Experimental Studies On Nitrogen And Phosphorus Budgets In Polyculture Systems Of Litopenaeus Vannamei, Cyclina Sinesis And Gracilaria Lichevoides

The shrimp industry plays important role in mariculture of China. The statistic data showed that the yield of shrimp or prawn in 2003 was 5.36×105 t, therefore, the influence of shrimp industry on marine environment deserves more attentions. With the development of mariculture, its impact on marine environment was concerned by more and more people. How to improve environment in culture system, reduce the accumulation of nutrients in culture system and decrease the negative impacts on marine ecosystem caused by effluence from shrimp ponds is a vital problem need to be solved. Nitrogen (N) and phosphorus (P) are important elements in aquatic ecology, whose conversion efficiency and deposit status in system are often used to evaluate aquaculture techniques, pattern and state of pollution within system. Therefore, it is very necessary to study budgets, distribution, dynamic and conversion efficiencies of N and P in aquaculture system. These studies were designed and conducted to investigate hydrochemistry, vertical distribution of N, P in sediments and budgets of N and P in systems of polyculture of Litopenaeus vannamei with Cyclina sinesis, L. vannamei with Gracilaria lichevoides, and L. vannamei with C. senensis and G. lichevoides with land-based experimental enclosures. The chief results were as followings:1. An Experimental Study on Nitrogen and Phosphorus Budgets in Polyculture of Litopenaeus vannamei with Cyclina sinesisFour stocking density of C. sinesis (7,15,30 and 45 ind/m~2, i.e., LC1, LC2, LC3 and LC4)) combined separately with one stocking density (30ind/m~2) of L. vannamei were arranged in 20 enclosures. The duration of experiment lasted for 60 d. The results showed that the shrimp feeds accounted for 83.1% N and 86.0% P of the total inputs in monoculture systems while 79.6%～85.0% N and 86.2%～90.6% P in polyculture systems.