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A sediment record of trophic state change in an Arkansas (USA) reservoir |
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| Authors: | Byron Winston Sonja Hausmann Jaime Escobar William F Kenney |
| Institution: | 1. Department of Crop, Soil and Environmental Sciences, University of Arkansas, 114 Plant Sciences Building, Fayetteville, AR, 72701, USA 2. Academy of Natural Sciences of Drexel University, 1900 Benjamin Franklin Parkway, Philadelphia, PA, 19103, USA 3. Departamento de Ingeniería Civil y Ambiental, Universidad del Norte, Km 5 Via Puerto Colombia, Barranquilla, Colombia 4. Center for Tropical Paleoecology and Archaeology, Smithsonian Tropical Research Institute (STRI), Panama City, Panama 5. Land Use and Environmental Change Institute, University of Florida, Gainesville, FL, 32611, USA |
| Abstract: | Reservoir sediments are used cautiously in paleolimnological studies because of dating uncertainties, possible sediment disturbances and even concerns that indicators of trophic status may behave differently in reservoirs as opposed to natural lakes. We measured loss on ignition (LOI), carbon to nitrogen ratio (C:N), diatom abundance, total nitrogen (TN), total phosphorus (TP), TN:TP ratio, and carbon and nitrogen isotopes (δ13C and δ15N) in an 83-cm sediment core to track recent trophic status changes in Beaver Reservoir, Northwest Arkansas, USA. Measurements showed that LOI, TN, TP and diatom abundance increased significantly from the bottom to the top of the core (p < 0.001). The C:N ratio and δ13C indicated a predominantly algal source for organic matter in the sediments. Increases in TN and TP were positively correlated with human population growth (p < 0.01) and the TN:TP ratio recorded a shift from phosphorus to nitrogen limitation around 1990. This shift may have encouraged cyanobacterial growth that caused episodes of taste and odor problems in the reservoir. This study suggests that despite concerns about sediment dating and disturbance, reservoir sediments can provide valuable information on past water quality changes. |
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