Aquatic Sciences Meeting, Albuquerque 2001

PC17 Phytoplankton Physiology and Ecology

Date: Thursday, February 15, 2001

Location: Southwest Hall

Roberts, B, J, Cornell University, Ithaca, USA, bjr11@cornell.edu

Howarth, R, W, Environmental Defense, Boston, USA, rwh2@cornell.edu

INTERACTION OF NUTRIENT AND LIGHT AVAILABILITY AS REGULATORS OF PRIMARY PRODUCTION IN FRESHWATER PELAGIC ECOSYSTEMS: A PRELIMINARY EXAMINATION

Autotrophs require both nutrients and light for growth. While considerable emphasis has been placed on assessing the role of nutrients or light in limiting aquatic photosynthesis, much less attention has been focused on the interaction of light and nutrients as limiting resources. In this study, 24 20-liter microcosm tanks were filled with water from oligotrophic Skaneateles Lake. Tanks were exposed to a 14:10 hour day:night cycle and a constant temperature in a growth chamber. Four replicate tanks of six treatments were used in a three by two factorial design. One saturating and two limiting light levels were created by differential layering of shade cloth. Two nutrient levels (mesotrophic and eutrophic conditions) were obtained by different daily additions of nitrogen and phosphorus at a 25:1 ratio. Rates of GPP and respiration were measured using the diel O2 method and samples were collected for nitrogen and phosphorus chemistry as well as chlorophyll a concentration throughout the ten-day experiment. On day 10, samples were collected for isotopic composition of dissolved O2 to quantify daytime respiration rates and these results may be presented.

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Aquatic Sciences Meeting, Albuquerque 2001

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