MICROBIAL ECOLOGY AND ENVIRONMENTAL SANITATION TERM PAPER Paper Tittle : Environmental Impact of Aquaculture and Countermeasures to Aquaculture Pollution in China By:
Romi Novriadi : 01107735 (Indonesia) & Erick O. Ogello: 01107682 (Kenya) A term paper Submitted to the Faculty of Bioscience Engineering in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Aquaculture) Ghent University, Belgium 2011 – 2012 Academic year
Summary Aquaculture is an important economic activity in many countries and perhaps contributes to poverty alleviation, employment creation and food security. China has so far been very successful in fish farming and is now the world’s largest fish producer (Cao et al. 2007). Types of aquaculture systems include cage in oceans and reservoirs, pens in lakes and marine ponds. Over 70 species are farmed in freshwater while shrimps, shellfish and fin fish characterize marine waters. In this paper, Cao et al. (2007) consider nitrogenous compounds from aquaculture wastewater as major contaminants in Chinese environment and if nitrogen becomes excessive, while other factors remain constant, eutrophication may occur. Apart from aquaculture wastewater pollution, habitat modification and salinization of soil and water have been captured as impacts of Chinas aquaculture development. In this review, we found that shrimp cage culture discharged 1.2 X 1010 m3 of total discharge of waste water in 2002 (Cao et al. 2007). However, in 2005, industry and life sewage contributed 21.2 X104, 1.7X 104 and 162 X 104 tons of N, P, and COD respectively, while shrimp cage culture contributed 1,198 t of N, 120 t of P and 23,960 t of COD (Cui et al. 2005). In comparison, the ratio of pollutants between aquaculture to land-based are N: 2.8%, P: 5.3% and COD: 1.8% (Cao et al. 2007; Cui et al. 2005). The current wastewater treatment methods are physical, chemical and biological method. New approaches such as polyethersulfone (PES) membrane and reverse osmosis (RO) have not been used due to high cost despite being efficient as documented by Nora aini et al. (2005). Finally, Cao, et al (2007) suggested that feed quality improvement, integrated aquaculture, wastewater treatment and government regulations are some of remedies needed to check aquaculture pollution not only in China but world over.
Motivation Motivation By Erick Ogello: This topic is directly linked to the course Microbial Ecology and Environmental Sanitation (MEES). In this course, we recognize the role of microbiological communities in biological waste water treatment. To date, biological wastewater treatment still remains the most popular method because it is cheap and environmentally friendly. We decided to critically analyze this paper to understand methods of reducing aquaculture pollution. In Kenya, due to a number of constraints, aquaculture is underdeveloped and contributes only 4% of the total national fish production. Due to increased demand for fish, the Kenyan Government has promoted fish farming by constructing over 47,000 fish ponds between 2009 to date. The increase in aquaculture activities is likely to raise environmental issues. Aquaculture wastewater treatment in Kenya is insignificant. However, this is expected to change significantly due to expected increase in aquaculture wastewater discharge. Industrial effluents and municipal discharge are still the major pollutants. Nevertheless, this topic of review is quite relevant to my country because proposals for sustainable aquaculture development in the paper are applicable in my country. As an aquaculturist with a bias interest in water quality assessment and pollution control, I find this topic very applicable in my professional career. Through this paper, I am able to appreciate that aquaculture is indeed a source of environmental pollution. I am therefore obliged to ensure that nutrients from aquaculture effluents are within recommended limits before discharged into the ambient environment. This can be achieved to a larger extent by using quality feeds, promotion of integrated aquaculture, wastewater management and strengthening government regulations. Motivation By Romi Novriadi: This paper is very related to the Microbial Ecology and Environmental Sanitation (MEES) course. Because from this paper we know that the aquaculture has greatly contributed of N and P waste to the environment. And with the increasing of nutrients in the environment it will be the good medium for bacterial growth. although China has tried to operate the waste water treatment, but without a good understanding about the environmental impact on the growth of bacteria, all of the waste water treatment system will be useless. therefore it is very important to study about Microbial metabolism, Microbial ecology and also the Microbial detection techniques, that all we can learn on this course. In Indonesia, Aquaculture is the fastest growing food industry. Statistics recorded growth of 11% per year and is able to absorb the 2.5 million jobs yearly (Ministry of Fisheries). In 2007, total Indonesian aquaculture was 2.7 million tons and was ranked the third largest after China and India. Meanwhile, China which has a beach and a river less than Indonesia is able to produce 32.7 million tons per year. But the rapid development of aquaculture in Indonesia has negative impacts, especially on the environment. One of the inhibit factors that influence the level of production in Indonesian fisheries is the degradation of water quality. This condition is usually triggered by a desire to raise or pursue the target of production that does not take into account the carrying capacity of the environment and environmental conditions of raw water sources. The impact posed is the decline in water quality and sediment levels, which ultimately will stimulate the occurrence of disease, crop failure, or a decrease fisheries production levels in Indonesia. This is what has motivated me to choose this article for discussion because this article has the same relationship with the Aquaculture environmental conditions in Indonesia.
