Marine Pollution Bulletin xxx (2015) xxx–xxx
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Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters H.M. Leung a, S.K.S. Leung b, C.K. Au c, K.C. Cheung b, Y.K. Wong d, A.O.W. Leung a, K.K.L. Yung a,⇑ a
Department of Biology, Hong Kong Baptist University, Hong Kong Special Administrative Region Institute of Vocational Education, Hong Kong Vocational Training Council, Hong Kong Special Administrative Region c Department of History, Hong Kong Shue Yan University, Hong Kong Special Administrative Region d School of Science and Technology, The Open University of Hong Kong, Hong Kong Special Administrative Region b
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Fish culture zone Principle Component Analysis Pearl River Delta E. coli Mariculture Ma Wan
a b s t r a c t The objective of the study is to evaluate the effect of fish cultivation on water quality in fish culture zone (FCZ) and analysed by Principle Component Analysis (PCA). 120 surface water samples were collected from Hong Kong Waters (60 samples in Victoria Harbour and another 60 in Ma Wan FCZ). Significant difference was found in dissolved oxygen (MW: 59.6%; VH: 81.3%), and Escherichia coli (MW: 465 CFU/ 100 ml; VH: 162.5 CFU/100 ml). Three principle components are responsible for water quality variations in the studying sites. The first component included E. coli (0.625) and dissolved oxygen (0.701). The second included E. coli (0.387) and ammonical-nitrogen (0.571). The third included E. coli (0.194) and ammonical-nitrogen (0.287). This framework provides information to assess the relative contribution of eco-aquaculture to nutrient loads and the subsequent risk of eutrophication. To conclude, a rigorous monitoring of water quality is necessary to assess point and nonpoint source pollution. Besides, appropriate remediation techniques should be used to combat water pollution and achieve sustainability. Ó 2015 Elsevier Ltd. All rights reserved.
The Pearl River Delta (PRD) is the main region for fish culture in Guangdong Province, and fish export has been a major source of economic revenue (Ding et al., 2014). Thousands of tonnes of fish are exported to Hong Kong every year. However, it had been found that samples from fish farms (Zhou and Wong, 2000) and local markets (Cheung et al., 2008) contained 17.5–267 ng/g dry wt THg and 70–340 ng/g wt THg, respectively. Hence, rather high levels of Hg were found in fish from the PRD, if not also other environmental pollutants. On average, Hong Kong people consume fish or shellfish at least four times a week, the above findings agree with that of Dickman and Leung (1998) that fish consumption is a major source of dietary exposure to pollutants in Hong Kong. From the stand point of productivity, a good water quality is important to support various activities of fish and that include feeding, breeding, digestion, excretion and reproduction. Apart from the feed quality and feeding method, water quality is one of most critical factors affecting the fish production (Bronmark and Hansson, 2005). Water quality parameters can be divided into three main categories: physical (salinity, temperature); chemical (pH, conductivity, dissolved oxygen) and biological (Delince, ⇑ Corresponding author at: Department of Biology, Hong Kong Baptist University, 224 Waterloo Road, Kowloon Tong, Hong Kong Special Administrative Region. E-mail address: [email protected] (K.K.L. Yung).
