Favored competition of Uroglena sp. against coexisting microorganisms in spring of lower temperatures: clarification through a systematic incubation study.

Abstract

Uroglena sp. is a major contributor to the fishy odor in drinking water, with temperature being a key factor regulating its growth. However, no study has yet detailed its effect on Uroglena sp.'s growth. Uroglena sp. mainly blooms in spring when temperatures are lower, though similar lower temperatures are also present in autumn and winter. Therefore, the objectives of this study were to investigate the growth and decline behavior of Uroglena sp. under different temperatures and to assess the impact of microorganism composition in different samples on the growth of Uroglena sp. To achieve the objectives of this study, surface water samples collected in May (spring), September (autumn), and January (winter) were incubated under different temperatures. Findings revealed that Uroglena sp. exhibited higher and more prolonged growth at a low temperature of 5 °C. Within the temperature range of 10 to 20 °C, Uroglena sp. exhibited less vigorous growth and lysed more rapidly. No growth was observed at 30 °C. The limited growth of Uroglena sp. at higher temperatures is attributed to an increased abundance of bacteria and competition with other microalgae including Nitzschia sp., Sphaerocystis sp., Scenedesmus sp., Fragilaria sp., Attheya sp., Golenkinia sp., Melosira sp., and Dinobryon sp. This indicates that the coexistence of microalgae and bacteria plays a significant role in the growth of Uroglena sp. The maximum concentration of Uroglena sp. during incubation was higher for the water sample of May compared to the sample of September and January, which reached about 2500 colony/mL at 5 °C for the sample of May. The generally higher growth of Uroglena sp. with the sample of May suggests that less significant microalgae competition in the season could create more favorable conditions for the bloom of Uroglena sp.