Discussion Several authors have documented that aquaculture has grown big enough to impact on environment and this has attracted attention of both environmental activists and researchers in equal measure (Boyd 2003; Goldburg and Triplett 1997; Naylor et al. 1998, 2000). We too have reasons to worry that environmental quality might be compromised further if mitigation measures are not implemented immediately. According to Wang et al. (2005), quality and quantity of aquacultural waste not only depend on culture method and species but on feed quality and pond husbandry. In this review, the most important concern is nutrients from aquaculture effluents and negative effects of biodiversity due to escape of introduced aquaculture species (Cao et al. 2007). Chinese freshwater aquaculture produces 71% of total production yearly (Cao et al. 2007) because it takes place in all freshwater bodies. Kenyan freshwater aquaculture is confined to extensive pond production systems which account for 1% of national production while mariculture is at infancy (Mwangi 2008). However, impacts on environment cannot be ignored. In Indonesia, Shrimp farming occur in pens or cages and generate concentrated amounts of N and P from excrete and uneaten food (Chu et al, 2002). For every 1 ton of fish produced, 42 - 66 Kg of N and 7.2 -10.5 Kg of P is produced (Strain and Hargrave 2005). We agree that aquaculture contributes to nutrients in receiving waters just as in our countries. However, we do not agree that cage culture is the sole contributor to nutrient loading in ambient waters as shown by (Cao et al. 2007). For example TN and TP in upstream were 55.6mg/L and 61.5mg/L respectively. In cages, 57.3mg/L and 63.7mg/L were recorded while 56.7mg/L and 63.6mg/L were found downstream (Fig. 1). In our view, there was no significant difference between TP in upstream and TP in cage. The same apply to TN. We think that agricultural runoff should be checked as well. Between cages and downstream, we expected the TP and TN to reduce due to plant uptake yet the results show a constant figure (Figure 1).
Figure 1: comparison of some nutrients between cage and surrounding (adapted from Ning et al. 2006)
In terms of species of culture, the authors said shrimp culture was the greatest polluter compared to fish culture. This is in agreement with studies of Cui et al. (2005) where shrimp culture produced COD > 5000mg/L while fish culture generated BOD of 1500mg/L (Figure 2). However explanations to these variations are lacking in the discussion. We think this might have been due to the fact that shrimp culture is not only Figure 2: comparison of nutrients between species of culture characterized by greater stocking (adapted from Cui et al. 2005) density but need special diet perhaps with higher protein and calcium content. We further expected discussion on feeding habits, feeding regime and general management in the two species. Studies of Novriadi et al. (2010) in Indonesian cages showed declining trend of water quality due to increase of N, P and COD culture (Table 1) similar to Cao et al. (2007) in China. All these observations have been attributed degradation of feed remains and fish excrete. Table 1: Data on water quality in floating net cages in Indonesia
Parameter Ammonia (NH3-N) Nitrat (NO3-N) Nitrit (NO2-N) COD Ortho Phospat
Unit mg/l mg/l mg/l mg/l mg/l
Method SMEWW 4500-NH3 SNI 06-2480 SMEWW 4500-NO2-B JIS K3602 SMEWW-4500-P-D
June 2010 < 0,0003 0,043 < 0,0007 2,312 0,032
Dec. 2010 0,02 0,052 < 0,0007 2,411 0,036
Source : (Novriadi et al. 2010)
According to Novriadi et al. (2010), trash fish feed produce more feed wastes and cause greater impacts due to poor Feed Conversion Ratio (FCR) than pelleted feeds. We agree that since it is not practical to control effluents in open water cage culture, improving and regulating feed may reduce waste generated. Gondwe et al. (2011) found a strong relationship between feed supply and fish harvested in Lake Malawi cage culture. They further found a linear relationship between the amount of feed added and C (r2=0.996), N (r2=0.968) and P (r2=0.997) loads from the cages. Gondwe et al. (2011) concluded that if cage culture continues to expand in Lake Malawi, it will become an important new source of nutrient loading to the lake and could lead to degradation of water quality as the substantial nutrient loads from cages and the low N: P loading ratio
