Effects of humic acid on nutrient removal efficiency of aquatic duckweed (Lemna minor) and both growth performance, and hemato-biochemical parameters of Nile tilapia (Oreochromis niloticus) cultured in water recirculating system

Abstract

This study was carried out to evaluate the effects of humic acid (HA) on the nutrient removal efficiencies of aquatic duckweed plant (Lemna minor) from a water recirculating system used to culture Nile tilapia (Oreochromis niloticus) fish for 30 days. The HA was added to water at three concentrations of 0 (Control), 1.5, and 3 mg/L in triplicate. Water quality parameters, growth performance, and some hemato-biochemical parameters of the fish in variable HA concentrations were compared. The total ammonia nitrogen (TAN) and total phosphorous (TP) removal efficiency of L. minor increased with increasing the HA concentration from 0 mg/L to 3 mg/L (p < 0.05). The concentration of nitrate (NO₃⁻) in the HA-3 mg/L was higher than that in the other groups on days 20 and 30 of the fish cultivation period (p < 0.05). The growth performance of fish improved in the HA-3 mg/L compared to the other groups. The addition of different concentrations of HA to water had no adverse effect on the hematological properties of the Nile tilapia. The plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) levels in the HA-0 mg/L and HA-1.5 mg/L groups were higher than in the HA-3 mg/L (p < 0.05). No significant differences in the plasma glucose and cholesterol levels were observed between the HA-groups (p > 0.05), while the triglyceride level increased in the HA-3 mg/L compared to the control (p < 0.05). These results indicated that adding HA to water could be an effective method to enhance the bioremediation performance of the aquatic duckweed plants as biofilter and thus improve water quality, subsequently, fish growth performance in RASs.

NOVELTY STATEMENT

The current study applied aquatic duckweed plant (Lemna minor) as a new biofilter in a water recirculating system used to culture Nile tilapia (Oreochromis niloticus) fish. The effects of three concentrations of humic acid (HA) as water additive on the nutrient removal efficiency of L. minor from water were investigated. HA improved bioremediation performance of the aquatic duckweed plant.

Keywords:

• Aquaculture
• humic acid
• nutrient recovery
• phytoremediation
• water quality

Acknowledgments

The authors would like to express thanks to the staff of the Faculty of Natural Resources and Environment of Ferdowsi University of Mashhad (FUM) for their support in carrying out this research.

Ethics statement

The experiments on fish in this study were performed based on FUM animal ethic rights and Directive 2010/63/EU of the European Parliament and of the Council of 22 September 2010 on the protection of animals.

Authors’ contributions

Mehrdad Sarkheil: Conceptualization, Design of the experiments, Statistical analysis of data, Writing the first draft of the manuscript; Saeed Zahedi: Contribution to design of the experiments, Preparation of fish feed, Contribution to manuscript revision; Omid Safari: Conceptualization, Methodology, Statistical analysis of data; Hamidreza Ahmadniaye Motlagh: Hematological and biochemical analysis, Contribution to manuscript revision. All authors read and approved the submitted version.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data were included in the article. Supplemental data are available from the corresponding author upon reasonable request.

Additional information

Funding

This work was funded by FUM under grant [No: 2/57643].