HR: 0800h
AN: H51D-1166    [Abstracts]
TI: Linkages between flood, aquatic organic matter, and food web processes in the Okavango Delta, Botswana
AU: * Mladenov, N
EM: mladenov@colorado.edu
AF: University of Colorado, INSTAAR, 450 UCB, Boulder, CO 80309-0450 United States
AU: Murray-Hudson, M
EM: mmurray-hudson@mopipi.ub.bw
AF: Harry Oppenheimer Okavango Research Centre, Private Bag 285, Maun, 285 Botswana
AU: Mosepele, K
EM: kmosepele@mopipi.ub.bw
AF: Harry Oppenheimer Okavango Research Centre, Private Bag 285, Maun, 285 Botswana
AU: Lindholm, M
EM: markus.lindholm@bio.uio.no
AF: University of Oslo, Dept of Biology, Postboks 1066 Blindern, Oslo, 0316 Norway
AB: The Okavango Delta of Botswana is a pristine but threatened wetland that ranges in size from 15,000 - 28,000 km2. Previous research has shown that an annual flooding event exerts controls on the quantity and chemical quality of aquatic organic matter (OM) at the Delta scale. In permanently-inundated areas, the perennial water supply maintains low dissolved organic carbon (DOC) concentrations and more microbial sources of OM, as evidenced by low specific UV absorbance and high fluorescence index values. In seasonally-inundated areas, the annual flood causes a pulse of DOC (over 5 mg C/L) and a shift to vegetation-derived DOC, as a result of the inundation of vegetation and soils. Because seasonal floodplains, which encompass 10,000 - 12,000 km2 of the Okavango Delta, become productive grazing areas after the flood and because a dominant portion of fish biomass production takes place in seasonal floodplains, the productivity of these areas is significant for higher trophic levels. Planned water developments upstream of the Delta may shorten/flatten the hydrological pulse and impact the transport and mobilization of organic matter within the Delta. The impacts of reduced flows on extent and duration of flooding have been examined. However, the secondary effects on biological productivity have received less attention. We hypothesize that varying sources of OM, controlled by the hydrologic regime of the Delta, and OM transformations from bacterial and UV degradation exert an influence on floodplain productivity. This study presents results of leaching and photodegradation experiments and observations of changes in algal populations and floodplain standing stock to demonstrate important linkages between biological, ecological, and hydrological processes in the Okavango Delta. Our results support that the DOC that is mobilized by the flood supports heterotrophic microbial populations which, in turn, support the biological productivity of seasonal floodplains.
DE: 9305 Africa
DE: 4806 Carbon cycling
DE: 4817 Food chains
DE: 4852 Photochemistry
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting