Frost, P. C. Arizona State University, pcfrost@asu.edu
Elser, J. C. Arizona State University,
Turner, M. A. Freshwater Institute, mturner@mbnet.mb.ca

 
EFFECTS OF LIGHT, CARBON, AND PHOSPHORUS ON THE STOICHIOMETRY OF BENTHIC ALGAE GROWTH
 
Variation in algal elemental composition (C:N:P) is hypothesized to be related to the relative availability of light and nutrients (the light:nutrient hypothesis or LNH). Laboratory and field studies with phytoplankton have shown increased cellular carbon:phosphorus (C:P) ratios under high light, low phosphorus conditions. Although well-studied in planktonic algae, LNH remains untested in benthic environments such as littoral zones of lakes. An experiment conducted at the Experimental Lakes Area (ELA), in northwestern Ontario, Canada during summer 1998 used nutrient diffusing substrates to test the effects of light, inorganic carbon and phosphorus on benthic algal growth and elemental composition. Algae were collected and analyzed from clay pots enriched with phosphorus and inorganic carbon after incubation for four weeks under high and low light conditions. Decreased light led to lower algal biomass but enrichment did not affect algal biomass. Contrary to LNH, C:P ratios, indexed by AFDW:P, were highest under low light conditions while phosphorus and carbon treatments yielded no difference in algal C:P. These results are opposite of expectations based on LNH and suggest that additional factors specific to littoral ecosystems (e.g. constraints imposed by boundary layers) need to be considered in future studies of the ecological stoichiometry of benthic food webs.
 
Day: Wednesday, Feb. 3
Time: 02:00 - 02:15pm
Location: Sweeney Center
 
Code: SS49WE0200S