would enhance algal growth and favor noxious and potentially toxic cyanobacteria species to the potential detriment of fish farming and other users of the aquatic resources of Lake Malawi. The authors did not compare the results with any existing water quality standards in China. This should have shown whether values were within recommended standards or not. Water quality regulations developed by governmental agencies usually have effluent standards and rules for issuing and enforcing permits for individual effluent (Goldsteen 1999; FAO 1997). There should have been some minimal comparison with other standards for example Boyd and Gautier (2000) documented maximum allowable limits of aquaculture effluents in Global Aquaculture Alliance report as TP < 0.3mg/L, TN <0.3mg/L and BOD < 30mg/L. we also find that results of other important parameters such as pH, total suspended solids and dissolved oxygen are missing in the paper yet so important in environmental microbial dynamics. Moreover, as microbial ecologists, it would be interesting to hear the dynamics of microbial presence as a function of anoxic conditions caused by increased BOD and COD in aquaculture systems. Microbial examination was only done for pen culture in Lake Taihu where Yang et al. (2003) discovered that phytoplankton abundance was three times higher than in non culture areas. He further found heterotrophic bacteria abundance increased 3 to 4 fold. Such results are lacking in all other aquaculture systems despite being our special focus in this course. In our view, the data as presented by the authors have not been statistically analyzed. The authors never conducted own research but reviewed past studies. However we think that results as at 2010 may have been different. The doubt on research methodology may have negative bearing on results. The authors concur that little information is available on number of fish that escape from aquaculture facilities yet they emphasis that aquaculture contributes to loss of biodiversity through interbreeding with native stocks. Penczak et al. (1982) estimated about 5% of caged rainbow trout escaped each year. In as much as we agree with the thinking, we still feel that there is no concrete data to support this. Poor environmental quality may result in the occurrence of disease, whether it is caused by parasites, bacteria or viruses. We indeed expected to have some data on fish or shrimp mortalities as a result of diseases due to poor environmental conditions. Snieszko (1974) expressed a diagrammatical expression of how environment, pathogens, host and diseases are interrelated in a given aquatic environment as shown in figure 3 below.
Figure 3 Interrelationship between host, environment and pathogens (adapted from Snieszko, SF, 1974)
Best management practices (BMPs) are a critical component to any successful fish farming operation as also described by Boyd & Tucker (2000). BMPs can allow farmers to reduce the likelihood of catastrophic loss by having a plan in places that acknowledges where potential problems may occur in their farming operation and what actions to take when they do. If properly implemented BMPs will cover a wide range of items from managing water quality to limiting predation. The recommendations of this review did not mention about BMPs. Generally, this paper does not predict whether China will exceed aquaculture carrying capacity. In conclusion, our general opinion about the paper is that the paper is good because of the warnings it brings about aquaculture as potential environmental pollutant. We find it quite educative and we further recommend the following new research ideas: 1. Application of Fish and Environmental Health Management. 2. Research on the possible integrated environmental management systems including use of natural and constructed wetlands to treat aquaculture effluents. 3. Encourage the governments to make their own rules about special zone for Aquaculture. 4. Encouragement of organic aquaculture as a new technology. 5. Biomonitoring approach of aquaculture effluent in receiving waters.
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