Yolk immunoglobulin (IgY), a polyclonal antibody, has garnered considerable attention for its role in conferring passive immunity against bacterial and viral diseases. This paper comprehensively reviews the current research on the fundamental structure and physicochemical properties of IgY. Additionally, the paper emphasize the diverse applications of IgY in preventing and treating bacterial and viral diseases, offering valuable insights for future research and the broader utilization of IgY in aquaculture.

Investigations on phytoplankton community and environmental factors were carried out in Sansha Bay and adjacent open waters of Fujian,in August of 2021.A total 46 species in 26 genera were detected in this study.There were 18 species in 13 genera in Sansha Bay,all of which belonged to Bacillariophyta.There were 41 species in 23 genera in adjacent open waters,of which 32 species belonged to Bacillariophyta,accounting for 76.2% of all species;10 species belonged to Pyrrophyta,accounting for 23.8%.The cell abundance of phytoplankton in Sansha Bay ranged from 5.2×10² to 1.2×10⁴ cells /L,with the average of 6.0×10⁴cells/L,and that in adjacent open waters ranged from 3.9×10⁴ to 9.7×10⁵ cells /L,with the average of 2.8×10⁵ cells/L.The similarity coefficient of community was 0.36,which suggested that the two communities belonged to medium dissimilarity.The abundance and the number of species of phytoplankton was significantly negatively correlative to inorganic nitrogen and phosphate.The plankton community in Sansha Bay became isolated due to the close topography.Local mass cultivation of Crassostrea gigas imposed a giant predator pressure on plankton which exhibited the character of lower abundance and less species.