Diatom-inferred water pH variability in response to climate change and acid deposition in subtropical peatlands

Xu Chen; Suzanne McGowan; Xianyu Huang; Yanmin Cao; Xue Bai; Junlu Li; Linghan Zeng; Shuangyu Xu; Jia Peng

doi:10.1016/j.watres.2025.124153

Diatom-inferred water pH variability in response to climate change and acid deposition in subtropical peatlands

Water Res. 2025 Jul 3:286:124153. doi: 10.1016/j.watres.2025.124153. Online ahead of print.

Authors

Xu Chen¹, Suzanne McGowan², Xianyu Huang³, Yanmin Cao⁴, Xue Bai³, Junlu Li³, Linghan Zeng³, Shuangyu Xu³, Jia Peng⁵

Affiliations

¹ Hubei Key Laboratory of Regional Ecology and Environmental Change, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430078, PR China; Observation and Research Station of Shenongjia Dajiuhu Wetland Earth Critical Zone, Ministry of Natural Resources, Wuhan 430078, PR China. Electronic address: xuchen@cug.edu.cn.
² Department of Aquatic Ecology, Netherlands Institute of Ecology, Wageningen, 6708 PB, the Netherlands; Departments of Biology and Physical Geography, University of Utrecht, Postbus 80125, 3508 TC Utrecht, the Netherlands.
³ Hubei Key Laboratory of Regional Ecology and Environmental Change, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430078, PR China; Observation and Research Station of Shenongjia Dajiuhu Wetland Earth Critical Zone, Ministry of Natural Resources, Wuhan 430078, PR China.
⁴ College of Resources and Environment, South-Central Minzu University, Wuhan 430074, PR China.
⁵ Hubei Key Laboratory of Regional Ecology and Environmental Change, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430078, PR China; Observation and Research Station of Shenongjia Dajiuhu Wetland Earth Critical Zone, Ministry of Natural Resources, Wuhan 430078, PR China; Department of Aquatic Ecology, Netherlands Institute of Ecology, Wageningen, 6708 PB, the Netherlands.

PMID: 40651444
DOI: 10.1016/j.watres.2025.124153

Abstract

Lake acidification emerged as one of the most pressing environmental issues in the 20th century, while peatland acidification is less investigated. Diatom assemblages in one hundred fourteen surface samples of eleven peatlands in South China and in peat cores of two peatlands covering a 200-year period were investigated. Ordination analyses revealed that water pH was the most important variable influencing diatom distribution in surface samples. Accordingly, a diatom-based pH transfer function was developed using a weighted averaging model with tolerance downweighting and inverse deshrinking, and applied to diatom records of two ²¹⁰Pb-dated sediment cores from Dajiuhu Peatland (Hubei Province) and Niangniangshan Peatland (Guizhou Province). Before the 1950s, declines in acid-tolerant diatom taxa coincided with rising diatom-inferred pH in both peatlands, indicating a regional shift toward less acidic conditions. This regional shift probably resulted from warming-accelerated bedrock weathering and alkalinity generation. Thereafter, the expansion of acid-tolerant diatoms mainly responded to enhanced atmospheric acid deposition, suggesting that its impacts outweigh those of climate warming. Temporal changes in diatom assemblages showed similar trends in the two distant peatlands, suggesting that acidification might be a widespread phenomenon in subtropical peatlands of South China after the 1950s. In spite of recent reductions in atmospheric deposition from 2010, diatom-inferred water pH continued to decline, indicative of delayed recovery from anthropogenic acidification in these headwater peatlands. The results provide novel insight into the timing and extent of peatland acidification in South China, and can inform sustainable management of semi-aquatic ecosystems under a changing environment.

Keywords: Acidification; Climate warming; Peaty environment; pH reconstruction; peat sediment.