探討清淤機對南美白對蝦養殖之微生物相影響與益生菌優化策略

Abstract

清淤機可有效地移除水中有機物和降低有毒物質含量。但過去清淤機的研究多著重於水體物理及化學指標，而忽略了微生物這個養殖重要因子。微生物已被證實是維持養殖環境穩定及提高養殖效率的重要因素。因此，本研究旨在探討清淤機對微生物的影響，並以此為基礎改善清淤機的效果。研究中藉由次世代定序，分析養殖池水、蝦腸道和底泥的微生物相。結果顯示，在所有樣本中占比最高的菌門皆相同。但在底泥樣本中，所涵蓋的門相對於池水和腸道是較豐富的。清淤機和沒有清淤機組相比，在Alpha多樣性雖沒有顯著差異，但在Beta多樣性則有顯著差異。在LEfSe分析中，清淤機組中跟病原菌有關的菌屬，如：Mycobacterium、Elizabethkingia及Shewanella豐度提高，而與水質有關的菌屬，如：Bacillus、Salinimicrobium及Salinarimonas豐度則下降。同樣地，在代謝功能途徑預測上，清淤機組和非清淤機組比較，在感染性疾病豐度較高，而跟氮、硫代謝相關的豐度則下降。因此為了減低清淤機可能的不良影響，將具氨代謝潛力的益生菌，以1x106 CFU/ml濃度加到試驗動物水體中，以篩選潛在有益此系統的益生菌。結果不論是在半淡鹹水或是海水養殖條件下，B. pumilus D5和T. denitrificans皆能提升水中氨分解效率。綜合上述，在白蝦養殖池中使用清淤機，確實會影響微生物相組成和功能。因此，若在養蝦池中使用清淤機，可能需有額外的微生物相關介入，而B. pumilus D5和T. denitrificans是可能改善此系統的候選益生菌。

The sludge removing system can effectively remove organic elements, thereby reducing the content of toxic substances in shrimp culture ponds. However, the studies related to sludge removing system mostly focused on the impacts in physical and chemical parameters, while ignored to consider microorganisms that were the crucial factor in maintaining a stable farming environment and improving farming efficiency in aquaculture. Therefore, this study aims to investigate the effect of sludge removing system on microorganisms and further to improve the effect of sludge removing system based on the results. In this study, the microbiota in water, shrimp gut, and sediment samples from both desilting and non-desilting ponds were analyzed by next-generation sequencing. The results showed that the phyla with the highest proportion were the same in all samples. There was no significant difference in alpha diversity but a significant difference in beta diversity between the groups with and without sludge removing system. In the LEfSe analysis, pathogenic bacteria, such as Mycobacterium, Elizabethkingia , and Shewanella were more in the sludge removing system group. Moreover, the bacteria related to nutrient metabolism, such as Bacillus, Salinimicrobium, and Salinarimonas were more in the non-sludge removing system group. The sludge removing system group had higher level of functions related to infectious diseases but lower level of functions related to metabolisms of nitrogen and sulfate. In order to reduce the negative effects of sludge removing system, potential probiotics for the system were selected by evaluating the ability of bacteria in ammonia decomposition through adding bacteria in the water with shrimp at 1x106 CFU/ml. The results reveal that B. pumilus D5 and T. denitrificans increased the efficiency of ammonia decomposition in both seawater and brackish water. In conclusion, using sludge removing system indeed influenced the composition and functions of microbiota in white shrimp farming ponds. Thus, a bacteria-related intervention should be applied when using sludge removing system, B. pumilus D5 and T. denitrificans could be the potential probiotics for optimizing the system.