The influence of forest type on microbial-nutrient relationships in tropical mangrove sediments

Microbial productivity, nutrient chemistry and rates of nutrient regeneration were examined in muds of different mangrove forests within the Fly Delta, Papua New Guinea, to assess the effect of forest type on microbial and nutrient processes, and their interactions. Three major forest types were examined: Rhizophora-Bruguiera, Nypa and Avicennia-Sonneratia forests. For most variables, variations within a forest type were as great as, or greater than, differences between forest types. A high-intertidal Nypa site was most different in edaphic characteristics compared to five low-intertidal stations (two stations in each forest type) suggesting that differences among forest types in earlier studies were mainly a function of tidal elevation rather than species-specific ability of mangroves to influence redox and nutrient status. Dissolved inorganic nutrients were dominated by high (~ 200–500 μM) concentrations of silicates, but porewater phosphate levels were usually below detection limits (