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Ecology

Stable isotope analysis of a vast range of materials pertaining to ecological research allows researchers to access information not readily attainable by other standard analytical techniques. Stable isotopes are frequently used by ecologists as tracers in biological systems, enabling the tracking of elemental cycling within an ecosystem. Variation in the isotopic signatures of different geographic regions allows isotopes to be utilised as tracers of migration, whilst the principles of isotopic fractionation allow biogeochemical processes to be interrogated to levels of details unattainable from elemental compositions alone.

For example, carbon isotopes can be used to determine the primary production source responsible for energy flow in an ecosystem, whereas nitrogen isotopes are useful in identifying the trophic level position of an organism. Sulphur isotopes can distinguish benthic producers from pelagic producers, as well as marsh plant from phytoplankton producers.

Developing our understanding of these innate relationships between living organisms and their environment through stable isotope analysis aids our stewardship of the natural world to ensure that future generations enjoy the same wonders that we do today.

Publications on ecology using our instruments

Our customers use our instruments to do some amazing research in the ecology application field. To show you how they perform their research and how they use our IRMS instruments, we have collected a range of peer-reviewed publications which cite our products. You can find the citations below and then follow the links to the publishing journal should you wish to download the publication.

If you would like to investigate our available citations in more detail, or email the citation list to yourself or your colleagues then take a look at our full citation database.

155 results:

The cultural eutrophication of Lac la Biche, Alberta, Canada: a paleoecological study
Canadian Journal of Fisheries and Aquatic Sciences (1970)
D W Schindler, Alexander P Wolfe, Rolf Vinebrooke, Angela Crowe, Jules M Blais, Brenda Miskimmin, Rina Freed, Bianca Perren

A multiproxy paleoecological investigation of Lac la Biche, a large boreal lake in northeastern Alberta, Canada, revealed that the lake was eutrophic before European settlement but has undergone additional cultural eutrophication in the past 30 to 50 years. Annual fluxes to sediments of phosphorus, nitrogen, carbon, and inorganic sediments have increased with time. A declining N–P ratio has increasingly favored nitrogen-fixing cyanobacteria. Increased deposition of microbial pigments and diatom frustules and a recent shift in diatom species also indicate increasing eutrophication. Biogenic silica increased with time, but there is no evidence of a near-surface decline that would indicate silica limitation. Stable isotopes suggest that an increasing proportion of carbon deposited in sediments is of in-lake origin, indicating increased productivity. In the basin nearest the town of Lac La Biche, an increase in d15N followed the construction of the sewage treatment plant, but more recently, decreased d15N in both basins suggests that nitrogen fixation has become a more important source of nitrogen. Despite documented damage to the fishery of the lake, zooplankton fossils do not show evidence of a strong trophic cascade. The study illustrates the power of a multiproxy approach in obtaining reliable paleolimnological conclusions.

Burrowing and foraging activity of marsh crabs under different inundation regimes
Journal of Experimental Marine Biology and Ecology (2017)
Katelyn Szura, Richard A. McKinney, Cathleen Wigand, Autumn Oczkowski, Alana Hanson, John Gurak, Melanie Gárate

New England salt marshes are susceptible to degradation and habitat loss as a result of increased periods of inundation as sea levels rise. Increased inundation may exacerbate marsh degradation that can result from crab burrowing and foraging. Most studies to date have focused on how crab burrowing and foraging can impact the dominant low marsh plant species, Spartina alterniflora. Here we used a mesocosm experiment to examine the relationship of foraging and burrowing activity in two dominant New England crab species, Sesarma reticulatum and Uca pugilator, and the combined effect of inundation, on the dominant high marsh plant species Spartina patens using a 3×2 factorial design with three crab treatments (Sesarma, Uca, control) at two levels of inundation (low, high). Plants were labeled with a nitrogen (N) stable isotope tracer to estimate plant consumption by the two crab species. At both levels of inundation, we found that S. reticulatum had a significant negative impact on both above- and below-ground biomass by physically clipping and uprooting the plants, whereas U. pugilator had no significant impact. Low inundation treatments for both crab species had significantly greater aboveground biomass than high inundation. Stable N isotope tracer levels were roughly the same for both S. reticulatum and U. pugilator tissue, suggesting that the impact of S. reticulatum on S. patens was not through consumption of the plants. Overall, our results suggest the potential for S. reticulatum to negatively impact marsh stability, and that effects of crab foraging behavior may be heightened by increased inundation.

