Evaluating the role of sediment‐bacteria interactions on Escherichia coli concentrations at beaches in southern Lake Michigan. Issue 12 (20th December 2013)

• Record Type: Journal Article
• Authors: Thupaki, Pramod; Phanikumar, Mantha S.; Schwab, David J.; Nevers, Meredith B.; Whitman, Richard L.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 12(2013:Dec.)
• Page Start: 7049
• Page End: 7065
• Publication Date: 2013-12-20
• Subjects: sediment‐bacteria interactions -- Escherichia coli -- beach safety; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2013JC008919
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract : [1] Association of bacteria with suspended sediment in the water column complicates the assessment and prediction of nearshore water quality. We examine the impact of sediment‐bacteria interactions on Escherichia coli (EC) levels at beaches in southern Lake Michigan using three‐dimensional EC fate and transport models with and without explicit descriptions of sediment‐bacteria interactions. We simulate hydrodynamics using a nested‐grid numerical model and use a semiparametric wave model to compute wave heights and net bottom shear stress. The attachment‐detachment dynamics of bacteria in the water column are modeled using a linear partition coefficient. The numerical models were tested against data, collected in summer 2008, which included measurements of EC at three beaches and multiple ADCP deployments for currents and waves. Our results indicate that the model that accounts for sediment‐bacteria interactions describes the observed data significantly better and that sediment, directly and indirectly, interacts with bacteria to influence their fate and transport. The improvement results from the model's ability to describe the multiple short‐duration, low‐intensity resuspension events at our sampling sites. A major resuspension event was noted during the simulation period but the sampling frequency during the event was inadequate to resolve the details of the peak. Using the linear isotherm model to simulate attachment‐detachment dynamics of bacteria in the water column, we found that the fraction of bacteria attached to suspended sediment particles in the water column is highly variable in the vertical at offshore locations but nearly constant closer to the shore. Key Points: The model with sediment‐bacteria interactions predicts EC levels better Attached fraction of bacteria is highly variable in the water column New model predicts higher mean and lower peak EC concentrations