1992; Mood, 2004). All living organisms have an optimal zone for water quality parameters in which they perform optimally. A sharp drop or rise beyond this zone has adverse effects on their body functions (Davenport, 1993). As water quality is one of the most critical factors in fish productivity, access to an adequate, regular and constant supply of good quality water is necessary in mariculture. However, the influence of water quality in mariculture may be due to deposition of heterogeneous organic wastes resulting from the degradation of food supplies and fish excretion. The subsequent increase in oxygen consumption causes progressively anoxic conditions at the water interface, which may lead to the mobilisation of various pollutants such as heavy metals (Zhang et al., 2014) and persistent organic pollutants (Wang et al., 2015). Therefore, close monitoring and adequate management of water quality are fundamental to the success of mariculture. The objective of this study was to assess marine water quality in the fish culture zone (FCZ), in an attempt to evaluate the effect of fish cultivation on water quality in FCZ. Ma Wan (MW) is an small island with an area of 0.97 square kilometres (240 acres) located between Lantau Island and Tsing Yi Island in the southern waters of Hong Kong (Fig. 1). There are 13,200 m2 of estaurine aquaculture (Wong and Cheung, 2003) rafts in the MW FCZ operated by about 50 aquaculturists. Fish species of
http://dx.doi.org/10.1016/j.marpolbul.2015.01.028 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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H.M. Leung et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
higher market value, such as orange-spotted grouper (Epinephelus coioides), goldlined seabream (Rhabdosargus sarba), and giant grouper (Epinephelus lanceolatus) are cultivated there. Totally 120 marine water samples were taken at six sites in MW FCZ and six sites in Victoria Harbour (VH). Ten water samples were taken in each site. Samples were filled up into the plastic bottom to prevent air trap into the sample and transported it to laboratory as soon as possible. Samples were then mixed thoroughly for homogeneity before being measured. Physical parameters, which include sea temperature (measured in situ), dissolved oxygen (DO), pH, electrical conductivity (EC), salanity, were measured immediately by a calibrated Horiba Water Quality Mulitmeter. Chemical and biological parameters, i.e. ammonia, phosphorusphosphate, Biological oxygen Demand (BOD) and Escherichia coli,
in water samples were analysed subsequently by USEPA standard methods. Variables input for the Principle Component Analysis (PCA) included temperature, DO, pH, EC, salanity, ammonical-nitrogen, BOD, phosphorus-phosphate and E. coli. Totally 1200 raw data were included, the data were first examined by Kaiser–Meyer– Olkin (KMO) statistics and Bartlett’s test for suitability for PCA, before they were processed using the Primer 6 software. Those tests are measures of sampling adequacy that use the proportion of variance. The KMO value must be greater than 0.5, and the significance level of the Bartlett’s test must be less than 0.05 (Wu et al., 2010; Gyawali et al., 2012). The number and importance of uncorrelated principal components extracted from the water quality parameters are presented in a scree plot. When the eigenvalue
Shenzhen
Hong Kong
Hong Kong
Shenzhen
Ma Wan FCZ
.
MW 4
MW 6
MW 5
MW 1 MW 2
MW 3 VH 1 VH 2
VH 3 VH 5 VH 6
VH 4
Fig. 1. Sampling sites: Ma Wan fish culture zone (MW-1, MW-2, MW-3, MW-4, MW-5, and MW-6) and Victoria Habour (VH-1, VH-2, VH-3, VH-4, VH-5, and VH-6).
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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H.M. Leung et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
of a principal component is equal to, or greater than, 1, the result of the principal component analysis is considered significant (Pejman et al., 2009; Garizi et al., 2011). To minimise the variations among the variables for each factor, the factor axes were varimax-rotated. Rotating the principal components can produce a meaningful representation of the underlying factors by decreasing the contribution of variables with minor significance and increasing the contribution of those with more significance (Kebede and Kebedee, 2012). All data were subjected to one-way ANOVA using SPSS 11.0 software for further analysis. Means and standard derivations were calculated based on four replicates. Means were compared by Duncan’s Multiple Range test and T-test at 0.05 significance level (Little and Hills, 1978). The physical properties of water samples of MW and VH were analysed (Table 1). The temperature, pH, electrical conductivity, salinity were ranged from 22.03 to 23.74 °C, 7.86 to 8.25, 47.0 to 57.4 ms/cm, 29.8 to 30.9 ppt respectively. As far as the chemical properties are concerned, phosphate-phosphorus, ammonicalnitrogen and BOD-5 were ranged from 0.02 to 0.06 mg/L, 0.28 to 0.41 mg/L and 3.31 to 4.79 mg/L, respectively. Significant differences ( 1) control 60.06% of variations in water quality. The first component is the most significant principal, which represent 24.12% of the variance in water quality. The second component explains 19.11% of variance in the water quality, while the third component interprets 16.83%, of variance in the water quality. Principal component 1 contributes to 24.12% of the variation, and is highly influenced by E. coli and dissolved oxygen. Principal components 2 and 3 are responsible for 19.11% and 16.83% of the variance respectively, and are moderately influenced by E. coli and ammonical-nitrogen in water. In comparison with some international standards of marine water quality for fish cultivation (Table 3), the water qualities at both sampling sites generally complied with the Australian and New Zealand Environment Conservation Council: Water Quality Guidelines (ANZECC, 2000), the ASEAN Marine Environmental Quality Criteria (AMWQC, 1999), the Water Quality Objectives issued by Hong Kong Government (HKSAR, 2014), Taiwan Environmental Protection Administration (TEPA, 2014) and California Environmental Protection Agency (CEPA, 2014).
