Identification of the predatory ciliate S. histriomuscorum in Open-pond cultivation of the microalga, Dunaliella salina and investigation of its control strategies

Aminikhoei, Zahra; Ajdari, Ashkan; Ghaffari, Hadi; Khallaghi, Behzad

doi:10.48311/jfst.2025.79576.0

Identification of the predatory ciliate S. histriomuscorum in Open-pond cultivation of the microalga, Dunaliella salina and investigation of its control strategies

Document Type : Original Research

Authors

Zahra Aminikhoei ¹

Ashkan Ajdari ¹

Hadi Ghaffari ²

Behzad Khallaghi ³

¹ Agricultural Research Education and Extension Organization (AREEO), Iranian Fisheries Science Research Institute (IFSRI), offshore fisheries Research Center, Chabahar, Iran.

² Agricultural Research Education and Extension Organization (AREEO), Iranian Fisheries Science Research Institute (IFSRI), Tehran, Iran.

³ Makran Blue Algae Company, Science and Technology Park of Sistan and Baluchestan Province, Chabahar Campus, Iran

10.48311/jfst.2025.79576.0

Abstract

The microalga Dunaliella salina is a valuable biological source in the food and pharmaceutical industries due to its ability to produce natural beta-carotene. Its industrial-scale production relies on open pond cultivation systems, which are cost-effective but highly vulnerable to biological contamination, particularly from predatory grazers. Therefore, identifying and developing efficient control methods for these grazers is essential for the successful cultivation of D. salina. In this study, the ciliate Stylonychia histriomuscorum was first identified as the dominant grazer in an open pond culture by monitoring population dynamics daily. Subsequently, a controlled in vitro experiment was designed to evaluate methods for its control. The effects of three salinity levels (130, 150, and 180 g/L), six pH levels (6.5 to 9.5), and four chemical compounds (urea, ammonium sulfate, ammonium chloride, and ammonium nitrate) were investigated. Results showed that increased salinity had no significant effect on the S. histriomuscorum population, while pH alterations negatively affected both the alga and the ciliate. In contrast, the addition of ammonium nitrate significantly reduced the grazer population with no adverse effects on D. salina growth. Therefore, using 0.5 g/L of ammonium nitrate is an effective strategy for controlling S. histriomuscorum contamination in open pond cultures of D. salina.

Keywords

: Microalgae

Dunaliella salina

Open pond

predator

ciliate

Subjects