Effect of Mariculture on Planktonic Protist: A Case Study in a Marine Ranch of Northern Yellow Sea, China.

Mariculture exerts a direct influence on planktonic eukaryotic microorganisms protists. Previous studies have focused on phytoplankton, while the heterotrophic and parasitic protistan groups are unknown. Currently, in Muping Marine Ranch (MR) which is along the littoral zone of northern Yellow Sea of China, environmental DNA methods were employed to investigate the diversity and seasonal dynamics of near shore planktonic protists in response to mariculture. Through an integrated analysis of functional groups and a comparison to adjacent sea areas, we found a dominance of harmful algae blooms (HAB) species nearshore MR, and a significant reduction in the diversity of planktonic protists including photosynthetic, heterotrophic and parasitic groups. High nutrient and low salinity were suggested to drive the dominance of HAB species nearshore MR, which in return might inhibit predators, saprophytes and algal parasites. Our investigations revealed an Olisthodiscus luteus outbreak in spring, as well as significant seasonal variations in the planktonic protist community, which might be caused by the changes of temperature. The offshore hypoxia reduced the abundance of phytoplankton but increased mixotrophs and animal parasites of the protistan community nearshore MR. This study highlights the influence of mariculture on the overall community function of planktonic protists, and is helpful to assess the mariculture's impact on water health. [ABSTRACT FROM AUTHOR]