McKay, R. M. Bowling Green State University, rmmckay@bgnet.bgsu.edu
Urban, N. M. Michigan Technological University, nurban@mtu.edu
Green, S. A. Michigan Technological University, sgreen@mtu.edu

 
IN SITU IMMUNOLOGICAL ASSESSMENT OF PHYTOPLANKTON FE DEFICIENCY IN WATERS OFF THE KEWEENAW PENINSULA, LAKE SUPERIOR
 
Low availability of Fe is believed to constrain phytoplankton growth over vast regions of the world oceans. In contrast, Fe deficiency is rarely invoked in freshwater systems. Rather, limitation by phosphate remains a central tenet of modern day limnology. Several recent lines of evidence, however, call into question the universality of P limitation in the Laurentian Great Lakes. Notably, results of recent bottle assays lend support to the concept of Fe deficiency in the Great Lakes. Here we report on preliminary field assessment of phytoplankton Fe deficiency in Lake Superior using in situ immunological probes for flavodoxin and ferredoxin. Under conditions of Fe deficit, ferredoxin is replaced by flavodoxin as a redox catalyst in cyanobacteria and microalgae. As a result, accumulation of flavodoxin can be used to assess phytoplankton Fe deficiency. Sampling was performed in conjunction with the KITES project at stations located off the Keweenaw Peninsula during cruises in May and July, 1998. Phytoplankton biomass sampled from nearshore and offshore stations occupied during each cruise was flash frozen and total protein was resolved by SDS-PAGE and assayed by Western immunodetection. Flavodoxin was detected amongst diatoms sampled by vertical net tow with a gradient in flavodoxin accumulation evident between nearshore and offshore stations. Flavodoxin was not detected amongst surface water assemblages in May or July nor was it detected following macronutrient amendment of offshore waters performed during the July cruise. Our in situ immunological assessment will be discussed with respect to unique physical properties associated with the shore-parallel Keweenaw current.
 
Day: Thursday, Feb. 4
Time: 02:00 - 02:15pm
Location: Sweeney Center
 
Code: SS28TH0200S