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WETLAND SOILS

Substrate-Induced Respiration for Phosphorus-Enriched and Oligotrophic Peat Soils in an Everglades Wetland

^a Everglades Research & Education Center, Univ. of Florida, 3200 E. Palm Beach Rd., Belle Glade, FL 33430
^b Wetland Biogeochemistry Lab., Soil and Water Science Dep., Univ. of Florida, P.O. Box 110510, Gainesville, FL 32603

^* Corresponding author (alwr{at}ifas.ufl.edu).

Nutrient enrichment may alter patterns of heterotrophic microbial activity (HMA) in wetland soils and influence organic matter decomposition dynamics. The response of the heterotrophic microbial community to C substrates (alcohols, amides, amino acids, aromatics, plant residues, and polysaccharides) was measured as CO₂ and CH₄ production in detritus and soil (0–10 cm) collected from P-enriched and oligotrophic areas of Water Conservation Area 2a (WCA-2a) of the Everglades. The wetland was characterized by decreasing P levels from peripheral to interior, oligotrophic areas. Denitrification and SO₄ reduction appeared to be the primary metabolic pathways at the P-enriched site, whereas the contribution of methanogenesis to organic matter decomposition was greater in the oligotrophic interior of the wetland. Methane production averaged 38 and 48% of the total CO₂ + CH₄ production for P-enriched and oligotrophic detritus, respectively. Basal CO₂ production of detritus was 36% higher at the P-enriched than the oligotrophic site, but CH₄ production was 43% greater at the oligotrophic site. All C substrates enhanced CO₂ and CH₄ production, indicating that labile organic C may be limiting in this wetland, and the types of C substrates used by the heterotrophic microbial community varied between P-enriched and oligotrophic sites. Substrate-induced respiration was 71 and 48% greater at the P-enriched than the oligotrophic site for detritus and soil, respectively. Nutrient loading, particularly P, promoted the development of a N-limited system near the periphery of the wetland, while the oligotrophic interior was characterized by P-limited conditions. Continued nutrient loading into oligotrophic areas of WCA-2a may enhance HMA and stimulate organic matter decomposition and nutrient regeneration, and further contribute to undesirable changes to the Everglades ecosystem.

Abbreviations: HMA, heterotrophic microbial activity • SIR, substrate-induced respiration • WCA-2a, Water Conservation Area 2a