Aquatic Sciences Meeting, Albuquerque 2001

CS37 Zooplankton

Date: Wednesday, February 14, 2001, Time: 2:45:00 PM

Location: Aztec

McClelland, J, W, Georgia Institute of Technology, Atlanta, USA, james.mcclelland@biology.gatech.edu

Holl, C, , Georgia Institute of Technology, Atlanta, USA, choll66@prodigy.net

Montoya, J, P, Georgia Institute of Technology, Atlanta, USA, joseph.montoya@biology.gatech.edu

STABLE NITROGEN ISOTOPE COMPOSITION OF AMINO ACIDS IN ZOOPLANKTON: EVIDENCE FOR THE IMPORTANCE OF N FIXATION IN THE SUBTROPICAL NORTH ATLANTIC

Determining the importance of anthropogenic versus natural contributions of nitrogen to the biosphere largely hinges on how much oceanic N-fixation contributes to the global nitrogen budget. This term has been difficult to quantify. Zooplankton delta-15N, however, provides a time-integrated signal of the relative contributions of deep-water nitrate and new fixed nitrogen to planktonic food webs. Bulk zooplankton from the subtropical North Atlantic have lower delta-15N values where nitrogen fixers are abundant. Delta-15N of different amino acids from the bulk samples span a 16 per mil range, and yet show the same trend as do the bulk samples. The wide range in delta-15N for different amino acids within bulk samples reflects their unique synthesis pathways and uses. Decreases in delta-15N of amino acids among samples reflect increases in contributions of fixation-derived nitrogen. This relationship is supported by comparisons of the amino acid footprint of the nitrogen fixer Trichodesmium with that of zooplankton with different delta-15N values. The footprints of Trichodesmium and zooplankton are strikingly similar where zooplankton delta-15N values are low, and they diverge as the delta-15N values of zooplankton increase.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks