‐limited systems leads to increased nitrification, which produces 15 N‐enriched NH 4 and N‐depleted NO 3 . As many forest plants prefer NH 4 − they become enriched in 15 N in such circumstances. This change in plant 15 N will subsequently also occur in the soil surface horizon after litter‐fall, and might be a useful indicator of N saturation, especially since there is usually an increase in 15 N with depth in soils of N‐limited forests. Generally, interpretation of 15 N measurements requires additional independent data and modelling, and benefits from a controlled experimental setting. Modelling will be greatly assisted by the development of methods to measure the 15 N of small dynamic pools of N in soils. Direct comparisons with parallel low tracer level 15 N studies will be necessary to further develop the interpretation of variations in 15 N in soil‐plant systems. Another promising approach is to study ratios of 15 N: 14 N together with other pairs of stable isotopes, e.g. 13 C: 12 C or 18 O: 16 O, in the same ion or molecules. This approach can help to tackle the challenge of distinguishing isotopic source effects from fractionations within the system studied. CONTENTS Summary 179 I. Introduction 180 II. Units, causes of isotope effects, stoichiometry, modelling 181 III. N dynamics and variations in 15 N abundance in soil‐plant systems 183 IV. Applications 189 V. Conclusions and suggestions for future research 197 Acknowledgements 198 References 198

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Postmortem preservation and alteration of in vivo bone collagen isotope ratios in relation to palaeodietary reconstruction

1985-10-01

Michael J. DeNiro

Signature of ancient population growth in a low-resolution mitochondrial DNA mismatch distribution.

1994-08-01

Henry Harpending

A mismatch distribution is a tabulation of the number of pairwise differences among all DNA sequences in a sample. In a population that has been stationary for a long time … A mismatch distribution is a tabulation of the number of pairwise differences among all DNA sequences in a sample. In a population that has been stationary for a long time these distributions from nonrecombinant DNA sequences become ragged and erratic, whereas a population that has been growing generates mismatch distributions that are smooth and have a peak. The position of the peak reflects the time of the population growth. The signature of an ancient population expansion is apparent even in the low-resolution mtDNA typings described by Merriwether et al. (1991). The smoothness of the mismatch distribution, an indicator of population expansion, is hardly affected by population structure, whereas mean sequence divergence increases in a pooled sample from highly isolated subpopulations.

Toward an Integration of Landscape and Food Web Ecology: The Dynamics of Spatially Subsidized Food Webs

1997-11-01

Gary A. Polis , Wendy B. Anderson , Robert D. Holt

We focus on the implications of movement, landscape variables, and spatial heterogeneity for food web dynamics. Movements of nutrients, detritus, prey, and consumers among habitats are ubiquitous in diverse biomes … We focus on the implications of movement, landscape variables, and spatial heterogeneity for food web dynamics. Movements of nutrients, detritus, prey, and consumers among habitats are ubiquitous in diverse biomes and can strongly influence population, consumer-resource, food web, and community dynamics. Nutrient and detrital subsidies usually increase primary and secondary productivity, both directly and indirectly. Prey subsidies, by movement of either prey or predators, usually enhance predator abundance beyond what local resources can support. Top-down effects occur when spatially subsidized consumers affect local resources by suppressing key resources and occasionally by initiating trophic cascades. Effects on community dynamics vary with the relative amount of input, the trophic roles of the mobile and recipient entities, and the local food web structure. Landscape variables such as the perimeter/area ratio of the focal habitat, permeability of habitat boundaries, and relative productivity of trophically connected habitats affect the degree and importance of spatial subsidization.

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Canonical correspondence analysis and related multivariate methods in aquatic ecology

1995-09-01

Cajo J. F. ter Braak , P.F.M. Verdonschot

Source partitioning using stable isotopes: coping with too many sources

2003-07-01

Donald L. Phillips , Jillian W. Gregg

USING STABLE ISOTOPES TO ESTIMATE TROPHIC POSITION: MODELS, METHODS, AND ASSUMPTIONS

2002-03-01

David M. Post

The stable isotopes of nitrogen (δ15N) and carbon (δ13C) provide powerful tools for estimating the trophic positions of and carbon flow to consumers in food webs; however, the isotopic signature … The stable isotopes of nitrogen (δ15N) and carbon (δ13C) provide powerful tools for estimating the trophic positions of and carbon flow to consumers in food webs; however, the isotopic signature of a consumer alone is not generally sufficient to infer trophic position or carbon source without an appropriate isotopic baseline. In this paper, I develop and discuss methods for generating an isotopic baseline and evaluate the assumptions required to estimate the trophic position of consumers using stable isotopes in multiple ecosystem studies. I test the ability of two primary consumers, surface-grazing snails and filter-feeding mussels, to capture the spatial and temporal variation at the base of aquatic food webs. I find that snails reflect the isotopic signature of the base of the littoral food web, mussels reflect the isotopic signature of the pelagic food web, and together they provide a good isotopic baseline for estimating trophic position of secondary or higher trophic level consumers in lake ecosystems. Then, using data from 25 north temperate lakes, I evaluate how δ15N and δ13C of the base of aquatic food webs varies both among lakes and between the littoral and pelagic food webs within lakes. Using data from the literature, I show that the mean trophic fractionation of δ15N is 3.4‰ (1 sd = 1‰) and of δ13C is 0.4‰ (1 sd = 1.3‰), and that both, even though variable, are widely applicable. A sensitivity analysis reveals that estimates of trophic position are very sensitive to assumptions about the trophic fractionation of δ15N, moderately sensitive to different methods for generating an isotopic baseline, and not sensitive to assumptions about the trophic fractionation of δ13C when δ13C is used to estimate the proportion of nitrogen in a consumer derived from two sources. Finally, I compare my recommendations for generating an isotopic baseline to an alternative model proposed by M. J. Vander Zanden and J. B. Rasmussen. With an appropriate isotopic baseline and an appreciation of the underlying assumptions and model sensitivity, stable isotopes can help answer some of the most difficult questions in food web ecology.

Quantitative measurement of food selection

1974-01-01

J�rgen Jacobs

Determination of Carbonate and Organic Matter in Calcareous Sediments and Sedimentary Rocks by Loss on Ignition: Comparison With Other Methods

1974-01-01

Walter E. Dean

ABSTRACT A modified ignition loss method is described for determining organic and carbonate carbon in calcareous sedimentary materials using equipment found in most laboratories. The method has been found to … ABSTRACT A modified ignition loss method is described for determining organic and carbonate carbon in calcareous sedimentary materials using equipment found in most laboratories. The method has been found to equal or excel the accuracy and precision of other methods tested and has the advantage of being considerably faster if large numbers of samples are to be analyzed.

