Characteristics Of Nutrients And Remediation Of Sediments In Aquaculture Ponds

Aquatic products with higher nutritional value have been favored by more and more consumers. With the rising of people’s living standard and the development of society, the demand for aquatic product is gradually increasing. The proportion of pond culture of agricultural increased significantly. Aquaculture pond is a relatively closed and fragile ecosystem, and sediment is an important part of the pond ecosystem. This study was conducted in Chonghu fisheries of Gong’an county, Hubei province. The aim of the thesis were tracing the fate of organic matter derived from pond sediments in the Ctenopharyngodon idellus ponds and Pelteobaggrus fulvidraco ponds using stable isotope analysis, analyzing characteristics of nutrients accumulation in two different aquaculture models ponds and discussing characters of nutrients migration in aquaculture pond sediment after different remediation technologies in pond sediment. Results of these studies as follows:(1) Our studies showed that the main food sources of Ctenopharyngodon idellus in the new aquaculture ponds were artificial diets, POM, sediment organic matter and macrozoobenthos. The contribution ratio of artificial diets was 42.30%. In the old Ctenopharyngodon idellus aquaculture ponds, the contribution ratio of artificial diets was 83.81%. In the new Pelteobagrus fulvidraco aquaculture ponds, the contribution ratio of artificial diets, sediment organic matter, macrozoobenthos, periphyton and POM to Pelteobagrus fulvidraco were 31.42%, 22.94%, 19.53%, 13.24% and 12.59%. The main food source of Pelteobagrus fulvidraco was sediment organic matter in the old Pelteobagrus fulvidraco aquaculture ponds. The contribution ratio of sediment organic matter was 92.16%. In the old Pelteobagrus fulvidraco aquaculture ponds, organic matter and artificial diets accumulated were the main sources of sediment organic matter. In Ctenopharyngodon idellus aquaculture ponds, organic matter in pond sediment was originally from soil organic matter and artificial diets. The contribution ratio of soil organic matter exceeded 50%. The contribution rate of soil organic matter and diets overtook 70% of Ctenopharyngodon idellus aquaculture ponds. The differences of each source contribution in pond sediment organic matter were not significant. Soil organic matter and diets were the main source of sediment organic matter in the new Pelteobagrus fulvidraco aquaculture pond. While, the contribution ratio of soil organic matter declined, and the contribution ratio of artificial diets, POM and periphyton in the sediments increased in the old Pelteobagrus fulvidraco aquaculture ponds. Main source of organic matter in pond sediments was heavily influenced by long-term aquaculture activity.(2) The TC, TN and TP contents in old ponds of different aquaculture models were significantly higher than in the new ponds(P<0.01). In vertical directions, TC, TN and TP contents in sediment columns showed no obvious trends in the new ponds. There was significant increase of TC, TN and TP contents from surface to bottom in sediment columns in the old ponds. The result indicated nutrients accumulation showed an increasing trend in aquaculture pond. Statistical analysis indicated that there was a significantly negative relationship between TC, TN, TP contents and APA. There was no significant difference in APA in different aquaculture period ponds of Ctenopharyngodon idellus mainly cultured. However, APA in the new ponds significantly higher than the old ponds of Pelteobaggrus fulvidraco mainly cultured(P<0.01), which indicated that the APA in sediment may be affected by fishing and the forms of the nutrients in the sediment.(3) The contents of total nitrogen, total phosphorus, activity of alkaline phosphatase and loss on ignition in sediments were significantly lower by phytoremediation than those in control group(P<0.01). The contents of loss on ignition in sediments sample were significantly lower by quicklime remediation than those in control group(P<0.01). Concentrations of Orthophosphate and Chlorophyll-a were significantly higher in the water sample by phytoremediation than those of control group(P<0.01) in the ponds refilled with water. The concentration of total phosphorus in the water was lower by phytoremediation than those in control group(P<0.05). There was a lower concentration of total phosphorus and Orthophosphate in water by exposure than those in the control group(P<0.05), without significant difference in hydration index in the group of quicklime. The concentration of total phosphorus in the sediment of phytoremediation was shown to be significantly declined, even in the ponds refilled with water, the best remediation efficiency under the phytoremediation.