HR: 13:45h
AN: B53A-02    [Abstracts]
TI: Bioavailability of Dissolved Organic Carbon and Nitrogen From Tropical Montane Rainforest Streams Across a Geologic age Gradient
AU: * Wiegner, T N
EM: wiegner@hawaii.edu
AF: University of Hawaii at Hilo, Marine Science Department, 200 W. Kawili Street, Hilo, HI 96720 United States
AB: Dissolved organic matter (DOM) is metabolically important in streams. Its bioavailability is influenced by organic matter sources to streams and inorganic nutrient availability. As forest canopies and soils develop over time, organic matter inputs to streams should switch from algal to watershed sources. Across this succession gradient, nutrient limitation should also change. This study examines how chemical composition and bioavailability of DOM from tropical montane rainforest streams on Hawaii change across a geologic age gradient from 4 ky to 150 ky. Dissolved organic C (DOC) and N (DON) concentrations, chemical characteristics, and bioavailability varied with site age. With increasing stream age, DOC and DON concentrations, DOM aromaticity, and the C:N of the stream DOM increased. Changes in stream DOM chemistry and inorganic nutrient availability affected DOM bioavailability. Fifty percent of the DOC from the 4 ky site was bioavailable, where little to none was bioavailable from the older streams. Inorganic nutrient availability did not affect DOC bioavailability. In contrast, DON bioavailability was similar (12%) across sites and was affected by inorganic nutrient availability. This study demonstrates that the chemistry and metabolism of streams draining forests change with ecosystem age and development.
DE: 1806 Chemistry of fresh water
SC: Biogeosciences [B]
MN: 2005 Joint Assembly