GSA Poster 2013 Denver - Johnny Wimpee
1
Using Thecamoebian Populations to Evaluate Historical Water Quality in Todds Lake in Murfreesboro, Tennessee Jesse C. Watts and Melissa Lobegeier Department of Geosciences, Middle Tennessee State University, Murfreesboro, TN, 37132 Abstract Study Area Acknowledgments Materials and methods Figure 2: Map of sediment collection sites in Todds Lake. Rutherford Blvd. is the road that cuts across the lake (Map by: Google Earth) Wetlands Estonoa Oxbow Lake Figure 1: View to the northwest of Todds Lake across Rutherford Blvd. Figure 4: A view of lily pads to the southeast toward the head waters of the lake Wetlands Estonoa Oxbow Lake We wish to thank Kathryn Tackett, Kyle Wiseman, Amy Gilley, Amanda Brown, Emily Silveira, Johnny Wimpee and Joyce Miller. Literature Cited Results Ogden, C.G., 1988, Fine structure of the shell wall in the soil testate amoeba Cyclopyxis kahli (Rhizopoda), Journal of Protozoology, 35, p. 537‐540. Water quality is and will continue to be an important environmental concern. Todds Lake is a small freshwater, artificial reservoir in Murfreesboro, Tennessee that was created in the 1930s by damming a wetland. Murfreesboro has experienced tremendous growth and rapid urbanization in the past decade with the population of the city increasing 50.5% from 2000 to 2010. Todds Lake is located in the Stones River Watershed and is fed by Black Fox Spring, which travels through several subdivisions receiving runoff from lawns and driveways before ending in Todds Lake. The lake is also surrounded by urban development such as additional subdivisions, a strip mall and a gas station and may be receiving runoff from those areas that could be negatively affecting the water quality within the lake. Thecamoebians are benthic testate amoebae that have been used in multiple studies in North America and Europe as indicators of pollution and water quality in lacustrine environments. Analysis of thecamoebian populations from sediment samples collected in Todds Lake in recent years indicates that the lake is a stressed eutrophic environment with low diversity assemblages and abundant Centropyxis aculeata observed in the samples. The shells of thecamoebians preserve easily so these organisms can yield historical data on water quality. The fossilization potential of thecamoebians gives them an advantage over other freshwater micro‐ and macroinvertebrates. This study will compare populations of thecamoebians from sediment samples in Todds Lake with those found in samples taken from a sediment core to determine if there have been changes in the ecological condition of the lake and wetland over the last century. Surface sediment samples and short cores were taken by hand at various sites and the locations were recorded with a GPS device. Each sample is sieved using 45 and 500 µm sieves. This process removes the large organic matter from the sample and the mud is separated from the thecamoebians. Once washed the sediment is preserved in isopropyl alcohol, and refrigerated. Using a microscope and a fine tipped brush, the thecamoebians are picked out of each sample and then placed onto a numbered slide. Two cores were collected. One was collected using a small‐diameter coring device and the other was collected using a universal coring device. Age dating using Pb‐210 isotopic dating will be completed in the next few months. The cores were sectioned in 1 cm slices and then washed in the same way as the sediment samples. Figure 5: Histograms of the relative abundance of thecamoebians species in surface samples Figure 3: Electron scanning microscope image of (1) Centropyxis aculeata “aculeata”, (2) Difflugia oblonga “tenuis”, (3) Difflugia corona, (4) Cyclopyxis kahli, (5) Difflugia oblonga “spinosa”, (6) Difflugia corona Todds Lake appears to be more negatively impacted closer to the busy Rutherford Boulevard. Sample KAT012, which is located closest to the road (Figs 1 and 2), shows an increase in the relative abundance of Centropyxis aculeata “aculeata” and Centropyxis aculeata “discoides” (Fig. 5). Centropyxids are environmental generalists that can tolerate intermediate to poor water quality environments. KAT001 and KAT003, located furthest from Rutherford Blvd., have absent to low relative abundances of centropyxids, suggesting a relative increase in water quality further away from the drainage coming from the road. 0 10 20 30 40 50 60 70 KAT001 0 10 20 30 40 50 60 70 KAT003 0 10 20 30 40 50 60 70 KAT008 0 10 20 30 40 50 60 70 KAT009 0 10 20 30 40 50 60 70 KAT010 0 10 20 30 40 50 60 70 KAT012 0 10 20 30 40 50 60 70 Todds 2-3cm 0 10 20 30 40 50 60 70 Todds 5-6cm 0 10 20 30 40 50 60 70 Todds 8-9cm Figure 6: Histograms of the relative abundance of thecamoebians species in core samples We found a high relative abundance of Cyclopyxis kahli in the Todds Lake core samples. Cyclopxis kahli is known to inhabit soils as well as fresh water environments (Ogden, 1988). The abundance of this species may show that soil erosion could have potentially introduced them into the lake. 0 10 20 30 40 50 60 70 REU22 2-3 cm 0 0.5 1 1.5 2 2.5 KAT001 KAT003 KAT008 KAT009 KAT010 KAT012 SDI J D 0 0.5 1 1.5 2 2.5 Todds 2-3 cm Todds 5-6 cm Todds 8-9 cm REU22 2-3 cm SDI J D Figure 7: Calculated values for the Shannon Diversity Index (SDI), Pielou’s equitability index (j) values and Margalef’s richness index (d) values for the surface samples and core samples The Shannon Diversity Indices for both the surface samples and core samples are between 2.13 and 0.92. Surface samples further from Rutherford Blvd., KAT001 and KAT003, have higher SDI values than the sample closest to the road, KAT012. This indicates that environmental impacts are greater closer to the road. 4
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Transcript of GSA Poster 2013 Denver - Johnny Wimpee
Using Thecamoebian Populations to Evaluate Historical Water Quality in Todds Lake in Murfreesboro, Tennessee
Jesse C. Watts and Melissa Lobegeier Department of Geosciences, Middle Tennessee State University, Murfreesboro, TN, 37132
Abstract Study Area
Acknowledgments
Materials and methods
Figure 2: Map of sediment collection sites in Todds Lake.Rutherford Blvd. is the road that cuts across the lake(Map by: Google Earth)
Wetlands Estonoa
Oxbow Lake
Figure 1: View to the northwest of Todds Lake acrossRutherford Blvd.
