CS29 Phytoplankton & Primary Production
Date: Monday, June 10, 2002
Time: 3:45:00 PM
Location: Oak Bay
 
RobertsBJ, Cornell University, Ithaca, USA, bjr11@cornell.edu
Howarth, R, W, Marine Biological Laboratory, Woods Hole, USA, rwh2@cornell.edu
 
INTERACTION OF NUTRIENT AND LIGHT AVAILABILITY AS REGULATORS OF DIEL PATTERNS IN RESPIRATION IN PELAGIC ECOSYSTEMS: AN EXAMINATION USING OXYGEN STABLE ISOTOPES
image
In order to fully understand the functioning of an aquatic ecosystem, it is essential to accurately estimate not only NEP, but also GPP and respiration. By examining changes in both 16-O and 18-O pools of dissolved O2 over time, daytime rates of R can be directly quantified and consequently gross rates of photosynthesis and ecosystem respiration can be more accurately calculated. In this study, the roles of nutrients and light in influencing the day:night ratio of R were assessed. Four replicate microcosm tanks of six treatments were used in a three by two factorial design (one saturating and two limiting light levels by mesotrophic and eutrophic nutrient conditions). Rates of GPP and R, as well as N and P chemistry and chlorophyll a concentration were monitored throughout the 8-day experiment. On day 8, samples were collected for 16-O and 18-O to quantify daytime respiration rates. Nutrient level, irradiance level, and the interaction of the two factors resulted in significant differences in SRP, chlorophyll a, as well as ecosystem rates of daytime R, GPP and ER in freshwater pelagic microcosms.