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<p>Nutrient stoichiometry is a pivotal yet underexplored driver of ecosystem function in <i>Apostichopus japonicus</i> pond mariculture during summer heat. A survey of seven ponds in Dalian (July 2022) combined multivariate ordination, hierarchical partitioning (HP), and structural equation modeling (SEM) to assess how nitrogen–phosphorus (N/P) dynamics regulate phytoplankton. Nutrient concentrations differed significantly among ponds (<i>P</i> &lt; 0.05), with culture ponds exhibiting nitrogen enrichment (e.g., NH₄⁺-N 0.04 ± 0.03&#xa0;mg/L in pond #7 vs 0.01 ± 0.01&#xa0;mg/L in pond #3), while the control pond had higher phosphorus levels. Phytoplankton consisted of 18 species across two phyla, predominantly diatoms (95.5%), with dinoflagellates (4.5%) present only in ponds with balanced stoichiometry. Diversity indices varied widely (Simpson 0.1859–0.7189; Shannon 0.3884–1.4480), with lower values in high N/P ponds. Principal Coordinates Analysis (PCoA) indicated strong separation along N–P gradients (first two axes 87.49%). HP analysis showed that community variation was primarily driven by total nitrogen (TN) (57.91%), followed by N/P ratio (36.60%) and TN/TP ratio (5.29%). SEM analysis revealed TN as a central node (TN–TP  –0.60; TN–NH₄⁺-N  –0.25; TN–NO₂⁻-N 0.28; TP–PO₄<sup>3</sup>⁻-P 0.55). Together, nitrogen enrichment, phosphorus limitation, and bioturbation by sea cucumbers led to diatom-dominated, low-diversity states. Actionable N/P management strategies—optimized water quality biological regulation to reduce nitrogen loading, targeted phosphorus supplementation, and real-time stoichiometric monitoring—are proposed to stabilize communities and mitigate bloom risks.</p>

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Regulation of phytoplankton community structure by nitrogen-phosphorus stoichiometry in Apostichopus japonicus culture ponds under summer high-temperature conditions

  • 期刊论文

  • 发表日期：

    2026年1月24日

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  • Kaihua Geng,
  • Sitong Li,
  • Jianlong Liu,
  • Zhijian Yin,
  • Dingxian Xu,
  • Shiwei Wang,
  • Yuting Cong,
  • Li Wang,
  • Yuan Wang,
  • Jing Gu,
  • Yanan Lu,
  • Lianshun Wang,
  • Guojun Yang,
  • Hua Wang

摘要

Nutrient stoichiometry is a pivotal yet underexplored driver of ecosystem function in Apostichopus japonicus pond mariculture during summer heat. A survey of seven ponds in Dalian (July 2022) combined multivariate ordination, hierarchical partitioning (HP), and structural equation modeling (SEM) to assess how nitrogen–phosphorus (N/P) dynamics regulate phytoplankton. Nutrient concentrations differed significantly among ponds (P < 0.05), with culture ponds exhibiting nitrogen enrichment (e.g., NH₄⁺-N 0.04 ± 0.03 mg/L in pond #7 vs 0.01 ± 0.01 mg/L in pond #3), while the control pond had higher phosphorus levels. Phytoplankton consisted of 18 species across two phyla, predominantly diatoms (95.5%), with dinoflagellates (4.5%) present only in ponds with balanced stoichiometry. Diversity indices varied widely (Simpson 0.1859–0.7189; Shannon 0.3884–1.4480), with lower values in high N/P ponds. Principal Coordinates Analysis (PCoA) indicated strong separation along N–P gradients (first two axes 87.49%). HP analysis showed that community variation was primarily driven by total nitrogen (TN) (57.91%), followed by N/P ratio (36.60%) and TN/TP ratio (5.29%). SEM analysis revealed TN as a central node (TN–TP  –0.60; TN–NH₄⁺-N  –0.25; TN–NO₂⁻-N 0.28; TP–PO₄3⁻-P 0.55). Together, nitrogen enrichment, phosphorus limitation, and bioturbation by sea cucumbers led to diatom-dominated, low-diversity states. Actionable N/P management strategies—optimized water quality biological regulation to reduce nitrogen loading, targeted phosphorus supplementation, and real-time stoichiometric monitoring—are proposed to stabilize communities and mitigate bloom risks.