Guidelines and recommended terms for expression of stable‐isotope‐ratio and gas‐ratio measurement results

2011-08-19

Tyler B. Coplen

To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the … To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Système International d'Unités, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented.

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Getting to the fat of the matter: models, methods and assumptions for dealing with lipids in stable isotope analyses

2007-01-16

David M. Post , Craig A. Layman , D. Albrey Arrington +3 more

Nutritional constraints in terrestrial and freshwater food webs

2000-11-01

James J. Elser , William F. Fagan , Robert F. Denno +7 more

STABLE ISOTOPES IN ECOSYSTEM STUDIES

1987-11-01

Bruce J. Peterson , Brian Fry

▪ Abstract The literature on effects of habitat fragmentation on biodiversity is huge. It is also very diverse, with different authors measuring fragmentation in different ways and, as a consequence, … ▪ Abstract The literature on effects of habitat fragmentation on biodiversity is huge. It is also very diverse, with different authors measuring fragmentation in different ways and, as a consequence, drawing different conclusions regarding both the ...Read More

Subcommission on geochronology: Convention on the use of decay constants in geo- and cosmochronology

1977-10-01

Rudolf H. Steiger , E. Jäger

Stable Isotopes in Plant Ecology

2002-11-01

Todd E. Dawson , Stefania Mambelli , Agneta H. Plamboeck +2 more

▪ Abstract The use of stable isotope techniques in plant ecological research has grown steadily during the past two decades. This trend will continue as investigators realize that stable isotopes … ▪ Abstract The use of stable isotope techniques in plant ecological research has grown steadily during the past two decades. This trend will continue as investigators realize that stable isotopes can serve as valuable nonradioactive tracers and nondestructive integrators of how plants today and in the past have interacted with and responded to their abiotic and biotic environments. At the center of nearly all plant ecological research which has made use of stable isotope methods are the notions of interactions and the resources that mediate or influence them. Our review, therefore, highlights recent advances in plant ecology that have embraced these notions, particularly at different spatial and temporal scales. Specifically, we review how isotope measurements associated with the critical plant resources carbon, water, and nitrogen have helped deepen our understanding of plant-resource acquisition, plant interactions with other organisms, and the role of plants in ecosystem studies. Where possible we also introduce how stable isotope information has provided insights into plant ecological research being done in a paleontological context. Progress in our understanding of plants in natural environments has shown that the future of plant ecological research will continue to see some of its greatest advances when stable isotope methods are applied.

Variation in trophic shift for stable isotope ratios of carbon, nitrogen, and sulfur

2003-07-04

James H. McCutchan , William M. Lewis , Carol Kendall +1 more

Use of stable isotope ratios to trace pathways of organic matter among consumers requires knowledge of the isotopic shift between diet and consumer. Variation in trophic shift among consumers can … Use of stable isotope ratios to trace pathways of organic matter among consumers requires knowledge of the isotopic shift between diet and consumer. Variation in trophic shift among consumers can be substantial. For data from the published literature and supplementary original data (excluding fluid‐feeding consumers), the mean isotopic shift for C was +0.5±0.13‰ rather than 0.0‰, as commonly assumed. The shift for C was higher for consumers analyzed as muscle (+1.3±0.30‰) than for consumers analyzed whole (+0.3±0.14‰). Among consumers analyzed whole, the trophic shift for C was lower for consumers acidified prior to analysis (−0.2±0.21‰) than for unacidified samples (+0.5±0.17‰). For N, trophic shift was lower for consumers raised on invertebrate diets (+1.4±0.21‰) than for consumers raised on other high‐protein diets (+3.3±0.26‰) and was intermediate for consumers raised on plant and algal diets (+2.2±0.30‰). The trophic shift for S differed between high‐protein (+2.0±0.65‰) and low‐protein diets (‐0.5±0.56‰). Thus, methods of analysis and dietary differences can affect trophic shift for consumers; the utility of stable isotope methods can be improved if this information is incorporated into studies of trophic relationships. Although few studies of stable isotope ratios have considered variation in the trophic shift, such variation is important because small errors in estimates of trophic shift can result in large errors in estimates of the contribution of sources to consumers or in estimates of trophic position.

Influence of diet on the distribution of nitrogen isotopes in animals

1981-03-01

Michael J. DeNiro , Samuel Epstein

Stable Isotope Ecology

2006-01-01

Brian Fry

Influence of diet on the distribution of carbon isotopes in animals

1978-05-01

Michael J. DeNiro , Samuel Epstein

Environmental isotopes in hydrogeology

1998-03-01

A Machine Learning-Based Assessment of Proxies and Drivers of Harmful Algal Blooms in the Western Lake Erie Basin Using Satellite Remote Sensing

2025-06-24

Neha Joshi , Armeen Ghoorkhanian , Jongmin Park +2 more | Remote Sensing

The western region of Lake Erie has been experiencing severe water-quality issues, mainly through the infestation of algal blooms, highlighting the urgent need for action. Understanding the drivers and the … The western region of Lake Erie has been experiencing severe water-quality issues, mainly through the infestation of algal blooms, highlighting the urgent need for action. Understanding the drivers and the intricacies associated with algal bloom phenomena is important to develop effective water-quality remediation strategies. In this study, the influences of multiple bloom drivers were explored, together with Harmonized Landsat Sentinel-2 (HLS) images, using the datasets collected in Western Lake Erie from 2013 to 2022. Bloom drivers included a group of physicochemical and meteorological variables, and Chlorophyll-a (Chl-a) served as a proxy for algal blooms. Various combinations of these datasets were used as predictor variables for three machine learning models, including Support Vector Regression (SVR), Extreme Gradient Boosting (XGB), and Random Forest (RF). Each model is complemented with the SHapley Additive exPlanations (SHAP) model to understand the role of predictor variables in Chl-a estimation. A combination of physicochemical variables and optical spectral bands yielded the highest model performance (R2 up to 0.76, RMSE as low as 8.04 µg/L). The models using only meteorological data and spectral bands performed poorly (R2 < 0.40), indicating the limited standalone predictive power of meteorological variables. While satellite-only models achieved moderate performance (R2 up to 0.48), they could still be useful for preliminary monitoring where field data are unavailable. Furthermore, all 20 variables did not substantially improve model performance over models with only spectral and physicochemical inputs. While SVR achieved the highest R2 in individual runs, XGB provided the most stable and consistently strong performance across input configurations, which could be an important consideration for operational use. These findings are highly relevant for harmful algal bloom (HAB) monitoring, where Chl-a serves as a critical proxy. By clarifying the contribution of diverse variables to Chl-a prediction and identifying robust modeling approaches, this study provides actionable insights to support data-driven management decisions aimed at mitigating HAB impacts in freshwater systems.

