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: 10:45:00 AM

Location: San Miguel

Kieber, D, J, State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210, USA, djkieber@syr.edu

Mopper, K, , Washington State University, Pullman, WA 99164, USA, mopper@wsu.edu

Qian, J, , Washington State University, Pullman, WA 99164, USA,

Zafiriou, O, C, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA, ozafiriou@whoi.edu

PHOTOCHEMICAL FORMATION OF DISSOLVED INORGANIC CARBON IN SEAWATER AND ITS IMPACT ON THE MARINE CARBON CYCLE

Photochemical remineralization of dissolved organic matter (DOM) in seawater can occur both directly through the photochemical formation of dissolved inorganic carbon (DIC) and indirectly through coupled photochemical and biological pathways. We determined photochemical production rates of DIC at inshore, coastal and oligotrophic stations in the Northwest Atlantic Ocean. DIC production rates ranged from approximately 20 nM/hr in surface, oligotrophic seawater to over 100 nM/hr in coastal seawater. Corresponding rates of CO photoproduction ranged from 1-5 nM/hr. Sparging with helium had very little effect on DIC production compared to air-saturated samples, suggesting that DIC production is primarily due to the direct cleavage of DOM and does not involve dissolved oxygen. Based on observed CO and DIC photoproduction rates, from 0.2-1.5% of DOC is directly remineralized daily, yielding a photochemical half-life for DOC in surface seawater of 46-347 days. Half-life estimates are further reduced when photochemically enhanced microbial utilization of substrates is considered. Photochemical remineralization rates were 4-8% of rates of primary productivity. Our initial results indicate that abiotic photochemical remineralization is an important carbon flux in the oceans.

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Aquatic Sciences Meeting, Albuquerque 2001

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