Millie, D. USDA-ARS, dmillie@nola.srrc.usda.gov
Fahnenstiel, G. NOAA-GLERL, fahnenstiel@glerl.noaa.gov
Schofield, O. Rutgers University, oscar@ahab.rutgers.edu
Lohrenz, S. University of Southern Mississippi, slohrenz@usm.edu

 
IMPACT OF A RECCURENT SEDIMENT PLUME ON LAKE MICHIGAN PHYTOPLANKTON
 
A recurrent plume of resuspended silt- and clay-like particles occurs annually during the spring isothermal period within southern Lake Michigan. Although light availability has been hypothesized to regulate, in part, Lake Michigan phytoplankton, linkages between the plume and the spring diatom bloom are unknown. We are evaluating the impacts of the plume on the lake's phytoplankton and in situ water-column optics. Our intent was to assess the influence of light availability (see Lohrenz et al.) on phytoplankton biomass and associated rate processes. The plume appeared to alter the intensity and composition of the spring bloom; generally, values of total chlorophyll biomass values at stations severely impacted by the plume were slightly greater than values at less-impacted stations. Centric diatoms, particularly species of Cyclostephanos and Aulacoseira, constituted the greatest proportion of the assemblages and appeared to have greater light-harvesting ability (as determined by microphotometric techniques) than other common phytoplankton, possibly explaining their dominance during this episodic event. Although no great differences in bulk P-I parameters were observed, phytoplankton production appeared to be suppressed to a greater degree at nearshore stations severely impacted by the plume than at the less-impacted offshore stations.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS52TH0589S