Research Technical Reports

Nitrogen stable isotope fractionation along trophic level pathways in deep sea bamboo corals

Myrvold, C.R., T.M. Hill, H.J. Spero, and T. Guilderson

Poster presentation at the American Geophysical Union Meeting, San Francisco, CA. December 2008.

ABSTRACT

Deep-sea bamboo corals (order Gorgonacea, family Isididae) found on seamounts on the California Margin (37° 22'N – 31° 54'N) have the potential to record annual to subannual changes in water mass chemistry over long periods of time (75-300 years). These corals are composed of a two-part skeleton of calcite internodes segmented by proteinaceous organic nodes. Radiocarbon analyses of the organic nodes show the presence of the anthropogenic bomb spike, reflecting a surface-derived food source for the corals (pre-bomb values of -81.3 per mil - -116. per mil, post-bomb values of 61.8 per mil - 81.3 per mil). Nitrogen stable isotopic analyses of the organic nodes (average d15N = 13.78 per mil – 18.30 per mil) suggest that the corals feed on surface-derived organic matter, although not directly on sinking particulate organic matter but rather on an intermediary such as zooplankton. This study examines the nitrogen stable isotopic content of surface water plankton, bamboo coral polyp material, and bamboo coral organic node material sampled along the California Margin in 2007. Comparing these data with previously established zooplankton nitrogen stable isotope data will enable investigation of the pathway of surface water organic sources to bamboo coral organic material.

Suggested Citation:

Myrvold, C.R., T.M. Hill, H.J. Spero, and T. Guilderson. 2008. Nitrogen stable isotope fractionation along trophic level pathways in deep sea bamboo corals. Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract PP43A-1510.