Table 1 Physio-chemical properties of water sampled in two sites. Average value indicated by ⁄ is significantly different according to T-test at 5% level. Within the same row of each parameter at the same site, means with the same letter are not significantly different according to Duncan’s Multiple Range test at 5% level. Site
Sampling Temperature point (°C)
Average (±SD)
pH
Average (±SD)
Conductivity Average (ms/cm) (±SD)
Victoria Harbour (VH)
VH1 VH2 VH3 VH4 VH5 VH6
22.03 ± 0.08a 22.13 ± 0.02a 22.51 ± 0.08a 22.54 ± 0.07a 22.68 ± 0.03a 22.46 ± 0.05a
22.3 ± 0.25 8.24 ± 0.08a 8.25 ± 0.02a 8.24 ± 0.02a 8.23 ± 0.04a 8.24 ± 0.05a
7.86 ± 0.07a 57.4 ± 0.20a 47.7 ± 0.24a 47.0 ± 0.49a 47.1 ± 0.26a 47.2 ± 0.23a
8.17 ± 0.15 81.7 ± 0.51a 74.7 ± 0.13b 77.1 ± 0.14b 88.4 ± 0.16b 76.1 ± 0.27b
47.3 ± 0.32a 30.8 ± 0.18a 30.9 ± 0.16a 30.5 ± 0.14a 30.6 ± 0.12a 30.7 ± 0.10a
48.9 ± 4.14 90.1 ± 0.28a
22.39 ± 0.05a 22.43 ± 0.05a 22.30 ± 0.04a 22.79 ± 0.06a 23.74 ± 0.04a 23.37 ± 0.06a
22.8 ± 0.59 8.16 ± 0.03a 8.15 ± 0.04a 8.16 ± 0.09a 8.15 ± 0.01a 8.09 ± 0.05a
8.23 ± 0.02a 47.2 ± 0.14a 46.0 ± 0.04a 47.0 ± 0.23a 47.1 ± 0.25a 49.9 ± 0.23a
8.15 ± 0.04 58.2 ± 0.19ab 69.3 ± 0.06a 63.7 ± 0.19a 42.9 ± 0.13c 66.3 ± 0.10a
47.1 ± 0.16a 30.6 ± 0.03a 29.8 ± 0.25a 30.4 ± 0.05a 30.4 ± 0.09a 29.8 ± 0.03a
47.3 ± 1.31 57.7 ± 0.39ab 59.6 ± 9.38⁄ 30.6 ± 0.13a 30.2 ± 0.37
Ma Wan (MW) MW1 MW2 MW3 MW4 MW5 MW6
Dissolved Oxygen (%)
Average (±SD)
Salinity (ppt)
81.3 ± 6.57
30.7 ± 0.07a 30.7 ± 0.14
Site
Sampling point
Phosphatephosphorus (mg/L)
Average (±SD)
Ammonicalnitrogen (mg/L)
Average (±SD)
BOD (mg/L)
Average (±SD)
E. coli (CFU/ 100 ml)
Victoria Harbour (VH)
VH1 VH2 VH3 VH4 VH5 VH6
0.03 ± 0.01a 0.05 ± 0.02a 0.02 ± 0.01a 0.04 ± 0.01a 0.03 ± 0.01a 0.05 ± 0.01a
0.03 ± 0.012 0.31 ± 0.06a 0.29 ± 0.05a 0.38 ± 0.04a 0.41 ± 0.04a 0.28 ± 0.05a
0.37 ± 0.05a 3.58 ± 0.24a 4.45 ± 0.05a 3.74 ± 0.14a 3.62 ± 0.08a 4.79 ± 0.14a
0.34 ± 0.05 120 ± 4.12b 135 ± 3.08b 210 ± 4.23a 185 ± 2.32b 240 ± 5.42a
3.56 ± 0.30a
3.95 ± 0.52
85 ± 3.03c
Ma Wan (MW)
MW1 MW2 MW3 MW4 MW5 MW6
0.02 ± 0.01b 0.06 ± 0.02a 0.03 ± 0.01b 0.04 ± 0.01b 0.02 ± 0.01b 0.05 ± 0.01b
0.03 ± 0.016 0.31 ± 0.02a 0.29 ± 0.03a 0.35 ± 0.04a 0.43 ± 0.02a 0.39 ± 0.03a
0.38 ± 0.01a 3.64 ± 0.18a 4.49 ± 0.05a 3.77 ± 0.08a 3.31 ± 0.15a 3.91 ± 0.07a
0.35 ± 0.05 320 ± 3.84b 395 ± 5.03b 255 ± 1.34c 590 ± 3.45b 740 ± 4.53a
4.12 ± 0.14a
3.87 ± 0.41
490 ± 4.65b
Average (±SD)
Average (±SD) 162.5 ± 58.8
465 ± 179.9⁄
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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Table 2 Rotated component matrix. Component
Water temperature pH DO EC Salanity PO4 NH4–N BOD E. coli Eigenvalue Contribution (%)
Eigenvalues 1
2
3
0.065 0.095 0.701 0.172 0.154 0.210 0.497 0.330 0.625 1.69 24.12
0.478 0.415 0.337 0.257 0.232 0.133 0.571 0.039 0.387 1.22 19.11
0.388 0.256 0.097 0.026 0.274 0.382 0.287 0.022 0.194 1.04 16.83
Table 3 Comparison of present data with standards. Parameters
Present study
Standard
Reference
pH
7.77–7.95
DO (%)
42.6–90.1
EC (ms/cm) Salinity (ppt) Phosphate-phosphorus (mg/L) Ammonical-nitrogen (mg/L) BOD (mg/L) E. coli (CFU/100 ml)
46.0–57.4 29.8–30.9 0.02–0.06
6–9 6.5–8.5 54% 44% 55–60 33–37 0.05–0.06
ANZECC (2000) AMWQC (1999) ANZECC (2000) AMWQC (1999) ANZECC (2000) CEPA (2014) ANZECC (2000)
