Plankton Management as Disease Control in Shrimp Cultivation
Plankton management is necessary in cultivation because plankton cannot be separated from cultivation ponds and will always be there, the difference is the amount in the water. Plankton can thrive in waters, especially in shrimp cultivation ponds, rich in organic material resulting from the accumulation of leftover shrimp feces and dead plankton bodies. Apart from absorbing organic material, plankton has other positive benefits, such as natural shrimp food and as a provider of oxygen in ponds. However, we need to realize that plankton can bring disease to our shrimp directly or indirectly.
Plankton drop
Plankton drop is a condition when there is a decrease in the number of plankton in the cultivation pond water. Generally, plankton drops often occur during the rainy season, this is due to changes in water pH, reduced concentrations of minerals and micronutrients, and low intensity of incoming sunlight. The occurrence of this plankton drop will cause a buildup of organic material which is used for the growth of disease-carrying pathogenic bacteria in cultivation ponds, one of which is Vibrio sp.
Blooming plankton
Blooming plankton is a condition when plankton is abundant in cultivation ponds due to the abundance of nutrients, especially Nitrogen and Phosphorus. Blooming algae needs to be watched out for because it can cause low water transparency so the water brightness decreases. The water will be dark green. At night DO is not available at the bottom of the pond and causes the accumulation of toxic compounds such as ammonia, nitrite, and hydrogen sulfide. If DO is too low or below 4 ppm, the shrimp will rise to the surface, shrimp growth will be slow and there is a high risk of death.
The blooming of phytoplankton turns out to be correlated with the increase in pathogenic bacteria Vibrio spp. in cultivation ponds. Rehnstam-Holm et al (2010) stated that the increasing concentration of diatom plankton was in line with the increasing concentration of Vibrio spp. Fu et al (2023) specified in their research that diatoms containing chitin contain most of the Vibrio, of which Vibrio parahaemolyticus is the largest concentration. On the other hand, Vibrio is not found in phytoplankton of the Chlorella type.
Plankton management
The abundance and diversity of plankton is a parameter to control, if it is too much it is dangerous for shrimp, but if it is not enough it will also affect the quality of cultivation water. In cultivation ponds, Vibrio parahaemolyticus attaches to plankton to survive environmental changes and predators such as protozoa (Martinez-Urtaza et al., 2012). Another survey regarding Vibrio sp. Also carried out by Jesser & Noble (2018) shows that there is a correlation between Vibrio species and algae that carry out photopigment :
Controlling the abundance and diversity of plankton will be easier if there is a laboratory in each pond to determine the abundance and type of plankton. However, not all farmers have a laboratory to carry out checks. One of the easiest ways for farmers to control plankton is through water brightness. According to Romadhona et al. (2016), the recommended brightness value for cultivating vaname shrimp in ponds is 30 – 40 cm. If the brightness is below 30 cm, it is recommended to replace it or use a probiotic treatment, especially those that can reduce the abundance of plankton.
Author: Jery Prastiyo
Stellar job!