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<p>Our speaker for the EOAS colloquium this week Fri Apr 5 at 3:30 in CAR 101 will be
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<p><b>Dr. Hillary Close, </b>Univ of Miami</p>
<div>Title: </div>
<div><font size="+1"><b>Distinguishing the roles of microbial and metazoan heterotrophy in the ocean carbon cycle</b></font></div>
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<div>Abstract:</div>
<div>The downward flux of organic matter in the ocean is a major carbon cycle component, contributing both to the sequestration of atmospheric carbon and to the diets of animals in the deep ocean. Microbial and metazoan heterotrophy are the major agents acting
on organic matter to reduce its downward flux through the water column; both the intensity of heterotrophy at the ocean’s surface and the vertical distribution of heterotrophy beneath the surface help to control the ocean carbon budget. I will describe my
recent work using natural variations in the stable isotopes of organic compounds to expose the varying net effects of microbial and metazoan heterotrophy on a range of particle sizes involved in vertical carbon flux. Using multiple simultaneous parameters
from compound-specific isotope analysis of amino acids, I will introduce a new classification system for the trophic history of detrital organic matter. Under this multivariate framework, I distinguish seasonal variability in the prevalence of zooplankton-
versus microbially-altered detritus in the oligotrophic Pacific, and I identify evidence for the transfer of microbially-altered small particles into the higher food web at mesopelagic depths.
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