The Relationship Between Organic Matter and Phytoplankton Structure in The Aquaculture Zone of Karimunjawa: Non-Metric Multi-Dimensional Scalling (NMDS) and k-Dominance Curves Analysis Approach

The marine ecosystem surrounding Menjangan Besar Island in Karimunjawa is a vital site for aquaculture, significantly contributing to the local economy. However, this practice induces organic enrichment that may disrupt ecological balance. This study investigates the relationship between organic matter and phytoplankton community structure in the aquaculture zone, employing non-metric multidimensional scaling (NMDS) and k-dominance curves for analysis. Fieldwork conducted in October 2021 focused on three sites: monoculture cages, Integrated Multi-Trophic Aquaculture (IMTA) polyculture cages, and a reference site. A purposive random sampling method yielded 16 phytoplankton species. NMDS analysis (stress value: 0.03) revealed distinct clustering among sampling stations, indicating variations in phytoplankton community structure. The graphical approach, employing NMDS and k-dominance curves, effectively identifies stations with varying levels of diversity and evenness. The monoculture site (L1S1) exhibited the highest dominance and the lowest diversity. , whereas In contrast, the reference site (L3S1) and the polyculture site (L2S2) demonstrated the highest diversity, corresponding to the lowest dominance among all sampling stations. These patterns suggest that polyculture systems exhibit greater ecological stability compared to monoculture systems. Furthermore, the NMDS analysis revealed a clear clustering pattern among sampling stations, reflecting distinct differences in phytoplankton community structure across monoculture, polyculture, and reference locations. These findings highlight the complex interactions between aquaculture practices and phytoplankton dynamics, emphasizing the need for sustainable management strategies in marine ecosystems.