Water quality management is a cornerstone for success in the aquaculture of white shrimp, Litopenaeus vannamei. Excess nutrients, originating from uneaten feed and waste, can lead to eutrophication and negatively impact the health of the animals. Traditionally, photoautotrophically grown microalgae (dependent on sunlight) have been used to balance the pond ecosystem. However, a recent study explores a promising alternative: the use of the microalga Chlorella pyrenoidosa cultivated heterotrophically (without the need for light and using organic carbon sources).
The research, conducted by scientists from the Yellow Sea Fisheries Research Institute and the Qingdao Institute of Bioenergy and Processes in an outdoor shrimp farming system, evaluated whether substituting traditional photoautotrophic Chlorella vulgaris with heterotrophic C. pyrenoidosa could enhance water purification and regulate the microbial community without compromising shrimp growth. The results offer key insights into the potential of this innovative technique.
Key findings
- Inoculation with heterotrophically grown Chlorella pyrenoidosa did not negatively affect the growth or weight gain rate of Litopenaeus vannamei shrimp compared to the traditional method.
- This method demonstrated greater efficiency in removing key nutrients such as phosphate (PO43−−P) and ammonia nitrogen (NH4+−N), contributing to improved water quality.
- The use of heterotrophic Chlorella helped regulate and maintain more stable levels of pH, biochemical oxygen demand (BOD), and chemical oxygen demand (COD).
- It fostered greater diversity and richness in the pond’s microbial community, promoting the abundance of beneficial bacteria such as Proteobacteria, Actinobacteria, Luteolibacter, and Exiguobacterium.
How was the study conducted?
The researchers designed a 30-day experiment in two outdoor earthen ponds. Both were stocked with L. vannamei shrimp at a density of 80 individuals per cubic meter. The key difference was the water treatment:
- CP Pond: Inoculated with a solution of Chlorella pyrenoidosa grown under heterotrophic conditions.
- CV Pond: Served as the control and was treated with photoautotrophically grown Chlorella vulgaris, the conventional method.
Throughout the trial, researchers collected regular samples to analyze crucial water quality parameters (pH, phosphates, ammonia nitrogen, nitrites, nitrates, BOD, and COD), algae density, shrimp growth, and the composition of bacterial communities.
Impact on water quality: The heterotrophic advantage
One of the most significant findings was the superior ability of heterotrophic Chlorella pyrenoidosa to maintain optimal water conditions. The CP pond showed higher efficiency in removing phosphate (PO43−−P) and ammonia nitrogen (NH4+−N), two of the main compounds contributing to eutrophication. This suggests that heterotrophic C. pyrenoidosa is more effective at assimilating these nutrients, thereby actively cleaning the water.
Furthermore, the CP pond exhibited better pH regulation, maintaining it within a more stable and lower range (between 7.5 and 8.3), which is ideal for shrimp development. Additionally, the levels of biochemical oxygen demand (BOD) and chemical oxygen demand (COD), which indicate the amount of organic pollutants, were consistently lower in the pond treated with heterotrophic Chlorella.
A richer and more beneficial microbial community
Microbial balance is vital for the health of an aquaculture pond. The study revealed that inoculation with heterotrophic C. pyrenoidosa not only improved physicochemical parameters but also increased the diversity and richness of the bacterial community. Specifically, an increase was observed in the proportion of beneficial bacterial phyla such as Proteobacteria and Actinobacteria. Proteobacteria are known for their role in water purification by removing nitrogen and phosphorus, while Actinobacteria can degrade complex organic matter.
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At the genus level, the CP pond showed a greater abundance of bacteria like Luteolibacter and Exiguobacterium. Previous studies have associated Luteolibacter with enhanced organic matter decomposition and Exiguobacterium with efficient nitrate degradation—both key processes for maintaining a healthy aquatic environment.
What about shrimp growth?
For any producer, the fundamental question is whether a new technique affects crop performance. In this regard, the results were conclusive: no statistically significant differences were observed in shrimp growth between the two ponds. The weight gain rate (approximately 157% in the CP pond and 159% in the CV pond) and the specific growth rate were virtually identical. This demonstrates that implementing heterotrophic Chlorella can offer substantial environmental benefits without sacrificing crop productivity.
Conclusion: A step towards more sustainable aquaculture
This study shows that substituting photoautotrophic Chlorella with heterotrophically grown C. pyrenoidosa is a viable and advantageous strategy for L. vannamei cultivation. This method not only improves nutrient removal and stabilizes key water parameters but also fosters a more diverse and healthy aquatic microbiome. The findings open the door for using heterotrophically cultivated microalgae as an effective tool for water quality control, promoting a more efficient and sustainable shrimp aquaculture industry.
The study was funded by the Key Deployment Project of the Centre for Ocean Mega-Research of Science, Chinese Academy of Sciences, the Key Research and Development Program of Shandong Province, and the China Agriculture Research System (CARS-47).
Contact
Zhen Meng
Yellow Sea Fisheries Research Institute/ Marine Fish Breeding and Biotechnology Laboratory, Chinese Academy of Fishery Sciences
Qingdao, Shandong 266071, China
Email: mengzhen@ysfri.ac.cn
Reference (open access)
Song, C., Meng, Z., Zhang, B., Yang, L., Sun, X., Zhang, Z., & Song, X. (2025). Substituting photoautotrophic with heterotrophic Chlorella species for water quality regulation and microbial community modification in Litopenaeus vannamei pond culture. Aquaculture Reports, 44, 103049. https://doi.org/10.1016/j.aqrep.2025.103049
Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.
