Twiner, M. J. University of Western Ontario, mtwiner@julian.uwo.ca
Trick, C. J. University of Western Ontario, cyano@julian.uwo.ca

 
NUTRITIONAL CONTROL OF GROWTH AND TOXICITY OF THE COASTAL RAPHIDOPHYTE, HETEROSIGMA SP.
 
The unicellular marine Raphidophyte, Heterosigma sp. is associated with coastal fish kills in Japan, New Zealand and in Canada. This phytoplankter is common in many coastal waters but is reported to be toxic in specific geological areas. Formation of Heterosigma blooms has been linked to excess flux of nutrient input, such as iron and organic nitrogen, as well has physical conditions of light and temperature. While the exact mechanism of toxicity is unknown, the production of the reactive oxygen species (ROS = superoxide and hydrogen peroxide) have been implicated. To elucidate the toxicity of Heterosigma, the environmental regulation of ROS production by eight isolates of Heterosigma was investigated. Hydrogen peroxide production among the isolates was highly variable, but isolate specific. Ambient levels of hydrogen peroxide are a product of both production and consumption, the latter of which is primarily controlled by cellular catalases. Rates of production were determined using a modified fluorometric assay, where production was elevated over 20-fold in the presence of a catalase inhibitor. The role of iron as a regulator of hydrogen peroxide production will be used to illustrate the balance between photo-induced hydrogen peroxide production and the attenuation of produced hydrogen peroxide by cell associated catalases.
 
Day: Friday, Feb. 5
Time: 12:00 - 12:15pm
Location: Eldorado Hotel
 
Code: SS42FR1200E