Resistance and resilience of small-scale recirculating aquaculture systems (RAS) with or without algae to pH perturbation

Abstract

The experimental set-up of this study mimicked recirculating aquaculture systems (RAS) where water quality parameters such as dissolved oxygen, pH, temperature, and turbidity were controlled and wastes produced by fish and feeding were converted to inorganic forms. A key process in the RAS was the conversion of ammonia to nitrite and nitrite to nitrate through nitrification. It was hypothesized that algae inclusion in RAS would improve the ammonia removal from the water; thereby improving RAS water quality and stability. To test this hypothesis, the stability of the microbiota community composition in a freshwater RAS with (RAS+A) or without algae (RAS-A) was challenged by introducing an acute pH drop (from pH 7 to 4 during three hours) to the system. Stigeoclonium nanum, a periphytic freshwater microalga was used in this study. No significant effect of the algae presence was found on the resistance to the acute pH drop on ammonia conversion to nitrite and nitrite conversion to nitrate. Also the resilience of the ammonia conversion to the pH drop disruption was not affected by the addition of algae. This could be due to the low biomass of algae achieved in the RAS. However, with regard to the conversion step of nitrite to nitrate, RAS+A was significantly more resilient than RAS-A. In terms of overall bacterial communities, the composition and predictive function of the bacterial communities was significantly different between RAS+A and RAS-A.

Analysis of changes in nutrient salts and other water quality indexes in the pond water for largemouth bass (micropterus salmoides) farming

“…The slowing down of the reproduction rate of beneficial algae in a pond can also lead to the generation of nitrite nitrogen. Nitrite nitrogen and ammoniacal nitrogen in a pond can be absorbed in large quantities through a series of chemical reactions when there are sufficient beneficial algae in the pond [ 10 ]. However, a large amount of ammoniacal nitrogen and nitrite nitrogen cannot be absorbed when beneficial algae are not sufficient.…”

Effects of Stigeoclonium nanum , a freshwater periphytic microalga on water quality in a small-scale recirculating aquaculture system

“…Procedure for DNA extraction and PCR was conducted following methods described in our previous study (Mohamed Ramli et al, ). Macherey Nagel genomic DNA extraction kit (Nucleospin ® Soil, Düren, Germany) was used for DNA extraction.…”

“…The RAS set-up ( Figure 1) as described in a previous study was used (Mohamed Ramli, Giatsis, Md Yusoff, Verreth, & Verdegem, 2018). The RAS set-up ( Figure 1) as described in a previous study was used (Mohamed Ramli, Giatsis, Md Yusoff, Verreth, & Verdegem, 2018).…”

“…This experiment consisted of two small-scale triplicated experimental treatments, RAS with microalgae (RAS+A) and RAS without microalgae (RAS-A) as the control treatment. The RAS set-up (Figure 1) as described in a previous study was used (Mohamed Ramli, Giatsis, Md Yusoff, Verreth, & Verdegem, 2018). RAS-A had the same configuration as RAS+A except that no microalgae were grown in the microalgae tanks.…”

Integration of Algae to Improve Nitrogenous Waste Management in Recirculating Aquaculture Systems: A Review

“…These studies have demonstrated benefits of integration of algae in the systems for nitrogenous waste management. Works related to algae integration in RAS is limited, and no recent report was found except for studies by the authors ( Ramli et al, 2018a , b ) that deal with algae-bacteria interactions in a RAS. Van Rijn (2013) reported that integration of phototrophic organisms (such as algae) in a RAS was mainly restricted to outdoor RAS due to the large areas required for photosynthesis.…”