Plankton diversity in Raja Ampat: Foundation of the coral reef trophic structure

Raja Ampat, located within the Coral Triangle, features multiple management zones, including core, open access, and tourism areas. Planktons, as the base of the marine food web, play a vital role in sustaining coral reef ecosystems. Understanding their diversity is essential for evaluating ecosystem health and informing conservation efforts. This study aimed to assess plankton biodiversity in the coral reef ecosystem of Raja Ampat. Sampling was conducted in January 2018 across multiple sites from surface waters using a 23 μm mesh net. The samples were preserved in Lugol’s solution, quantified microscopically, and morphologically identified. Biodiversity indices were analyzed using the Shannon-Wiener index (H’), evenness (E), and dominance (C), whereas spatial patterns were examined using Bray-Curtis cluster analysis. In total, 11–21 phytoplankton taxa were recorded, including Cyanophyceae, Bacillariophyceae, Dinophyceae, and Chlorophyceae. Zooplankton consisted of 2–6 taxa from Protozoa, Crustacea, and Chaetognatha. Phytoplankton diversity was the highest in Arefi (H’ = 2.21) and the lowest in Paniki Besar. Cluster analysis identified three phytoplankton groups and two zooplankton groups. These findings highlight the spatial variation in plankton communities and emphasize their value as indicators of coral reef ecosystem structure and health in the Raja Ampat.