Aquaculture and Fisheries Group, Wageningen University, Wageningen, The Netherlands.
Department of Biological and Agricultural Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
PLoS One. 2018 Apr 16;13(4):e0195862. doi: 10.1371/journal.pone.0195862. eCollection 2018.
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.
本研究的实验设置模拟了循环水产养殖系统（RAS），其中控制了水质参数，如溶解氧、pH 值、温度和浊度，并将鱼类和饲料产生的废物转化为无机形式。RAS 的一个关键过程是通过硝化作用将氨转化为亚硝酸盐和亚硝酸盐转化为硝酸盐。假设在 RAS 中添加藻类会提高水中氨的去除率；从而改善 RAS 的水质和稳定性。为了验证这一假设，通过将系统的 pH 值从 7 急剧降至 4（在三小时内），挑战了含有（RAS+A）或不含藻类（RAS-A）的淡水 RAS 中微生物群落组成的稳定性。本研究使用了淡水附生微藻 Stigeoclonium nanum。藻类的存在对氨转化为亚硝酸盐和亚硝酸盐转化为硝酸盐的耐急性 pH 下降没有显著影响。藻类的添加也不会影响氨对 pH 下降破坏的恢复力。这可能是由于在 RAS 中获得的藻类生物量低。然而，就亚硝酸盐向硝酸盐的转化步骤而言，RAS+A 比 RAS-A 更具弹性。就整体细菌群落而言，RAS+A 和 RAS-A 之间的细菌群落组成和预测功能存在显著差异。