0.28–0.43 3.32–4.79 85–740
0.21 2–6 610
HKSAR (2014) TEPA (2014) HKSAR (2014)
Except the dissolved oxygen (DO), all measured parameters between the two sampling sites fell into comparable ranges. The possible reason would be there is strong natural flow and most water movement is tidal. Due to this large movement, the channel is a good settlement basin for the pollutants either brought from upstream or by the flood tides. In addition, the minimal water exchange process also increases the self-cleaning power of the channel. The water qualities of two sites were similar due to the prohibition of pollutants loaded into the habitat set by Hong Kong law. Besides, algal blooms, sewage effluents and all fish feed and fish wastes disposed directly are three major environmental impacts resulting from low DO found in mariculture farm. Such low DO waters do not cause impacts during high tide due to dilution effect. However, impact was significant in low tide. This is because as DO levels in the marine habitat can fluctuate greatly with the amount of bacteria present in the site, Therefore, when DO declines below threshold levels, which vary depending upon the species, mobile animals must move to waters with higher DO; immobile species often perish. If the concentration of DO fall further, many species will often become stressed and immobile species may die (hypoxia). A second condition, known as anoxia, occurs when the water becomes totally depleted of oxygen and results in the death of any organism that requires oxygen for survival. Such indicator is important because DO affects the growth, survival, distribution, behaviour and physiology of fish. By comparing the current seawater temperature with the report (HKEPD, 2013), the current temperature was higher than in the past. Anthropogenic activities or global warming have significant impacts on marine environment by increasing seawater temperature. The study was in line with Al-Rashidi et al. (2009) that the seawater temperature in Kuwait Bay has increased by an average 0.6 °C per decade, about three times higher than the global average rate reported by the Intergovernmental Panel on Climate Change (IPCC). Seawater temperature is one of the key indicators that
affect directly the marine fauna and flora and alter its life (Mann and Lazier, 2005). High seawater temperature weakens the immune system of low-tolerance fishes and creates unfavorable conditions making potential events of massive Fishkill (AlMarzouk et al., 2005). In recent years, multivariate analyses such as cluster and principal components analysis have been widely applied to evaluate the temporal and spatial characteristics of water quality. Several studies (Singh et al., 2005; Ozbay et al., 2009; Kamble and Vijay, 2011; Yab et al., 2011) have classified the monitoring stations based on selected water quality parameters to determine and identify the stations affected most by pollution in a water system. Principal Components Analysis (PCA) has been widely applied to reduce the amount of water data and summarise the statistical correlations among water quality parameters, with a minimal loss of the original information (Helena et al., 2000). PCA, as the multivariate analytical tool, is used to