HAB Impacts on Seafood Safety in Kenya Coastal Waters

Harmful Algal Blooms (HABs) are increasingly recognized as major environmental and public health concerns due to their impact on seafood safety, marine ecosystems, fisheries, and coastal livelihoods. In Kenya’s coastal waters, rising anthropogenic pollution, nutrient enrichment, and climate‑driven oceanographic changes may be enhancing the proliferation of harmful phytoplankton capable of producing marine biotoxins. These toxins can accumulate in seafood species consumed by humans, posing risks to public health and threatening sustainable Blue Economy development.

This study assessed the occurrence, distribution, and environmental drivers of HAB species and evaluated associated seafood safety risks along the Kenyan coast. Seasonal seawater and seafood samples were collected from selected coastal ecosystems and fish landing sites. Phytoplankton species were identified and enumerated using standard microscopy and taxonomic methods, while environmental parameters including temperature, salinity, dissolved oxygen, nutrients, pH, and chlorophyll‑a were measured to determine factors influencing HAB dynamics. Selected seafood species were screened for potential marine biotoxins using appropriate analytical techniques.

Preliminary findings revealed the presence of several potentially harmful phytoplankton genera, including Pseudo‑nitzschia, Dinophysis, Alexandrium, and Gambierdiscus, across sampled sites. Total phytoplankton abundance ranged from 1.2 × 10³ to 8.7 × 10⁴ cells L⁻¹, with higher concentrations recorded in nutrient‑enriched and environmentally stressed areas. Pseudo‑nitzschia spp. exhibited the highest abundance, reaching 3.5 × 10⁴ cells L⁻¹ during the northeast monsoon season. Environmental parameters varied across sites, with elevated nitrate (0.42–2.81 mg L⁻¹) and phosphate (0.08–0.67 mg L⁻¹) levels positively associated with increased HAB abundance.

Spatial variability in HAB occurrence was linked to river discharge, aquaculture activities, and urban runoff. Community surveys indicated that over 68% of fishers and seafood vendors had limited awareness of HAB‑related seafood safety risks. These findings highlight increasing HAB occurrence in Kenya’s coastal waters and underscore the need for continuous monitoring, environmental management, and early‑warning systems to safeguard seafood safety and support sustainable Blue Economy development.