Association between pore water sulfide concentrations and the distribution of mangroves

At Humingbird Cay, Exuma, Bahamas, distributions of both Rhizophora mangle (red mangrove) and Avicennia germinans (black mangrove) are closely correlated with amounts of hydrogen sulfide (H2S) in the soil. R. mangle is primarily distributed within large areas of low to moderate H2S concentrations (mean = 40 mg/l). H2S levels under A. germinans are lower (mean = 22 mg/l), but the area immediately beyond their root zone often has extremely high sulfide concentrations (mean = 120 mg/l). These results suggest that past attempts to explain mangrove distribution in terms of monotonic soil gradients, the dispersal characteristics of propagules, and interspecific competition are incomplete, and that it will be necessary to examine the link between soil sulfur chemistry and mangrove distribution more fully.