A mammoth task: stable isotope analyses as a tool to prevent illegal trade of elephant ivory

2025-06-24

Maria E. A. Santos , Pavel Toropov , Prem N. Agarwal +5 more | Frontiers in Ecology and Evolution

Although mammoth ivory was claimed as a substitute to elephant ivory, there are several issues with the current methods to differentiate the two ivory, which provided a loophole to laundering … Although mammoth ivory was claimed as a substitute to elephant ivory, there are several issues with the current methods to differentiate the two ivory, which provided a loophole to laundering and illegal trade. To contribute to developing efficient tools to distinguish ivory samples, we applied a relatively cheap and fast protocol using stable isotope ratios of carbon ( δ 13 C), hydrogen ( δ 2 H), nitrogen ( δ 15 N), oxygen ( δ 18 O), and sulfur ( δ 34 S). We compared the isotope ratios of the two ivory types and found statistically significant ( p -value&lt;0.01) differences in the Wilcoxon tests for δ 2 H, δ 18 O, δ 13 C and δ 34 S, but no significant difference for δ 15 N. There was no overlap between δ 2 H and a small overlap for δ 18 O, while δ 13 C, δ 15 N, and δ 34 S of most mammoth samples were within the larger isotopic range values of the elephant samples. The PCA also pointed to a higher contribution of δ 2 H (96.9%) followed by δ 18 O (2.7%) to differentiate the ivory types. Our results showed SIA as an efficient tool to distinguish elephant and mammoth ivory, and we recommend using a multi-elements SIA approach focusing on δ 2 H and δ 18 O. While it is essential to address the social issues related to the ivory trade, including reducing human-elephant conflict and increasing financial support to Siberian carver communities, alternatives for natural ivory should also be sought, combined with strict policy changes to combat illegal trade and protect the African and Asian elephant populations.

Tracking Photo-Oxidation Reactions of Aquatic Organic Matter Using Triple Oxygen Isotopes

2025-06-24

Daniel R. Crocker , Kevin Sutherland , Benjamin Freudenberg +4 more | ACS Earth and Space Chemistry

Nuclear Alterations and Micronuclei Assessment on the Erythrocytes of Oreochromis Niloticus From Selected Areas of Pampanga River and Candaba Swamp

2025-06-24

Ma. Lourdes R. Esteban , Monaliza M. Cayanan , Renato Dela Pena +2 more

<title>Abstract</title> The study demonstrated the cytotoxicity and genotoxicity potentials of the water in four designated stations of Pampanga River and Candaba Swamp (S1. Danga River, Macabebe, Pampanga, S2. Sulipan River, … <title>Abstract</title> The study demonstrated the cytotoxicity and genotoxicity potentials of the water in four designated stations of Pampanga River and Candaba Swamp (S1. Danga River, Macabebe, Pampanga, S2. Sulipan River, Apalit River, S3. San Agustin, Candaba Swamp, S4. Dukma River, Candaba Swamp) based on Nucleus Alteration (NA) and Micronuclei (MN) assessment on the erythrocytes of Nile tilapia (Oreochromis niloticus). T-test showed all station (S1-1.85, S2-1.37, S3-3.04 and S4-2.11) have significantly higher micronuclei compared to the reference mean (0.040). Lobed and blebbed nuclei in S4. significantly exceeded the reference mean (0.11). Notched and nuclei in all stations significantly exceeded the reference mean (0.003) with S3 as highest (6.30), followed by S1(3.30), S2(2.22) and S4(1.41). Finally, binucleated cells were also significantly higher than the reference (0.022) with S3 as the highest (1.70) followed by S1 (0.70), S4 (0.40) and S2(0.00). S3 had the highest mean of micronuclei, notched cells, and binucleated cell. S4 mean for lobed and blebbed nuclei significantly exceeded the reference. S1 exceeded the reference mean of micronuclei, notched and binucleated cells, while samples from S2 exceeded the reference mean of micronuclei and notched nuclei. Presence of cadmium and copper could have contributed on the induction of NA and MN.

Comparing fluorometric methods (in vivo vs extracted) for cyanoHAB monitoring in six Rhode Island ponds

2025-06-23

Stephen D. Shivers , Jeffrey W. Hollister , Stéphane Fournier +2 more

Harmful algal blooms caused by cyanobacteria (cyanoHABs) are detrimental to human and environmental health and can be difficult to monitor without specialized training and equipment. A variety of instruments have … Harmful algal blooms caused by cyanobacteria (cyanoHABs) are detrimental to human and environmental health and can be difficult to monitor without specialized training and equipment. A variety of instruments have been developed to measure cyanoHAB indicators (i.e., chlorophyll a or phycocyanin) that do not require advanced laboratory processes (e.g., pigment extraction). We compared measurements from five in vivo fluorometers (Turner Trilogy in-vivo module, Turner Fluorosense, Turner Cyanofluor, bbe AlgaeTorch, and bbe Phycoprobe) to results from solvent-based extractions for chlorophyll a and phycocyanin at six different waterbodies in Rhode Island. We found a strong relationship between extracted phycocyanin and in vivo fluorometers (R2 ranging from 0.78-0.96). We found less consistency between in vivo measurements of chlorophyll a and the extracted results (R2 between 0.34 and 0.82). Some variability in the chlorophyll a results can be explained by differences in the phytoplankton community across the different sampling sites. Phycocyanin results from in vivo fluorometry were also strongly related with cell counts, which implies that phycocyanin measurements from these instruments can be a good proxy for cell counts. Many federal, state, and local entities use cell counts of cyanobacteria to determine when to issue health or contact advisories for waterbodies. Producing accurate cell counts requires highly specialized training/equipment, processing time, and counts can vary greatly between technicians. The results from this study encourage further adoption of in vivo fluorometry and phycocyanin for cyanoHAB monitoring efforts.

