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SULFUR CYCLING IN THALASSIA TESTUDINUM SEAGRASS BED SEDIMENTS
Citation:
Yates, D F., R L. Quarles, AND J Rivord. SULFUR CYCLING IN THALASSIA TESTUDINUM SEAGRASS BED SEDIMENTS. Presented at SWS/GERS Joint Society Meeting, Pensacola Beach, FL, March 30 - April 02, 2005.
Impact/Purpose:
Conference presentation
Description:
Quarles, Robert L., Jessica A. Rivord and Richard Devereux. In press. Sulfur Cycling in Thalassia testudinum Seagrass Bed Sediments (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems of the Gulf of Mexico and Southeastern United States, 6-9 October 2004, Pensacola Beach, FL. (ERL,GB R1025).
Sulfate reduction rates (SRR) were determined in two Santa Rosa Sound (N.W. Florida) T. testudinum seagrass beds in two successive years. Triplicate sediment cores were taken at six week intervals from three stations in progressively deeper water (approximating 1, 1.5, and 3 m), and thus having progressively less light available at the seagrass canopy. In 2002, depth integrated SRR (diSRR), were highest in June and July (maximum of 306 mmoles/m2/d), and significantly lower in September and November (maximum of 109 mmoles/m2/d) when the seagrasses were senescing. However, September 2002 diSRR, when temperatures were still warm (28 ?C), were as low as diSRR in November 2002 (20 ?C). Although this suggests that September temperatures might have supported higher SRR, organic carbon provided by either seagrasses or degradation of benthic algae was a limiting factor. In contrast, September 2003 diSRR at the shallow and mid depth stations were significantly higher than at the respective stations in June and July. This might be due to plant stress induced by low salinity (12ppt) from heavy rains in July. Recovery of the plants or increased algal production would provide organic carbon input to the sediments to support sulfate reduction. Reduced sulfur pools at each station were relatively stable with time, but demonstrated depth-specific differences. There was an apparent threshold of below ground biomass below which porewater sulfate was depleted and above which sulfate was enriched. Sulfate depletion in seagrass bed sediments during the growing season might be developed as an ecological indicator of seagrassess stress.
Will be poster session.