reduce a set of original variables and to extract a small number of latent factors (principal components, PCs) for analysing relationships among the observed variables (Mahmud et al., 2007). By comparing the water quality parameters by PCA, a significant difference of E. coli levels was found in water between two sampling sites, although the water current is high in the study site. Since the currents at two sites were not similar, the results obtained truly reflecting the effect of fish culture towards water quality in two sites. Therefore, it may pose hazard to human’s health as human contact with and consumption of fishes presents hazards from a range of bacterial zoonotic infections, contamination of fishes and fish products with E. coli is a widespread concern in food handling and hygiene practices, and E. coli have been linked to foodborne illness, with fishes or fish products likely serving as a vehicle (Piérard et al., 1999; Terajima et al., 1999; McCoy et al., 2011). The other possible reasons for the elevation of E. coli present in water may be subjected to change the sediment properties over time in reclamation project, leading to causing algal bloom occurred around the mariculture (Sadally et al., 2014). In the early 1940s, fish farming was introduced in Hong Kong turning a vast amount of arable lands into mariculture in New Territories. The transformation of potential high yielding variety nutrients and into mariculture increased the yield of both cultivations and simultaneously deteriorated the water quality nearby the fish farm. Therefore, prolonged ‘‘contamination’’ caused by mariculture accelerates leaching base materials and alter sediment quality and rapidly depletes marine water quality because it delivered high volume of organic matter, inorganic effluents and toxic chemicals to the ecosystem that result in hypernitrification and eutrophication (Martínez-Córdova et al., 2014). As a results, oxygen depletion in water leads to grow in E. coli and poor feeding of fish, starvation, reduced growth and more fish mortality, either directly or indirectly. Since the principal source of oxygen in water is atmospheric air and photosynthetic planktons. Obtaining sufficient oxygen is a greater problem for aquatic organisms than terrestrial ones during eutrophication. The data obtained from the study of water quality in two sites was compared with the water quality guideline to protect the aquatic life (i.e., ANZECC, AMEQC, HKEPD, TEPA, and CEPA). Water quality guideline is very useful to screen sediment contamination by comparing water contaminant concentration with the corresponding quality guideline, provide useful tools for screening sediment chemical data to identify pollutants of concern and prioritise problem sites. According to the results, the water quality in VH was similar to the date pressed in the marine water quality report issued by HKEPD (2013). Before the sewage diversion, nutrients were an impact issue in Victoria Harbour. Algal bloom in these waters was occurred throughout the year. Starting in December 2002, the majority of sewage effluent which was discharged into
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
H.M. Leung et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
