Subject Area 5.1: Microbial studies and technologies supporting waste disposal, management, and remediation of municipal and industrial hazardous wastes
Review Article
创新的名人名言Environmental Impact of Aquaculture and Countermeasures to Aquaculture Pollution in China*
Ling Cao1, Weimin Wang1**, Yi Yang 2, Chengtai Yang 1, Zonghui Yuan3, Shanbo Xiong4 and James Diana5
1College of Fisheries, Key Lab of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education,
Huazhong Agricultural University, Wuhan, Hubei 430070, China
2Aquaculture and Aquatic Resources Management, School of Environment, Resources and Development, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathum Thani, 12120, Thailand
3National Reference Laboratory of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan
4College of Food and Science Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
5School of Natural Resources and Environment, University of Michigan, Ann Arbor, USA
of Agriculture (MOA), the total production in 2005 amounted to 51.0 million metric tons, making up one quarter of the world total (Natural Bureau of Statistics of China 2005). Aquaculture contributes to 65% of the total fishery produc-tion, among which freshwater aquaculture is a major part. Without doubt, China's aquaculture will continue to play an important role in the global supply of fish in the future. However, along with the development, concerns are evoked about the possible effects of ever-increasing aquaculture waste both on productivity inside aquaculture systems and on the ambient aquatic ecosystem. Aquaculture may con-tribute to the degradation of the environment, but it is still paradoxically dependent on the supply of clean waters. Tra-ditional farming systems (e.g., extensive pond farming) domi-nate aquaculture production in many regions, but the are now slowly being replaced by intensive western oriented tech-niques. Rapid scale growth of intensive mariculture systems can often lead to adver impacts on the environment. In-tensive fish and shrimp farming, being defined as through-put-bad systems, have a continuous or pul relea of nutrients that adds to eutrophication (Troell et al. 1999). Nitrogenous compounds (ammonia, nitrite, and nitrate) are considered as major contaminants in aquaculture wastewa-ter. Ammonia is the principal nitrogenous waste produced by aquatic animals. Past, obsolete technologies and incom-plete arrangement of waste management systems in aquac-ulture contribute a lot to the deterioration of the aquacul-ture environment. Ackefors & Enell (1994) estimated that 9.5 kg P and 78 kg N per to
n of fish are relead into the water column per year when the feed conversion coefficient is 1.5 and the contents in the feed are 0.9% P and 7.2% N. Approximately 72% N and 70% P in feed are not retained by fish. With improvements in feed composition, digestibil-ity, and feed conversion efficiency in recent years, the dis-charge is probably now reduced to 7.0 kg P and 49.3 kg N per ton of fish per year (Chopin et al. 1999). Aquaculture pollution accidents at a number of 2067 happened in 1999 and 2000, leading to a loss in economy of 0.132 billion dol-lars (Yang et al. 2002).
Aimed at ttling the increasingly aggravated environmen-tal problems raid by aquaculture waste, the Chine gov-ernment should adopt a ries of regulations and controls. Aquaculture systems which incorporate waste treatment and effluent reu facilities are rapidly being developed becau they have the advantage of minimal water input and waste-water discharge while allowing full control of the cultural environment (Midlen & Redding 1998, Van Rijn 1996). The forms of aquaculture waste treatment systems may vary, but they can generally be classified into three categories: physi-cal treatment, chemical and biological methods. Many studies have been conducted to examine the aquaculture waste treat-ment efficiency of different treatment system (Cheng et al. 2002, Xiao et al. 2006). However, the disadvantages of each treatment are also obvious, such as excessive sludge pro-duction, unstable performance, and nitrate accumulation. Thus, rearch on new methods for aq
uaculture wastewater treatment is under way. The purpo of this review was to study the current status of aquaculture in China, analyze the compromi of aquaculture waste and evaluate common waste treatment methods applied in aquaculture in China.1Main features
1.1Aquaculture in China
1.1.1Freshwater aquaculture
易阳和老外
Freshwater aquaculture is a major part of the Chine fish-ery industry. It takes place in ponds, lakes, rivers, rervoirs and rice paddy fields, which are wide spread in almost the whole of China. Both main freshwater and marine aquacul-ture areas which are also considered as pollution hot spots are indicated in Fig. 1. The growing trend of aquaculture in China is shown in Fig. 2.
Pond culture is the most important method among freshwa-ter aquaculture. The pond yield accounted for over 71% of the total inland aquaculture in 2003. Most pond culture activities are found along the Yangtze River basin Delta and the Pearl River Delta covering 7 provinces: Jiangshu, Guangdong, Hubei, Hunan, Anhui, Jiangxi and Shangdong provinces (e Fig. 1).
