Browsing by Subject "ethanol storage"

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    Data and R code for a zooplankton ethanol storage correction factor.
    (2023-04-05) Blechinger, Tristan; Link, Denver; Nelson, Jenna KR; Hansen, Gretchen JA; blech024@umn.edu; Blechinger, Tristan; University of Minnesota Department of Fisheries, Wildlife, and Conservation Biology
    This data set contains fresh and ethanol fixed zooplankton samples collected from five Minnesota lakes during June 2022. The data were collected with five paired sites at each lake. The samples were filtered to remove detritus, phytoplankton, and predatory invertebrates. After filtering, each sample was split between fresh processing and ethanol storage. Ethanol storage samples remained in storage for approximately one month. Samples were sent to the UC-Davis Stable Isotope Facility for analysis. Stable isotope values in addition to lake name, DOW, and site of collection are included in the data file. Bayesian Hierarchical models were used to establish correction factors for ethanol storage. Statistical analysis was performed using the R package brms and model output can be found in respective .rds files. Details for each file can be found in the readme file.
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    Isotopic Correction Factors for Zooplankton Storage
    (2023) Blechinger, Tristan; Link, Denver; Nelson, Jenna KR; Hansen, Gretchen JA
    Stable isotope analysis is an increasingly popular method of food web monitoring and is leading to an increased understanding of how energy and pollutants move within an ecosystem. This technique involves the use of δ13C and δ15N stable isotopes for specific dietary tracking among trophic levels based on their present ratios; in aquatic ecosystems, zooplankton are frequently used to represent the baseline pelagic trophic level. Upon collection, zooplankton samples are often preserved in ethanol prior to processing and analysis. However, this method has varying effects on isotopic signatures of tissues, leading to a potentially inaccurate isotopic position. In order to determine a correction factor to account for ethanol preservation, zooplankton were collected at 25 sites across five Minnesota lakes. Zooplankton stable isotope data were analyzed using a mixed effects model that showed ethanol preservation leading to significant δ13C enrichment (SE = 0.064, t-value = 17.951) and no significant change in δ15N. The random lake effect had no significant impact on the outcome. This correction factor will enhance the accuracy and efficacy of stable isotope analysis for freshwater food webs by providing more reliable baseline isotope values upon which these studies rely, and provide a procedure for other correction factors to be determined.