Impact of food type on respiration, fractionation and turnover of carbon and nitrogen stable isotopes in the marine amphipod Gammarus aequicauda (Martynov, 1931)
Journal of Experimental Marine Biology and Ecology (2017)
François Remy, François Darchambeau, Aurélie Melchior, Gilles Lepoint

This study experimentally determined the impact of food source type on turnover rate and trophic enrichment factors (TEFs or ∆) of δ13C and δ15N, as well as on respiration rate, in captive populations of the marine amphipod Gammarus aequicauda. Gammarus aequicauda (318 individuals) were fed ad libitum with three food sources animal, algae, and dead Posidonia oceanica leaves (also called “litter”), varying in palatability, digestibility, nutritional qualities and isotopic compositions, for between four and six weeks in a controlled feeding experiment. The resulting death rate was lower for the amphipods fed with animal treatment (30.9%) than for individuals fed with algal (65.9%) or litter treatment (64.4%), indicating a better fitness of the individuals fed with the animal food source. Respiration rates also differed highly among the treatments. Animal treatment showed higher respiration rates than algal and litter treatments, potentially due to the toxicity of the algae and the very low nutritional quality of the litter. Amphipods fed with these treatments might have entered in a “low activity state” to cope with these unsuitable food sources, inducing low respiration rates. Due to the very low assimilation and toxicity of the algae source, turnover rate for δ13C was impossible to determine. Turnover rate for δ13C was much faster (half-life=12.55days) for amphipods fed with the animal food source than for amphipods fed with litter (half-life=51.62days), showing the faster assimilation of the most nutritionally optimal food sources by G. aequicauda. Turnover for δ15N was impossible to determine because the amphipods were already at isotopic equilibrium at the beginning of the experiment. Despite the detritus feeder status of Gammarus aequicauda, TEFs for the animal treatments were in accordance with values generally found for carnivorous organisms (∆13C=0.9±0.7‰; ∆15N=2.9±0.6‰). TEFs for the litter treatment were in accordance with values generally corresponding to detritivorous organisms (∆13C=1.2‰; ∆15N=1.0±0.4‰). SIAR mixing model outputs obtained with these new TEF values were more constrained and coherent than outputs obtained with general literature TEFs. This study thus demonstrated the non-negligible impact of the food source on Gammarus aequicauda physiological status, fitness and turnover rates, but also on TEFs—highlighting the importance of TEF experimental calculations for every potential food source of a given organism to ensure more robust isotopic data interpretation.

Inter-annual variability in trophic patterns of jumbo squid (Dosidicus gigas) off the exclusive economic zone of Peru, implications from stable isotope values in gladius
Fisheries Research (2017)
Yunkai Li, Yi Gong, Yuying Zhang, Xinjun Chen

The jumbo squid Dosidicus gigas plays an important role in marine food webs in the eastern Pacific Ocean, as not only a voracious predator but also a valuable prey source. In this study, the proostracum (a morphological part of the gladius) from 45 samples were selected over three years and were serially sampled based on growth information obtained from the statolith. The δ13C and δ15N values along the proostracum were used to reconstruct the feeding variations of D. gigas and to evaluate the potential effects of 2009–10 El Niño event on the variability of their trophic patterns. The results show a strong variation in δ13C and δ15N values along the proostracum for all the squid; changes that could be determined by temporal variation of foraging as well as migration among regions with distinct baselines. An El Niño event could decrease the variation of trophic patterns of squid through compressing the space and time for foraging and migration. These results support our general hypothesis that a time-based consecutive sampling of the gladius can back-calculate an ontogenetic shift and the possible migration patterns of squids more precisely and comprehensively and suggest that the isotopic values of D.gigas might be influenced much more by their migration behavior.

Resource partitioning in gurnard species using trophic analyses: The importance of temporal resolution
Fisheries Research (2017)
Joo Myun Park, Troy F. Gaston, Jane E. Williamson

Dietary habits and intra- and inter-specific trophic ecology of co-occurring Lepidotrigla mulhalli and L. vanessa from south-eastern Australia were analysed using stomach content and stable isotope ratios (δ13C and δ15N). Both species are bottom-feeding carnivores that consumed mainly benthic crustaceans, but teleosts were also abundant in the diet of larger L. vanessa. Non-metric multidimensional scaling (nMDS) ordination and analysis of similarity (ANOSIM) of dietary data revealed significant inter-specific dietary differences; i.e. food resource partitioning. Carbon (δ13C) and nitrogen (δ15N) stable isotope values were similar between L. mulhalli and L. vanessa, however, suggesting similar trophic positioning. Ontogenetic changes in diet composition and stable isotope values were evident. As L. vanessa grew, they preyed upon larger individuals, such as teleosts and caridean shrmips, but no such trend was observed in the diets of L. mulhalli. Adults of both species were significantly enriched in 15N relative to juvenile conspecifics thus supporting these data. Consequently, in this study, both methodologies, i.e. stomach content and stable isotope analyses, provided evidence of inter- and/or intra-specific dietary segregations and trophic niche partitioning between co-occurring L. mulhalli and L. vanessa off Tasmanian waters.

