Potential for Sulfate Reduction in Mangrove Forest Soils: Comparison between Two Dominant Species of the Americas.

and are globally occurring mangrove genera with different traits that place them in different parts of the intertidal zone. It is generally accepted that the oxidizing capacity of roots is larger than that of roots, which initiates more reduced conditions in the soil below the latter genus. We hypothesize that the more reduced conditions beneath stands lead to more active sulfate-reducing microbial communities compared to stands. To test this hypothesis, we measured sulfate reduction traits in soil samples collected from neighboring and stands at three different locations in southern Florida. The traits measured were sulfate reduction rates (SRR) in flow-through reactors containing undisturbed soil layers in the absence and presence of easily degradable carbon compounds, copy numbers of the gene, which is specific for sulfate-reducing microorganisms, and numbers of sulfate-reducing cells that are able to grow in liquid medium on a mixture of acetate, propionate and lactate as electron donors. At the tidal locations Port of the Islands and South Hutchinson Islands, steady state SRR, gene copy numbers and numbers of culturable cells were higher at the than at the stands, although not significantly for the numbers at Port of the Islands. At the non-tidal location North Hutchinson Island, results are mixed with respect to these sulfate reduction traits. At all locations, the fraction of culturable cells were significantly higher at the than at the stands. The dynamics of the initial SRR implied a more active sulfate-reducing community at the intertidal stands. It was concluded that in agreement with our hypothesis stands accommodate a more active sulfate-reducing community than stands, but only at the tidal locations. The differences between and stands were absent at the non-tidal, impounded location.