This investigation on the plankton community of
E. sinensis breeding earthen ponds was conducted in April 2020. Samples were collected at each larval stage, and the corresponding water environmental factors were determined synchronously. The results showed that the difference in water temperature (WT) and pH at different larval stages was very small, whereas the concentrations of nutrients increased throughout the metamorphic process. Phosphate, total nitrogen, and total phosphorus were significantly different among all larval stages. Additionally, the concentration of nitrogen and phosphorus was significantly correlated with physical factors and the feed used. Overall, 16 phytoplankton species were detected, including 9 Bacillariophyta species, 4 Pyrrophyta species, 3 Cyanophyta species, 2 Chlorophyta species, and 1 Chrysophyta species; 11 zooplankton species were observed, including 6 Copepod species, 3 Protozoa species, 1 Rotifera species, and 1
Artemia species (feed). The phytoplankton richness was slightly higher in the Zoe I and megalopa stages than that in the other stages. For phytoplankton, the Margalef index range was 0.26–0.46, Shannon index range was 0.12–0.77, Pielou index range was 0.04–0.29, and the Simpson index range was 0.04–0.50. All diversity indices for the phytoplankton exhibited similar trends, decreasing from Zoeae I to megalopa, indicating that the phytoplankton community became less stable throughout the aquaculture process. The overall diversity index for zooplankton exhibited an opposite trend, with a higher diversity index at the megalopa stage than at the Zoe I stage. For zooplankton, the Margalef index range was 0.26–0.60, the Shannon index range was 0.01–0.66, the Pielou index range was 0.01–0.23, and the Simpson index range was 0.003–0.36. The Mantel test indicated that the diversity of phytoplankton and zooplankton were both significantly affected by the feed, DO, and PO
4 3–. The plankton community and dominant species exhibited a clear succession process. Non-metric multidimensional scaling analysis indicated that both phytoplankton and zooplankton communities were distributed along the NMDS1 axis. Plankton communities were significantly different between larval stages (PERMANOVA,
P<0.05). Multivariate analysis indicated that the difference in plankton community distribution was primarily affected by a combination of feed, abiotic factors, and biotic factors. The phytoplankton community was mainly affected by rotifers, PO
4 3–, NH
4 + , DO, NO
2 – , TP, and WT; the zooplankton community was primarily affected by the feed, WT, DO, and PO
4 3–. The results of variance decomposition analysis demonstrated that the feed was the largest single explanation for the variation in phytoplankton community distribution. Alternatively, environmental factors were the largest single explanation for the variation in zooplankton communities, followed by feed. Biological factors, feed, and environmental factors jointly explained most of the variation in both phytoplankton and zooplankton communities.
Isochrysis galbana,
Skeletonema costatum,
Chlorella pyrenoidosa,
Chattonella marina,
Nitzschia longissimi, and
Navicula marina were the dominant species of phytoplankton; their abundances were affected by the feed and SiO
3 2–.
Tintinnopsis nana,
Strombidium sp.,
Calanoida larva, Zoaea,
Brachionus plicatilis, and
Artemia nauplii were the dominant species of zooplankton; their abundances were affected by environmental factors (NH
4 + , WT, pH, and NO
3 – ) and the diversity of phytoplankton. In conclusion, as the first investigation on plankton community succession in a Chinese mitten crab nursery pond, we revealed that phytoplankton and zooplankton communities both have clear successional processes. During the aquaculture process, the diversity of phytoplankton decreased while that of zooplankton increased. PO4 3–, feed (rotifers and
Artemia nauplii), and DO are the primary factors that affect the plankton community. Our results provide essential data for maintaining the environmental health of
E. sinensis larval-rearing ponds and the ecological control of plankton communities in aquaculture farms.