Search

Stable isotope analysis (SIA) is widely used in ecology, but samples are usually analysed in specialist facilities. Like any complex process, SIA is susceptible to human error. Despite the best efforts of the SIA laboratory, errors may occasionally remain in results released to clients.We used our experiences as ecologists and laboratory analysts to identify human error scenarios to which SIA performed anywhere might be susceptible. These scenarios ran from sample selection and submission by the ecologist, to the final results report from the SIA laboratory. Several scenarios involved errors hard to find by visual examination, by either ecologist or analyst.The ecologist can prevent pre‐submission errors by formalising their sample submission process, and can best perform a final results quality check by submitting their own quality control material with a matrix similar to that of the samples. Prevention of laboratory errors is best accomplished by a comprehensive risk‐based quality management system and a continual improvement, no‐blame laboratory culture.We recommend that the ecologist views the entire sample selection, submission and laboratory analysis as an integrated whole, establishing their own quality management processes to run alongside those of the SIA facility. This recommendation applies to any ecological methodology where samples are sent to a specialist facility for analysis. [ABSTRACT FROM AUTHOR]

Stable isotope studies have repeatedly shown marine nutrient incorporation from seabirds, anadromous fish and tidal wrack into terrestrial and freshwater ecosystems. However, little is known about the physiological consequences of marine-derived nutrient subsidies. Protein content and lipid storage are important physiologically, and the C : N ratio is a widely used proxy that reflects changes in these quantities. In this study we tested the response of C : N ratios in stream biota to the presence of marine-derived nutrients from Westland petrels, a forest breeding seabird. Samples of different stream invertebrate functional feeding groups, predatory freshwater fish, coarse particulate organic matter and riparian soil and vegetation came from four reference streams and four streams with a wide range of seabird densities. Samples were analysed for percentage C, percentage N and δ15N using isotope ratio mass spectrometry. The data were tested against petrel colony size, stream size and distance from colony to sampling site. Despite increased δ15N accompanying petrel presence (as reported previously), Westland petrels had no effect on stream biota C : N ratios, regardless of colony presence or absence or colony size. Despite the nutrients provided by petrels, we conclude that petrel N replaced rather than enhanced non-marine N in these stream ecosystems. Studies have shown that nutrients from marine ecosystems can be incorporated into terrestrial and freshwater ecosystems through vectors such as salmon and seabirds. However, little is known about the physiological consequences of these marine nutrients. Despite detecting seabird-derived nutrient in the streams in this study, we found that seabird nitrogen replaced existing nitrogen rather than making stream biota more nitrogen rich. [ABSTRACT FROM AUTHOR]

Stable isotope analysis ( SIA) is widely used in ecology but is usually performed by specialist facilities. Consequently, the reliability of SIA data depends completely on the facility's quality systems unless ecologists take steps themselves. Although widely recommended, practical advice on how to do this is lacking., Here, we outline preparation of 150 vials of an in-house quality control material ( QCM) based on air-dried soil as an exemplar and describe methods of data analysis applicable to any QCM matrix. Homogeneity testing of the candidate material involves duplicate analysis of 10 randomly chosen vials, a Cochran test for outliers and 1-way anova. Given that many ecologists find SIA expensive, we propose that an ecologist preparing a soil QCM pretest for homogeneity using a simple colorimetric analysis of a soil quantity (bicarbonate-extractable P) sensitive to inhomogeneity., Once pretest homogeneity has been established, homogeneity under SIA can be tested. We obtained a 1-way anova P value of 0·824 in our laboratory pretest, then 0·782 ( δ13C) and 0·125 ( δ15N). QCM stability should also be confirmed., Submission of each batch of samples for SIA should be accompanied by a vial of the QCM, labelled as a normal sample. Control charting of the results then allows detection of within-batch issues encompassing any component of the analytical process (transport to the laboratory, sample preparation and subsampling, sample analysis, results calculation and reporting) and assessment of long-term analytical control. Any issue thus identified can form the basis of a conversation with the SIA laboratory about the affected batch of samples. [ABSTRACT FROM AUTHOR]

This study investigated the role of the invasive mallow Lavatera arborea in the terrestrial ecosystem of a flourishing seabird island in SE New Zealand using natural abundance stable isotope ratios (13C/12C; 15N/14N, reported as δ13C and δ15N). Foliage samples of L. arborea came from transects encompassing three distinct environments (plateau, slope, storm-washed flat) across the island. Samples of potential marine nutrient sources (beach-cast kelp; seabirds using the island) were also collected, to contextualise the L. arborea data. Samples of invertebrate taxa (exotic and indigenous) from multiple ecosystem guilds were hand-collected; a bee, a sap-sucking Homoptera, a litter-feeding tenebrionid beetle, various carrion-feeding flies, a predatory carabid beetle, a salticid spider, and (from a seabird cadaver) Dermestes sp. exuviae. Discarded skins from the gecko Hoplodactylus maculatus were collected from moulting sites. Highly enriched δ15N values showed that L. arborea from all three environments utilised seabird N, even though breeding seabirds were absent from the storm-washed flat. The isotopic signatures of the Homoptera, and the tenebrionid and carabid beetles could be accounted for entirely by food webs based on L. arborea. Bee and salticid spider isotopic signatures could be accounted for by varying contributions from L. arborea. The flies and Dermestes were (as expected) linked to carrion from either the island or the adjacent mainland. In contrast, gecko data indicated direct dependence on seabirds, although the exact relationship was unclear. Our study therefore showed that L. arborea is an integral part of the terrestrial ecosystem of the island across multiple trophic levels from pollinators to top-level predators. [ABSTRACT FROM AUTHOR]