Cross‐Shelf Transport of Organic Matter: A New Source of Fuel for the Existence of Intense Oxygen Minimum Zone in the Bay of Bengal

2025-06-23

V. V. S. S. Sarma , R. Sreevidhya , P Aswathi +3 more | Geophysical Research Letters

Abstract The first evidence of cross‐shelf transport of organic matter for supporting the carbon demand in the intense oxygen minimum zone (OMZ) in the northwestern Bay of Bengal (BoB) is … Abstract The first evidence of cross‐shelf transport of organic matter for supporting the carbon demand in the intense oxygen minimum zone (OMZ) in the northwestern Bay of Bengal (BoB) is reported. The spread of high concentrations of particulate organic carbon and nitrogen with their isotopic composition close to shelf sediments was observed from shelf to offshore in the OMZ between 200 and 700 m, supporting high organic carbon demand. Using the mean current speed at these depths, the organic carbon transported from the shelf is estimated to contribute two‐thirds of the carbon demand in the OMZ. This explains the occurrence of OMZ in the BoB despite low export production. The simulation of OMZ by numerical models may be improved by incorporating cross‐shelf transport of organic matter.

Predation alters community structure through multiple trophic cascades

2025-06-23

R. BAKER , Cy L. Mott , Howard H. Whiteman | Journal of Animal Ecology

Predation plays a crucial role in shaping community structure and can initiate trophic cascades that alter abundances across adjacent trophic levels. Intraspecific variation among predators could lead to varying levels … Predation plays a crucial role in shaping community structure and can initiate trophic cascades that alter abundances across adjacent trophic levels. Intraspecific variation among predators could lead to varying levels of top-down control with implications for trophic cascade strength. In this experiment, we manipulated body size variation in populations of predatory mole salamanders (Ambystoma talpoideum) within mesocosms and monitored a suite of biotic responses. We predicted that predator populations with increased body size variation would have limited top-down control due to weaker interactions with greater numbers of prey species. Conversely, we predicted that populations with similar sized predators would have strong control over fewer prey species, leading to trophic cascades. Salamander presence affected nearly every parameter measured, suppressing some populations (e.g. invertebrate predators) and facilitating others (e.g. invertebrate collectors), triggering multiple trophic cascades across several trophic channels, including both 'green' and 'brown' pathways. However, only a few invertebrate taxa responded to variation in predator body size, and in nearly all these instances, those taxa responded more strongly to treatments with increased body size variation than to treatments with similarly sized predators. In contrast to our hypothesis, predator size variation may promote individual dietary specialization of differently sized predators, resulting in strong control of focal prey. These results demonstrate that predators can have pervasive and multichannel effects on all trophic levels within communities, regardless of size structure and that increased body size variation can lead to stronger top-down control.

Lake Water Composition in Oceanic Islands: Insights from REE Content and 87Sr/86Sr Isotopic Ratio

2025-06-21

J. Virgílio Cruz , César Andrade , Letícia Ferreira +1 more | Water

A study was carried out with a representative data set of volcanic lakes from the Azores archipelago. A total of 672 samples were collected during four field surveys conducted over … A study was carried out with a representative data set of volcanic lakes from the Azores archipelago. A total of 672 samples were collected during four field surveys conducted over the year and along the depth. Following water sampling, temperature, pH, and EC were measured, the dissolved CO2 and alkalinity were determined by titration, and aliquots were taken to perform analysis of major, minor and trace elements, as well as 18O/16O, 2H/1H and 87Sr/86Sr isotopic ratios. Waters are of meteoric origin and from the Na-HCO3 to Na-Cl types. The 87Sr/86Sr ranges between 0.709194 and 0.704294, and most of the lakes depict less radiogenic values than seawater, suggesting a potential contribution from rock dissolution. Along the reciprocal of the Sr vs. 87Sr/86Sr plot, most samples suggest a linear trend between rock values and rainwater. Samples display considerable variability in the ∑REE, ranging from 0.83 µg L−1 to 13.54 µg L−1, and when chondrite normalized, depict a negative slope, showing an enrichment in light REEs compared to heavy REEs. This pattern is consistent with the one from Azores rocks and bottom sediments from some lakes, and most lakes depict Eu anomalies, resulting from interaction between water and sediments or from incongruent mineral dissolution.

Spatial variation of stable hydrogen and oxygen isotopes in tap water in Brazil

2025-06-20

João Paulo Sena‐Souza , Fábio José Viana Costa , Tiago Borges Kisaka +7 more | The Science of The Total Environment

Carbon and nitrogen stable isotopic profiling of chimpanzees and other primate hairs in Kalinzu Forest Reserve, Uganda

2025-06-19

Takumi Tsutaya , Natsumi Aruga , Naoto Ishikawa +6 more | bioRxiv (Cold Spring Harbor Laboratory)

Abstract Stable isotope analysis is a widely used tool in primate ecology for investigating diet and environment, with numerous studies focusing on chimpanzees. However, few studies have explored the dietary … Abstract Stable isotope analysis is a widely used tool in primate ecology for investigating diet and environment, with numerous studies focusing on chimpanzees. However, few studies have explored the dietary niche of chimpanzees in comparison to other primates or examined intra-individual dietary variability. This limitation hinders the understanding of the comparability of isotopic data with the wealth of behavioral observational data in primate ecology. In this study, we report the carbon and nitrogen stable isotope ratios of hairs from wild chimpanzees and four other primate species in the Kalinzu Forest Reserve, Uganda. Bulk analysis revealed that both plant foods and chimpanzees in Kalinzu exhibited lower carbon isotope ratios than expected for the region’s rainfall. Additionally, preliminary compound-specific nitrogen isotope analysis of amino acids was conducted, revealing that chimpanzees in Kalinzu have a lower degree of faunivory than the sympatric Cercopithecus primates. Furthermore, ultra-fine sectioning of a hair sample was conducted to investigate dietary variation over daily to weekly timescales. In one adult male chimpanzee, carbon and nitrogen isotope ratios fluctuated by more than 1‰ within approximately 10 days. These findings highlight the importance of recognizing uncontrolled ecological variability and hidden intra-individual dietary changes when interpreting stable isotope data in relation to behavior and environmental traits.

