The dynamics of Chlorella spp. abundance and its relationship with water quality parameters in intensive shrimp ponds

Abstract

Chlorella spp. is a plankton genus belonging to the phylum Chlorophyta and is commonly found in the shrimp farming ponds. This plankton might serve as natural feed especially for the post-larvae stage shrimps. This study aims to investigate the dynamics of Chlorella spp. abundance and its correlation with the N:P ratio in the intensively managed shrimp ponds. The study was conducted using a causal ex-post facto design with data collection through purposive sampling. The results showed that the plankton abundance in the observed ponds was moderate consisted of 4 class and 7 genera. The dominant genus was Chroococcus spp. and Chlorella spp. with abundance ranging from 2.50E+05 to 2.60E+05 cells/mL. Plankton abundance correlated with water quality conditions, including pH of 7.9, salinity of 19-20‰, temperature of 28.50-28.75°C, dissolved oxygen of 5.12-5.39 mg/L, nitrite of 0.035-0.072 mg/L, phosphate of 0.011-0.025 mg/L, organic matter of 95.77-102.32 mg/L, and alkalinity of 125-130 mg/L. There was also correlation between the increase in plankton biomass and nutrient solubility. The abundance of Chlorella spp. was negatively correlated with the N:P ratio of the water in the ponds. Based on dynamic model analysis, the most ideal N:P ratio is 1:20 from several simulations of 1:10, 1:20, 1:30, and 1:40. The dynamics of Chlorella spp. abundance followed an oscillatory pattern from the beginning of cultivation to harvest with the most ideal N:P ratio of 1:20. This understanding is important for making environmental engineering concepts in pond aquatic ecosystems.