The remaining five Coenocorypha snipes are restricted to remote islands in the New Zealand archipelago, so their ecology is difficult to study directly. To ascertain habitat types and ecological interactions across the different taxa and locations, we measured the Δ13C and Δ15N of feathers from known individual Auckland Island snipe C. aucklandica aucklandica (Adams I., n = 12; Enderby I., n = 4; Rose I., n = 8), Chatham Island snipe C. pusilla (Rangatira, n = 10), and Campbell Island snipe (Coenocorypha undescribed sp.; n = 1). Data for Snares snipe C. a. huegeli (North East I., n = 1) came from the literature. Developmental stage (nestling, juvenile, adult) and sex were statistically indistinguishable. Although significant differences in Δ13C occurred between islands, the overall range was small (mean ± standard deviation, -22.7 ± 0.9‰). The restricted Δ13C show that the snipe we sampled occupied a consistent habitat regardless of taxa, island size, and disturbance history. Conversely, the range in Δ15N was large at c. 18.5‰ and implied occupation of sites with a wide range of nutrient status. The δ15N from Adams I. (mean 5.9 ± 1.7‰) was much lower than the other islands (mean 19.2 ± 2.0‰) and could only be explained by including a 15N-depleted site not affected by seabirds or seals. Auckland Island snipe therefore integrate seabird breeding and nonbreeding areas as well as inhabiting locations with seals and high seabird densities. Consequently, Coenocorypha snipes provide connectances between marine animals on land and the wider terrestrial environment and so may be considered for (re)-introduction to predator-proof mainland New Zealand restoration sites. [ABSTRACT FROM AUTHOR]

Marine nitrogen (N) has been traced into terrestrial and freshwater food chains at petrel (Aves: Procellariiformes) colonies on the South Island of New Zealand, but the effects of N or other marine-derived nutrients on the productivity of mainland forests are unknown. Mean ring widths in matai (Prumnopitys taxifolia; n = 3) and rimu (Dacrydium cupressinum; n = 2) trees growing in a Westland petrel (Procellaria westlandica) colony were 0.9-1.4 mm yr-1, similar to ring widths reported elsewhere. However, series of much wider rings in cores showed that trees in a petrel colony can experience periods of accelerated growth. δ15N values of whole wood were, at 3.2-11.1‰, significantly enriched in comparison to other temperate forest trees. The highest δ15N values were at the cambial and pith ends of different cores, so isotopic fractionation during N remobilisation is unlikely to have been significant. The radial extent of 15N enrichment suggests that petrels have bred at the site since at least the mid 18th century. [ABSTRACT FROM AUTHOR]

1. Stable isotope ratios of aquatic invertebrates, aquatic mosses and leaves of riparian plants were used to determine whether marine-derived nutrients from breeding colonies of the Westland petrel (Procellaria westlandica) were incorporated into the food webs of small streams in New Zealand. 2. The δ15N signatures of all plants and animals examined were higher by 3.6-4.6‰ in small streams draining catchments with petrel colonies than in nearby streams where petrels were absent. δ13C values of leaves from terrestrial plants were also enriched by about 2‰ where petrels were present, but the carbon ratios of aquatic species were depleted in 13C, rather than enriched, suggesting that any marine signal was over-ridden by isotopic shifts related to photosynthetic fractionation. 3. A high marine-nitrogen signal was maintained along the 3 km length of Scotchman Creek with the δ15N values of leptophlebiid mayflies and predatory insects ranging from 7.4-9.5 and 9.2-11.9‰, respectively. 4. Most nutrients derived from petrels are likely to be translocated to streams via the soil, which they enter in the form of excreta, spilled food, feathers, dead chicks, and abandoned eggs. However, because changes in δ15N values are brought about by soil processes such as volatilisation of ammonia, nitrification and denitrification, it is difficult to predict the exact isotope signature of nitrogen entering a stream. Tentative estimates of the proportion of marine-derived nitrogen in stream biota, calculated using a mass-balance approach, ranged from 28-38%. 5. Our findings indicate that marine nutrients transported inland by seabirds can be incorporated into the food webs of streams. In pre-human times when there were many more seabird colonies on mainland New Zealand than exist today, marine-derived nutrients introduced by birds may have had significant effects on nitrogen cycling and the productivity of New Zealand streams. [ABSTRACT FROM AUTHOR]