Food web reconstruction of Barmaky, the oldest post‐<scp>LGM</scp> hunter‐gatherer site in north‐western Ukraine

2025-06-19

Lilian Reiss , Kerstin Pasda , Christoph Mayr +4 more | Boreas

The site of Barmaky currently marks the oldest Epigravettian occupation of north‐western Ukraine shortly after the Last Glacial Maximum (LGM), dated to around 19 cal. ka BP. Stable isotope analyses … The site of Barmaky currently marks the oldest Epigravettian occupation of north‐western Ukraine shortly after the Last Glacial Maximum (LGM), dated to around 19 cal. ka BP. Stable isotope analyses of bone collagen from six terrestrial mammals and two bird species show a comparatively highly structured palaeo‐food web. Characteristic are high δ 15 N values in mammoth ( Mammuthus primigenius ) bone collagen compared with other herbivores and δ 13 C values showing niche partitioning between mammoth and hare on the one hand and reindeer on the other. These findings may indicate differentiated herbivore niches, with different diets and habitats between herbivorous groups. Additionally, different mobility patterns could cause isotopic scatter in food webs. To better understand the context of early post‐LGM mammoth behaviour, we compare the mammoth δ 15 N values of Barmaky (19.0 cal. ka BP; 7.2±0.1‰) with those of Yudinovo (lower layer: 19.1/18.3–15.1 cal. ka BP and upper layer: 14.8–13.8 cal. ka BP; 7.3±1.0‰), Yeliseevichi (17.6 cal. ka BP; 5.7±0.8‰) and Mezhyrich (18.5–17.5 cal. ka BP; 4.3±0.8‰). At all sites, δ 15 N values of mammoths are comparatively high, except for Mezhyrich and a single specimen from Barmaky. In comparison with sedentary hares, mammoths from Barmaky suggest a non‐locally dominated δ 15 N signal, while the mammoths from Mezhyrich show the local isotope signal. We also discuss the potential role of differences in temperature, precipitation and permafrost development for the different locations. Results from climate models indicate a gradient in temperature and precipitation with possible implications for food availability in the mammoth steppe.

The early history of the correlation of the terrestrial Eemian stage with the marine isotope stages

2025-06-18

Jan Mangerud | Quaternary Science Reviews

Seasonal migration dynamics of the rice leaf folder Cnaphalocrocis medinalis across the South China Sea

2025-06-17

Xianyong Zhou , Ran Yan , Dazhong Liu +5 more | Journal of Pest Science

Sequential multi-isotope sampling through a Bos taurus tooth from Stonehenge, to assess comparative sources and incorporation times of strontium and lead

2025-06-17

Jane Evans , Richard Madgwick , Vanessa Pashley +4 more | Journal of Archaeological Science

Geochemical fingerprinting of extra virgin olive oils based on radiogenic strontium isotopes

2025-06-17

Samuel Pelacani , Simone Tommasini , Mattia Ferrari +4 more | The Science of The Total Environment

Ensuring an efficient Extra Virgin Olive Oil (EVOO) traceability is fundamental to support a sustainable produced food. To date assessing geographical origin of EVOO is a challenging issue, especially if … Ensuring an efficient Extra Virgin Olive Oil (EVOO) traceability is fundamental to support a sustainable produced food. To date assessing geographical origin of EVOO is a challenging issue, especially if the authenticity is evaluated based on objective parameters beyond subjectivity or paper certifications. Consequently, technical approaches are becoming increasingly complex, such as the use of radiogenic 87Sr/86Sr to link the soil of the origin to the EVOO. We present a novel database of geological and organic 87Sr/86Sr values (n = 133) from Tuscany, using newly analyzed samples and literature data, to establish the first comprehensive bioavailable Sr isotope baseline for this region. We show that the 87Sr/86Sr of EVOO is a powerful fingerprint if we consider the olive mill processes. To this end a two-component mixing approach based on olive fruits and tap water was used to assess the contribution of different sources of 87Sr/86Sr to EVOO. The isoscape of bioavailable 87Sr/86Sr was generated using a novel geoinformatics framework for a representative Tuscan territory with an high quality standard EVOO production. Results show that the 87Sr/86Sr values of Tuscany EVOOs range from 0.70854 to 0.70974. The median value, equal to 0.70911, is higher than Tunisian (0.70861) and northern Spanish (0.70837) EVOOs. The proof of concept shown in this research is highly relevant for geographic EVOO traceability as it allows a complete evaluation of the critical path in using the Sr isotope signature for provenance study.

Stable Isotope In-Vivo Labeling for Mass-Spectrometry Identification of Paternal Metabolites Transferred from Sperm to Oocyte During Fertilization

2025-06-17

Luca Roberto , Gilda Cobellis , Concetta Ambrosino +2 more | Journal of Visualized Experiments

Variation in relationships of δ13C and δ15N between lethal and nonlethal samples in fishes

2025-06-17

Nitsa M. Platis , Yoichiro Kanno , Brien P. Rose +1 more | North American Journal of Fisheries Management

ABSTRACT Objective We summarized variation in muscle–fin isotope relationships in studies of freshwater fishes and evaluated whether season and body condition explained variation in muscle–fin relationships in a field study. … ABSTRACT Objective We summarized variation in muscle–fin isotope relationships in studies of freshwater fishes and evaluated whether season and body condition explained variation in muscle–fin relationships in a field study. Methods We reviewed published relationships of δ13C and δ15N values from muscle and fin tissue samples in fishes and compared them to relationships in a large sample of muscle and fin tissue samples that we collected from two small-bodied fishes, juvenile Brown Trout Salmo trutta and Mottled Sculpin Cottus bairdii. We evaluated the importance of season and body condition (dry matter content and C:N) in our muscle–fin relationships using multiple regression with model selection. Results Correlations between muscle and fin δ13C and 15N values within studies were high, but the variance in relationships across studies was large, even for the same species. Muscle and fin δ13C and δ15N values in our field study were also strongly positively correlated (r ≥ 0.89), with minor muscle–fin differences for Brown Trout (Δδ13C = −0.71 ± 0.42‰, Δδ15N = 0.13 ± 0.38‰) and Mottled Sculpin (Δδ13C = −0.73 ± 0.29‰, Δδ15N = −0.21 ± 0.31‰). Slopes of our muscle–fin relationships for δ13C (β1 = 0.796‒0.911) and δ15N (β1 = 0.826‒0.872) were similar to average literature values (δ13C: β¯1 = 0.824; δ15N: β¯1 = 0.875), but again, the variance in published relationships was large. Incorporating season and body condition in models improved muscle–fin relationships. Conclusions High variance in muscle–fin isotopic relationships makes it difficult to rely on previously established models. We found that body condition improved the fit of muscle–fin relationships, suggesting that the large variance among the previous studies might be due to unmeasured predictors. Incorporating additional predictors, such as energy status, could reduce variation in muscle–fin relationships and increase their applicability across systems.

