Eutrophication-driven Trichodesmium erythraeum blooms in Karimunjawa National Park, Indonesia

Аннотация

Harmful algal blooms (HABs) are increasingly frequent due to anthropogenic nutrient enrichment, posing significant ecological and economic threats. It includes hypoxia, toxin production, and a decline in tourism due to odour pollution. This study investigates the HAB event in Karimunjawa National Park (KNP) on September 19, 2023, attributed to nutrient loading from inadequate wastewater treatment in the shrimp pond. The bloom coincided with the shrimp harvest season, indicating a strong correlation between pond effluents and coastal eutrophication. To identify the dominant algal species and primary environmental drivers of bloom formation, nutrients and water quality parameters were analysed using field and satellite observations from three locations in KNP. Pearson’s correlation analysis was applied to assess linear relationships among variables, while principal component analysis (PCA) was employed to determine key contributors to HAB development. The findings indicate that Trichodesmium erythraeum was the dominant bloom-forming species, proliferating due to biogeochemical imbalances induced by excessive nutrient enrichment. Phosphate (r=0.952), silicate (r=0.832), ammonia (r=0.670), and nitrate (r=0.653) were identified as key factors influencing bloom dynamics. Lower ammonia concentrations suggest uptake by phytoplankton, whereas microbial decomposition contributed to elevated phosphate levels. Additionally, high sunlight exposure (r=0.877) and low-currents hydrodynamic conditions (r=0.197) further facilitated bloom persistence. These findings underscore the urgent need for enhanced wastewater management policies in shrimp ponds and stricter environmental policies to mitigate future HABs occurrences and protect marine ecosystems and coastal economies.