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Biogeochemical processes in land-ocean interfaces, surface estuaries, subterranean estuaries and sediment-water interface
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Impacts of watershed hydrologic modification on freshwater drainage and productivity in small estuaries: Example from three small sub-tropical estuaries, SW Florida, USA
P-C2-15
Eliot Atekwana* , Department of Geological Sciences, 101 Penny Hall, University of Delaware, Newark, DE 19716, USA
Lenore P. Tedesco, The Wetlands Institute, 1075 Stone Harbor Boulevard, Stone Harbor, NJ 08247-1424, USA
Presenter Email: eatekwan@udel.edu |
| Small estuaries are sensitive to anthropogenic hydrologic alterations of their watersheds, yet such alterations on hydrologic mixing, productivity and carbon cycling are not often assessed. We measured axial variations in physical, chemical and stable oxygen and carbon isotopes of water from three small sub-tropical estuaries in southwest Florida, USA, to assess the effects of variable anthropogenic watershed modification on freshwater drainage, hydrologic mixing and productivity. The Blackwater River estuary is pristine and receives freshwater drainage as sheet flow and groundwater. Anthropogenic alteration of Faka Union's watershed included extensively canalling with focus freshwater discharge to the estuary via a weir. Anthropogenic alteration of the Henderson Creek watershed is from residential and agricultural activities and water is drained by a canalled system and with water from the watershed periodically released into the estuary via a weir. The watershed alterations are such that water the head of Faka Union was severely freshened and that of Henderson Creek was saline compared to head of Blackwater River estuary. The stable oxygen isotope-salinity relationship indicates a two component mixing with identical stable oxygen isotope freshwater endmember for all three estuaries. The dissolved inorganic carbon (DIC) concentrations which were ~50% higher in the head of Faka Union and Henderson Creek than Blackwater River and the DIC concentrations decreased with increase in the stable carbon isotopes of DIC to the estuary mouths. Higher DIC concentrations were concomitant with higher dissolved oxygen (DO) concentrations in the Faka Union indicating photosynthetic driven productivity, while in Henderson Creek, higher DIC concentrations with lower DO concentrations is driven by water column respiration. We conclude that anthropogenic alteration of freshwater drainage pathways into small estuaries result in markedly different salinity regimes, productivity and carbon cycling. |
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