OPTIMIZATION OF PHOSPHORUS AND POTASSIUM CONCENTRATIONS TO ENHANCE Chaetoceros amami PRODUCTIVITY AS LIVE FEED FOR PEARL OYSTER (Pinctada maxima)

Abstract

Chaetoceros amami is a highly nutritious phytoplankton that plays an important role as natural feed for pearl oysters (Pinctada maxima), with its productivity influenced by the availability of phosphorus (P) and potassium (K). This study aimed to analyze the effect of phosphorus and potassium concentrations on the productivity of C. amami using a factorial Completely Randomized Design (CRD) with two factors, namely phosphorus (0, 1, 2, 3 parts per million/ppm) and potassium (0, 3, 6 ppm), with 3 replications, resulting in 36 experimental units. Treatment codes were expressed as combinations of PxKy, where x and y indicate the concentrations of phosphorus and potassium (ppm), respectively; P0K0 served as the control. Nitrogen was kept constant at 7.5 ppm. The parameters observed included peak cell density, relative growth, doubling time, and water quality, measured every 12 hours for 72 hours. The results showed that the treatments and the phosphorus-potassium interaction significantly affected peak cell density and relative growth (p<0.05), but had no significant effect on doubling time (p>0.05). The P1K3 treatment exhibited the best performance (density of 2,592,000 cells/ml; relative growth of 101.3%; doubling time of 48.9 hours), representing an increase of 19.3–47.5% compared to the control, while the P3K0 treatment showed the lowest performance due to nutrient imbalance and phosphorus toxicity. This study recommends the combination of 1 ppm phosphorus and 3 ppm potassium as the optimal formulation for efficient and economical mass production of C. amami, supporting the cultivation of pearl oysters (P. maxima).