Journal article
Low Denitrification, Anammox, and Dissimilatory Nitrate Reduction to Ammonium Rates in a Low Disturbance Mangrove‐Saltmarsh System Using an in Situ Intact Chamber Method
Journal of geophysical research. Biogeosciences, Vol.131(9), pp.1-25
09/2026
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Abstract
Mangroves and saltmarshes can remove anthropogenic nitrogen (N) moving from the land to the ocean, but many previous N cycling measurements used destructive sampling procedures that excluded important habitats such as crab burrows, pneumatophores, and saltmarsh vegetation. In this study, a new intact chamber method using 15 NO 3 − labeling was developed to quantify in situ denitrification, anammox, and DNRA rates in different habitats across a low disturbance mangrove‐saltmarsh system. No anammox was detected, likely due to the low nutrient concentrations. Denitrification rates were 0.4–36 times higher than DNRA rates. The highest denitrification rates were measured in crab burrows (36.4 μmol N m −2 h −1 ) and saltmarsh (26.6 μmol N m −2 h −1 ), while DNRA rates were highest in saltmarsh (7.4 μmol N m −2 h −1 ) and pneumatophores (2.1 μmol N m −2 h −1 ). Rates were scaled using a detailed habitat map, giving a total of 17.1 kg N ha −1 yr −1 being removed via denitrification in the mangrove system, 17.0 in the saltmarsh system, 17.5 in the open water system, and 17.1 in the mangrove‐saltmarsh‐open water system. Furthermore, 2.5 kg N ha −1 yr −1 was recycled by DNRA in the mangrove system, 2.9 in the saltmarsh system, 1.9 in the open water system, and 2.5 in the saltmarsh‐mangrove‐open water system. The low denitrification and DNRA rates compared to previous studies likely reflect minimal anthropogenic disturbance and associated low nitrogen availability at the study site, but this needs to be confirmed with replicated measurements using the new intact chamber method at a high nutrient concentration mangrove‐saltmarsh site. Mangroves and saltmarshes act like natural filters, removing nitrogen (N) from land runoff before it enters the ocean. This is vital because high nitrate and ammonium concentrations can cause toxic algal blooms and habitat loss. This study used a new “intact chamber” method to measure nitrogen process rates without damaging natural features such as crab burrows, mangrove roots, and saltmarsh vegetation. Traditional methods mostly exclude these structures. Microbial processes such as denitrification and anammox can turn nitrate and ammonium into harmless nitrogen gas that leaves the system. Conversely, dissimilatory nitrate reduction to ammonium (DNRA) is a process where nitrate is reduced to ammonium, recycling N in the system. In the studied mangrove‐saltmarsh‐open water system 17.1 kg N ha −1 yr −1 was removed through denitrification, while only 2.5 kg N ha −1 yr −1 was recycled by DNRA. No anammox was detected. These rates were lower than those measured in most other mangrove‐saltmarsh studies, which is probably caused by the low nitrogen concentrations at the study site. Habitats with crab burrows, saltmarsh vegetation, and mangrove roots were much more active than bare sediment, suggesting that nitrogen removal rates in coastal wetlands were often underestimated. A novel intact chamber method was used to measure in situ denitrification, anammox, and DNRA rates in mangrove‐saltmarsh habitats Denitrification rates were higher than DNRA, both were higher in crab burrows, saltmarsh vegetation, and pneumatophores than bare sediment Denitrification and DNRA rates were low compared to other studies in mangroves and saltmarshes, probably due to low nutrient concentrations
Details
- Title
- Low Denitrification, Anammox, and Dissimilatory Nitrate Reduction to Ammonium Rates in a Low Disturbance Mangrove‐Saltmarsh System Using an in Situ Intact Chamber Method
- Creators
- Britte C. van Haastregt - Southern Cross UniversityDirk V. Erler - Southern Cross UniversityJacob Z.‐Q. Yeo - Southern Cross UniversityBradley D. Eyre - Southern Cross University
- Publication Details
- Journal of geophysical research. Biogeosciences, Vol.131(9), pp.1-25
- Publisher
- American Geophysical Union
- Number of pages
- 25
- Grant note
- Open access publishingfacilitated by Southern Cross University, as part of the Wiley ‐ Southern CrossUniversity agreement via the Council of Australasian University Librarians.
- Identifiers
- 991013403070402368
- Copyright
- © 2026 The Author(s).
- Academic Unit
- Faculty of Science and Engineering; Science
- Language
- English
- Resource Type
- Journal article