Kaldy, J. E.. Texas A&M University, kaldy@nitro.tamu.edu
Eldridge, P. E.. US EPA, eldridge.peter@epamail.epa.gov
Cifuentes, L. A.. Texas A&M University, cifuente@ocean.tamu.edu

 
DOC RELEASE FROM THE SEAGRASS THALASSIA TESTUDINUM TO THE SEDIMENTS: INVERSE MODELING AND EXPERIMENTAL DATA
 
The seagrass Thalassia testudinum (Turtle grass) is the dominant macrophyte in southern Laguna Madre, TX accounting for about 90% of primary production. Using inverse modeling methods and field measurements of biomass and growth we developed a model of carbon and nitrogen flow through a Thalassia plant. The optimization model is a series of linear equations and inequality constraints which describe material flows between seagrass tissues and the environment. Model simulations indicate thatabout 60% (165 mMCm-2d-1) of the gross primary production (GPP) was allocated to above-ground tissues, 40% (123 mMCm-2d-1) to below-ground tissues, and 22% (63 mMCm-2d-1) was lost as DOC primarily to the pore waters. Tracer analysis (scaled to literature accumulation rates) indicates that 10% of 13C label should show up in the sediment pore water DOC after 10 days. We experimentally enriched the DIC in seagrass mesocosms to 1000 per mil and sampled porewater DOC after a 14 day incubation. Although quantification of the pore water DOC-13C signal is ongoing, preliminary data indicate an enrichment of at least 10 per mil and may be as high as 60 per mil. Experimental 13C enrichment supports the model predictions that 10% of GPP is released as DOC by below-ground tissues.
 
Day: Tuesday, Feb. 2
Time: 09:30 - 09:45am
Location: Eldorado Hotel
 
Code: CS56TU0930E