Marginal Calluna populations are more resistant to climate change, but not under high-nitrogen loads
Plant Ecology (2016)
Maren Meyer-Grünefeldt, Kristina Belz, Leonor Calvo, Elena Marcos, Goddert von Oheimb, Werner Härdtle

The dominant plant species of European heathlands Calluna vulgaris is considered vulnerable to drought and enhanced nitrogen (N) loads. However, impacts may vary across the distribution range of Calluna heathlands. We tested the hypothesis that Calluna of southern and eastern marginal populations (MP) are more resistant to drought events than plants of central populations (CP), and that this is mainly due to trait differences such as biomass allocation patterns. Furthermore, we hypothesised that N fertilisation can offset differences in drought susceptibility between CP and MP. We conducted a full-factorial 2-year greenhouse experiment with Calluna plants of CP and MP and quantified growth responses in terms of biomass production, allocation and tissue δ13C signatures. Biomass production, shoot–root ratios and tissue δ13C values of 1-year-old plants were higher for CP than for MP, indicating a higher drought susceptibility of CP. These trait differences were not observed for 2-year-old plants. N fertilisation increased shoot–root ratios of 1- and 2-year-old plants and across populations due to a stimulation of the aboveground biomass allocation. As a consequence, population-related differences in drought susceptibility were offset for N-fertilised plants. We concluded that Calluna plants originating from different populations developed adaptive traits to local climates, which determined their drought sensitivity. However, the higher drought resistance of MP can be attenuated by an N-induced increase in shoot–root ratios. This suggests that analyses on plant growth responses to global change should include multi-factor approaches with a focus on different populations throughout a species’ distribution range.
Tags: C , N , soi , ec , cc , EA

Environmental assessment of freshwater ecosystems of the Sava River watershed and Cerkniško Lake, Slovenia, using the bioindicator species Fontinalis antipyretica : insights from stable isotopes and selected elements
Isotopes in Environmental and Health Studies (2016)
Špela Mechora, Tjaša Kanduč

Ten locations in the Notranjska region, Slovenia, with different land use in the catchment (town, village and agricultural areas), including reference points with different geological composition considered as unpolluted sites, were sampled for water and aquatic moss to evaluate environmental assessment in fresh water systems of the Sava River watershed. Samples of fresh water and Fontinalis antipyretica were taken in all four seasons during the years 2010 and 2012. The water chemistry of the investigated locations was dominated by , while concentrations of seasonally ranged from 2.1 to 6.4 mg L−1 and at one of the reference sites did not exceed 1.3 mg L−1. δ13CDIC values seasonally ranged from −13.3 to −8.1 ‰ and indicated waters dominated by degradation of organic matter and dissolution of carbonates. δ13Cplant values of F. antipyretica seasonally ranged from −45 to −32.9 ‰ and of δ15Nplant from −0.2 to 6.5 ‰. The higher δ15N value of 6.5 ‰ found in F. antipyretica was related to agricultural activity i...

Short-term fasts increase levels of halogenated flame retardants in tissues of a wild incubating bird.
Environmental research (2016)
Sarah C Marteinson, Ken G Drouillard, Jonathan Verreault