Rervoir, lake, river and channel fish farming contributes most to the remaining fresh aquatic production, by making Fig. 2: China aquaculture production by year (unit: million metric tons)
u of cages and nets in open-waters. Rice paddy fish and crab farming has developed into an important and growing commercial activity for rural residents in mountainous ar-eas where open water resources are not available or limited. More than 70 main freshwater aquatic species are farmed in China. Most of them are fish (about 60 species). The most common farmed species are grass carp, silver and bighead carp, common carp and crucian carp. Another important category is crustaceans, 1.1 million tons in 2003.
1.1.2Marine aquaculture
Marine aquaculture in China consists of both land-bad and offshore aquaculture, with the latter mostly operated in shallow as, mud flats and protected bays. Land-bad marine aquaculture applied on abalone, turbot, flounder and other fish species offer high economic values in both north and south coastal provinces. The main production types of offshore aquaculture are floating and mi-floating raft cul-ture, net cage culture, a ground sowing, vertical (hanging) culture and pond on tidal areas. By the year 2003, the total marine aquaculture area has reached 1,532,152 hectares. Of this, the offshore area ud is 590,455 hectares, while the mud flat ud is 676,184 hectares and land bad farm-ing areas reprent 265,513 hectares. Four a regions were involved in marine aquaculture including Bohai Sea, Yellow Sea, East China Sea and South China Sea. Most important
marine aquaculture provinces are Shandong, Fujian, Guang-dong, Liaoning, Zhejiang and Guangxi provinces (e Fig. 1). More than 90% of the total marine production comes from the provinces, who production volumes exceeded 800,000 tons in 2003. There are four main categories: ma-rine fish (finfish), crustaceans (shrimp and crab), mollusks (shellfish) and aweeds (algae).
论文大赛Table 1 shows output and area of marine shellfish cultured in China in 2002. Almost 90% of farmed marine finfish comes from the following 5 provinces: Guangdong, Fujian, Shangdong, Zhejiang and Liaoning. In 2003, Guangdong province had the largest production of farmed fish approxi-mately 195,524 tons (Natural Bureau of Statistics of China 2005). Fujian province has 119,226 tons. Others are rang-ing from 26,000 to 81,000 tons. In northern China, Liaoning and Shandong are two important marine fish farming prov-inces (Natural Bureau of Statistics of China 2005). The main species are flounder, turbot, halibut, a bream, Fugu, perch, greenling, mullet fish, etc. In some places there are trials on large yellow croaker and red drums. In southern China, Guang-dong, Fujian and Zhejiang are important marine fish farm-ing provinces. There are more wide ranges of warm water or tropical fish species being farmed. Main species are grou-pers, large yellow croaker, a bream and snapper fish, red drum, Fugu, perch, cobia, amberjack, pompano, etc.1.2Environmental impacts of aquaculture
excel随机数生成后岗村
1.2.1Habitat modification
Mangrove conversion to shrimp ponds has contributed to the negative press received by aquaculture. This transfor-mation results in loss of esntial ecosystem rvices gener-ated by mangroves, including the provision of fish/crustacean nurries, wildlife habitat, coastal protection, flood control, diment trapping and water treatment. Fish pens and cages also degrade nearshore habitats through their physical instal-lations on a grass beds and diment communities, or through deposits of uneaten feeds (Primavera 2006).
1.2.2Aquaculture waste西可以组什么词
The quality and quantity of waste from aquaculture depends mainly on culture system characteristics and the choice of spe-cies, but also on feed quality and management (Wang et al. 2005). From intensive aquaculture systems, the principal wastes are solid wastes, chemicals, and therapeutics. The relea of bacteria, pathogens and farmed species escapees should also be included as waste components (Liu et al. 2002).
Solid wastes, otherwi known as particulate organic mat-ter, often consist of feces or uneaten food. A build up of solid wastes within the system should be prevented as it can cau oxygen depletion a
nd ammonia toxicity when it de-compos. Organic wastes are prent in three main forms in the recirculation system: ttled solids-accumulate on the bottom of the tank; suspended solids-float in the water col-umn and will not ttle out of water; fine and dissolved sol-ids-float in the water column and can cau gill irritation and health damage to fish. The urine and feces from the aquatic animals can cau high content of ammonia nitro-gen and an increa of BOD (biochemical oxygen demand). Ammonia is the main nitrogenous waste that is produced by fish via metabolism and is excreted across the gills. Ni-trite is a naturally occurring intermediate product of the ni-trification process. The nitrate ion (NO
3
–) is the most oxi-dized form of nitrogen in nature and is relatively non-toxic to fishes (Zhang & Chen 2004). However, when nitrate con-centrations become excessive and other esntial nutrient factors are prent, eutrophication and associated algae blooms can become a rious environmental problem.
