Harmful Algal Blooms, driven by human activities and warming waters, lead to ecosystem degradation and methane emissions. A new methodology has been developed to quantify climate benefits from HAB mitigation in various eligible systems, ensuring durability and environmental integrity through conservative baselines, strict safeguards, and deferred crediting. This methodology combines short-term intervention with long-term monitoring to ensure real, measurable, and verifiable carbon removal and avoidance. Key features include dual crediting pathways, strong permanence safeguards, robust MRV, operational flexibility, conservative accounting, and high-impact co-benefits.