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Patterns in stable isotope ratios of particulate material from the eastern US continental shelf
Citation:
Mckinney, Rick, B. Kreakie, A. Oczkowski, AND J. Prezioso. Patterns in stable isotope ratios of particulate material from the eastern US continental shelf. Advances in Stable Isotope Techniques and Applications Conference (ASITA), Philadelphia, PA, June 19 - 21, 2016.
Impact/Purpose:
Stable isotope measurements of nitrogen and carbon (δ15N, δ13C) in estuarine, nearshore, and open ocean ecosystems are often utilized in order to characterize human influences, elucidate food web dynamics, or better understand nitrogen cycling. Reliable information about the spatial distribution of base-level stable isotope values, often represented by primary producers, is critical to interpreting values in these ecosystems. While base-level isotope data are generally readily available for estuaries, nearshore coastal waters, and the open ocean, waters of the continental shelf have been less studied. This study is a first step towards developing a surrogate for base-level isotopic signature for the United States’ eastern continental shelf in the Western Atlantic Ocean, from the Gulf of Maine to Cape Hatteras. This and subsequent studies of stable isotope dynamics on the shelf can inform both nearshore and open ocean research efforts, providing an important link along the marine continuum.
Description:
Stable isotope measurements of nitrogen and carbon (δ15N, δ13C) in estuarine, nearshore, and open ocean ecosystems are often utilized in order to characterize human influences, elucidate food web dynamics, or better understand nitrogen cycling. Reliable information about the spatial distribution of base-level stable isotope values, often represented by primary producers, is critical to interpreting values in these ecosystems. While base-level isotope data are generally readily available for estuaries, nearshore coastal waters, and the open ocean, waters of the continental shelf have been less studied. To address this and as a first step towards developing a surrogate for base-level isotopic signature in this region we collected surface and bottom samples from the United States’ eastern continental shelf in the Western Atlantic Ocean, from the Gulf of Maine to Cape Hatteras, periodically between 2010 and 2013. During the study particulate matter δ15N values ranged from 0.80 to 17.37 ‰, and δ13C values from -26.37 to -15.58 ‰ over the region. We used spatial autocorrelation analysis and random forest modeling to examine the spatial trends and potential environmental drivers of the stable isotope concentrations. While we found no significant spatial trends in the data, we saw trends towards lower values for both nitrogen and carbon at the seaward edge of the shelf. Conversely, higher δ15N and δ13C values were observed on the landward edge of the shelf, in particular in the southern portion of the sampling area. Across all sites, the magnitude of the difference between the δ15N of bottom and surface PM significantly increased with water depth (r2 = 0.41, df = 35, p < 0.001), while δ13C values did not change. We found a significant positive correlation between δ15N and δ13C values for surface PM in each of the three marine ecoregions that make up the study area. Stable isotope dynamics on the shelf can inform both nearshore and open ocean research efforts, providing an important link along the marine continuum.