Assessing the effects of silicate addition on phytoplankton composition and copepod production in an inorganic fertilization system.

In the past, diatoms were considered the primary food source for copepods in both wild and aquaculture settings. However, recent studies have found that diatoms have defense mechanisms against predators, making them unsuitable as copepod feed. This study assessed the impact of addition of 100 μg L−1 of silicate to an inorganic nutrition formula containing 700 μg L−1 nitrogen, 100 μg L−1 phosphorus, and 100 μg L−1 iron. Our objective was to assess the impact of increased diatom abundance on copepod production. The experiment was carried out in 1000 L outdoor tanks over a period of 20 days, with adult Pseudodiaptomus annandalei copepods, introduced into each tank on the second day at an initial density of 10 ind. L−1. The results indicated that adding silicate reduced the prevalence of Chlorophyta, replaced by a higher proportion of Dinophyta, and eventually dominated by diatoms. While silicate had a positive effect on diatom culture, it had a negative effect on copepod production. Adding silicate to the inorganic fertilization method resulted in increased costs, leading to a significant increase in the unit production cost of copepods. [ABSTRACT FROM AUTHOR]