Sediment Resuspension Dynamics in Canopy- and Meadow-Forming Submersed Macrophyte Communities
Abstract
We examined the impacts of macrophyte beds dominated by a canopy-forming (Myriophyllum sibiricum) and a meadow-forming (Chara) species on shear stress near the sediment interface and resuspension in the large (1,620 ha) and shallow (1.25 m) lake Cristina, Minnesota. The surface sediments in the vicinity of an adjacent M. sibiricum and Chara station, located in the northern region of the lake, exhibited a high moisture content (85 percent), low sediment density (0.2 g/mL), and high organic matter content (16 percent), indicative of fine-grained, flocculant sediment. The critical shear stress (tau sub-c) of these sediments, measured experimentally in the laboratory using a particle entrainment simulator, was low (1.4 dynes/cm2) and indicated a strong potential for resuspension at moderate wind speeds in the absence of submersed macrophytes. Between late July and September 1998, theoretical shear stress (tau), calculated using wind data, and wave theory (i.e., assuming no macrophyte biomass in the lake to obstruct wave activity) exceeded the experimentally derived sediment critical shear stress 16 percent of the time. However, in situ turbidity at both the canopy-forming M. sibiricum and meadow-forming Chara station was low and rarely increased when tau exceeded tau sub-c, indicating that both macrophyte beds reduced sediment resuspension in the lake. In situ shear stress, measured using calibrated gypsum spheres, was high near the open water lake surface during periods of high winds.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2000
- Accession Number
- ADA380814
Entities
People
- John W. Barko
- William F. James
Organizations
- Engineer Research and Development Center