Figure 4: A view of lily pads to the southeast toward the head waters of the lake
Wetlands Estonoa
Oxbow Lake
We wish to thank Kathryn Tackett, Kyle Wiseman, Amy Gilley,Amanda Brown, Emily Silveira, Johnny Wimpee and JoyceMiller.
Literature Cited
Results
Ogden, C.G., 1988, Fine structure of the shell wall in the soiltestate amoeba Cyclopyxis kahli (Rhizopoda), Journal ofProtozoology, 35, p. 537‐540.
Water quality is and will continue to be an importantenvironmental concern. Todds Lake is a smallfreshwater, artificial reservoir in Murfreesboro,Tennessee that was created in the 1930s by damminga wetland. Murfreesboro has experienced tremendousgrowth and rapid urbanization in the past decadewith the population of the city increasing 50.5% from2000 to 2010. Todds Lake is located in the StonesRiver Watershed and is fed by Black Fox Spring, whichtravels through several subdivisions receiving runofffrom lawns and driveways before ending in ToddsLake. The lake is also surrounded by urbandevelopment such as additional subdivisions, a stripmall and a gas station and may be receiving runofffrom those areas that could be negatively affecting thewater quality within the lake. Thecamoebians arebenthic testate amoebae that have been used inmultiple studies in North America and Europe asindicators of pollution and water quality in lacustrineenvironments. Analysis of thecamoebian populationsfrom sediment samples collected in Todds Lake inrecent years indicates that the lake is a stressedeutrophic environment with low diversityassemblages and abundant Centropyxis aculeataobserved in the samples. The shells of thecamoebianspreserve easily so these organisms can yield historicaldata on water quality. The fossilization potential ofthecamoebians gives them an advantage over otherfreshwater micro‐ and macroinvertebrates. This studywill compare populations of thecamoebians fromsediment samples in Todds Lake with those found insamples taken from a sediment core to determine ifthere have been changes in the ecological condition ofthe lake and wetland over the last century.
Surface sediment samples and short cores were takenby hand at various sites and the locations wererecorded with a GPS device. Each sample is sievedusing 45 and 500 µm sieves. This process removes thelarge organic matter from the sample and the mud isseparated from the thecamoebians. Once washed thesediment is preserved in isopropyl alcohol, andrefrigerated. Using a microscope and a fine tippedbrush, the thecamoebians are picked out of eachsample and then placed onto a numbered slide.
Two cores were collected. One was collected using asmall‐diameter coring device and the other wascollected using a universal coring device. Age datingusing Pb‐210 isotopic dating will be completed in thenext few months. The cores were sectioned in 1 cmslices and then washed in the same way as thesediment samples.
Figure 5: Histograms of the relative abundance of thecamoebians speciesin surface samples
Figure 3: Electron scanning microscope image of (1) Centropyxisaculeata “aculeata”, (2) Difflugia oblonga “tenuis”, (3) Difflugia corona, (4) Cyclopyxis kahli, (5) Difflugia oblonga “spinosa”, (6) Difflugia corona
Todds Lake appears to be more negatively impactedcloser to the busy Rutherford Boulevard. SampleKAT012, which is located closest to the road (Figs 1and 2), shows an increase in the relative abundance ofCentropyxis aculeata “aculeata” and Centropyxisaculeata “discoides” (Fig. 5). Centropyxids areenvironmental generalists that can tolerateintermediate to poor water quality environments.KAT001 and KAT003, located furthest fromRutherford Blvd., have absent to low relativeabundances of centropyxids, suggesting a relativeincrease in water quality further away from thedrainage coming from the road.
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Figure 6: Histograms of the relative abundance of thecamoebians species in coresamples
We found a high relative abundance of Cyclopyxis kahli inthe Todds Lake core samples. Cyclopxis kahli is known toinhabit soils as well as fresh water environments (Ogden,1988). The abundance of this species may show that soilerosion could have potentially introduced them into thelake.
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Figure 7: Calculated values for the Shannon Diversity Index (SDI), Pielou’sequitability index (j) values and Margalef’s richness index (d) values for the surface samples and core samples
The Shannon Diversity Indices for both the surface samplesand core samples are between 2.13 and 0.92. Surfacesamples further from Rutherford Blvd., KAT001 andKAT003, have higher SDI values than the sample closest tothe road, KAT012. This indicates that environmentalimpacts are greater closer to the road.
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