Nitrogen and phosphorous budgets for integrated culture of whiteleg shrimp Litopenaeus vannamei with red seaweed Gracilaria corticata in zero water exchange system

In this study, a 2×3 factorial design with two levels of shrimp density (25 and 50 shrimp per m2) and three levels of red algae density (0, 200 and 400g per m2) was applied to calculate nitrogen and phosphorous budgets in the integrated culture of Litopenaeus vannamei with Gracilaria corticata during 45 days in a zero water exchange system. Juveniles of L. vannamei (5.82±0.11 g) and G. corticata were cultured in 18 round 1 m3 poly ethylene tanks. Water temperature, dissolved oxygen (DO), pH and salinity were measured once every 3 days. Results indicated that shrimp density had a significant effect on pH and DO in the morning and in the afternoon. The algal density didn’t have a significant effect on pH and DO in culturing tanks (p>0.05). According to the results of this study, the main source of nitrogen and phosphorus input to the tanks during a 45- day culturing period was from feeds. Shrimp and algal densities significantly affect the concentration of total ammonia, nitrite, nitrate and phosphate in water and an increase in shrimp density led to an increase of these compounds whereas, increasing the algal density led to the reduction of these compounds. Results indicated that increasing the density of G.corticata in all treatments, led to an increase in biomass of harvested shrimp and the co-culture of G. corticata with L.vannamei decreased the amount of nitrogen and phosphorus in both water and sediments and improved the water quality of L.vannamei culture.