Differential Nitrogen Source Utilization Drives Growth Dynamics of Chlorella spp. in Walne Medium

Abstract

Microalgae, particularly Chlorella spp., play a crucial role as primary producers and natural feed in aquaculture systems, making their efficient cultivation especially important in response to the rising global demand for sustainable protein sources. This study aims to analyze the effect of different nitrogen sources, namely NaNO₃, KNO₃, and urea ((NH₂)₂CO), on cell density and specific growth rate of Chlorella spp. A laboratory-based experimental design with a completely randomized design was applied using three treatments with replications. Data were collected through daily observation of cell density using a haemocytometer over a 14-day culture period and analyzed descriptively through growth curves and specific growth rate calculations. The results showed that all treatments exhibited similar growth patterns consisting of lag, exponential, stationary, and decline phases, with peak growth occurring on the ninth day. However, NaNO₃ produced the highest cell density (4.6×10⁷ cells mL^-1) and growth rate (0.173 day⁻¹), followed by urea and KNO₃. These findings indicate that Chlorella spp. can adapt to different nitrogen forms, although nitrate remains the most efficient source. Importantly, urea demonstrated comparable performance, suggesting its potential as a cost-effective alternative in microalgae cultivation. This study contributes theoretically to understanding nitrogen utilization in microalgae and practically offers insights for optimizing culture media to improve efficiency in aquaculture applications.