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Purpose <p>Mudflats stand out as significant carbon sinks within coastal wetlands, broadly distributing along the salinity gradient of the estuary. The shifts in the microecological environment caused by alternating wetting and drying (AWD) are crucial drivers affecting the accumulation of microbial derived carbon (MDC). However, the varied salinity intensified by climate warming may introduce an unpredictable element, complicating the assessment of carbon sequestration potential in mudflats.</p> Methods <p>To gain insight into the response of MDC to AWD and salinity, a laboratory simulation experiment was conducted using a customized tidal simulator. Mudflat soils collected in June 2023 were exposed to a semidiurnal wetting-drying cycle under three salinity gradients (5‰, 20‰, and 35‰). Soils were sampled at days 1, 30, and 100 to analyze physicochemical properties, microbial biomass (via PLFAs), and specific MDC fractions.</p> Results <p>The results revealed that MDC, including microbial biomass carbon (MBC), extracellular polymeric substances carbon (EPSC), and bacterial necromass carbon (BNC), appeared different accumulated models, in response of AWD and salinity. Specifically, to cope with the salt accumulation resulting from AWD, salt-tolerant microorganisms adopt the “high-salt-in” and “compatible solute” strategies to boost MBC accumulation while also secreting abundant EPS to safeguard their cells. Meanwhile, the high-salinity environment disrupted microbial cells and promoted BNC formation, yet, also inhibiting its further degradation by microorganisms.</p> Conclusion <p>The following conclusions were drawn by comparing accumulated MDC content across three salinity environments. Firstly, a certain threshold of EC (specifically 4.10 in a laboratory setting) will inhibit the accumulation of MBC. Secondly, the lower-survival microbial biomass in higher salinity environment will be the limit factor weakening the accumulation rate of BNC. In summary, AWD favor the accumulation of MDC in mudflats, whereas increased salinity due to climate warming may weaken the contribution of MDC to SOC.</p>

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Drying and rewetting cycles promote microbial-derived carbon accumulation in mudflats, but salinity stress inhibits the process

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Chunyu Tang,
  • Huanxin Luo,
  • Ziyi Xing,
  • Yifei Shen,
  • Jianyu He,
  • Peimin He,
  • Jianxin Wang

摘要

Purpose

Mudflats stand out as significant carbon sinks within coastal wetlands, broadly distributing along the salinity gradient of the estuary. The shifts in the microecological environment caused by alternating wetting and drying (AWD) are crucial drivers affecting the accumulation of microbial derived carbon (MDC). However, the varied salinity intensified by climate warming may introduce an unpredictable element, complicating the assessment of carbon sequestration potential in mudflats.

Methods

To gain insight into the response of MDC to AWD and salinity, a laboratory simulation experiment was conducted using a customized tidal simulator. Mudflat soils collected in June 2023 were exposed to a semidiurnal wetting-drying cycle under three salinity gradients (5‰, 20‰, and 35‰). Soils were sampled at days 1, 30, and 100 to analyze physicochemical properties, microbial biomass (via PLFAs), and specific MDC fractions.

Results

The results revealed that MDC, including microbial biomass carbon (MBC), extracellular polymeric substances carbon (EPSC), and bacterial necromass carbon (BNC), appeared different accumulated models, in response of AWD and salinity. Specifically, to cope with the salt accumulation resulting from AWD, salt-tolerant microorganisms adopt the “high-salt-in” and “compatible solute” strategies to boost MBC accumulation while also secreting abundant EPS to safeguard their cells. Meanwhile, the high-salinity environment disrupted microbial cells and promoted BNC formation, yet, also inhibiting its further degradation by microorganisms.

Conclusion

The following conclusions were drawn by comparing accumulated MDC content across three salinity environments. Firstly, a certain threshold of EC (specifically 4.10 in a laboratory setting) will inhibit the accumulation of MBC. Secondly, the lower-survival microbial biomass in higher salinity environment will be the limit factor weakening the accumulation rate of BNC. In summary, AWD favor the accumulation of MDC in mudflats, whereas increased salinity due to climate warming may weaken the contribution of MDC to SOC.