Under this award the PIs will examine environments with "extreme" chemical gradients that accentuate chemical differences between biogenic carbonate and ambient conditions as well as those of "normal" deep-sea conditions. Extreme isotopic gradients present at cold methane seeps provide an ideal habitat to examine the effects of carbon isotopic disequilibrium (up to 40 0/00), between foraminiferal calcite and dissolved inorganic carbon (DIC) of ambient water. Recent work suggests that biological factors ("vital effects") and/or ambient isotopic compositions influence carbon isotopic signatures of foraminiferal calcite. Consequently, the proposed work will test the following hypotheses: 1) Infaunal foraminifera cluster in microhabitats within the sediments; 2) Food type influences foraminiferal carbon isotope values; 3) The presence of symbionts is variable within and between species, and this variability is reflected in carbon isotopic signatures. The work should provide insight to the important question of what controls the carbon isotopic composition of benthic foraminiferal tests (shells)? Answers to this question will be crucial for paleoenvironmental reconstructions in both seep and non-seep environments. The funds will also be used to include community outreach (local school presentations; web site development) and interdisciplinary, hands-on training of several future scientists at undergraduate, graduate, and post-doc levels, including under-represented groups.
