Abstract:

This dataset includes bulk carbon (delta-13C), nitrogen (delta-15N), total mercury (tHg) concentrations, and trophic position estimates of four species of seabird (Brown Pelican, Black Skimmer, Royal Tern, Laughing Gull), six species of fish (Gulf Menhaden, Atlantic Croaker, Pinfish, Sand Seatrout, Flathead Grey Mullet, White Mullet), and three species of invertebrates (White Shrimp, Blue Crab, and Eastern Oyster) that were collected from coastal Louisiana from May to December following the Deepwater Horizon Oil Spill in 2010. Organisms were collected as part of NOAA’s Natural Resource Damage Assessment (NRDA) and were frozen (-80°C) until tissues could be extracted (muscle from seabirds, fish and shrimp; whole body from oysters and crabs) and prepared for isotope and mercury analyses. Trophic position was then calculated by incorporating delta-15N values into the single baseline equation from Post (2002). We used primary consumers (oysters) as the baseline with an assumed trophic position of 2, and a trophic discrimination factor of 3.4‰.

Suggested Citation:

Lamb, K., Polito, M.J., Brasso, R., Lopez-Duarte, P.. 2020. Carbon and Nitrogen Stable Isotope Values, Trophic Position, and Mercury Concentration of Invertebrates, Fishes, and Seabirds in Coastal Louisiana, 2010-05-27 to 2010-12-12. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/2HZM8PBN

Publications:

Lamb, K. J., Midway, S. R., Brasso, R. L., López-Duarte, P. C., Kimball, M. E., & Polito, M. J. (2022). Mercury biomagnification in a coastal Louisiana food web following the 2010 Deepwater Horizon oil spill. Frontiers in Environmental Science, 10. https://doi.org/10.3389/fenvs.2022.937124

Purpose:

This dataset was developed to examine the trophic structure and mercury dynamics in the coastal Louisiana food web from primary consumers (oysters) to top predators (seabirds).

Data Parameters and Units:

NA=not available; BDL=below method detection limit; Sample_ID: user defined code assigned to every sample; Sample_ID_2: second code that may have been assigned by another organization upon collection; Collection_Date: MM-DD-YY the samples were collected; Year: year samples were collected; Area: location description for the particular area where samples were collected; Latitude: latitude of sampled sites in decimal degrees; Longitude: longitude of sampled sites in decimal degrees; Species: lowest taxonomic unit to which the specimen could be identified (Genus species); Common_Name: generally used name; Node_code: short version of node group; Node_group: refers to the functional group the species belongs to according to existing literature; Tissue_Collected: tissue type or matrix that was analyzed (muscle, whole body); Total_Hg_conc: total mercury concentration in parts per million (ppm); d13C: stable carbon isotope values (delta-13C) in per mil units (‰); d13C_lipid_normalized: stable carbon isotope values (delta-13C) corrected for lipid content with Post et al (2007) equation in per mil units (‰); %C: elemental concentration of carbon (%); d15N: stable nitrogen isotope values (delta-15N) in per mil units (‰); %N: elemental concentration of nitrogen (%); CN_ratio: Carbon to Nitrogen Ratio calculated as %C divided by %N; Trophic_Position: trophic position (unitless) of organism relative to primary consumers (oysters) calculated using single baseline equation from Post (2002) and an isotopic discrimination factor of 3.4 (‰).

Methods:

All seabird species, blue crabs and oysters were collected as part of NOAA’s Natural Resource Damage Assessment following the Deepwater Horizon oil spill in 2010. Organisms were collected between May 2010 and December 2010 at various locations centered around Barataria Bay, Louisiana, including Grand Isle. Organisms remained in cold storage following collection until they were released to be processed at Louisiana State University in September 2016. Seabirds were dissected for muscle tissue, whereas, oysters and blue crab whole bodies were homogenized in preparation for stable isotope analysis. Fish muscle tissue samples were obtained from an archived sample set collected by Dr. Matt Kimball et al in 2010. Samples were processed and dissected at Rutgers University by students under Dr. Paola Lopez-Duarte before being analyzed for mercury and stable isotopes. Delta-13C values were normalized for lipid content using the Post et al (2007) equation: delta-13C(normalized)= delta-13C(untreated)-3.32*1.9*CN_ratio. Trophic position was calculated using the delta-15N values of the consumer and the following Post 2002 equation: delta_15N(consumers) – delta_15N(oysters)/3.4 + 2.

Instruments:

Carbon (delta-13C) and nitrogen (delta-15N) stable isotope values were analyzed at the Stable Isotope Ecology Laboratory at Louisiana State University (LSU), Baton Rouge, Louisiana, using a Costech ECS4010 Elemental Analyzer (Costech, Valencia, California, USA) coupled to a Thermo Scientific Delta XP Isotope Ratio Mass Spectrometer (Thermo Scientific, San Jose, California, USA). Total mercury concentrations were analyzed by the Brasso Laboratory at Southeast Missouri University using a Nippon MA-3000 direct mercury analyzer.

Error Analysis:

The analytical precision for stable isotopes, based on standard deviations of repeated reference materials were 0.1‰ and 0.2‰ for delta-13C and delta-15N, respectively. For total mercury analysis, mean percent recovery for TORT-3 was 98 % ± 2%, and the method detection limit was 0.001.

Provenance and Historical References:

Post, D. M. (2002). Using stable isotopes to estimate trophic position: models, methods, and assumptions. Ecology, 83(3), 703-718. doi: 10.1890/0012-9658(2002)083[0703:usitet]2.0.co;2 Post, D. M., Layman, C. A., Arrington, D. A., Takimoto, G., Quattrochi, J., & Montaña, C. G. (2007). Getting to the fat of the matter: models, methods and assumptions for dealing with lipids in stable isotope analyses. Oecologia, 152(1), 179–189. doi:10.1007/s00442-006-0630-x

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