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<p>Mangrove systems are major blue-carbon reservoirs, storing 4.4 to 11.7 petagrams of organic carbon globally and supporting diverse microalgal communities that drive primary productivity and coastal carbon cycling. The Sundarban, one of the world’s largest (3,629.57 km<sup>2</sup>) mangrove-dominated coastal systems, holds a substantial carbon stock (26.62 Tg). Rising salinity and anthropogenic pressure are altering the diversity of microalgal communities, highlighting the importance of identifying resilient taxa capable of sustaining carbon fixation. To address this need, we conducted whole-genome metagenomic profiling of degraded mangrove soils. The data revealed six dominant microalgal taxa adapted to prevailing salinity and nutrient stress. These six taxa were subsequently isolated from the same habitats, and a 16-day ambient CO<sub>2</sub> (420&#xa0;ppm) screening was undertaken to evaluate the specific growth rate and biomass gain of the algae. Among them, three physiologically resilient strains <i>Chlorella</i> sp., <i>Limnospira platensis</i>, and <i>Leptolyngbya boryana</i> were selected for controlled CO<sub>2</sub>-enrichment concentrations (0.04%, 0.05%, 0.20%, 10%) to mimic future climate change scenarios. Among those microalgae, the <i>Leptolyngbya boryana</i> showed the highest biomass yield (1.31&#xa0;g L<sup>−1</sup>), carbon content (0.52&#xa0;g C g<sup>−1</sup> dry weight), and CO<sub>2</sub>-fixation rate (up to 149&#xa0;mg CO<sub>2</sub> L<sup>−1</sup> d<sup>−1</sup>). Metagenomic analysis further identified that <i>L. boryana</i> possessed the strongest representation of carbon-fixation pathways like Calvin-Benson-Bassham (CBB) cycle and the reductive TCA (rTCA) cycle, regulated by enriched key genes such as <i>cbbL</i>, <i>cbbS</i>, <i>gap2</i>, <i>zwf</i>, and <i>accC</i>. Therefore, this result positions <i>L. boryana</i> as a promising microalgal candidate for carbon sequestration in future CO₂-rich environments under saline coastal ecology.</p>

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Identification of key carbon-fixation pathways and underlying genes for higher CO2 fixation of mangrove-associated microalgae

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Sujit Kumar Nayak,
  • Pratap Bhattacharyya,
  • Chinmay Pradhan,
  • Partha Sarathi Tripathy,
  • Soumya Ranjan Padhy,
  • Shiva Prasad Parida,
  • Arpita Moharana,
  • Monalisha Rath,
  • Anweshita Nayak,
  • Soumya Shephalika Dash,
  • Sudipta Kumar Das,
  • Himani Priya

摘要

Mangrove systems are major blue-carbon reservoirs, storing 4.4 to 11.7 petagrams of organic carbon globally and supporting diverse microalgal communities that drive primary productivity and coastal carbon cycling. The Sundarban, one of the world’s largest (3,629.57 km2) mangrove-dominated coastal systems, holds a substantial carbon stock (26.62 Tg). Rising salinity and anthropogenic pressure are altering the diversity of microalgal communities, highlighting the importance of identifying resilient taxa capable of sustaining carbon fixation. To address this need, we conducted whole-genome metagenomic profiling of degraded mangrove soils. The data revealed six dominant microalgal taxa adapted to prevailing salinity and nutrient stress. These six taxa were subsequently isolated from the same habitats, and a 16-day ambient CO2 (420 ppm) screening was undertaken to evaluate the specific growth rate and biomass gain of the algae. Among them, three physiologically resilient strains Chlorella sp., Limnospira platensis, and Leptolyngbya boryana were selected for controlled CO2-enrichment concentrations (0.04%, 0.05%, 0.20%, 10%) to mimic future climate change scenarios. Among those microalgae, the Leptolyngbya boryana showed the highest biomass yield (1.31 g L−1), carbon content (0.52 g C g−1 dry weight), and CO2-fixation rate (up to 149 mg CO2 L−1 d−1). Metagenomic analysis further identified that L. boryana possessed the strongest representation of carbon-fixation pathways like Calvin-Benson-Bassham (CBB) cycle and the reductive TCA (rTCA) cycle, regulated by enriched key genes such as cbbL, cbbS, gap2, zwf, and accC. Therefore, this result positions L. boryana as a promising microalgal candidate for carbon sequestration in future CO₂-rich environments under saline coastal ecology.