A wide range of chemicals is ud in aquaculture industry, including compounds applied to construction materials (sta-bilizers, pigments, antifoulants etc.), pigments incorporated into feeds, dis
infectants and chemotherapeutants. Antimi-crobials are administered in the diet and most end up in the environment in association with uneaten food and feces. Many studies reported increas in resistance and even mul-tiple resistances in pathogens as a result of the widespread u of antimicrobials by aquaculture (Kerry et al. 1994). The abu of chemicals can also kill the effective microbes which probably accounts for an unbalance of the aquatic ecology system. It is widely argued that translocated species
Table 1: Output and area of marine shellfish cultured in China (2002) (Wang & Zheng 2004)
or strains may carry exotic dias that could spread and devastate indigenous wild populations and that farmed stock escape and become established, again to the detriment of wild stocks. There is little quantitative information on the numbers of animals that escape from aquaculture operations. Penczak et al (1982) estimated that about 5% of caged rainbow trout escaped each year. The fear is that feral animals become established and reduce biodiversity through habitat modifi-cation, competition, or by interbreeding with native stocks.
1.2.3Pollution caud by aquaculture wastewater
If continuously discharged wastewater without treatment,which contains high concentration of nitrogen and phos-phorus nutrients, may result in a remarkably chronic eleva-tion of the total organic matter contents, especially in badly managed or poorly located sites. Conquently, a ries of negative ecological impacts may occur: (1) rious oxygen deficit caud by the decomposing of organic substances. (2)eutrophication or algae bloom caud by the accumulation of organic nutrients like nitrogen and phosphorus, which pro-motes a high biomass in the superficial water . Apart from in-cread phytoplankton production, eutrophication can cau many other effects which may be more nsitive and relevant indicators such as changes in: energy and nutrient fluxes, pe-lagic and benthic biomass and community structure, fish stocks,dimentation, nutrient cycling, and oxygen depletion (Gre-gory & Zabel 1990, Fang et al. 2004). (3) Water deteriora-tion will bring about low productivity (4) Dias may break out. Aside from this, inadequate handling of wastewater has rious conquences for human health, the environment and economic development (Enelld & Lof 1983). It contami-nates water supply, increasing the risk of infectious dia and deteriorating groundwater and other local ecosystems,for instance after flooding.
1.2.4Salinization of soil and water
Pumping large volumes of underground water to achieve brackish water salinity in the 1980s to mid-1990s led to the lowering of groundwater levels, emptying of aquifers, land subsidence and salinization of adjacent land and waterways in China. Even when fresh water is no longer pumped from aquifers, the discharge of salt water from shrimp farms lo-cated behind mangroves still caus salinization in adjoin-ing rice and other agricultural lands (Primavera 2006).
战网登陆不上2Results
2.1
Ca study on freshwater aquaculture in China
2.1.1Pen aquaculture in lake
Lake Taihu is the third largest freshwater lake in China,with total water area of 2338 km 2. The main form of aquac-ulture in Lake Taihu is pen-fish-culture. Aquaculture has been limited to East Taihu, a macrophyte-dominated bay in the southeast part of the lake with an area of 131 km 2,in which 2833 hm 2 are ud for aquaculture (Yang et al. 2003).Within this area, it is estimated that the environmental load of nitrogen and phosphorous of 1 t fish production are 141 kg and 14 kg, respecti
vely (Yang et al. 2003). In pen-fish-cul-ture areas, incread nutrient loading leads to rapid growth of phytoplankton, zooplankton, and bacteria. After one year of fish farming, the phytoplankton abundance was three times higher than in non-culture areas, and heterotrophic bacteria abundance incread 3- to 4-fold (Yang et al. 2003).Total organic carbon, total nitrogen, and total organic ni-trogen in surface diments incread by 141, 87.5, and 86%respectively, after 2 years of fish culturing (Li 2004). Re-cently, fish culturing has been replaced by the more profit-able freshwater crab culturing, which will increa the in-put of feed, and further increa the deposit of organic materials from the remnants of feed. From 1984 to 1993,fish and crab production of pen aquaculture in East Lake Taihu amounted for 11,165 t and 109 t, respectively. Nitro-gen and phosphorous load to this lake were 1,634 t and 166t, respectively. Compared to non-aquaculture areas, NH 4+-N and phosphorous load of this area incread 55% and 46%, respectively. For the whole Taihu Lake in 1993, nitro-gen, NH 4+-N, phosphorous and COD contents incread 55%, 180%, 43% and 91% respectively compared to that of 1983 (Yang et al. 2003). The change of water quality in East Lake Taihu influenced by aquaculture in 1990s is pre-nted in Table 2. Aquaculture in East Taihu increas nu-trient concentrations in water and diments, which accel-erates eutrophication and marsh development.
