Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium.
Earlier observations in mangrove sediments of Goa, India have shown denitrification to be a major pathway for N loss. However, percentage of total nitrate transformed through complete denitrification accounted for <0-72% of the pore water nitrate reduced. Here, we show that up to 99% of nitrate removal in mangrove sediments is routed through dissimilatory nitrate reduction to ammonium (DNRA). The DNRA process was 2x higher at the relatively pristine site Tuvem compared to the anthropogenically-influenced Divar mangrove ecosystem. In systems receiving low extraneous nutrient inputs, this mechanism effectively conserves and re-circulates N minimizing nutrient loss that would otherwise occur through denitrification. In a global context, the occurrence of DNRA in mangroves has important implications for maintaining N levels and sustaining ecosystem productivity. For the first time, this study also highlights the significance of DNRA in buffering the climate by modulating the production of the greenhouse gas nitrous oxide.
Marine Microbiology Laboratory, National Institute of Oceanography, CSIR, Dona Paula, Goa-403004, India.
Sheryl Oliveira
SO
Fernandes
Patricia C
PC
Bonin
Valérie D
VD
Michotey
Nicole
N
Garcia
P A
PA
LokaBharathi
D058440:Denitrification; D017753:Ecosystem; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D006801:Humans; D007194:India; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D058458:Nitrogen Cycle; D009586:Nitrogen Fixation; D009609:Nitrous Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D043982:Rhizophoraceae / Q000254:growth & development / Q000378:metabolism; D053833:Wetlands
D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D009609:Nitrous Oxide; D009584:Nitrogen