Victoria Harbour was collected via the Strategic Sewage Disposal Scheme (SSDS) deep tunnel to Stonecutters Island sewage treatment plant (SCISTP) and discharged into waters after chemically enhanced primary treatment. Therefore, DO in the water is likely to improve and the concentration of nutrients was decreased in marine water. The implementation of environmental policy and sediment treatment greatly improved the water quality to remedy ecological degradation in the past as evidenced by the present study. Water quality at the two sites studied complied with international standards; nevertheless, regular studies of water pollutant levels is recommended to monitor the impacts of MW and other FCZs to waters in Hong Kong and the relationship between fish consumption and their levels in human bodies, is necessary to improve and update information on the water quality in mariculture in order to establish a framework for their proper management and control in future. Therefore, in order to keep the water quality of Hong Kong Waters, continue with the enforcement control of all waste water discharges and the rectification of illegal discharges of foul water to the harbour is needed. Acknowledgement The authors thank KW Sin, HC Fung, WH Chan, HH Cheung for technical support. References Al-Marzouk, A., Duremedz, R., Yuasa, K., Al-zenki, S., Al-Gharabally, H., Munday, B., 2005. Fish kill of Mullet Liza klunzingeri in Kuwait Bay: The role of Streptococcus agalactiae and the influence of temperature. In: Walker, P., Lester, R., Bondad-Reantaso, M.G. (Eds.), Diseases in Asian Aquaculture V. Fish Health Section, Asian Fisheries Society, Manila, pp. 143–153. Al-Rashidi, T.B., El-Gamily, H.I., Amos, C.L., Rakha, K.A., 2009. Sea surface temperature trends in Kuwait Bay, Arabian Gulf. Nat. Hazards 50, 73–82. AMWQC, 1999. ASEAN Marine Environmental Quality Criteria. ANZECC, 2000. Water Quality Guidelines. Australian and New Zealand Environment Conservation Council. Bronmark, C., Hansson, L.A., 2005. The Biology of Lakes and Ponds. Oxford University Press, Oxford, p. 285. CEPA, 2014. Califormia State Water Resources Control Board. Cheung, K.C., Leung, H.M., Wong, M.H., 2008. Metal concentrations of common freshwater and marine fish from the Pearl River Delta, South China. Arch. Environ. Contam. Toxicol. 54, 705–715. Davenport, Y., 1993. Responses of the Blennius pholis to fluctuating salinities. Mar. Eco. Progr. Ser. 1, 101–107. Delince, G., 1992. The Ecology of the Fish Pond Ecosystem with Special Reference to Africa. Kluwer Academic Publishers, London, p. 230. Dickman, M.D., Leung, K.M.C., 1998. Mercury and organochlorine exposure from fish consumption in Hong Kong. Chemosphere 37, 991–1015. Ding, J., Ge, X., Casey, B., 2014. ‘‘Blue competition’’ in China: Current situation and challenges. Mar. Policy 44, 351–359. Garizi, A.Z., Sheikh, V., Sadoddin, A., 2011. Assessment of seasonal variations of chemical characteristics in surface water using multivariate statistical methods. Int. J. Environ. Sci. Technol. 8, 581–592. Gyawali, S., Techato, K., Yuangyai, C., Monprapusson, S., 2012. Evaluation of surface water-quality using multivariate statistical technique: a case study of U-tapao river basin, Thailand. KMITL Sci. Technol. J. 12, 7–20.
