Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Thursday, February 15, 2001, Time: 11:45:00 AM

Location: San Miguel

Bronk, D, A, College of William and Mary/VIMS, Gloucester Point, USA, bronk@vims.edu

Sanderson, M, P, College of William and Mary/VIMS, Gloucester Point, USA, mps@vims.edu

Koopmans, D, J, University of Georgia, Athens, USA, dirk@arches.uga.edu

CONTRIBUTION OF PHOTOCHEMICAL AMMONIFICATION TO PLANKTON NUTRITION IN TWO RIVERS, AND A COASTAL AND OPEN OCEAN ENVIRONMENT

Recent findings in aquatic systems suggest that photochemical processes can affect the release of labile nitrogen from dissolved organic matter. The degree that this process contributes to plankton nitrogen nutrition is unknown. We quantified rates of photochemical release of ammonium (i.e. photochemical ammonification) in three environments: the Savannah and Altamaha Rivers in Georgia (spring, summer, and fall), the South Atlantic Bight (SAB; summer), and the Eastern Tropical North Pacific (ETNP; summer), and compared them to rates of ammonium uptake measured in parallel with N15 techniques. Water from each site was filtered through a 0.2 micron Supor filter and incubated in quartz tubes using natural sunlight for 6 to 8hrs. Treatments included a light, dark, and light and dark plus poison. Photoproduction of ammonium was observed in 5 of 10 incubations in the rivers, 3 of 4 incubations in the SAB, and 10 of 13 incubations in the ETNP. When it was measurable, photochemical ammonification appeared to supply 18 +/- 19, 37 +/- 29, and 32 +/- 29% of the measured ammonium uptake in the Georgia rivers, SAB, and ETNP respectively.

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Aquatic Sciences Meeting, Albuquerque 2001

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