Effects of sedimentation thickness of shrimp pond cleaning discharges onAcanthus ilicifoliusseedlings

Abstract

In landward coastal zones of most mangrove swamps in China, there are many shrimp ponds with surface sediments rich in nutrients such as N and P. During pond cleaning periods, some of these surface sediments are usually directly discharged into mangrove swamps after being flushed by using high鄄pressure hydraulic giants. Gradually, these sediments from shrimp ponds will accumulate on the floor of mangrove swamps, resulting in the increase in sedimentation thickness. However, the effects of sedimentation of shrimp pond cleaning discharges on mangrove ecosystems are still unknown. Therefore, to study their responses and endurances in growth and physiological characteristics, four thickness treatments (0, 2, 4, 8 cm) were applied to simulate the sedimentation condition of shrimp pond discharges into the mangrove swamp, and Acanthus ilicifolius seedlings were cultivated under these treatments for 424 days. In terms of growth indexes, including stem diameter, stem height, leaf number, leaf area, total biomass and relative growth rate, growths of A. ilicifolius seedlings were promoted due to the sedimentation of shrimp pond cleaning discharges. The growth condition of A. ilicifolius seedlings under four treatments followed the order of 8 cm > 4 cm > 2 cm > 0 cm. Results also indicated that a small quantity of cleaning discharges (sedimentation thickness of only 2 cm) could obviously enhance the growth of A. ilicifolius seedlings, and this enhancement would not be stronger comparing with the increasing of