Roles of planktonic metabolism in CO ₂ fluxes along the river-estuary continuum in a rapidly uplifting catchment of eastern Taiwan
- 1National Taiwan University (Taipei, Taiwan, Province of China)
Abstract
The contribution of river metabolism to carbon cycling remains poorly examined in catchments susceptible to the modulation of active tectonics. In these high-energy mountainous systems, chronically high turbidity and frequent sediment mobility create an unstable fluid regime that may impact planktonic metabolism and its contribution to aquatic carbon transformation. Using the Beinan River in southeastern Taiwan as a model system, this study aimed to quantify the potential rates of planktonic autotrophy and heterotrophy, and to identify the potential community members involved in these processes. To address this, river water samples were collected across wet and dry seasons for incubations with ¹³ C-labeled dissolved inorganic carbon and amino acids. Our results revealed that metabolic rates were consistently higher in the wet season than in the dry season, with heterotrophic catabolic rates exceeding autotrophic carbon fixation by one to two orders of magnitude, indicating strong net heterotrophy. The obtained rates were further scaled up, resulting in a catchment-scale CO ₂ evasion of 7.89×10 ⁷ mol yr ⁻¹ , which constitutes about 3.8 % of the CO ₂ flux derived from pyrite-induced carbonate weathering, oxidation of petrogenic carbon, and the river-air exchange. The microbial community structures varied seasonally at upstream sites, with more abundant lithoautotrophic sulfur- and ammonia/nitrite-oxidizing taxa in the wet season, as opposed to more abundant phototrophs or heterotrophs in the dry season. This study highlights that even in oligotrophic, physically dynamic mountainous systems prone to rapid uplift and erosion, planktonic metabolisms constitute a measurable and vital component of the riverine carbon cycle.
Versions
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BibTeX
@article{chen2026roles,
title = {{Roles of planktonic metabolism in CO ₂ fluxes along the river-estuary continuum in a rapidly uplifting catchment of eastern Taiwan}},
author = {Jhen-Nien Chen and Pei-En Chen and Yu-Shiang Yen and Tzu-Hsuan Tu and Lu-Yu Wang and Wan-Yin Lien and Yueh-Ting Lin and Pei-Ling Wang},
journal = {Biogeosciences},
year = {2026},
month = oct,
doi = {10.5194/bg-23-6781-2026},
url = {https://bg.copernicus.org/articles/23/6781/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Roles of planktonic metabolism in CO ₂ fluxes along the river-estuary continuum in a rapidly uplifting catchment of eastern Taiwan
AU - Jhen-Nien Chen
AU - Pei-En Chen
AU - Yu-Shiang Yen
AU - Tzu-Hsuan Tu
AU - Lu-Yu Wang
AU - Wan-Yin Lien
AU - Yueh-Ting Lin
AU - Pei-Ling Wang
PY - 2026
DA - 2026/10/02
JO - Biogeosciences
DO - 10.5194/bg-23-6781-2026
UR - https://bg.copernicus.org/articles/23/6781/2026/
AB - The contribution of river metabolism to carbon cycling remains poorly examined in catchments susceptible to the modulation of active tectonics. In these high-energy mountainous systems, chronically high turbidity and frequent sediment mobility create an unstable fluid regime that may impact planktonic metabolism and its contribution to aquatic carbon transformation. Using the Beinan River in southeastern Taiwan as a model system, this study aimed to quantify the potential rates of planktonic autotrophy and heterotrophy, and to identify the potential community members involved in these processes. To address this, river water samples were collected across wet and dry seasons for incubations with ¹³ C-labeled dissolved inorganic carbon and amino acids. Our results revealed that metabolic rates were consistently higher in the wet season than in the dry season, with heterotrophic catabolic rates exceeding autotrophic carbon fixation by one to two orders of magnitude, indicating strong net heterotrophy. The obtained rates were further scaled up, resulting in a catchment-scale CO ₂ evasion of 7.89×10 ⁷ mol yr ⁻¹ , which constitutes about 3.8 % of the CO ₂ flux derived from pyrite-induced carbonate weathering, oxidation of petrogenic carbon, and the river-air exchange. The microbial community structures varied seasonally at upstream sites, with more abundant lithoautotrophic sulfur- and ammonia/nitrite-oxidizing taxa in the wet season, as opposed to more abundant phototrophs or heterotrophs in the dry season. This study highlights that even in oligotrophic, physically dynamic mountainous systems prone to rapid uplift and erosion, planktonic metabolisms constitute a measurable and vital component of the riverine carbon cycle.
SN - 1726-4189
ER -