The structure changes of microbial food web during the culture of grass carp larvae

The microbial food web, including phytoplankton, microzooplankton and bacteria, is an important part of the aquatic ecosystem. Microplankton are the natural bait of larvae, and larvae are influenced by microbiota. However, little is known about the functions of microbial food web in fish culture pond. In the present study, we investigated the dynamic changes of microbial food web in grass carp larvae culture ponds, then measured the grazing relationship among mesozooplankton, microzooplankton and phytoplankton, and further explored the relationship between the aquatic bacteria in culture pond and the intestine bacteria in grass carp larvae. Firstly, the density of phytoplankton was lowest while zooplankton was highest on day 3 of larvae culture. The grazing experiments indicated that the grazing capacity of zooplankton decreased on phytoplankton, while the grazing capacity of mesozooplankton increased on microzooplankton with culture time. Secondly, aquatic bacterial di-versity increased with culture time when plankton changed. Actinobacteria, Proteobacteria, and Bacteroidetes were the dominant bacteria in water. Finally, the species increased and abundance decreased in dominant bacteria of larvae intestine with culture time. The larvae intestinal microbiota exceeded the aquatic microbiota in terms of bacterial diversity on day 7 of larvae culture. And the similarity between the microbiota of the intestine and aquaculture water increased with culture time. Therefore, microbial food web affected the intestinal microbiota of larvae. These results provide a primary investigation into the structural changes of microbial food web in grass carp larvae culture ponds, and may help us to solve the problems of ecological environment and larvae culture.

Automated summary

The microbial food web, consisting of phytoplankton, microzooplankton, and bacteria, plays a crucial role in the aquatic ecosystem. However, little is known about its functions in fish culture ponds. This study investigated the changes in the microbial food web in grass carp larvae culture ponds and explored the relationships between aquatic bacteria and intestinal bacteria in grass carp larvae.