Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States
Field measurements of water quality in Iowa lakes contradict paleolimnological studies that used 210Pb dating techniques in 33 lakes to infer accelerating eutrophication and sediment accumulation in recent decades. We tested this hypothesis by analyzing a series of water quality measurements taken i...
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| Format: | Article |
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MDPI AG
2018-01-01
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| Series: | Geosciences |
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| Online Access: | http://www.mdpi.com/2076-3263/8/2/40 |
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| author | Roger W. Bachmann Mark V. Hoyer Daniel E. Canfield |
| author_facet | Roger W. Bachmann Mark V. Hoyer Daniel E. Canfield |
| author_sort | Roger W. Bachmann |
| collection | DOAJ |
| description | Field measurements of water quality in Iowa lakes contradict paleolimnological studies that used 210Pb dating techniques in 33 lakes to infer accelerating eutrophication and sediment accumulation in recent decades. We tested this hypothesis by analyzing a series of water quality measurements taken in 24 of these lakes during the period 1972–2010. There was little change in the trophic state variables. Total phosphorus and algal chlorophylls did not increase, and Secchi depths did not decrease with no evidence that the lakes had become more eutrophic. Changes in daily sediment loads in the Raccoon River also did not match the paleolimnological inferred rates of soil erosion for the period 1905–2005, and an independent estimate of soil erosion rates showed a decline of 40% in the 1977 to 2012 period rather than an increase. We hypothesized that sediment mixing by benthivorous fish could be responsible for violating the basic assumption of 210Pb sediment dating that the sediments are not disturbed once they are laid down. We developed a mathematical model that demonstrated that sediment mixing could lead to false inferences about sediment dates and sediment burial rates. This study raises the possibility that sediment mixing in Iowa lakes and similar shallow, eutrophic lakes with benthivorous fish may cause significant sediment mixing that can compromise dating using 210Pb dating of sediment cores. |
| first_indexed | 2024-12-12T01:27:13Z |
| format | Article |
| id | doaj.art-8031315f66e24b5189931b1901f551c5 |
| institution | Directory Open Access Journal |
| issn | 2076-3263 |
| language | English |
| last_indexed | 2024-12-12T01:27:13Z |
| publishDate | 2018-01-01 |
| publisher | MDPI AG |
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| series | Geosciences |
| spelling | doaj.art-8031315f66e24b5189931b1901f551c52022-12-22T00:43:04ZengMDPI AGGeosciences2076-32632018-01-01824010.3390/geosciences8020040geosciences8020040Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United StatesRoger W. Bachmann0Mark V. Hoyer1Daniel E. Canfield2School of Forest Resources and Conservation, University of Florida, Gainesville, FL 32611, USASchool of Forest Resources and Conservation, University of Florida, Gainesville, FL 32611, USASchool of Forest Resources and Conservation, University of Florida, Gainesville, FL 32611, USAField measurements of water quality in Iowa lakes contradict paleolimnological studies that used 210Pb dating techniques in 33 lakes to infer accelerating eutrophication and sediment accumulation in recent decades. We tested this hypothesis by analyzing a series of water quality measurements taken in 24 of these lakes during the period 1972–2010. There was little change in the trophic state variables. Total phosphorus and algal chlorophylls did not increase, and Secchi depths did not decrease with no evidence that the lakes had become more eutrophic. Changes in daily sediment loads in the Raccoon River also did not match the paleolimnological inferred rates of soil erosion for the period 1905–2005, and an independent estimate of soil erosion rates showed a decline of 40% in the 1977 to 2012 period rather than an increase. We hypothesized that sediment mixing by benthivorous fish could be responsible for violating the basic assumption of 210Pb sediment dating that the sediments are not disturbed once they are laid down. We developed a mathematical model that demonstrated that sediment mixing could lead to false inferences about sediment dates and sediment burial rates. This study raises the possibility that sediment mixing in Iowa lakes and similar shallow, eutrophic lakes with benthivorous fish may cause significant sediment mixing that can compromise dating using 210Pb dating of sediment cores.http://www.mdpi.com/2076-3263/8/2/40210Pb datingpaleolimnologyeutrophicationcarbon burialbioturbationsediment mixingdiatom-inferred phosphorus |
| spellingShingle | Roger W. Bachmann Mark V. Hoyer Daniel E. Canfield Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States Geosciences 210Pb dating paleolimnology eutrophication carbon burial bioturbation sediment mixing diatom-inferred phosphorus |
| title | Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States |
| title_full | Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States |
| title_fullStr | Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States |
| title_full_unstemmed | Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States |
| title_short | Possible Sediment Mixing and the Disparity between Field Measurements and Paleolimnological Inferences in Shallow Iowa Lakes in the Midwestern United States |
| title_sort | possible sediment mixing and the disparity between field measurements and paleolimnological inferences in shallow iowa lakes in the midwestern united states |
| topic | 210Pb dating paleolimnology eutrophication carbon burial bioturbation sediment mixing diatom-inferred phosphorus |
| url | http://www.mdpi.com/2076-3263/8/2/40 |
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