Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

To determine the effects of decalcification and the accuracy of untreated dentin analysis, compound-specific Carbon isotope analysis was performed on decalcified and raw sperm whale tooth dentin. The differences in the amino acid isotope values and molar composition are reported. The sperm whale tooth came from the California Current System.

Related Reference:
All sampling and analytical information are supplied in: Brault EK, Koch PK, Gier E, Ruiz-Cooley RI, Zupcic J, Gilbert KN, McCarthy MD (2014) Effects of decalcification on bulk and compound-specific nitrogen and carbon isotope analyses of dentin. Rapid Communications in Mass Spectrometry 28: 2744-2752.

Related Datasets:
Brault 2014 - Bulk Carbon and Nitrogen isotopes
Brault 2014: Compound-specific Nitrogen in sperm whale dentin

Materials and methods for analysis are described in detail in the text. Briefly, a homogenized sample of sperm whale dentin was split into sub-samples. Three received "Conventional" extractraction (decalcification with 0.5N HCl, rinsing with water to neutrality, freeze-drying) and three were not treated ("Raw"). Samples were hydrolyzed with 6 N HCl for 20 h at 110°C, then trifluoroacetic anhydride (TFAA) derivatives were prepared. Samples were analyzed for amino acid carbon and nitrogen isotope composition on a Thermo Trace gas chromatograph coupled to a Thermo Finnigan DeltaPlus XP isotope ratio mass spectrometer. Ideally, samples were injected 3x, and reported isotopic values represent means and standard deviations (stdv) in ‰ relative to the V-PDB standard. For several lysine (Lys) samples, the δ13C value is based on a single injection, so stdv is not calculated. Details on columns used, injection, and furnace ramp parameters are presented in the paper. The amino acid δ13C values were determined from the measured values of the amino acid with corrections based on an amino acid mixture standard for which isotopic values had been independently determined by offline elemental analyzer analysis. Using this approach, the δ13C values of 13 amino acids could be reproducibly quantified: alanine (Ala), glycine (Gly), threonine (Thr), serine (Ser), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), hydroxyproline (Hpro), aspartic acid + asparagine (Asp), glutamic acid + glutamine (Glu), phenylalanine (Phe), and lysine (Lys). The amino acid molar percentages (Mol %) were determined from the peak areas using an external standard approach and based on the amino acid standard versus sample peak areas. For Mol %, data for Hpro and Pro are combined, and reported under Pro.

BCO-DMO Processing:

- added conventional header with dataset name, PI name, version date, reference information
- renamed parameters to BCO-DMO standard
- reformatted columns and rows to a simple flat file
- replaced hyphens with nd (no data)

Description from NSF award abstract:
Anthropogenic and natural climatic perturbations drive changes in population dynamics of species, the structure and function of food webs, and biogeochemical processes. The PIs propose a comparative analysis of three major ecosystems to investigate temporal change in the structure of mesopelagic food webs.

The PIs will investigate temporal changes in the structure of mesopelagic food webs in three major ecosystems: the California Current, Eastern Tropical Pacific, and the Peru-Humboldt Current over the past 50 years using a globally distributed apex predator as an indicator species. The predator is the sperm whale, Physeter macrocephalus, and the PIs will use stable isotope ratios of carbon and nitrogen as indicators of habitat and diet. Isotope values from bulk tissues of teeth and skin (C and N) as well as specific amino acids (N) will be used to address two primary objectives: (a) examine temporal patterns in the trophic position of sperm whales (as an indicator of changes in mesopelagic trophic structure) and baseline isotopic values (as indicators of nutrient cycling); and (b) use isotopic values, which vary among systems, to define the population structure of sperm whales from past and present times, and connectivity among populations.

This project will be conducted by researchers from academia and NOAA/NMFS with expertise in stable isotope analysis, trophic ecology, and ecosystem-based management of protected species. As such, it represents an opportunity for collaboration between scientists with complementary skills and from diverse institutions to compare structure and function of ecosystems across the eastern Pacific. Moreover, it represents a collaboration between academia and a federal agency with research and management responsibilities. The project will support a postdoctoral scholar (Iliana Ruiz-Cooley), a Ph.D. student, and undergraduate students to enhance their career and collaborative opportunities. The PIs anticipate that the results of their study will provide unique data to evaluate the effects of perturbations within and among mesopelagic ecosystems. This information may allow the scientific community to relate trends in climate to changes in trophic position of top predators and nutrient cycling, allowing more robust understanding of possible responses to future warming. Finally, as the first systematic applications of compound-specific stable isotope analysis to marine mammals, the project should be highly instructive for future evaluations of the feeding ecology, population structure and dynamics of endangered marine mammals. As such, this novel approach and unique historic perspective will be directly applicable for stock assessment and management.