Nitrogen and phosphorous budgets for integrated culture of Litopenaeus vannamei with red sea algae Gracilaria corticata under zero water exchange system

Abstract In this study, a 2×3 factorial design  with two levels of  shrimp density (25 and 50 shrimp per m-2) and three  levels of   red algae density (0, 200 and 400g per m-2) was applied to calculate  nitrogen and phosphorous budgets in integrated culture of Litopenaeus vannamei with Gracilaria corticata  during 45 days under zero water exchange system. Juvenile 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 each 3- day.  Results indicated that shrimp density had a significant effect on pH and DO in the morning and in the afternoon. The algae density didn’t have a significant effect on pH and DO 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 feed. Shrimp and algae densities significantly affect the concentration of total ammonia, nitrite, nitrate and phosphate in water and an increase in shrimp density led to increase of these compounds whereas, increasing the algae density led to reduction of these compounds. Results indicated that increasing the density of G.corticata in all treatments, led to increase in biomass of harvested shrimp and the co-culture of G. corticata with L.vannamei decrease the amount of nitrogen and phosphorus in both water and sediments and improve the water quality of L.vannamei culture.