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Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Baseline
Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters H.M. Leung a, S.K.S. Leung b, C.K. Au c, K.C. Cheung b, Y.K. Wong d, A.O.W. Leung a, K.K.L. Yung a,⇑ a
Department of Biology, Hong Kong Baptist University, Hong Kong Special Administrative Region Institute of Vocational Education, Hong Kong Vocational Training Council, Hong Kong Special Administrative Region c Department of History, Hong Kong Shue Yan University, Hong Kong Special Administrative Region d School of Science and Technology, The Open University of Hong Kong, Hong Kong Special Administrative Region b
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Fish culture zone Principle Component Analysis Pearl River Delta E. coli Mariculture Ma Wan
a b s t r a c t The objective of the study is to evaluate the effect of fish cultivation on water quality in fish culture zone (FCZ) and analysed by Principle Component Analysis (PCA). 120 surface water samples were collected from Hong Kong Waters (60 samples in Victoria Harbour and another 60 in Ma Wan FCZ). Significant difference was found in dissolved oxygen (MW: 59.6%; VH: 81.3%), and Escherichia coli (MW: 465 CFU/ 100 ml; VH: 162.5 CFU/100 ml). Three principle components are responsible for water quality variations in the studying sites. The first component included E. coli (0.625) and dissolved oxygen (0.701). The second included E. coli (0.387) and ammonical-nitrogen (0.571). The third included E. coli (0.194) and ammonical-nitrogen (0.287). This framework provides information to assess the relative contribution of eco-aquaculture to nutrient loads and the subsequent risk of eutrophication. To conclude, a rigorous monitoring of water quality is necessary to assess point and nonpoint source pollution. Besides, appropriate remediation techniques should be used to combat water pollution and achieve sustainability. Ó 2015 Elsevier Ltd. All rights reserved.
The Pearl River Delta (PRD) is the main region for fish culture in Guangdong Province, and fish export has been a major source of economic revenue (Ding et al., 2014). Thousands of tonnes of fish are exported to Hong Kong every year. However, it had been found that samples from fish farms (Zhou and Wong, 2000) and local markets (Cheung et al., 2008) contained 17.5–267 ng/g dry wt THg and 70–340 ng/g wt THg, respectively. Hence, rather high levels of Hg were found in fish from the PRD, if not also other environmental pollutants. On average, Hong Kong people consume fish or shellfish at least four times a week, the above findings agree with that of Dickman and Leung (1998) that fish consumption is a major source of dietary exposure to pollutants in Hong Kong. From the stand point of productivity, a good water quality is important to support various activities of fish and that include feeding, breeding, digestion, excretion and reproduction. Apart from the feed quality and feeding method, water quality is one of most critical factors affecting the fish production (Bronmark and Hansson, 2005). Water quality parameters can be divided into three main categories: physical (salinity, temperature); chemical (pH, conductivity, dissolved oxygen) and biological (Delince, ⇑ Corresponding author at: Department of Biology, Hong Kong Baptist University, 224 Waterloo Road, Kowloon Tong, Hong Kong Special Administrative Region. E-mail address: [email protected] (K.K.L. Yung).
