Unbalanced N:P Ratio: On Phytoplankton Abundance and Survival Rate of the Whiteleg Shrimp (Litopenaeus vannamei)

This study aimed to investigate the impact of an unbalanced N:P ratio on the planktonic ecosystem and the growth of the whiteleg shrimp (Litopenaeus vannamei) in aquaculture systems. Conducted at the Marine Aquaculture Laboratory, Faculty of Fisheries and Marine Science (FPIK), IPB University, the research utilized a completely randomized design (CRD) with four treatments (Control = 16:1, A = 20:1, B = 25:1, C = 30:1) and three replications. Shrimp seeds weighing 3.51 ± 0.07 grams were stocked at a density of 23 shrimp per unit and fed four times daily with a diet comprising 7% of their biomass per day, using crumble feed with 36% protein content over a 30-day maintenance period. Results revealed that increasing the N:P ratio led to higher phytoplankton abundance, with the highest levels observed in treatment C (30:1) from days 7 to 28. The analysis of water quality parameters revealed fluctuations in total ammonia nitrogen (TAN), nitrite, nitrate, and phosphate levels throughout the study. On day 0, significant differences in TAN, nitrite, and nitrate levels were noted between treatments (P<0.05). TAN levels decreased by day 7, with the control treatment showing significant differences from treatments A and B, excluding treatment C (P>0.05). From days 21 to 28, TAN levels continued to decrease without significant differences among treatments (P>0.05). Nitrite levels increased on day 7 and stabilized until day 28, showing no significant differences (P>0.05). Nitrate levels decreased on day 7, with the control treatment significantly differing from treatments A, B, and C (P<0.05). Phosphate levels fluctuated throughout the observation period, with significant differences only on day 28 between treatment A and C (P<0.05). Histopathological examination of shrimp pancreases revealed tissue damage, including vacuoles and necrosis across all treatments. While temperature, salinity, and dissolved oxygen (DO) levels remained within the optimal range, pH levels were not optimal, likely due to organic matter decomposition in the water. This study highlights the complex interactions between nutrient ratios and aquatic health, emphasizing the need for careful management in shrimp aquaculture.