Sediment deposition and sources into a Mississippi River floodplain lake; Catahoula Lake, Louisiana

Floodplain lakes are important wetlands on many lowland floodplains of the world but depressional floodplain lakes are rare in the Mississippi River Alluvial Valley. One of the largest is Catahoula Lake, which has existed with seasonally fluctuating water levels for several thousand years but is now in an increasingly hydrologically altered floodplain. Woody vegetation has been encroaching into the lake bed and the rate of this expansion has increased since major human hydrologic modifications, such as channelization, levee construction, and dredging for improvement of navigation, but it remains unknown what role those modifications may have played in altering lake sedimentation processes. Profiles of thirteen ¹³⁷Cs sediment cores indicate sedimentation has been about 0.26 cm y^− 1 over the past 60 years and has been near this rate since land use changes began about 200 years ago (²¹⁰Pb, and ¹⁴C in Tedford, 2009). Carbon sequestration was low (10.4 g m^− 2 y^− 1), likely because annual drying promotes mineralization and export. Elemental composition (high Zr and Ti and low Ca and K) and low pH of recent (