HR: 0830h
AN: B31C-0317    [PDF]
TI: Organic Carbon Sources in Coastal Southeast Alaskan Streams
AU: * Hood, E
EM: eran.hood@uas.alaska.edu
AF: Environmental Science Program, University of Alaska Southeast 11120 Glacier Hwy, Juneau, AK 99801 United States
AU: Edwards, R T
EM: rtedwards@fs.fed.us
AF: U.S. Forest Service, Pacific Northwest Research Station, 2770 Sherwood Lane, Suite 2A, Juneau, AK 99801 United States
AU: D'Amore, D V
EM: ddamore@fs.fed.us
AF: U.S. Forest Service, Pacific Northwest Research Station, 2770 Sherwood Lane, Suite 2A, Juneau, AK 99801 United States
AU: Lange, B J
EM: blange@fs.fed.us
AF: Environmental Science Program, University of Alaska Southeast 11120 Glacier Hwy, Juneau, AK 99801 United States
AU: Lange, B J
EM: blange@fs.fed.us
AF: U.S. Forest Service, Pacific Northwest Research Station, 2770 Sherwood Lane, Suite 2A, Juneau, AK 99801 United States
AB: Dissolved organic matter (DOM) is abundant in southeast Alaskan watersheds and plays an important role in the biological and physical processes in these aquatic systems. Nearly 30% of the land area in southeast Alaska is classified as wetlands, a large proportion of which are peatlands. Peatlands are thought to provide substantial DOM to surface waters. Another important source of carbon to streams is spawning anadromous salmon. This study examines how streamwater concentrations of DOC are influenced by 1) catchments soils and vegetation, particularly wetland extent and 2) the presence or absence of anadromous fish. Our goal is to characterize the quantity and quality of different DOM sources and to develop an understanding of how these sources influence seasonal trends in streamwater DOM in coastal freshwater systems in southeast Alaska. Surface water and well samples were collected on two contrasting streams near Juneau, Alaska: Peterson Creek, a brownwater, high-carbon stream in a wetland-dominated catchment and McGinnis Creek, a clearwater stream draining upland spruce forest and alpine tundra. Both streams have runs of pink, coho, and chum salmon from July-September. Streamwater DOC concentrations on Peterson Creek averaged 5-6 mg C L$^{-1}$ during the early summer and increased to 8-12 mg C L$^{-1}$ during late July and August. Streamwater DOC concentrations on McGinnis Creek were typically less than 1 mg C L$^{-1}$ during the early summer but increased dramatically to 4-9 mg C L$^{-1}$ during spates in August. Well samples collected upslope from the streamwater sampling sites on Peterson and McGinnis Creeks had a similar range in DOC concentrations (10-40 mg C L$^{-1}$), however the wells on McGinnis Creek showed much higher seasonal variability. Our initial results suggest that the seasonal increase in DOC in both streams is primarily associated with the flushing of soluble organic carbon from catchment soils by late summer rains. However, leaching of DOC from salmon carcasses may also be significant in July-September. We are currently using chemical fractionation and UV spectroscopy to determine how the character and reactivity of DOC in Peterson and McGinnis Creeks changes on a seasonal basis. In addition, fluorescence spectroscopy is being used to assess seasonal changes in the precursor material for streamwater DOC in both study catchments.
DE: 0400 Biogeosciences
DE: 1055 Organic geochemistry
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
DE: 1890 Wetlands
SC: Biogeosciences [B]
MN: 2003 Fall Meeting