CALCIUM AND PHOSPHATE CONCENTRATIONS IN COASTAL WATERS AT THE PARIGI DUA FLOATING NET CAGE AQUACULTURE SITE, BANDA NAIRA, CENTRAL MALUKU, INDONESIA

Abstrak

This study assessed calcium (Ca) and phosphate concentrations in seawater at the Parigi Dua floating net cage (FNC) aquaculture site in Nusantara Village, Banda Naira, Central Maluku, Indonesia. Seawater samples were collected at a depth of 8 m during August–September 2025. Calcium and phosphate were measured using Hanna HI758 Calcium Checker and Hanna HI713 Phosphate Checker instruments, respectively, while supporting water-quality parameters were measured in situ. The mean water temperature was 28.3 °C, salinity 30 ppt, pH 7.78, and dissolved oxygen (DO) 5.3 mg L⁻¹. Calcium concentrations were reported to range from 418 to 600 mg L⁻¹, with a mean of 509 mg L⁻¹. Phosphate concentrations were 0.11 mg L⁻¹ in August and 0.90 mg L⁻¹ in September, giving a reported mean of 0.505 mg L⁻¹. This mean is substantially higher than the 0.015 mg L⁻¹ phosphate criterion cited by the original study from Indonesian Government Regulation No. 22/2021. The findings identify phosphate enrichment as a priority for follow-up monitoring around the aquaculture site. However, the descriptive design and limited temporal sampling do not establish the source of phosphate or demonstrate that aquaculture was its cause. Further work should include replicated sampling across stations, depths, tides, and seasons, alongside quality assurance and source assessment.