Natural attenuation and engineering-based removal of marine algal toxins: current status and future perspectives

The global surge in harmful algal blooms (HABs), amplified by ocean warming and eutrophication, has intensified ecological and public health risks through the production of potent marine algal toxins. Given their ubiquitous occurrence, environmental persistence, and adverse effects on marine ecosystems and coastal economies, increasing efforts have been devoted to mitigating toxic HABs and associated toxin pollution. This review presents a systematic, integrated analysis of natural attenuation processes and engineering-based removal technologies for marine algal toxins, addressing a critical gap in which marine toxin treatment remains understudied relative to freshwater cyanotoxins. Natural attenuation through photodegradation and biodegradation provides baseline protection in marine environments, although removal efficiency varies substantially with light availability, temperature, and microbial community composition. Engineering-based technologies achieve substantially higher removal efficiencies but face operational challenges. We highlighted the removal performance, transformation products (TPs), and reaction pathways during natural attenuation and different remediation treatments, and predicted the biodegradability and multi-endpoint toxicity of each TP using in silico QSAR software. A key finding is that degradation can generate TPs with altered persistence, bioaccumulation potential, and toxicity relative to parent toxins, causing secondary risks that are often overlooked. This review therefore emphasizes the need for further research into toxin fate, comprehensive risk assessment, and effective management strategies.