Kresge, K. G.. Lehigh University, kgk4@lehigh.edu
Morris, D. G.. Lehigh University, dpm2@lehigh.edu

 
BACTERIA, UVR, AND DOC: A COMPLEX INTERACTION IN FRESHWATER LAKES
 
Solar ultraviolet radiation (UVR) may affect DOC availability and bacterial metabolism, thus influencing the flow of energy through the aquatic food web. UVR may stimulate bacterial activity by liberating labile substrates through photooxidation of DOC. UVR may also inhibit activity by direct damage or through formation of secondary products such as radicals and super-oxides. In freshwater ecosystems, the direct detrimental effects of UVR may also be mitigated by DOC, which strongly absorbs UVR. In order to unravel the complicated interaction between UVR, DOC, and bacterioplankton, we conducted experiments on two lakes in NE Pennsylvania. Bacterioplankton from the lakes and DOC from a variety of sources were exposed to natural sunlight which was modified using a combination of optical filters and water column attenuation in situ. This varied both the flux and spectral characteristics of UVR across the solar spectrum. The effects of UVR were assessed by measuring bacterioplankton productivity, cell counts, and extracellular enzyme activity. Preliminary results suggest that bacterial activity, as assessed by these parameters, varied substantially with respect to both spectral composition of light and DOC quality. Thus, DOC quality as well as quantity play an important role in determining the response of the microbial loop to UVR.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS33TH0442S