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<p>Green tides threaten coastal ecosystems worldwide, yet the physiological and environmental mechanisms driving their dynamics remain poorly resolved. On subtropical islands like Jeju, Korea, where nitrogen inputs are diverse, predicting bloom intensity is particularly challenging. Here we show that water column nutrient levels alone poorly correlated with bloom magnitude, whereas algal tissue nitrogen provides a more reliable indicator of nitrogen status and nutrient exposure history. Seasonal surveys across fourteen sites (2013–2015) revealed annual <i>Ulva</i> blooms exceeding 11,000 t, with stable isotope (δ<sup>15</sup>N) analysis indicating that blooms are likely sustained by mixed nitrogen sources rather than a single dominant source, although precise source attribution was not possible. Tissue nitrogen content closely tracked dissolved inorganic nitrogen, while nitrate reductase activity was decoupled from nitrate supply under nutrient-replete conditions and negatively associated with biomass accumulation; suppression of nitrogen reductase activity by ammonium feedback and self-shading within dense mats is inferred from these patterns but was not directly measured. By integrating environmental drivers with physiological traits, we provide mechanistic insights into bloom dynamics and highlight nitrogen management as a critical lever for mitigating green tides in vulnerable coastal ecosystems.</p>

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Nitrogen enrichment and Ulva green tide dynamics on Jeju Island: insights from biomass, physiological traits, and stable isotopes signatures

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月21日

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  • Kyeonglim Moon,
  • Eun Ran Baek,
  • Sun Kyeong Choi,
  • Hyun Woo Jeong,
  • Young Baek Son,
  • Sangil Kim,
  • Hyuk Je Lee,
  • Yun Hee Kang,
  • Sang Rul Park

摘要

Green tides threaten coastal ecosystems worldwide, yet the physiological and environmental mechanisms driving their dynamics remain poorly resolved. On subtropical islands like Jeju, Korea, where nitrogen inputs are diverse, predicting bloom intensity is particularly challenging. Here we show that water column nutrient levels alone poorly correlated with bloom magnitude, whereas algal tissue nitrogen provides a more reliable indicator of nitrogen status and nutrient exposure history. Seasonal surveys across fourteen sites (2013–2015) revealed annual Ulva blooms exceeding 11,000 t, with stable isotope (δ15N) analysis indicating that blooms are likely sustained by mixed nitrogen sources rather than a single dominant source, although precise source attribution was not possible. Tissue nitrogen content closely tracked dissolved inorganic nitrogen, while nitrate reductase activity was decoupled from nitrate supply under nutrient-replete conditions and negatively associated with biomass accumulation; suppression of nitrogen reductase activity by ammonium feedback and self-shading within dense mats is inferred from these patterns but was not directly measured. By integrating environmental drivers with physiological traits, we provide mechanistic insights into bloom dynamics and highlight nitrogen management as a critical lever for mitigating green tides in vulnerable coastal ecosystems.