Ardiansyah A, Fotedar R
Department of Environment and Agriculture, Curtin University, Perth, WA, Australia.
Agricultural Polytechnic State of Pangkep, Sulawesi Selatan, Indonesia.
Lett Appl Microbiol. 2016 Jul;63(1):53-9. doi: 10.1111/lam.12585.
Duckweed (Lemna minor L.) is a potential biofilter for nutrient removal and acts as a substrate for heterotrophic bacteria in recirculating aquaculture systems (RAS). Here, we determined the effects of harvesting frequency of duckweed on heterotrophic bacteria in RAS. Twelve independent RAS consisting of fish-rearing tank, biofilter tank and waste-collection tank were used to study the interactions between duckweed harvest frequencies up to 6 days and the composition, abundance and diversity of heterotrophic bacteria. After 36 days, heterotrophic bacteria in the biofilter tank were primarily Gram-negative cocci or ovoid, coccobacilli, Gram-negative bacilli and Gram-positive bacilli. Most bacterial genera were Bacillus and Pseudomonas while the least common was Acinetobacter. Duckweed harvested after every 2 days produced the highest specific growth rates (SGR) and total harvested biomass of duckweed, but harboured less abundant bacteria, whereas 6-day harvests had a higher growth index (GI) of duckweed than 2-day harvests, but caused a poor relationship between SGR and biomass harvest with the abundance and diversity of heterotrophic bacteria. Stronger correlations (R(2) > 0·65) between duckweed SGR and biomass harvest with the heterotrophic bacteria diversity were observed at 4-day harvest frequency and the control.
This study provides significant information on the interaction between the harvest frequency of duckweed and the composition, abundance and diversity of heterotrophic bacteria in recirculating aquaculture systems (RAS). Different harvest frequencies significantly influence the abundance and diversity of heterotrophic bacteria, which in turn may influence the nitrogen uptake efficiency of the system. The research is useful in improving the efficiency of removing nitrogenous metabolites in RAS directly by the duckweed and associated heterotrophic bacteria.
浮萍（小眼浮萍）是一种用于去除营养物质的潜在生物滤池，并且在循环水养殖系统（RAS）中作为异养细菌的底物。在此，我们确定了浮萍收获频率对RAS中异养细菌的影响。使用由养鱼池、生物滤池和废物收集池组成的12个独立RAS来研究长达6天的浮萍收获频率与异养细菌的组成、丰度和多样性之间的相互作用。36天后，生物滤池中异养细菌主要为革兰氏阴性球菌或卵形菌、球杆菌、革兰氏阴性杆菌和革兰氏阳性杆菌。大多数细菌属为芽孢杆菌属和假单胞菌属，而最不常见的是不动杆菌属。每2天收获的浮萍产生最高的特定生长率（SGR）和浮萍总收获生物量，但所含细菌丰度较低，而6天收获的浮萍生长指数（GI）高于2天收获的浮萍，但导致SGR与生物量收获与异养细菌的丰度和多样性之间关系不佳。在4天收获频率和对照条件下，观察到浮萍SGR和生物量收获与异养细菌多样性之间更强的相关性（R²>0·65）。
本研究提供了关于浮萍收获频率与循环水养殖系统（RAS）中异养细菌的组成、丰度和多样性之间相互作用的重要信息。不同的收获频率显著影响异养细菌的丰度和多样性，这反过来可能影响系统的氮吸收效率。该研究有助于直接通过浮萍和相关异养细菌提高RAS中含氮代谢物的去除效率。