2.1.2
Cage aquaculture in rervoir
Dahonghu Rervoir is located in southwest China with a total area of 40 km 2 (Ning et al. 2006). The main form of aquaculture in this rervoir is cage culture. Table 3 pre-nts comparison of physico-chemical parameters of water场地租赁费用
Table 2: Changes of water quality index in East Lake Taihu caud by aquaculture (Qin & Luo 2004)
Table 3: Comparison of physico-chemical parameters of water quality between cage inside and outside (Ning et al. 2006)
quality between cage inside and outside. Cage culture in Dahonghu Rervoir incread nutrients content which might easily induce eutrophication. The TN and TP contents of cage inside water were significantly higher than tho of cage outside water. Besides, in diments below cages, the TN and TP contents were 681 mg/l and 30.7 mg/l, respectively,which were significantly higher than the non-culture areas (P <0.05). The main impact of cage aquaculture is the in-crea in the load of N, P , and organic matter that enrich water and underlying diment. The amount of waste pro-duced by a cage farm will depend on a number of factors such as the stocking density, the feeding regime, and the feed-ing rate becau the three factors together determine the total amount of feeds to be ud.
2.2
Ca study on marine aquaculture in China
2.2.1Ponds
Generally, less than 1/3 of the nutrients in feed are removed by harvesting in intensive fish farming (Troell et al. 1999).For intensive shrimp pond farming, it is even less, ranging between 6 and 21% (Robertson & Phillips 1995). Waste produced by shrimp and fish ponds located around Bohai Sea an
d Yellow Sea was investigated by Cui et al. (2005).Bad on the assumption that FCR was 2, 7.9×104 metric tons of total shrimp production in Bohai Sea and Yellow Sea areas in 2002 indicated that more than 1.2×105 metric tons of uneaten feed was discharged into the a. According to statistical analysis, rough data of wastewater produced by shrimp culture in Yellow Sea and Bohai Sea in 2002 were shown in Table 4.
The average water depth for shrimp culture was 1.0 m, with daily water change at 7.5% of total. Total shrimp culture area was 1.37×105 hm 2. Thus, the daily discharge of waste-water from shrimp culture was 1.03×108 m 3. Within one culture period (120 d), the total discharge amount of waste-water was 1.2×1010 m 3 in 2002. Tovar et al. (2000) esti-mated that 1 t of fish production could cau 34.61 kg of
BOD, 14.25 kg of N and 2.57kg of P discharged into the a. According to marine fish production in Yellow Sea and Bohai Sea in 2002, 2028 t of N, 376 t of P and 5056 t of BOD could be discharged into the a (Table 5).
In Guangdong province in 2001, the environmental load of nitrogen and phosphorous produced from shrimp pond aquaculture were 4,508.7 t and 994.1 t, respectively (Table 6).In which, the discharge a
mount of COD, inorganic N, inor-ganic P and suspending solids contained in the wastewater,were 4,887.4 t, 136.8 t, 64.0 t and 17,689.6 t, respectively.The discharge amount of N and P from shrimp ponds were about 0.19% and 0.40% respectively that of the land-de-rived wastewater (Li et al. 2004).
2.2.2Cages in open-a waters
Being an esntially open system, cages are usually charac-terized by a high degree of interaction with environment and cage systems are highly likely to produce large bulk of wastes that are relead directly into the environment. There-fore, large-scale cage aquaculture development has been put into question and concerns have been raid that cage aquac-ulture produces large bulk of wastes that are rich in organic matter and nutrients and are relead into coastal and nearshore environment. For example, the contents of the organic matter in the diment in the cage culture area of Dapeng'ao Bay (dry weight ) ranged from 1.56% to 3.50%with average of 2.57%, and obviously higher than the nor-mal value in the diment along the Chine coast waters (1.0%~1.5%) and the first grade of the National Standard (2.0%) (Gan et al. 2006). The mean contents of the organic matter inside and outside the cage area were 2.66% and 2.42%, respectively. It showed that in open a cage cul-ture, high organic and nutrient loadings were gener
ated and culture areas were risking degradation. Feed wastage and pollutant loadings are much higher in open-a cage culture systems where trash fish is ud as feed (Wu 1995).
Table 4: Rough data of wastewater produced by shrimp culture in Yellow Sea and Bohai Sea in 2002 (Cui et al. 2005)
Table 5: Rough data of wastewater produced by fish culture in Yellow Sea and Bohai Sea in 2002 (unit: metric ton) (Cui et al. 2005)
