Impacts of suspended sediment on the ecosystem in Lake Michigan: A comparison between the 1998 and 1999 plume events

Abstract

[1] The impact of a reflective, recurrent coastal resuspension plume on the lower trophic food web system in Lake Michigan was examined using a 3-D coupled physical and biological model. Numerical experiments were conducted for the March 1998 and 1999 plume events. The comparison between modeling results of these 2 years shows that the spatial distributions of the biological fields (i.e., phosphorus, phytoplankton, detritus, etc.) were closely coupled to the physical environment associated with wind-induced threedimensional circulation and mixing. The influence of suspended sediment plumes on the lake ecosystem was reflected in heterotrophic (secondary) production rather than in the autotrophic (primary) production. Nutrients were maintained through nutrient release from suspended sediments within the plume, while it was supplied by current advection and diffusion in the interior. The cross-shore flux of nutrients was driven by episodic wind events with a period of about 5-7 days. The flux was offshore during northerly winds and onshore during southerly winds. Comparisons between energy fluxes among biological variables suggest that the microbial loop (detritus-heterotrophic bacteria and microzooplankton) played an important role in the ecosystem dynamics during plume events. Bacteria were good competitors with phytoplankton for inorganic phosphorus and were also a key supporter for growth of microzooplankton inside and outside the plume. As a result, the lower food web system could be divided into two decoupled loops: (1) detritus-bacteria-microzooplankton-large zooplankton and (2) nutrient-phytoplanktondetritus.

Coastal Sediment Dynamics and River Discharge as Key Factors Influencing Coastal Ecosystem Productivity in Southeastern Lake Michigan

“…The RCP is an episodic event resulting from wind-driven sediment resuspension and transport in coastal waters (Chen et al, 2004). The feature has generally been observed to occur in late winter to early spring, which coincides with development of the spring diatom bloom.…”

“…The El Niño (Kerr, 1998;McPhaden, 1999), which was accompanied by reduced ice cover and strong winter storms with winds out of the north that generated large waves (Beletsky et al, 2003). A series of studies demonstrated that the resultant resuspension event that occurred in 1998 was accompanied by reduced light availability for photosynthesis (Chen et al, 2004;Lohrenz et al, 2004;Vanderploeg et al, 2007).…”

“…We summarize results from a combined approach using in situ optical measurements and remote sensing to characterize sediment distributions and properties during resuspension events, we track algal distributions, and we assess basin-scale temporal and spatial patterns in primary production. Our (Millie et al, 2003;Bergmann et al, 2004;Chen et al, 2004;Vanderploeg et al, 2007).…”

A science plan for carbon cycle research in North American coastal waters. Report of the Coastal CARbon Synthesis (CCARS) community workshop, August 19-21, 2014

“…These models range from historical water quality management models without physical dynamics (Chapra, 1977) to advanced three-dimensional physical models (Bai et al, 2013). Many threedimensional models are only presently set up for physical simulations, while others include biogeochemistry (Chen et al, 2004;Pauer et al, 2011) and carbon cycling (Bennington et al, 2012. Given the vast differences among the LGL, it is common that models are set up independently for each lake.…”

Three‐dimensional hydrodynamic and sediment transport modeling to test the sediment focusing hypothesis in upland lakes

“…FVCOM, an open-source 3D finite-volume model developed originally for ocean applications (Chen et al 2004(Chen et al , 2011, was used to represent the wind-driven circulation. The equations of mass, momentum, and temperature conservation, cast in a bottom following r-coordinate system, are given as:…”