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2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 180-12
Presentation Time: 11:30 AM

A PALEOLIMNOLOGICAL STUDY OF THE STRANGE CASE OF LONG POND (GA, USA) : HIGH PHOSPHORUS INPUTS WITH A LACK OF EUTROPHICATION


TIDWELL, Chris, Geosciences, Georgia State University, 24 Peachtree Ave NE, Room 340, Atlanta, GA 30303, WATERS, Matthew, Department of Biology, Valdosta State University, Valdosta, GA 31698, DEOCAMPO, Daniel M., Geosciences, Georgia State University, 24 Peachtree Center Avenue Northeast, Atlanta, GA 30303 and KABENGI, Nadine, Department of Geosciences, Georgia State University, 24 Peachtree Center Avenue, Kell Hall, Atlanta, GA 30303, ctidwell1@student.gsu.edu

Eutrophication is an unwanted consequence of anthropogenic disturbance that poses a serious threat to fresh water systems. This study focuses on a 500cm sediment core of Long Pond, a sinkhole lake in South Georgia, which does not exhibit any evidence of eutrophication despite high concentrations of phosphorus (P) (> 3000 mg-1. L P) measured in the upper parts of its cored sediments. Chemical analyses have shown a strong correlation (r2>0.99) between P and aluminum (Al) throughout the 500cm core, suggesting the presence of an aluminophosphate phase potentially inhibiting eutrophication in the lake.

Evidence of abundant algae, phytoplankton, and diatoms in the lower depths of the core (500-300cm) suggests eutrophication was not prominent in most of the lake’s history. The absence of eutrophication still holds, despite a steady increase of the P concentrations in the upper sediments of the core (suggesting an influx of P from modern farming practices) to levels which would normally result in an increase of eutrophication markers.

The purpose of this study is to ascertain the nature of the correlation between P and Al as well as its origin and potential role as a detrital signal through the history of the lake sediment. To that purpose, the mineralogical profile of the lake sediments, as well as the mineralogical profile of surrounding sediments feeding into the lake, will be combined with paleo pH-proxies to provide a paleolimnological analysis of the lake. Preliminary XRD analysis of sediments collected throughout the core have indicated a typical mineralogy for the area, which is mostly dominated by quartz, along with minerals containing Fe, Mg, Mn, Ti, and Zn. Further XRD analysis of the clay fraction of samples will be conducted to determine the presence and nature of an aluminophosphate phase and examine its diagenesis. Findings from this work will elucidate the relationship between the P and Al in Long Pond and help explain the lack of eutrophication. These findings could be useful in preventing eutrophication in areas where human activities increase the runoff of P into the fragile ecosystems of lakes and ponds.

Session No. 180

T49. Mechanistic Insights into the Biogeochemical Processes Controlling Phosphorus Transport and Cycling
Tuesday, 3 November 2015: 8:00 AM-12:00 PM
Room 343 (Baltimore Convention Center)
Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.462
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