Porewater biogeochemistry and soil metabolism in dwarf red mangrove habitats (Twin Cays, Belize)

• Published in: Biogeochemistry Vol. 87; no. 2; pp. 181 - 198
• Main Authors: Lee, Rosalynn Y, Porubsky, William P, Feller, Ilka C, McKee, Karen L, Joye, Samantha B
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.02.2008; Springer; Springer Netherlands; Springer Nature B.V
• Subjects: Ammonium; Animal and plant ecology; Animal, plant and microbial ecology; Biogeochemistry; Biogeosciences; Biological and medical sciences; Brackish; Carbon; Dissolved inorganic carbon; Dissolved organic carbon; Dissolved organic phosphorus; Dry season; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Ecosystems; Environmental Chemistry; Evaporation; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Habitats; Keys; Life Sciences; Manganese; Mangrove forests; Mangrove soils; Marine and continental quaternary; Metabolism; Metabolites; Methane; Methanogenesis; Mineralization; Nitrification; Nitrogen; Nitrous oxide; Nutrients; Organic matter; Organic soils; Pore water; Rainy season; Seasonal variations; Seasons; Sedimentary soils; Sediments; Soil organic matter; Soil surfaces; Soils; Sulfates; Surface water; Surficial geology; Synecology; Synthesis and Emerging Ideas; Terrestrial ecosystems; Wetlands; Belize; ASW, Belize, Stann Creek Dist., Twin Cays; Sulfate reduction; Nutrients; Porewater; Dwarf mangrove; Redox metabolites; Methanogenesis; ponds; Central America; habitat; algal mats; nitrous oxide; ammonium; nitrites; sulfates; nitrates; manganese; methanogenesis; mangrove swamps; pore water; soils; phosphorus; sulfides; chlorides; biogeochemical methods; salinity; nitrogen; halides; phosphates; methane; iron; metabolism; seasonal variations; dissolved organic carbon
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-008-9176-9

Seasonal variability in biogeochemical signatures was used to elucidate the dominant pathways of soil microbial metabolism and elemental cycling in an oligotrophic mangrove system. Three interior dwarf mangrove habitats (Twin Cays, Belize) where surface soils were overlain by microbial mats were sampled during wet and dry periods of the year. Porewater equilibration meters and standard biogeochemical methods provided steady-state porewater profiles of pH, chloride, sulfate, sulfide, ammonium, nitrate/nitrite, phosphate, dissolved organic carbon, nitrogen, and phosphorus, reduced iron and manganese, dissolved inorganic carbon, methane and nitrous oxide. During the wet season, the salinity of overlying pond water and shallow porewaters decreased. Increased rainwater infiltration through soils combined with higher tidal heights appeared to result in increased organic carbon inventories and more reducing soil porewaters. During the dry season, evaporation increased both surface water and porewater salinities, while lower tidal heights resulted in less reduced soil porewaters. Rainfall strongly influenced inventories of dissolved organic carbon and nitrogen, possibly due to more rapid decay of mangrove litter during the wet season. During both times of year, high concentrations of reduced metabolites accumulated at depth, indicating substantial rates of organic matter mineralization coupled primarily to sulfate reduction. Nitrous oxide and methane concentrations were supersaturated indicating considerable rates of nitrification and/or incomplete denitrification and methanogenesis, respectively. More reducing soil conditions during the wet season promoted the production of reduced manganese. Contemporaneous activity of sulfate reduction and methanogenesis was likely fueled by the presence of noncompetitive substrates. The findings indicate that these interior dwarf areas are unique sites of nutrient and energy regeneration and may be critical to the overall persistence and productivity of mangrove-dominated islands in oligotrophic settings.