Sunda, W. G.. Beaufort Laboratory, NOAA, bsunda@hatteras.bea.nmfs.gov
Huntsman, S. G.. Beaufort Laboratory, NOAA, shuntsman@hatteras.bea.nmfs.gov

 
INTERACTIVE EFFECTS OF METAL ION CONCENTRATION AND LIGHT ON THE ACCUMULATION AND UTILIZATON OF IRON, MANGANESE AND ZINC IN A COASTAL DIATOM
 
Iron, manganese and zinc are all required for photosynthetic carbon fixation: Fe and Mn are integral components of metalloproteins involved in photosynthetic electron transport, and are thus directly needed to support the light reactions of photosynthesis, while Zn is present in carbonic anhydrase, needed for the supply of inorganic carbon to the Calvin cycle in the dark reactions of photosynthesis. In experiments with the diatom Thalassiosira pseudonana, decreases in light intensity increased the amount of cellular Fe or Mn needed to support a given growth rate and maximum growth rate. As a result, cells that were light-limited were more likely to be Fe- or Mn-limited and vise versa. Zinc requirement for growth, by contrast, was largely independent of light intensity, and consequently, decreases in photosynthetic carbon fixation rate at low light resulted in decreased cellular requirement for zinc. Thus, in contrast to Fe and Mn, cells that were limited by light were less likely to be Zn-limited. Light limitation of growth rate had no effect on uptake rates of Mn and Fe, but increased cellular Mn and Fe concentrations due to the fact that cellular metal at steady-state equals the cellular metal uptake rate divided by the growth rate. Similiar behavior was observed for zinc, but only at very low Zn ion levels, where zinc was limiting or near limiting under both high and low light. As a result of the differential light interactions, Fe and Mn are more likely to be limiting under low light conditions at the botom of the euphotic zone or within deep mixed layers, while Zn should show the opposite behavior.
 
Day: Thursday, Feb. 4
Time: 04:30 - 04:45pm
Location: Sweeney Center
 
Code: SS28TH0430S