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Background and Aims <p>With accelerating sea-level rise, estuarine mangroves are increasingly exposed to multiple stresses of prolonged flooding and elevated salinity. Although flooding duration (FD) and salinity are widely recognized as key constraints, how they interact to influence photosynthetic response through trait-based mechanisms remains unclear.</p> Methods <p>We established an <i>in situ</i> mesocosm experiment with <i>Acanthus ilicifolius</i>, a salt-sensitive mangrove species, in both oligohaline (OSZ) and mesohaline salinity zones (MSZ) of an estuary. We measured photosynthetic gas-exchange and leaf morphological traits across a broad FD gradient (0.3 to 16.1&#xa0;h·d⁻<sup>1</sup>) to assess variations in net photosynthetic rate (Pn) and its potential drivers.</p> Results <p>Pn exhibited a nonlinear (hump-shaped) response to FD, while elevated salinity suppressed this response and shortened the optimal FD. In OSZ, Pn varied independently of specific leaf area (SLA), leaf thickness (LT) and leaf dry matter content (LDMC), but was primarily constrained by stomatal conductance (Gs) via its regulation of intercellular CO₂ concentration (Ci), as indicated by positive coordination between both Pn and Gs with Ci. However, Pn showed positive coordination with LT and LDMC in MSZ, but decreased with increasing SLA and Ci, contrary to predictions of the leaf economics spectrum.</p> Conclusions <p>While <i>A</i>. <i>ilicifolius</i> can maintain photosynthesis through stomatal adjustment under prolonged flooding, elevated salinity disrupts this regulatory mechanism, triggering a shift from stomatal to non-stomatal limitations associated with altered leaf structure. These findings highlight the context-dependent nature of physiological response, providing a physiological explanation for the vulnerability of salt-sensitive mangrove regeneration under sea-level rise.</p>

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Salinity shifts trait-mediated photosynthetic response to flooding in a salt-sensitive mangrove species under sea-level rise

  • 期刊论文

  • 发表日期：

    2026年6月18日

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  • Muwen Niu,
  • Yasong Chen,
  • Dan Peng,
  • Ling Jin,
  • Karyne M. Rogers,
  • Xin Song,
  • Hao Wu,
  • Yihui Zhang

摘要

Background and Aims

With accelerating sea-level rise, estuarine mangroves are increasingly exposed to multiple stresses of prolonged flooding and elevated salinity. Although flooding duration (FD) and salinity are widely recognized as key constraints, how they interact to influence photosynthetic response through trait-based mechanisms remains unclear.

Methods

We established an in situ mesocosm experiment with Acanthus ilicifolius, a salt-sensitive mangrove species, in both oligohaline (OSZ) and mesohaline salinity zones (MSZ) of an estuary. We measured photosynthetic gas-exchange and leaf morphological traits across a broad FD gradient (0.3 to 16.1 h·d⁻1) to assess variations in net photosynthetic rate (Pn) and its potential drivers.

Results

Pn exhibited a nonlinear (hump-shaped) response to FD, while elevated salinity suppressed this response and shortened the optimal FD. In OSZ, Pn varied independently of specific leaf area (SLA), leaf thickness (LT) and leaf dry matter content (LDMC), but was primarily constrained by stomatal conductance (Gs) via its regulation of intercellular CO₂ concentration (Ci), as indicated by positive coordination between both Pn and Gs with Ci. However, Pn showed positive coordination with LT and LDMC in MSZ, but decreased with increasing SLA and Ci, contrary to predictions of the leaf economics spectrum.

Conclusions

While A. ilicifolius can maintain photosynthesis through stomatal adjustment under prolonged flooding, elevated salinity disrupts this regulatory mechanism, triggering a shift from stomatal to non-stomatal limitations associated with altered leaf structure. These findings highlight the context-dependent nature of physiological response, providing a physiological explanation for the vulnerability of salt-sensitive mangrove regeneration under sea-level rise.