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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 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]

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]