Exposure to grassland fire ash alters the life-history traits and causes morphological deformities in the aquatic insect Chironomus xanthus

2025-06-17

Ronnilda Maria Gonçalves Araujo , Dina Pacheco , Ana Marta Schafaschek +4 more | Environmental Pollution

Trait and Growth Responses to Sequential Environmental Change linked to Sensitivity in Synechococcus populations

2025-06-17

A. K. Sikder , Colin T. Kremer , Frederik De Laender | bioRxiv (Cold Spring Harbor Laboratory)

1. Environmental change often occurs as a sequence of stressors rather than as isolated events. While the individual and combined effects of multiple stressors are well studied, the ecological consequences … 1. Environmental change often occurs as a sequence of stressors rather than as isolated events. While the individual and combined effects of multiple stressors are well studied, the ecological consequences of sequential environmental change remain poorly understood. Such sequences, for example, a marine heatwave followed by seasonal herbicide runoff, are increasingly common under global change. 2. We investigated how legacy effects (the imprint of past environmental conditions) influence subsequent population performance and functional traits, and how these effects are mediated by strain-specific sensitivities. 3. Using a fully factorial design, we exposed six strains of the globally abundant pico-phytoplankton Synechococcus sp. to three environmental conditions: warming, herbicide exposure, and a control, under both chronic (same condition across time) and sequential (different conditions across time) regimes. We measured population performance (per-capita growth rate, maximum density) and key functional traits (cell size, chlorophyll content). 4. Population responses diverged significantly between chronic and sequential exposures, revealing a strong legacy effect. Trait changes were often decoupled from growth metrics, suggesting independent response axes. Strain identity and its interaction with past conditions explained substantial variation in both growth and trait responses. 5. We identify and conceptualise four distinct mechanisms of legacy effects during sequential change: overcompensation, amplification, constraint and depression, each linked to strain-specific responses. Consequently, incorporating legacy effects into predictions of biodiversity dynamics and ecosystem function under global change is therefore both feasible and essential.

Advancing Stable Isotope Analysis with Orbitrap-MS for Fatty Acid Methyl Esters and Complex Lipid Matrices

2025-06-17

Gabriel Franco dos Santos , Giovanni B. Bevilaqua , Alexis Gilbert +7 more | Journal of the American Society for Mass Spectrometry

Isotopic analysis plays a crucial role in different scientific fields, offering valuable insights that aid in elucidating biosynthetic pathways, determining geographic origin, and identifying product adulteration. Established mass spectrometry techniques … Isotopic analysis plays a crucial role in different scientific fields, offering valuable insights that aid in elucidating biosynthetic pathways, determining geographic origin, and identifying product adulteration. Established mass spectrometry techniques for isotopic analysis require the conversion of samples into gases prior to introduction into the systems. Moreover, the ionization process in these methods is destructive, potentially leading to the loss of essential molecular structure information. Thus, alternative analytical methods, such as Orbitrap-MS, could be a useful tool to determine stable isotope ratios. This paper describes an Orbitrap-based method using stearic acid methyl ester as a model molecule to determine the stable isotopic ratios of fatty acids and fatty acid methyl esters (FAMEs) in different vegetable butters. Orbitrap analyses were performed in positive ionization mode with both [M + H]+ and [M + Na]+ ions considered for the analysis. Nine standards (Std 1-Std 9) and three vegetable butters (cupuaçu, cocoa, and shea) were employed in the study. The standards were employed to develop the method and were measured using HPLC and a dual-inlet system. Both injections achieved high precision (<1.5‰) when compared with the IRMS data; however, the HPLC showed the most accuracy and was selected for direct injection measurement of the natural samples. Our results demonstrated the efficiency of the ESI-Orbitrap system in differentiating sources based on δ13C values. This study not only advances the use of high-resolution mass spectrometry for isotope analysis but also opens new avenues for applying stable isotopes in food sciences.

Vulnerability of soil food webs to chemical pollution and climate change

2025-06-17

Yu‐Rong Liu , Shuhai Wen , Brajesh K. Singh +7 more | Nature Ecology & Evolution

Bomb radiocarbon in otoliths and eye lenses of reef fishes from Atlantic waters of the southeastern U.S.

2025-06-17

Virginia R. Shervette , Jesús M. Rivera Hernández , Scott B. Van Sant +3 more | Environmental Biology of Fishes

Is it time to retire ∆?

2025-06-17

Roman A. Zubarev | bioRxiv (Cold Spring Harbor Laboratory)

Abstract The paradigm postulating that tissue stable isotopic ratios ( δ tissue ) equal those of the diet ( δ diet ) plus a small, quasi-constant isotope discrimination factor Δ … Abstract The paradigm postulating that tissue stable isotopic ratios ( δ tissue ) equal those of the diet ( δ diet ) plus a small, quasi-constant isotope discrimination factor Δ emerged in the late 1970s, establishing stable isotope analysis as a dietary proxy. Today, this framework is still widely used across multiple branches of science, despite growing contradicting evidence. Here, we reanalysed several well-controlled laboratory experiments and universally found that Δ not only varies strongly with δ diet , but also changes sign at a certain δ eq = δ diet = δ tissue value, which we term the Δ-equilibrium. The Δ-equilibrium phenomenon results from the sub-unity slope of the linear regression between δ diet and δ tissue and leads to converging of δ tissue values. The most frequently observed position of the Δ-equilibrium on the ( δ 13 C, δ 15 N) plane is (−21±1‰, 12±1‰). These findings firmly establish that stable isotopes are not neutral spectators but active participants in biochemical processes. If presented evidence holds in a much broader study, the paradigm δ tissue = δ food + Δ can finally be retired after half a century of service, being replaced by δ tissue = a × δ food + Const, where a is the newly defined isotope assimilation factor. The Δ-equilibrium position is then found as δ eq = Const/(1 - a). The reason for isotope convergence remains a subject for future research, but likely hypotheses include evolutionary adaptation and isotopic resonance.

