PARENT SESSION
Symposium 1: In the Footsteps of Lewis and Clark: Rediscovering Earth From Land to Sea - A Biogeoscience Perspective.
Organized by: PV Sundareshwar and J Elser
Monday, August 2, 8:00 AM to 11:30 AM, Oregon Ballroom 202.

Isotope sourcery and the importance of detritus in fueling food webs.

Fry, Brian^*,1, Galvan, Kari¹, Fleeger, John¹, Coleman, David², Carman, Kevin¹, Demopoulos, Amanda³, Currin, Carolyn⁴, Levin, Lisa⁵, Neira, Carlos⁵, ¹ Louisiana State Univeristy, Baton Rouge, LA² University of Georgia, Athens, GA³ University of Hawaii, Honolulu, HI⁴ NOAA National Ocean Service, Beaufort, NC⁵ Scripps Institute of Oceanography, La Jolla, CA

ABSTRACT- Food webs are almost always complex. One aspect of this complexity is that plant food resources at the base of food webs differ greatly in quality and quantity. In many systems, abundant plants and their dead remains (detritus) are easy for humans to see and count, but of low nutritional value or hard to access for consumers. Perhaps alternative cryptic plant species are really the key basal food resources, not detritus. These thoughts have fueled several decades of ecological research, in disparate fields and with different approaches. In an effort at synthesis, this talk considers terrestrial radiotracer experiments that bear on the importance of detritus in food webs, as well as related marine studies that used stable isotopes. Several studies show that energy from low-quality plant detritus is mostly dissipated in microbial food webs, while rarer, high-quality foods can fuel production of highest trophic levels. But there is also considerable variation in how individual food webs are poised with respect to the importance of low-quality-but-high-quantity detritus, and we consider indices that help predict this broad range of importance for detrital inputs.

Key words: radioisotopes, detritus, stable isotopes, food webs