Abstrak: Bakau menyokong himpunan kepelbagaian "epibiont" macroalgal atas akar dan batang terapung pokok bakau. Makroalga membekalkan nutrien kepada pengguna utama dalam rantaian makanan akuatik dan telah dilaporkan menjadi penyumbang besar kepada ekosistem marin. Kepelbagaian spesies, biomass, dan ciri-ciri habitat makroalga bakau telah dikaji di tiga stesen bakau di muara Sibuti, Sarawak, Malaysia, dari bulan November 2012 hingga Oktober 2013. Tiga kumpulan makroalga direkodkan dan telah didapati tumbuh pada akar terapung pokok bakau, iaitu Rhodophyta (Caloglossa ogasawaraensis, Caloglossa adhaerens, Caloglossa stipitata, Bostrychia anomala, dan Hypnea sp.), Chlorophyta (Chaetomorpha minima dan Chaetomorpha sp.), dan Phaeophyta (Dictyota sp.). Biomass makroalga tidak dipengaruhi (p>0.05) mengikut musim di habitat hutan bakau. Spesies makroalga iaitu Hypnea sp. menyumbang biomass yang paling tinggi di kedua-dua Stesen 1 (210.56 mg/cm 2 ) dan Stesen 2 (141.72 mg/cm 2 ), manakala biomass tertinggi disumbangkan oleh B. anomala (185.89 mg/cm2) di Stesen 3. Kajian ini menunjukkan bahawa taburan dan himpunan spesies daripada makroalga bakau dipengaruhi oleh parameter alam sekitar seperti nutrien dari air, pepejal terlarut, dan kemasinan di habitat muara bakau Sibuti, Sarawak.Kata kunci: Makroalga, Bostrychia anomala, Biomass, Bakau, Sarawak Abstract: Mangroves support diverse macroalgal assemblages as epibionts on their roots and tree trunks. These algae provide nutrients to the primary consumers in the aquatic food web and have been reported to be substantial contributors to marine ecosystems. The species diversity, biomass, and habitat characteristics of mangrove macroalgae were investigated at three stations in the Sibuti mangrove estuary, Sarawak, Malaysia, from November 2012 to October 2013. Three groups of macroalgae were recorded and were found to be growing on mangrove prop roots, namely Rhodophyta (Caloglossa * 2 ) at Station 3. This study shows that the species distribution and assemblages of mangrove macroalgae were influenced by environmental parameters such as water nutrients, dissolved solids, and salinity in the estuarine mangrove habitats of Sibuti, Sarawak.