Auer, M. T.. Michigan Technological University, mtauer@mtu.edu
Snopek, M. T.. Michigan Technological University, mlsnopek@mtu.edu
Elenbaas, K. D.. Michigan Technological University, kdelenba@mtu.edu

 
GRADIENTS IN BACTERIOPLANKTON STANDING CROP, COMMUNITY STRUCTURE AND PRODUCTION IN LAKE SUPERIOR IN RELATION TO THE THERMAL BAR
 
Gradients in bacterioplankton (BP) standing crop, community structure, and productivity in Lake Superior were made in the presence of a well-developed thermal bar (T = 4-9C). Thermal fronts are known to influence the rate and extent of cross-margin transport in lakes and oceans, potentially influencing nutrient and temperature regimes. Samples were collected in late May along three 30-km transects originating at Ontonagon (ON), Houghton (HN), and Eagle Harbor (EH). Bacterioplankton abundance (BP, direct counts) was greatest at the HN transect, with nearshore levels exceeding those of ON and EH sites by 2-3 orders of magnitude. A significant (2 order of magnitude) gradient in BP abundance was noted with distance offshore at HN, however little difference was evident along the ON or EH transects. BP production (thymidine incorporation) was also greatest in the HN nearshore, exceeding ON and EH levels by a factor of five. A significant onshore-offshore gradient in BP production was noted at HN as well. BP community structure (sole carbon source utilization patterns; BIOLOG), displayed significant differences both within and among transects. These findings demonstrate the existence of clear and substantial differences in BP distribution and activity which may reflect mediation of cross-margin transport by the thermal bar.
 
Day: Thursday, Feb. 4
Time: 03:30 - 03:45pm
Location: Eldorado Hotel
 
Code: SS52TH0330E