Carbon and nitrogen mineralization in sediments of the Bangrong mangrove area, Phuket, Thailand

Abstract

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 22:199-213 (2000) - doi:10.3354/ame022199 Carbon and nitrogen mineralization in sediments of the Bangrong mangrove area, Phuket, Thailand Erik Kristensen1,*, Frede Ø. Andersen1, Nikolaj Holmboe1, Marianne Holmer1, Nalinee Thongtham2 1Institute of Biology, Odense University, SDU, 5230 Odense M, Denmark 2Phuket Marine Biological Center, PO Box 60, Phuket 83000, Thailand *E-mail: ebk@biology.ou.dk ABSTRACT: Carbon and nitrogen mineralization were determined along a transect from a mangrove forest to a seagrass meadow in the Bangrong area, Phuket Island, Thailand. Vertical sediment profiles of carbon oxidation were measured as sulfate reduction rates (SRR) using the 35S technique and by monitoring net TCO2 and DOC production and Fe(III) reduction using anaerobic sediment incubations (Œjar¹ technique). Nitrogen transformations were measured simultaneously as net NH4+ and DON production. In addition, total benthic metabolism and net nitrogen exchange were determined as fluxes of O2, TCO2, DOC, and DIN (NO3- and NH4+) across the sediment-water interface. Rates of carbon and nitrogen transformations in this vascular-plant (high C:N)-dominated area were low compared with areas fuelled by detritus of marine origin (low C:N). It appears that the high content of structural biopolymers (e.g. lignocelluloses) hampers microbial activity. Suboxic respiration with Fe(III) as electron acceptor accounted for 70 to 80% of the total carbon oxidation in the rooted mangrove forest sediment, whereas SRR and aerobic respiration were responsible for about 20 and <6%, respectively. The role of SRR decreased to about 10% and aerobic respiration increased to 45-65% in an adjacent bioturbated mudflat, while Fe(III) respiration decreased to 30-40%. At the sand flat and seagrass meadow outside the mangrove forest, Fe(III) respiration only accounted for 15 and ~0%, respectively, whereas SRR was responsible for 20 to 45% of the total carbon oxidation. However, the most important electron acceptor in the area outside was oxygen (55 to 75%). The shift in dominance of electron acceptors along the transect is primarily related to the presence of roots and infauna, but the sediment composition (e.g. grain size, organic content and iron content) is believed to be an important co-factor. The net production of ammonium in the sediment was not balanced by fluxes of DIN across the sediment-water interface. The missing nitrogen was assigned to a rapid and efficient bacterial ammonium assimilation at the sediment surface as indicated by ammonium turnover times of about 1 d. KEY WORDS: Mangrove forest · Seagrass · Carbon · Nitrogen · Mineralization · Sulfate reduction · Fe(III) reduction · Benthic metabolism Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 22, No. 2. Online publication date: September 08, 2000 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2000 Inter-Research.