ASSESSMENT OF ENVIRONMENTAL SUITABILITY FOR SPINY LOBSTER (Panulirus homarus) AND RABBITFISH (Siganus sp.) POLYCULTURE BASED ON PHYTOPLANKTON COMMUNITY STRUCTURE IN FLOATING NET CAGES

Abstract

This study aims to analyze the composition and abundance of phytoplankton as a bioindicator of environmental suitability in a polyculture farming system of spiny lobster (Panulirus homarus) and rabbitfish (Siganus sp.) in floating net cages (FNC). Phytoplankton plays an important role in maintaining aquatic ecosystem stability and reflects water quality conditions through changes in community structure. Sampling was conducted at three points around the FNC using a purposive sampling method. The observed parameters included abundance, diversity, dominance, and evenness indices, which were analyzed descriptively to assess the condition of the waters. The results show that phytoplankton abundance falls within the eutrophic category, with moderate diversity (H’), high evenness (E), and low dominance (D). One external factor contributing to eutrophication in aquatic environments is aquaculture activities using FNC systems. Phytoplankton from the class Bacillariophyceae were found in the highest numbers, particularly the species Rhizosolenia sp. and Synedra sp. Several studies indicate that both species are naturally found in the stomach contents of lobsters and serve as natural feed for P. homarus and rabbitfish. Values of physical and chemical water quality parameters indicate that the FNC Ujung Betok waters remain suitable for aquaculture activities. Based on bioindikator analysis and the physical–chemical conditions of the waters, the Ujung Betok FNC is suitable for the polyculture farming of spiny lobster and rabbitfish.