HR: 1340h
AN: H13F-1382    [Abstracts]
TI: Is There Biogeochemical and Stable Isotopic Evidence of Canal Water Intrusion in the A.R.M. Loxahatchee National Wildlife Refuge?
AU: * Chang, C C
EM: ccchang@usgs.gov
AF: U.S. Geological Survey, Mailstop 434 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Kendall, C
EM: ckendall@usgs.gov
AF: U.S. Geological Survey, Mailstop 434 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: McCormick, P
EM: pmccormick@usgs.gov
AF: U.S. Geological Survey, Leetown Science Center, Kearneysville, WV 25430 United States
AU: Wankel, S
EM: sdwankel@usgs.gov
AF: U.S. Geological Survey, Mailstop 434 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Doctor, D
EM: dhdoctor@usgs.gov
AF: U.S. Geological Survey, Mailstop 434 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Elliiott, E
EM: eelliott@usgs.gov
AF: U.S. Geological Survey, Mailstop 434 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Newman, S
EM: snewman@sfwmd.gov
AF: South Florida Water Management District, PO Box 24680, West Palm Beach, FL 33416 United States
AB: Water, soil, plants and algae were collected in February 2004 from 130 sites in the Loxahatchee Refuge to investigate the effects of canal-water intrusion on the wetlands. Conductivity, temperature, alkalinity, and pH were measured in the field. Waters were analyzed for d18O and sediment, algae, particulate organic matter (POM) and macrophytes were analyzed for d13C and, d15N. This study was undertaken because of concerns that changes in water management strategies associated with the Everglades restoration may increase the extent of canal-water intrusion into the Refuge. Historically, rain was the predominant water source in the Refuge. However, water flow in the Everglades is now heavily managed and canal water with high nutrient concentrations from agricultural areas now enters the refuge. Though canal water can be released into the Refuge from specific structures, flow into the Refuge can be diffuse and enter from anywhere. There is substantially more flow down the western canal than the eastern one, and areas farther south are more susceptible to canal flows since elevation in the Refuge decreases from north to south. Data from the Loxahatchee Refuge indicate that d15N and C:N ratios are more variable than d13C (ca. -26 to -28 per mil). For instance, the averages and ranges for d15N were: cattails (-0.05), sawgrass ( +0.34), floc (+0.35), metaphyton (+0.74), sediment (+1.23), and POM (+2.76). The C:N ratios fell into three groups: sawgrass and cattail (59 and 40), metaphyton and sediment (ca. 20), and floc and POM (14 and 12). In an earlier collaboration with the USEPA-REMAP program, isotopes were used to elucidate food web relations and biogeochemical trends at several hundred sites across the Everglades. These studies showed that biota from the interior of the Refuge had higher d13C but lower d15N values than sites near the canals. Results of this more spatially intensive study in the Refuge will provide a more detailed investigation of the usefulness of isotopic techniques for identifying effects of canals on local biogeochemistry.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0496 Water quality
DE: 0497 Wetlands (1890)
SC: Hydrology [H]
MN: Fall Meeting 2005