Aquatic Sciences Meeting, Albuquerque 2001

SS01 Submerged Aquatic Vegetation and the Water Column (Environmental Connections)

Date: Tuesday, February 13, 2001, Time: 2:30:00 PM

Location: Galisteo

Kaldy, J, E, TAMU Oceanography, College Station, USA, Kaldy@nitro.tamu.edu

Cifuentes, L, A, TAMU Oceanography, College Station, USA, cifuentes@ocean.tamu.edu

Eldridge, P, M, US EPA, Coastal Ecology Branch, Newport, USA, eldridge.pete@epamail.epa.gov

Jones, W, B, TAMU Oceanography, College Station, USA, bjones@ocean.tamu.edu

Use of sediment porewater delta 13C-DOC Isotopes to validate predictions of inverse model analysis: mesocosm experiments and method development.

A model was developed to simulate the flow of a carbon tracer through a seagrass community and examine the role of these plants (seagrass, phytoplankton, microphytobenthos) in diagenetic processes. Model simulations suggest that Thalassia testudinum (Turtlegrass) excretes about 10% of net primary production as dissolved organic carbon (DOC) into root zone porewater. To test model predictions, we conducted a mesocosm experiment where the water column delta 13C dissolved inorganic carbon (DIC) was enriched to 5000 per mil. The tracer was followed through the system: from DIC to plants to pore-water DOC to bacteria. To analyze the DOC isotope ratio we coupled a Shimadzu TOC analyzer via cryofocusing traps to a GC-c-IRMS. Carbon dioxide was trapped from the TOC effluent and introduced directly to the GC-c-IRMS. Laboratory standards of known isotopic composition were used to validate the method. Phospholipid fatty acids (PLFA’s) were used as a bacterial biomarker to determine the incorporation of 13C into bacterial biomass. The enrichment experiment was used to validate model predictions about the importance of various producers to carbon dynamics.

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Aquatic Sciences Meeting, Albuquerque 2001

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