LI Lei1, DAI Ming2, ZHAO Yongchao3, CHEN Yusheng3, 

XU Chenglin3, WANG Shuaijie1, JIANG Mei1

(1. Key Laboratory of Aquaculture on Salinealkaline Land, Ministry of Agriculture and Rural Affairs, Fishery 

Engineering Technology Research Center for Salinealkaline Waters(Shanghai),East China Sea Fisheries 

Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China; 

2. Guangdong Provincial Key Laboratory of Fishery Ecology and Environment， South China Sea 

Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Guangzhou510300, China;  

3. Jiangsu Marine Fisheries Research Institute, Nantong， Jiangsu226007, China)

Abstract: Aquaculture has been a fastgrowing industry because of significant increases in demand for seafood throughout the world, aquaculture is an important source of human protein. It is growing more rapidly than any other segment of the animal culture industry. Aquaculture production of China has long ranked first in the world, pond aquaculture is an important part of marine aquaculture, and China is the country with the largest scale of pond aquaculture in the world. However, with the development of aquaculture, its impact on marine environment has been concerned by more and more people. Compared with the culture mode in the natural sea area, the traditional aquaculture pond ecosystem is an artificial open ecosystem established for economic purposes. The traditional aquaculture pond ecosystem is characterized by its small area, shallow pond water, simple nutrient structure, and fragile ecological balance. Its ecological structure and function are mainly affected by natural climate and human activities. The pollution sources of aquaculture ponds mainly include external pollution and internal pollution of cultured organisms. Pollution can lead to eutrophication of water bodies and accumulation of pollutants in sediments. Although some pollutants can be degraded through the pond's own physical, chemical and biological processes, due to lack of the material circulation function of the natural ecosystem, with the continuous expansion of the pond aquaculture scale and the continuous improvement of the breeding density, aquaculture sewage has become a potential pollution source. At present, the restoration technologies applied in the aquaculture industry mainly include physical, chemical and biological means. Among them, bioremediation methods (including aquatic plants, aquatic animals, and microbial methods) have become the potential optimal restoration method for the aquaculture industry, because its impact on aquaculture is small, there will be no secondary pollution, and the restoration effect is longlasting. The goal of bioremediation is to transform or degrade pollutants in the aquaculture environment. The single restoration of water and sediment pollutants has limited effect on the improvement of aquaculture environment. Comprehensive restoration is more important for aquaculture restoration. The selection of restoration species and the placement density control is the key to the success of comprehensive repair model. Studies have shown that aquatic plants such as Suaeda salsa can reduce the nutrient content of aquaculture water to a certain extent. Benthic polychaetes, especially Perinereis aibuhitensis, have become important sediment restoration species due to their diverse variety, wide distribution and strong adaptability, which can reduce the total organic nitrogen (TN) , total organic phosphorus (TP) , total organic carbon (TOC), sulfide, organic matter and other pollution indicators in sediments to a certain extent. In order to evaluate the bioremediation effect of integrated bioremediation of Suaeda glauca and Perinereis aibuhitensis on aquaculture ponds, we used Meretrix meretrix aquaculture ponds as a case study, indoor simulation experiment was carried out to study the trends of water eutrophication and sediment pollution by placing S. glauca and P. aibuhitensis. Eight groups were set up:A1：30 S.glauca; A2：20 S.glauca; A3：10 S.glauca; B：0.20 kg·m-2 P.aibuhetensis; C1：30 S.glauca and 0.20 kg·m-2 P.aibuhetensis; C2：20 S.glauca and 0.20 kg·m-2 P.aibuhetensis; C3：10 S.glauca and 0.20 kg·m-2 P.aibuhetensis; D：control group with only sediment and sea water. Results showed that both S. glauca and P. aibuhitensis grew well, dissolved inorganic nitrogen (DIN) presented different changing trends between different experimental groups, DIN of C1 experimental groups declined by 14.10%, DIN of C1 and C2 experimental groups increased by 18.06% and 42.89%, respectively. Dissolved inorganic nitrogen (DIP) presented the same changing trends between different experimental groups, dissolved inorganic phosphates (DIP) of C1, C2 and C3 experimental groups declined by 40.00%, 28.57% and 19.30%, respectively. The sulfide and total organic carbon content of bottom sediments presented the same changing various trends between different experimental groups, the sulfide content of C1, C2 and C3 experimental groups declined by 26.80%, 26.03% and 19.30%, respectively. TOC content of C1, C2 and C3 experimental groups declined by 48.07%, 38.71% and 43.47%, respectively. Results showed that integrated bioremediation of S. glauca and P. aibuhitensis had a certain effect on water eutrophication, sulfide and TOC in sediment. The nutrient absorption efficiency of S. glauca is related to the growth, root length and quantity of S. glauca. Bioturbation of P. aibuhitensis is the main factor affecting the changes of sulfide and TOC content in sediments. P. aibuhitensis has strong digging ability, dissolved oxygen can be transported to the deep layer of the sediment, and the reducing environment of the sediment is oxidized, which can reduce the content of sulfide in the sediment. P. aibuhitensis can directly feed on the organic matter in the sediment, which directly reduces the TOC content in the sediment; on the other hand, the microbial decomposition of the organic matter in the sediment is also an important factor in the decrease of TOC content. The excretion of P. aibuhitensis, the adsorptiondesorption process of suspended particulate matter and bioturbation all lead to the increase of nutrient exchange flux at the sedimentwater interface, but the increment gradually decreases with time. Results of this study showed that under certain experimental conditions, the restoration combination of 30, 20, 10 S. glauca and 0.20 kg·m-2 P. aibuhitensis stocking density had a certain removal effect on DIN, DIP in water, sulfide and TOC in sediments , among them, 30 S. glauca and 0.20 kg·m-2 density of P. aibuhitensis had the best comprehensive restoration effect. However, in the actual cultivation process of the pond, the growth of bait algae is a factor that must be considered in shellfish breeding. The breeding water body needs to maintain a certain concentration of nutrients. At the same time, in order to maintain the necessary photosynthesis intensity of the bait algae, the number of S. glauca is not the more the better, the coverage rate can only be maintained within a certain area, and the optimal proportion of comprehensive restoration needs to be further experimentally verified in combination with primary productivity and other indicators on site. This study could provide a theoretical and practical foundation for bioremediation of aquaculture ponds.

Keywords: aquaculture ponds; Suaeda glauca; Perinereis aibuhitensis; integrated bioremediation