Telah dilakukan penelitian tentang sebaran spasiotemporal spesies HAB di lokasi budidaya kerang hijau (Perna viridis), Kamal Muara, Jakarta Utara pada bulan Mei-Oktober 2011. Sampel diambil secara vertikal di sembilan stasiun dengan plankton-net, dan dilakukan pula pengukuran parameter lingkungan. Spesies HAB yang ditemukan berasal dari kelas Raphidophyceae, Bacillariophyceae, dan Dinophyceae, didominasi oleh Ceratium furca, Chaetoceros spp., Gonyaulax polygramma, Nitzschia spp., Prorocentrum micans, Skeletonema costatum, dan Thalassiosira spp. Berdasarkan peta isoplank diketahui bahwa sebaran terpadat terjadi pada bulan Mei dan Oktober, yaitu di stasiun dekat muara. Berdasarkan Analisis Komponen Utama (AKU) dan Analisis Faktorial Korespondensi (AFK), diketahui bahwa terdapat perbedaan faktor lingkungan penciri di setiap bulan pengamatan yang menyebabkan perbedaan sebaran spesies HAB tertentu. Research on spatiotemporal distribution of HAB species at green mussel (Perna viridis) farming area, Kamal Muara, North Jakarta has been conducted in May to October 2011. Samples were taken vertically at nine stations using plankton-net, and environmental parameters were also measured. The classes of HAB species found in this research were Raphidophyceae, Bacillariophyceae, and Dinophyceae, dominated by Ceratium furca, Chaetoceros spp., Gonyaulax polygramma, Nitzschia spp., Prorocentrum micans, Skeletonema costatum, and Thalassiosira spp. Based on isoplank map, the densest distribution was at stations near river mouth, especially in May and October. Based on the Principle Component Analysis (PCA) and Correspondence Analysis (CA) results, there were differences in environmental factor characterized each month, which will cause differences in the distribution of certain HAB species.