Table of Contents

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

Note: Preliminary data have been submitted to BCO-DMO, but are not yet available online. Final data are expected to be submitted and made available during the summer of 2014.

This dataset includes carbon and nitrogen isotope data of archaeological fish bones from Penobscot Bay, Gulf of Maine (44.18 ˚N, 68.92 ˚W).

Between 0.4 and 0.8 mg of collagen were analyzed for stable carbon and nitrogen isotope values using a ThermoFinnigan Delta Plus Advantage stable isotope ratio mass spectrometer (IRMS) coupled to a Costech elemental analyzer via a Conflo III combustion interface in the Environmental Geochemistry Laboratory, Department of Geology, Bates College. Stable isotope values are expressed in δ (‰) notation according to the following definition:

δ X(‰) = [(Rsample/Rstandard)-1]*1000

where X is 13C or 15N and R is 13C:12C or 15N:14N, and the standards were Pee Dee Belemnite (PDB) for carbon and AIR for nitrogen. The accuracy and precision of the IRMS, as determined by multiple analyses of a working standard (acetanilide: C8H9NO) run every sixth sample, was ± 0.2‰ for both δ13C and δ15N.

Approximately 1/3 of the samples run are working standards of different and known isotopic compositions. In a batch of 49 samples, for example, approximately 16 of these are working standards. (The δ13C values of the standards range between -18.6 and -30.9‰. The δ15N of the standards range from -11.0 to 14.5‰.) A linear regression is used to establish the relationship between the 13/12C and 15/14N ratios of the standards and the δ13C and δ15N values of the standards. This equation is then used to determine the δ13C and δ15N values of the unknowns. The limits of detection for N are 1 umole.

BCO-DMO Processing Notes:
- Modified parameter names;
- Sorted data alphabetically by common_name;
- Corrected typos in taxonomic names (e.g. 'Gatus' changed to 'Gadus').

Description from NSF award abstract:
Predicting the responses of marine ecosystems to natural and anthropogenic perturbation remains one of the greatest challenges to oceanography. In order to assess the significance of current changes in these systems and to predict possible future changes, oceanographers need to understand the ecological history of the ecosystem. The aim of this study is to create long-term records for the Gulf of Maine (GoM), a marginal shelf basin in the northwest Atlantic. Current knowledge of the resilience of the GoM ecosystem is based largely on studies focused on the last 70+ years. In this project, investigators will develop an understanding of ecosystem processes in the GoM extending back 4000 years by analyzing stable carbon (C), nitrogen (N) and sulfur (S) isotopes preserved in tissues of modern and ancient marine organisms to assess long-term trends in nearshore primary production, trophic connectivity, and food web dynamics.

The investigators will employ a combination of field, analytical, and modeling techniques to:
(1) determine the spatial scale over which organic matter derived from seagrasses, microalgae, and macroalgae is currently transferred into coastal food webs, and
(2) determine the timing, magnitude, and spatial extent of changes in nearshore primary production and trophic connectivity among organisms living in the GoM through the last 4000 years.

Tissue samples will be obtained from different coastal settings, museum collections, and three coastal archaeological sites in the GoM. The bulk organic fractions of primary producers and consumers will be analyzed for C, N, and S isotopes. The C isotope composition of essential amino acids (e.g., phenylalanine) will be measured, allowing for determination of the carbon source at the base of the food web. Nearshore food web interactions will be modeled by using the C, N and S isotope data and non-steady state equations that include competition-dependant changes in the consumers prey choice.