Exploring the trophic strategies of two large pelagic species inhabiting the Galapagos Marine Reserve

2025-06-16

Andrés Moreira‐Mendieta , Marjorie Riofrío‐Lazo , Jenifer Suárez-Moncada +1 more | Fisheries Research

Comparing Dual Water Equilibration Methods for Hydrogen Stable Isotope Analysis of Plant Carbohydrates and Proteinaceous Animal Samples

2025-06-16

Daniel B. Nelson , Ansgar Kahmen , Jochem Baan +3 more | Rapid Communications in Mass Spectrometry

The hydrogen stable isotope composition (δ 2H) of organic samples carries information about processes including hydrology, climate, ecology, and plant metabolism. Numerous methods exist to control for hydrogen in organic … The hydrogen stable isotope composition (δ 2H) of organic samples carries information about processes including hydrology, climate, ecology, and plant metabolism. Numerous methods exist to control for hydrogen in organic samples that can isotopically exchange with ambient water or vapor. We compared two established dual water steam equilibration approaches to control for exchangeable hydrogen in isotopic analysis: hot vacuum equilibration using the Uniprep autosampler and hot atmospheric pressure equilibration under varying equilibration temperatures and times. We evaluated how the extent of hydrogen isotope exchange and calculated exchange-corrected hydrogen stable isotope values varied among methods and sample types. More exchange could be achieved with atmospheric pressure methods compared to the Uniprep, and we confirmed that this was not a drying artifact. When direct comparisons were possible, atmospheric pressure methods yielded δ 2H values that agreed better with values from chemical derivatization, while Uniprep values agreed better with values provided for purchased reference materials based on room temperature equilibrations. Best long-term precision was achieved with fitted rather than prescribed isotope fractionation factors for equilibration. Different equilibration methods can give reproducible yet distinct results. This is due to varying degrees to which different methods access non-carbon-bound hydrogen that is difficult to liberate from interior hydrogen bonds in complex biological structures such as cellulose or keratins. The optimal method depends on the application.

Vertical distribution characteristics and source apportionment of nitrogen in the Longyangxia Reservoir in the upper reaches of the Yellow River

2025-06-16

Wei Wu , Yiyang Dong , Chen Li +3 more | PLoS ONE

Studying the biogeochemical cycle of biogenic nitrogen and its influence on hydrological processes and anthropogenic nitrogen input is of great significance for water resource management and the maintenance of aquatic … Studying the biogeochemical cycle of biogenic nitrogen and its influence on hydrological processes and anthropogenic nitrogen input is of great significance for water resource management and the maintenance of aquatic ecosystems in ecologically sensitive areas. Currently, there is a limited understanding of the sources contributing to nitrate levels during thermal stratification in deep and large reservoirs, as well as the transformation processes of nitrate under varying hydrological conditions. This study collected water samples from the Longyangxia Reservoir, located in the upper reaches of the Yellow River, during January and April of 2024. Utilizing hydrogeochemical analysis, multivariate stable isotope technology, the Bayesian isotope mixing model, and multivariate statistical analysis, we analyzed the vertical distribution characteristics of nitrogen in the reservoir across different periods. The transformations and sources of nitrogen were identified, and the contribution rates of each nitrogen source were estimated. The results indicate that January serves as the mixing period for the Longyangxia Reservoir, during which the differences in nitrogen concentration among the vertical water layers are relatively minimal. The concentration ranges for nitrate (NO₃⁻), dissolved organic nitrogen (DON), and ammonium (NH₄⁺) were observed to be 0.598–0.647 mg/L, 0.124–0.397 mg/L, and 0.015–0.157 mg/L, respectively. Beginning in April, the reservoir enters the thermal stratification period, characterized by higher concentrations of various nitrogen forms compared to the mixing period. During the stratification period, the concentration of various nitrogen forms within the vertical profile of the reservoir demonstrates a characteristic distribution of being low in the upper section, maximum values of total nitrogen (TN) and dissolved DON in the middle section, and maximum concentrations of NO₃⁻ and NH₄⁺ in the bottom section. Nitrate nitrogen and dissolved organic nitrogen are the primary forms of nitrogen present in the Longyangxia Reservoir, constituting 66.71% and 25.83% of the total dissolved nitrogen in January, and 62.39% and 21.59% in April, respectively. During the sampling period at Longyangxia Reservoir, the δ 15 N-NO 3 - values in the water ranged from 5.58 ‰ to 7.38 ‰, while the δ 18 O-NO 3 - values varied from −5.87 ‰ to 2.58 ‰. Nitrification is identified as the primary nitrogen conversion process occurring in the reservoir water. Under aerobic conditions, denitrification does not occur in aquatic environments. The dynamics of nitrate in the bottom layer are influenced by nitrification processes and the release of nitrogen from sediment. Soil organic nitrogen is the primary source of nitrate in Longyangxia water, contributing 42.1% and 51.8% during the sampling period, respectively. This study introduced sediment as an additional end member, highlighting that the contribution of sediment to nitrate in water is significant, accounting for 24% and 14.1%, respectively. This study offers valuable insights for precise nitrogen management and control in deep reservoirs by tracking nitrate sources and quantifying their contributions.

3,6-dibromocarbazole have a significant effect on diversity, community and function of soil microorganisms

2025-06-15

Baihui Shi , Changrui Liu , Jialin Wang +6 more | Journal of Hazardous Materials

Measures to Control Sunflower Broomrake

2025-06-15

K. Guseynov , E. Mustafaeva | Bulletin of Science and Practice

Pests, diseases and weeds cause great damage to agricultural crops. In recent years, the problem of the spread of broomrape in sunflower crops in Azerbaijan has become urgent. The existing … Pests, diseases and weeds cause great damage to agricultural crops. In recent years, the problem of the spread of broomrape in sunflower crops in Azerbaijan has become urgent. The existing measures to combat harmful organisms are powerless against this weed. Pollution of the arable layer with broomrape seeds forces farmers to change the place of sowing sunflower from year to year. A new approach to solving the problem is needed. To cleanse the soil from broomrape seeds, provocative sowings of corn, clover, mustard and rape are used. The named plants stimulate the germination of weed seeds, but broomrape does not settle on them. Dense sowings of sunflower for silage with immediate plowing after harvesting and the culture of early varieties of cabbage, also accompanied by plowing after harvesting, clean the soil well from broomrape seeds (new seeds do not have time to form). Peas or soybeans are also used for provocative sowings. If a combination of several methods is used, each of which does not provide effective control on its own, then the level of protection increases. Detailed schemes are given in the work.

