Abstract:

This dataset contains the bulk stable isotope values (delta-13C and delta-15N) and proportional fatty acid from tissue samples collected in the spring of 2016 for the food web project within the Coastal Waters Consortium III. It includes tissue samples collected from multiple consumers (fish, invertebrates, terrestrial vertebrates) as well as primary producers from salt marshes in southern Louisiana. Zero values represent measurements. “ND” indicates no data. 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) or Rutgers University (New Brunswick, NJ, USA). Sample collection information is also presented.

Suggested Citation:

Olin, Jill, Michael J. Polito, and Paola Lopez-Duarte. 2021. Southern Louisiana marsh food webs: Bulk stable isotope and fatty acid data from multiple consumers and primary producers collected from southern Louisiana salt marshes from 2016-05-01 to 2016-05-31. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/PPZ3DE7B

Purpose:

This dataset summarizes the bulk stable isotope values and proportional fatty acid composition of multiple consumers and producers in southern Louisiana salt marshes. The delta-13C values are indicators of energy sources, and delta-15N values indicate trophic position, therefore, this data can be used to understand trophic interactions. Fatty acid profiles of consumers reflect the fatty acids of their diet items; therefore, this 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; 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; Size: Size of the organism Size_Method: Details for each value in the “Size” column (CW=Carapace width in millimeters, DW=Disc width in millimeters, FL=Fork length in millimeters, TL=Total length in millimeters, WT=weight in grams); 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; 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, scientific names, common names, 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:

Tissues were freeze-dried for 24 to 48 hours and 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 isotope ratios of carbon and nitrogen lipid-free tissues were weighed into tin caps (0.5–1.0 mg) and the 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 Great Lakes Institute for Environmental Research Stable Isotope Analysis Facility.

Instruments:

Identification and quantification of FAME occurred on either a (1) 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 or (2) Shimadzu Gas Chromatograph 2010 with a flame ionization detector and a 60 m × 0.25 mm ID × 0.25mn film TR-FAME column from Thermo Scientific at Rutgers University.

Error Analysis:

For FAMEs derived from Ryerson University, 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). For FAMEs derived at Rutgers University, retention times were standardized to the easily identifiable peak of C16:0 (palmitic acid), and compared with those of FAME standards and FAMEs identified in a subset of samples analyzed on a gas chromatography mass spectrometer (TRACE Ultra/Polar Q by Thermo) at Dalhousie University. Precision, 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 of time 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, William W. 1989. Gas chromatography and lipids. P.J. Barnes and Associates (The Oily Press), Bridgewater, UK. Folch Jordi, M. Lees, and G.H. Sloane Stanley. 1957. A simple method for the isolation and purification of total lipides from animal tissues. Journal of Biological Chemistry 226(1):497-509. PMID: 13428781. DOI: 10.1016/S0021-9258(18)64849-5. Morrison, William R. and Lloyd M. Smith. 1964. Preparation of Fatty Acid Methyl Esters and Dimethylacetals from Lipids with Boron Fluoride-Methanol. Journal of Lipid Research, 5(4), 600-608. DOI: 10.1016/S0022-2275(20)40190-7.

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