Nitrogen uptake by Scenedesmus quadricauda and its responses over environmental factors

Nitrogen is a vital nutrient for the growth of microalgae. Understanding the mechanism of nitrogen uptake by algae plays a crucial role in addressing and mitigating. Harmful algal blooms. This study compares the nitrogen uptake kinetics of Scenedesmus quadricauda on different nitrogen substrates: NO₃^-, NH₄⁺, urea, and glycine. And the effects of four environmental factors on nitrogen uptake were also investigated. In the presence of four N substrates, Scenedesmus quadricauda took up four N substrates simultaneously. The order of uptake rates by Scenedesmus quadricauda was NH₄⁺ > urea > NO₃^- > glycine. Scenedesmus quadricauda exhibited a strong preference for urea and NH₄⁺. Moreover, the environmental factors of temperature, pH, and light intensity had significant effects on nitrogen uptake rates. Although changes in environmental factors affected nitrogen uptake rates, they did not alter the uptake preference for different nitrogen sources. Higher temperatures (35 °C), higher pH (9), optimal light intensity (7200 lx) and turbulence intensity (100 rpm) conditions were associated with the higher nitrogen uptake rates. The findings contribute to a better understanding of algal nitrogen metabolism and provide a basis for predicting and managing algal bloom occurrences in aquatic ecosystems.