Trophic niche variation in springtails across soil depth

2025-06-14

Jing‐Zhong Lu , Melissa Jüds , Linlin Zhong +3 more | European Journal of Soil Biology

Recording presence of Limnoriids in Scottish area

2025-06-12

Irene Guarneri , Pedro Palma | Biologia

A Comprehensive and Ultrasensitive Isotope Calibration Method for Soil Amino Compounds Using Orbitrap Mass Spectrometry

2025-06-12

Tao Li , Y.B. Li , Erika Salas +3 more | Analytical Chemistry

Bound amino compounds (amino acid and amino sugar polymers) comprise a significant proportion (∼40%) of soil organic nitrogen and therefore represent an essential source of nitrogen for plant and microbial … Bound amino compounds (amino acid and amino sugar polymers) comprise a significant proportion (∼40%) of soil organic nitrogen and therefore represent an essential source of nitrogen for plant and microbial nutrition. The analysis of their content and isotope enrichment still represents a significant challenge due to the low isotope enrichment levels reached under near-native soil conditions and the lack of isotopically labeled standards for some key amino compounds. In this study, we used both a 13C-labeled and an unlabeled amino acid mixture to establish isotope calibration curves for 16 amino compounds, using the 6-aminoquinolyl-N-hydroxysccinimidyl carbamate (AQC) derivatization method and ultrahigh-performance liquid chromatography with high-resolution Orbitrap mass spectrometry (UPLC-Orbitrap MS). Molecular ions of AQC-derivatives for all standard amino compounds were identified at the expected m/z values of the respective isotopologues. The isotope calibration curves exhibited excellent linear fits across the whole 13C enrichment range and polynomial fits in the low 13C enrichment range (R2 > 0.990). However, the polynomial fitting terms differed between individual amino acids. Subsequently, we developed equations to relate the calibrated regression terms to the physicochemical properties of the respective amino acids, here mainly the ratio of amino compound-C atoms to total C atoms in AQC-amino compound derivatives. Based on these regressions, we could ultimately predict isotope calibration curves for those amino compounds unavailable as 13C labeled standards, for example, muramic acid, hydroxyproline, and diaminopimelic acid. To test the model accuracy, we compared the outcomes of measured calibrations with predicted calibrations for amino acids where we had isotopically enriched standards. The results of linear regression between measured and predicted data were excellent, where R2 was >0.97, and mean absolute (percentage) deviations, MAD and MAPD, were 0.334 and 15.8%. Finally, we applied both standard and predicted calibration curves to low 13C amended soil samples and unlabeled controls to test the applicability of our model. The limit of detection (LOD) as the minimum detectable atom % 13C incorporation of amino compounds ranged from 0.0003 to 0.14 atom % among different amino compounds. This general predictive model can be used to comprehensively quantify isotope enrichments across the entire soil amino compound profile, including amino sugars and proteinogenic and nonproteinogenic amino acids, providing valuable insights for a better understanding of the overall fate of different amino compounds in soils and other complex environmental systems.

Cryptic isoprene emission of soybeans

2025-06-12

Mohammad Golam Mostofa , Abira Sahu , Yuan Xu +4 more | Proceedings of the National Academy of Sciences

Isoprene is the most abundant nonmethane biogenic hydrocarbon emitted by some plants, mostly trees. It plays critical roles in atmospheric chemistry by contributing to ozone and aerosol formation. Isoprene also … Isoprene is the most abundant nonmethane biogenic hydrocarbon emitted by some plants, mostly trees. It plays critical roles in atmospheric chemistry by contributing to ozone and aerosol formation. Isoprene also benefits plants, particularly under stress, through its signaling roles. Legume crops like soybean were thought to have evolutionarily lost isoprene synthase (ISPS) and are typically considered nonemitters. Here, we report that damage to soybean leaves by wounding or burning triggered a burst of isoprene emission from the undamaged part of the leaves. In silico analysis identified intact ISPS genes in the soybean genome, with features similar to known ISPSs. Protein made from these gene sequences catalyzed isoprene production in the presence of dimethylallyl diphosphate. Isoprene emission in soybeans was linked to reduced photosynthesis rates and stomatal conductance. Metabolomic analysis showed that leaf damage caused a surge in glyceraldehyde 3-phosphate and pyruvate levels, leading to an increase of most of the methylerythritol 4-phosphate pathway metabolites.

The effects of charring on sunflower (Helianthus annuus L) achenes and kernels: Taphonomic and behavioral implications

2025-06-12

John P. Hart | PLoS ONE

Sunflower ( Helianthus annuus L) is one of several seed-bearing annual plants that were domesticated in eastern North America 5000–3800 years ago. When found in the archaeological record the plant’s … Sunflower ( Helianthus annuus L) is one of several seed-bearing annual plants that were domesticated in eastern North America 5000–3800 years ago. When found in the archaeological record the plant’s fruits (achenes) are generally charred. Charring causes changes in the lengths and widths of achenes and their enclosed kernels. Correction factors for these changes derived from controlled heating experiments have been proposed to estimate the original size of charred achenes. The resulting corrected sizes are used to distinguish achenes from domesticated and wild sunflowers. The current study aimed to assess the accuracy of these correction factors and explore morphological differences in hulled and unhulled kernels after heating in 20°C increments from 200 to 420°C. The results indicate the proposed correction factors are inaccurate, potentially leading to type 1 and type 2 errors in assessing domestication status of achenes; the use of correction factors to identify domesticated sunflower achenes is not warranted. Rather, size comparisons of charred archaeological to charred wild contemporary sunflower achenes reported in a previous experiment are less likely to result in assignment errors. Results also indicate it is possible to distinguish between kernels that were hulled before charring from those that were not hulled based on length:width ratios and the presence of longitudinal ridges on unhulled kernels.

Stable Isotope Analysis of Alcoholic Beverages: A Review

2025-06-10

Alberto Roncone , Luana Bontempo | Beverages

Alcoholic beverages represent a sector of significant economic and cultural importance but are also susceptible to fraud and adulteration, which can compromise their quality and authenticity. Isotopic analyses have become … Alcoholic beverages represent a sector of significant economic and cultural importance but are also susceptible to fraud and adulteration, which can compromise their quality and authenticity. Isotopic analyses have become increasingly valuable tools for tracing the geographical origin and ensuring the quality control of products such as wine, beer, and distilled spirits. This literature review examines the main isotopic analysis techniques employed in this field, including Isotope Ratio Mass Spectrometry (IRMS) and Site-Specific Natural Isotope Fractionation by Nuclear Magnetic Resonance (SNIF-NMR), with a particular focus on the insights derived from the isotopic ratios of various elements, notably δ(2H), δ(13C), δ(18O), δ(15N) and δ(34S).