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TECHNICAL REPORTS
Wetlands and Aquatic Processes

Nutrient and Hydrology Effects on Soil Respiration in a Northern Everglades Marsh

W. F. DeBusk^,* and K. R. Reddy

Soil and Water Science Dep., Univ. of Florida, Gainesville, FL 32611-0510

^* Corresponding author (wdebusk{at}ene.com)

Received for publication October 17, 2001. Microbial respiration in peat and overlying plant litter, as influenced by water level and phosphorus enrichment, was evaluated for an Everglades (Florida, USA) marsh ecosystem by measuring CO₂ and CH₄ release from soil–water microcosms. Intact cores of peat, overlying plant litter, and surface water were collected at seven locations in cattail (Typha domingensis Pers.) and sawgrass (Cladium jamaicense Crantz) stands along a phosphorus (P) enrichment gradient in Water Conservation Area 2A (WCA-2A). Each soil–water microcosm was outfitted with a controlled air circulation system whereby outflow gas from the headspace could be analyzed for CO₂ and CH₄ to determine flux of C from the soil–water column to the atmosphere. Gaseous C flux was determined for flooded conditions (10-cm water depth) and for water levels of 0, 5, 10, and 15 cm below the peat surface. Overall, decreasing water level resulted in significantly increased C flux, although rates were significantly higher under flooded conditions than under nonflooded, saturated-soil conditions, presumably due to O₂ availability associated with algal photosynthesis within the litter layer in the water column. Carbon flux decreased significantly for sites increasingly distant from the primary hydrologic and nutrient inflows to WCA-2A. The microcosm study demonstrated that the C turnover rate was significantly increased by accelerated nutrient loading to the marsh, and was further enhanced by decreasing water level under drained conditions. Our results also demonstrated that photosynthesis within the water column is a potentially important regulator of C mineralization rate in the litter layer of the marsh system.

Abbreviations: WCA, Water Conservation Area

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