Childress, J. J.. University of California, Childres@lifesci.ucsb.edu
Thuesen, E. J.. The Evergreen State College, thuesene@elwha.evergreen.edu
Macko, S. A. University of Virginia, sam8f@virginia.edu

 
INSIGHTS INTO THE TROPHIC STRUCTURE IN A 2000 M WATER COLUMN FROM STABLE C AND N ISOTOPE STUDIES
 
The mechanisms suggested for organic matter movement through the water column are via predator/prey interactions and sedimention from shallower depths. In studying the trophic structure of midwater communities, isotopic methods do not rely on stomach content analyses and offer the advantage of integrating feeding patterns over a long period of time. We analyzed the 13C/12C and 15N/14N isotope ratios in 179 individual midwater animals captured from 9/9-12 in 1989 at depths from the surface to 1400 m in the 2000 m water column of San Clemente basin off Southern California. Overall del 13C values ranged from -18.5 to -23.5 and del 15N values ranged from 7 to 18.5 with neither showing a significant depth trend. However, there are increases in 15N with depth in some groups and the highest 15N values are at greater depths. There also appear to be animals at low trophic levels at all depths in the water column, with an upper limit of about 3 carnivore tiers throughout the food web. We interpret this to indicate that both sources of organic matter are important to the midwater community and that it utilizes sedimenting matter extensively.
 
Day: Tuesday, Feb. 2
Time: 09:15 - 09:30am
Location: Eldorado Hotel
 
Code: SS32TU0915E