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Daniel Conley

Daniel Conley

Professor

Daniel Conley

Changes in amorphous silica sequestration with eutrophication of riverine impoundments

Author

  • Laura D. Triplett
  • Daniel R. Engstrom
  • Daniel Conley

Summary, in English

The effect of eutrophication on particulate amorphous silica (ASi) sequestration was isolated and quantified in Lake St. Croix and Lake Pepin, two natural, human-impacted impoundments of the upper Mississippi River. In contrast to impoundments behind engineered dams, where silica (Si) fluxes may be changed by various aspects of dam construction, these two riverine lakes have long (9,000+ years) sedimentary sequences that record the entire span of cultural eutrophication and the resulting silica sequestration. The concentrations of dissolved silicate (DSi) and ASi in the lake inflows were measured for 1 year to obtain the total flux of bioavailable silica (TSib = DSi + ASi) to each impoundment. Historical rates of Si sequestration in each lake were determined using ASi burial in multiple sediment cores and modeled estimates of historical TSib fluxes. The Si trapping efficiency of each lake was found to have increased exponentially with cultural eutrophication (estimated two- to fivefold increase in Lake St. Croix and 9- to 16-fold increase in Lake Pepin over the last 100 years), indicating the degree to which eutrophication of impoundments can reduce silica export to downstream coastal and marine ecosystems. Because these two lakes presently exhibit different degrees of eutrophication, together they depict a relationship between phosphorus concentration and Si trapping efficiency that may be applied to other impoundments, including human-made reservoirs.

Department/s

  • Quaternary Sciences
  • BECC: Biodiversity and Ecosystem services in a Changing Climate

Publishing year

2012

Language

English

Pages

413-427

Publication/Series

Biogeochemistry

Volume

108

Issue

1-3

Document type

Journal article

Publisher

Springer

Topic

  • Geology

Keywords

  • Biogenic silica
  • Trapping efficiency
  • Mississippi River
  • Eutrophication
  • Riverine lake

Status

Published

ISBN/ISSN/Other

  • ISSN: 1573-515X