Many species are adapted for fasting during parts of their life cycle. For species undergoing extreme fasts, lipid stores are mobilized and accumulated contaminants can be released to exert toxicological effects. However, it is unknown if short-term fasting events may have a similar effect. The objective of this study was to determine if short successive fasts are related to contaminant levels in liver and plasma of birds. In ring-billed gulls (Larus delawarensis), both members of the pair alternate between incubating the nest for several hours (during which they fast) and foraging, making them a useful model for examining this question. Birds were equipped with miniature data loggers recording time and GPS position for two days to determine the proportion and duration of time birds spent in these two activities. Liver and plasma samples were collected, and halogenated flame retardants (HFRs) (PBDEs and dechlorane plus) and organochlorines (OCs) (PCBs, DDTs, and chlordane-related compounds) were determined. Most birds (79%) exhibited plasma lipid content below 1%, indicating a likely fasted state, and plasma lipid percent declined with the number of hours spent at the nest site. The more time birds spent at their nest site, the higher were their plasma and liver concentrations of HFRs. However, body condition indices were unrelated to either the amount of time birds fasted at the nest site or contaminant levels, suggesting that lipid mobilization might not have been severe enough to affect overall body condition of birds and to explain the relationship between fasting and HFR concentrations. A similar relationship between fasting and OC levels was not observed, suggesting that different factors are affecting short-term temporal variations in concentrations of these two classes of contaminants. This study demonstrates that short fasts can be related to increased internal contaminant exposure in birds and that this may be a confounding factor in research and monitoring involving tissue concentrations of HFRs in wild birds.

Urea and lipid extraction treatment effects on δ(15) N and δ(13) C values in pelagic sharks.
Rapid communications in mass spectrometry : RCM (2016)
Yunkai Li, Yuying Zhang, Nigel E Hussey, Xiaojie Dai

RATIONALE: Stable isotope analysis (SIA) provides a powerful tool to investigate diverse ecological questions for marine species, but standardized values are required for comparative assessments. For elasmobranchs, their unique osmoregulatory strategy involves retention of (15) N-depleted urea in body tissues and this may bias δ(15) N values. This may be a particular problem for large predatory species, where δ(15) N discrimination between predator and consumed prey can be small. METHODS: We evaluated three treatments (deionized water rinsing [DW], chloroform/methanol [LE] and combined chloroform/methanol and deionized water rinsing [LE+DW]) applied to white muscle tissue of 125 individuals from seven pelagic shark species to (i) assess urea and lipid effects on stable isotope values determined by IRMS and (ii) investigate mathematical normalization of these values. RESULTS: For all species examined, the δ(15) N values and C:N ratios increased significantly following all three treatments, identifying that urea removal is required prior to SIA of pelagic sharks. The more marked change in δ(15) N values following DW (1.3 ± 0.4‰) and LE+DW (1.2 ± 0.6‰) than following LE alone (0.7 ± 0.4‰) indicated that water rinsing was more effective at removing urea. The DW and LE+DW treatments lowered the %N values, resulting in an increase in C:N ratios from the unexpected low values of <2.6 in bulk samples to ~3.1 ± 0.1, the expected value of protein. The δ(13) C values of all species also increased significantly following LE and LE+DW treatments. CONCLUSIONS: Given the mean change in δ(15) N (1.2 ± 0.6‰) and δ(13) C values (0.7 ± 0.4‰) across pelagic shark species, it is recommended that muscle tissue samples be treated with LE+DW to efficiently extract both urea and lipids to standardize isotopic values. Mathematical normalization of urea and lipid-extracted δ(15) NLE+DW and δ(13) CLE+DW values using the lipid-extracted δ(15) NLE and δ(13) CLE data were established for all pelagic shark species. Copyright © 2015 John Wiley & Sons, Ltd.

Biodegradability of algal-derived organic matter in a large artificial lake by using stable isotope tracers.
Environmental science and pollution research international (2016)
Yeonjung Lee, Bomi Lee, Jin Hur, Jun-Oh Min, Sun-Yong Ha, Kongtae Ra, Kyung-Tae Kim, Kyung-Hoon Shin

In order to understand the biodegradability of algal-derived organic matter, biodegradation experiments were conducted with (13)C and (15)N-labeled natural phytoplankton and periphytic algal populations in experimental conditions for 60 days. Qualitative changes in the dissolved organic matter were also determined using parallel factor analysis and the stable carbon isotopic composition of the hydrophobic dissolved organic matter through the experimental period. Although algal-derived organic matter is considered to be easily biodegradable, the initial amounts of total organic carbon newly produced by phytoplankton and periphytic algae remained approximately 16 and 44 % after 60 days, respectively, and about 22 and 43 % of newly produced particulate nitrogen remained. Further, the dissolved organic carbon derived from both algal populations increased significantly after 60 days. Although the dissolved organic matter gradually became refractory, the contributions of the algal-derived organic matter to the dissolved organic matter and hydrophobic dissolved organic matter increased. Our laboratory experimental results suggest that algal-derived organic matter produced by phytoplankton and periphytic algae could contribute significantly to the non-biodegradable organic matter through microbial transformations.
Tags: C , N , soi , ec , po , EA