Catabolic diversity of periphyton and detritus microbial communities in a subtropical wetland

The catabolic diversity of wetland microbial communities may be a sensitive indicator of nutrient loading or changes in environmental conditions. The objectives of this study were to assess the response of periphyton and microbial communities in water conservation area- 2a ( WCA- 2a) of the Everglades to additions of C- substrates and inorganic nutrients. Carbon dioxide and CH4 production rates were measured using 14 days incubation for periphyton, which typiWes oligotrophic areas, and detritus, which is prevalent at P- impacted areas of WCA- 2a. The wetland was characterized by decreasing P levels from peripheral to interior, oligotrophic areas. Microbial biomass and N mineralization rates were higher for oligotrophic periphyton than detritus. Methane production rates were also higher for unamended periphyton ( 80 mg CH4- C kg - 1 d - 1) than detritus ( 22 mg CH4- C kg - 1 d - 1), even though the organic matter content was higher for detritus ( 80%) than periphyton ( 69%). Carbon dioxide production for unamended periphyton ( 222 mg CO2- C kg - 1 d - 1) was signiWcantly greater than unamended detritus ( 84 mg CO2- C kg - 1 d - 1). The response of the heterotrophic microbial community to added C- substrates was related to the nutrient status of the wetland, as substrate- induced respiration ( SIR) was higher for detritus than periphyton. Amides and polysaccharides stimulated SIR more than other C- substrates, and methanogenesis was greater contributor to SIR for periphyton than detritus. Inorganic P addition stimulated CO2 and CH4 production for periphyton but not detritus, indicating a P limitation in the interior areas of WCA- 2a. Continued nutrient loading into oligotrophic areas of WCA- 2a or enhanced internal nutrient cycling may stimulate organic matter decomposition and further contribute to undesirable changes to the Everglades ecosystem caused by nutrient enrichment.