Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment
The biogeochemistry of dissolved organic matter (DOM) is poorly understood in tropical coastal waters. Here, we quantified the biological and photochemical lability of dissolved organic carbon, nitrogen, and phosphorus, in the tropical coastal waters of Singapore. We conducted experiments during the...
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| Format: | Journal Article |
| Language: | English |
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2025
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| Online Access: | https://hdl.handle.net/10356/182651 |
| _version_ | 1824455660331335680 |
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| author | Chu, Jiangyong Lønborg, Christian Martin, Patrick |
| author2 | Asian School of the Environment |
| author_facet | Asian School of the Environment Chu, Jiangyong Lønborg, Christian Martin, Patrick |
| author_sort | Chu, Jiangyong |
| collection | NTU |
| description | The biogeochemistry of dissolved organic matter (DOM) is poorly understood in tropical coastal waters. Here, we quantified the biological and photochemical lability of dissolved organic carbon, nitrogen, and phosphorus, in the tropical coastal waters of Singapore. We conducted experiments during the inter-monsoon, the mid-southwest monsoon, and the late southwest monsoon seasons, which span the greatest range of biogeochemical conditions found in the area. The DOM lability was quantified as concentration changes during 90-d biodegradation and 7-d photoreactor incubations. Overall, DOM showed low lability, even though dissolved organic nitrogen and dissolved organic phosphorus accounted for most of the dissolved nitrogen and phosphorus. In the biodegradation experiments, only 5–15% of dissolved organic carbon, 0–7% of dissolved organic nitrogen, and 8–21% of dissolved organic phosphorus were degraded. The addition of labile dissolved organic carbon, intended to test priming effects and to ensure the microbes were not carbon-limited, had no measurable impact on the results. During our photochemical experiments only 2–10% of the dissolved organic carbon were degraded, while neither dissolved organic nitrogen nor dissolved organic phosphorus showed consistent photochemical losses. The DOM optical properties (absorbance and fluorescence spectra) showed limited or no changes during the biodegradation experiments but larger declines in the photochemical experiments. Overall, the biodegradation of DOM was highest during the inter-monsoon, when autochthonous DOM was most dominant, while photolability was greater during the terrestrial DOM-rich southwest monsoon. Our results illustrate that in some tropical coastal environments, DOM can be fairly resistant to biological and photochemical degradation, and thus does not represent a large stock of potentially available nutrients. |
| first_indexed | 2025-02-19T03:41:44Z |
| format | Journal Article |
| id | ntu-10356/182651 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2025-02-19T03:41:44Z |
| publishDate | 2025 |
| record_format | dspace |
| spelling | ntu-10356/1826512025-02-17T15:30:56Z Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment Chu, Jiangyong Lønborg, Christian Martin, Patrick Asian School of the Environment Earth and Environmental Sciences Dissolved organic matter Biodegradation Photodegradation The biogeochemistry of dissolved organic matter (DOM) is poorly understood in tropical coastal waters. Here, we quantified the biological and photochemical lability of dissolved organic carbon, nitrogen, and phosphorus, in the tropical coastal waters of Singapore. We conducted experiments during the inter-monsoon, the mid-southwest monsoon, and the late southwest monsoon seasons, which span the greatest range of biogeochemical conditions found in the area. The DOM lability was quantified as concentration changes during 90-d biodegradation and 7-d photoreactor incubations. Overall, DOM showed low lability, even though dissolved organic nitrogen and dissolved organic phosphorus accounted for most of the dissolved nitrogen and phosphorus. In the biodegradation experiments, only 5–15% of dissolved organic carbon, 0–7% of dissolved organic nitrogen, and 8–21% of dissolved organic phosphorus were degraded. The addition of labile dissolved organic carbon, intended to test priming effects and to ensure the microbes were not carbon-limited, had no measurable impact on the results. During our photochemical experiments only 2–10% of the dissolved organic carbon were degraded, while neither dissolved organic nitrogen nor dissolved organic phosphorus showed consistent photochemical losses. The DOM optical properties (absorbance and fluorescence spectra) showed limited or no changes during the biodegradation experiments but larger declines in the photochemical experiments. Overall, the biodegradation of DOM was highest during the inter-monsoon, when autochthonous DOM was most dominant, while photolability was greater during the terrestrial DOM-rich southwest monsoon. Our results illustrate that in some tropical coastal environments, DOM can be fairly resistant to biological and photochemical degradation, and thus does not represent a large stock of potentially available nutrients. Ministry of Education (MOE) National Research Foundation (NRF) Published version The research was funded by the Singapore Ministry of Education through an Academic Research Fund Tier 2 grant (MOE-MOET2EP10121-0007) and by the National Research Foundation, Singapore, Prime Minister’s Office, through the Marine Environment Sensing Network grant (NRF-NRI-2020-MESN), both to Patrick Martin, and by the China Scholarship Council through an award to Jiangyong Chu (award numbers [2020] 101 and [2021] 2047). During the drafting of the manuscript Christian Lønborg received funding from the Independent Research Fund Denmark Grant 1127-00033B. 2025-02-13T06:39:48Z 2025-02-13T06:39:48Z 2025 Journal Article Chu, J., Lønborg, C. & Martin, P. (2025). Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment. Limnology and Oceanography. https://dx.doi.org/10.1002/lno.12803 0024-3590 https://hdl.handle.net/10356/182651 10.1002/lno.12803 2-s2.0-85216554715 en MOE-MOET2EP10121-0007 NRF-NRI-2020-MESN Limnology and Oceanography 10.21979/N9/0LCM6V © 2025 The Author(s). Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography. This is an open access article under the terms of the Creative CommonsAttribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. application/pdf |
| spellingShingle | Earth and Environmental Sciences Dissolved organic matter Biodegradation Photodegradation Chu, Jiangyong Lønborg, Christian Martin, Patrick Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment |
| title | Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment |
| title_full | Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment |
| title_fullStr | Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment |
| title_full_unstemmed | Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment |
| title_short | Limited degradability of dissolved organic carbon, nitrogen, and phosphorus during contrasting seasons in a tropical coastal environment |
| title_sort | limited degradability of dissolved organic carbon nitrogen and phosphorus during contrasting seasons in a tropical coastal environment |
| topic | Earth and Environmental Sciences Dissolved organic matter Biodegradation Photodegradation |
| url | https://hdl.handle.net/10356/182651 |
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