Harmful blooms of cyanobacteria may extend over long time spans due to self-sustaining mechanisms. We hypothesized that settled blooms may increase redox-dependent P release and unbalance the stoichiometry of benthic nutrient regeneration (NH₄⁺:SiO₂:PO₄³⁻ ratios). We tested this hypothesis in the hypertrophic Curonian Lagoon, the largest in Europe. During summer, at peak chlorophyll and water temperatures, sediment cores were collected over 19 stations representing all the lagoon sedimentary environments. Sediment organic content, granulometry, aerobic respiration, and oxic and anoxic fluxes of dissolved inorganic nutrients and metals—Fe²⁺ and Mn²⁺—were measured. Loads and stoichiometry of regenerated nutrients were compared with those from the watershed. Analyzed sediments had elevated oxygen demand (−1.90 to −5.66 mmol O₂ m⁻² h⁻¹), generally uncoupled to their variable organic matter content (1–23%) and median particle size (30–300 μm). Under oxic conditions, summer internal recycling equaled (SiO₂) or exceeded, by a factor of ~66 and ~ 2, external loads of NH₄⁺ and PO₄³⁻, respectively. Transient anoxia produced a general decrease of NH₄⁺ and SiO₂ regeneration, likely due to decreased macrofauna activity or inefficient mineralization, whereas it doubled average PO₄³⁻ fluxes. In sandy, well-flushed areas, anoxia had a minor effect on PO₄³⁻, but stimulated a large production of Mn²⁺. Muddy sediments in lagoon areas with slow water renewal displayed large redox-dependent PO₄³⁻ mobility, coupled to Fe²⁺ release. Settled algal blooms and hypoxic conditions might unbalance benthic regeneration stoichiometry and sustain blooms. The sedimentary pool of Mn⁴⁺ may represent a natural buffer preventing iron reduction and PO₄³⁻ mobility.

由于自我维持的机制，蓝藻的有害繁殖可能会长期持续。我们假设沉淀的花朵可能会增加依赖于氧化还原的P释放，并使底栖养分再生的化学计量失衡（NH ₄ ⁺：SiO ₂：PO ₄ ³⁻比率）。我们在欧洲最大的肥厚库尔斯泻湖中验证了这一假设。夏季，在叶绿素和水温达到峰值时，在代表所有泻湖沉积环境的19个站点上收集了沉积物核心。沉积物的有机物含量，粒度，有氧呼吸以及溶解的无机营养物和金属（Fe ²⁺和Mn ^2+）的氧化和缺氧通量-被测量。将再生养分的负荷和化学计量与分水岭的负荷进行了比较。经分析的沉积物需氧量较高（-1.90至-5.66 mmol O ₂ m ^-2  h ^-1），通常与其可变有机物含量（1-23％）和中值粒径（30-300μm）无关。在有氧条件下，夏季内部循环等于（SiO ₂）或超过〜66和〜2倍，分别是NH ₄ ⁺和PO ₄ ^3-的外部负荷。瞬态缺氧使NH ₄ ⁺和SiO ₂普遍降低可能是由于大型动物活动减少或矿化效率低下引起的再生，而平均PO ₄ ^3-通量却翻了一番。在多雨的沙质地区，缺氧对PO ₄ ^3−的影响较小，但刺激了Mn ²⁺的大量产生。泻湖区泥浆沉积物的水更新较慢，显示出依赖氧化还原的大PO ₄ ^3-迁移率，并伴有Fe ^2+的释放。沉积的藻华和低氧条件可能会使底栖生物再生化学计量失衡并维持藻华。Mn ⁴⁺的沉积池可能代表天然的缓冲剂，可防止铁还原和PO ₄ ^3-迁移。