title: Nutrient variability and its influence on nitrogen processes in a highly turbid tropical estuary (Bangpakong, Gulf of Thailand).
abstract: Estuarine ecosystems in SE Asia have been poorly studied when compared to other tropical environments. Important gaps exist particularly in the understanding of their biogeochemical function and contribution to global change. In this work we looked into N-turnover in the water column and sediments of the Bangpakong estuary (13°N). A seasonal sampling program was performed along the salinity gradient covering different stretches of the estuary (68km). Key physical and chemical characteristics were also monitored in order to unravel possible environmental controls. Results showed the occurrence of active denitrification in sediments (5.7-50.9nmol N-N2/(cm(3)·hr)), and water column (3.5-1044pmol N-N2/(cm(3)·hr)). No seasonal or spatial variability was detected for denitrification potential in sediment samples. However, in the water column, the denitrification activity peaked during the transition season in the downstream sites coinciding with high turbidity levels. Therefore, in that period of the year, the water column compartment may be an important contributor to nitrate reduction within the estuary. The rather low nitrification rates detected were not always measurable, probably due to the reduced oxygen content and high siltation. This study is one of the few dealing simultaneously with sediments and water column processes in a highly turbid tropical estuary. Therefore, it emerges as a valuable contribution for the understanding of the dynamics of the nitrogen cycle in tropical environments by exploring the role of estuarine N microbial activity in reducing the effects of increased nitrogen loads.
authors.affiliation: Laboratory of Hydrobiology and Ecology, Institute of Biomedical Sciences, University of Porto, 4050-313 Porto, Portugal; Centre of Marine and Environmental Research, University of Porto, 4050-123 Porto, Portugal. Electronic address: bordalo@icbas.up.pt.
authors.forename: Adriano A
authors.initials: AA
authors.lastname: Bordalo
authors.affiliation: Department of Aquatic Sciences, Burapha University, Chonburi, Thailand.
authors.forename: Kashane
authors.initials: K
authors.lastname: Chalermwat
authors.affiliation: Laboratory of Hydrobiology and Ecology, Institute of Biomedical Sciences, University of Porto, 4050-313 Porto, Portugal; Centre of Marine and Environmental Research, University of Porto, 4050-123 Porto, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Teixeira
mesh_terms: D058440:Denitrification; D017753:Ecosystem; D004784:Environmental Monitoring; D063366:Estuaries; D009584:Nitrogen / Q000032:analysis*; D058458:Nitrogen Cycle; D013785:Thailand; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen
keywords: Bangpakong River; Denitrification; Nitrification; Nutrients; Tropical estuary