Abstract:

This dataset contains the bulk stable isotope values (delta-13C and delta-15N) and proportional fatty acid composition for marsh rice rat muscle tissue samples collected in 2015 and 2016 from six sites in southern Louisiana. Zero values represent measurements. The stable isotope samples were analyzed at the University of Windsor (Windsor, ON, Canada), the fatty acid samples were analyzed at Ryerson University (Toronto, ON, Canada). Sample collection information is also presented.

Suggested Citation:

Olin, J., Polito, M.J., Lopez-Duarte, P.. 2020. Marsh Rice Rat Ecological Tracers: Bulk Stable Isotope and Fatty Acid data from marsh rice rats collected in southern Louisiana salt marshes from 2015-06-01 to 2016-06-30. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-99y2-8j76

Purpose:

This dataset summarizes the bulk stable isotope values and proportional fatty acid composition for marsh rice rats. The delta-13C values are indicators of energy sources, and delta-15N values indicate trophic position, therefore, these data can be used to understand trophic interactions of marsh rice rats in these salt marshes. Fatty acids profiles of consumers reflect the fatty acids of their diet items, therefore, these data can be used to understand predator-prey interactions.

Data Parameters and Units:

Worksheet "Stable Isotope and Fatty Acid" CWC_ID: user defined code assigned to every sample; Other_ID: code that may have been assigned by other groups who collected the samples; Date: Month-Year the samples were collected; Season: season in which samples were collected (Autumn, Spring); Year: year samples were collected; Area: location description for the particular area where samples were collected; Site: user defined codes assigned to each sampling site; Treatment: Site condition based on SCAT map criteria (O=heavily oiled, U=very light or no oil observed); Habitat_Location: habitat description where samples were collected; Latitude: latitude of sampled sites in decimal degrees; Longitude: longitude of sampled sites in decimal degrees; Node_Group: refers to the functional group the species belongs to according to existing literature; Node_Code: short version of node group; Species: lowest taxonomic unit to which the specimen could be identified; Common_Name: generally used name; N: Number of samples representing data; Tissue_Type: tissue type or matrix that was analyzed; SIA_Laboratory: where the samples were analyzed for bulk stable isotopes; FAA_Laboratory: where the samples were analyzed for fatty acids; d13C: stable carbon isotope values in per mil units (‰); %C: elemental concentration of carbon (%); d15N: stable nitrogen isotope values in per mil units (‰); %N: elemental concentration of nitrogen (%); CN: Carbon to Nitrogen Ratio calculated as %C divided by %N; %Lipid_dry: Lipid content on dry weight basis; Fatty acid composition of each sample, measured as proportions for different fatty acids. Each fatty acid is identified by its nomenclature. Worksheet "FA_Information”: Molecular formula and types of the fatty acids reported in worksheet "Stable Isotope and Fatty Acid”. Please note MUFA = Monounsaturated Fatty Acids; PUFA = Polyunsaturated Fatty Acids; and SFA = Saturated fatty Acid.

Methods:

Rice rats were caught in baited Sherman live traps, dispatched and muscle tissue was collected from the chest area. Muscle tissue was freeze-dried for 24 to 48 hours, homogenized into a powder. Fatty acid profiles were quantified using a three-step procedure: (1) triplicate extractions of freeze-dried tissue in a 2:1 chloroform/methanol solution for gravimetric determination of the total lipid (Folch et al. 1957); (2) derivatization of FA methyl esters (FAME) using sulfuric acid in methanol (1:100 mixture; Morrison and Smith 1964, Christie 1989); and (3) identification and quantification of FAME. For stable isotopes, ground samples were lipid-extracted following standard chloroform-methanol practices (Folch et al. 1957), weighed into tin caps (0.5–1.0 mg) and the relative abundances of carbon (13C/12C) and nitrogen (15N/14N) were determined.

Instruments:

Fatty acid profiles were quantified using a Shimadzu Gas Chromatograph-2010Plus with a flame ionization detector and 100 m × 0.25 mm ID × 0.20 µm film SP-2560 column from Supelco at Ryerson University (Toronto, ON, Canada). Relative abundances of carbon (13C/12C) and nitrogen (15N/14N) were determined on a Thermo Finnigan DeltaPlus mass spectrometer (Thermo Finnigan San Jose, California, USA) coupled with an elemental analyzer (Costech, Valencia, California, USA) at the University of Windsor (Windsor, ON, Canada).

Error Analysis:

The FA standards were obtained from Supelco (37 component mix) and Nuchek (54 component mix). A known quantity of an internal standard (a-cholestane; Sigma 170 #C-8003) was added to each sample prior to extraction to provide an estimate of extraction efficiency. Seventy-three FAME were identified using Agilent Technologies ChemStation software via retention time and known standard mixtures and are reported as the percentage of total FA (% TFA). Precision for stable isotope ratios, assessed by the standard deviation of replicate analyses of four standards [NIST 1577c, internal lab standard (tilapia muscle), USGS 40, Urea (n = 64)], measured ≤ 0.15‰ for δ15N and ≤ 0.14‰ for δ13C for all the standards. Analytical accuracy based on the certified values of USGS 40 (n = 64) analyzed throughout runs showed a difference of -0.03‰ for δ15N and -0.07‰ for δ13C from the certified value. Instrumentation accuracy checked throughout the period that these samples were analyzed was based on NIST standards 8573, 8547 and 8574 for δ15N and 8542, 8573 and 8574 for δ13C (n = 20). The mean difference from the certified values were -0.17, -0.10 and -0.14‰ for δ15N, and -0.10, -0.06 and 0.14‰ for δ13C, respectively.

Provenance and Historical References:

Christie, W. W. (1989). Gas chromatography and lipids. PJ Barnes and Associates (The Oily Press), Bridgewater, UK Folch, J., Lees, M., & Stanley, G. S. (1957). A simple method for the isolation and purification of total lipids from animal tissues. Journal of biological chemistry, 226(1), 497-509. Morrison, W. R., & Smith, L. M. (1964). Preparation of fatty acid methyl esters and dimethylacetals from lipids with boron fluoride–methanol. Journal of lipid research, 5(4), 600-608.

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