1992; Mood, 2004). All living organisms have an optimal zone for water quality parameters in which they perform optimally. A sharp drop or rise beyond this zone has adverse effects on their body functions (Davenport, 1993). As water quality is one of the most critical factors in fish productivity, access to an adequate, regular and constant supply of good quality water is necessary in mariculture. However, the influence of water quality in mariculture may be due to deposition of heterogeneous organic wastes resulting from the degradation of food supplies and fish excretion. The subsequent increase in oxygen consumption causes progressively anoxic conditions at the water interface, which may lead to the mobilisation of various pollutants such as heavy metals (Zhang et al., 2014) and persistent organic pollutants (Wang et al., 2015). Therefore, close monitoring and adequate management of water quality are fundamental to the success of mariculture. The objective of this study was to assess marine water quality in the fish culture zone (FCZ), in an attempt to evaluate the effect of fish cultivation on water quality in FCZ. Ma Wan (MW) is an small island with an area of 0.97 square kilometres (240 acres) located between Lantau Island and Tsing Yi Island in the southern waters of Hong Kong (Fig. 1). There are 13,200 m2 of estaurine aquaculture (Wong and Cheung, 2003) rafts in the MW FCZ operated by about 50 aquaculturists. Fish species of
http://dx.doi.org/10.1016/j.marpolbul.2015.01.028 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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H.M. Leung et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
higher market value, such as orange-spotted grouper (Epinephelus coioides), goldlined seabream (Rhabdosargus sarba), and giant grouper (Epinephelus lanceolatus) are cultivated there. Totally 120 marine water samples were taken at six sites in MW FCZ and six sites in Victoria Harbour (VH). Ten water samples were taken in each site. Samples were filled up into the plastic bottom to prevent air trap into the sample and transported it to laboratory as soon as possible. Samples were then mixed thoroughly for homogeneity before being measured. Physical parameters, which include sea temperature (measured in situ), dissolved oxygen (DO), pH, electrical conductivity (EC), salanity, were measured immediately by a calibrated Horiba Water Quality Mulitmeter. Chemical and biological parameters, i.e. ammonia, phosphorusphosphate, Biological oxygen Demand (BOD) and Escherichia coli,
in water samples were analysed subsequently by USEPA standard methods. Variables input for the Principle Component Analysis (PCA) included temperature, DO, pH, EC, salanity, ammonical-nitrogen, BOD, phosphorus-phosphate and E. coli. Totally 1200 raw data were included, the data were first examined by Kaiser–Meyer– Olkin (KMO) statistics and Bartlett’s test for suitability for PCA, before they were processed using the Primer 6 software. Those tests are measures of sampling adequacy that use the proportion of variance. The KMO value must be greater than 0.5, and the significance level of the Bartlett’s test must be less than 0.05 (Wu et al., 2010; Gyawali et al., 2012). The number and importance of uncorrelated principal components extracted from the water quality parameters are presented in a scree plot. When the eigenvalue
Shenzhen
Hong Kong
Hong Kong
Shenzhen
Ma Wan FCZ
.
MW 4
MW 6
MW 5
MW 1 MW 2
MW 3 VH 1 VH 2
VH 3 VH 5 VH 6
VH 4
Fig. 1. Sampling sites: Ma Wan fish culture zone (MW-1, MW-2, MW-3, MW-4, MW-5, and MW-6) and Victoria Habour (VH-1, VH-2, VH-3, VH-4, VH-5, and VH-6).
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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H.M. Leung et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
of a principal component is equal to, or greater than, 1, the result of the principal component analysis is considered significant (Pejman et al., 2009; Garizi et al., 2011). To minimise the variations among the variables for each factor, the factor axes were varimax-rotated. Rotating the principal components can produce a meaningful representation of the underlying factors by decreasing the contribution of variables with minor significance and increasing the contribution of those with more significance (Kebede and Kebedee, 2012). All data were subjected to one-way ANOVA using SPSS 11.0 software for further analysis. Means and standard derivations were calculated based on four replicates. Means were compared by Duncan’s Multiple Range test and T-test at 0.05 significance level (Little and Hills, 1978). The physical properties of water samples of MW and VH were analysed (Table 1). The temperature, pH, electrical conductivity, salinity were ranged from 22.03 to 23.74 °C, 7.86 to 8.25, 47.0 to 57.4 ms/cm, 29.8 to 30.9 ppt respectively. As far as the chemical properties are concerned, phosphate-phosphorus, ammonicalnitrogen and BOD-5 were ranged from 0.02 to 0.06 mg/L, 0.28 to 0.41 mg/L and 3.31 to 4.79 mg/L, respectively. Significant differences ( 1) control 60.06% of variations in water quality. The first component is the most significant principal, which represent 24.12% of the variance in water quality. The second component explains 19.11% of variance in the water quality, while the third component interprets 16.83%, of variance in the water quality. Principal component 1 contributes to 24.12% of the variation, and is highly influenced by E. coli and dissolved oxygen. Principal components 2 and 3 are responsible for 19.11% and 16.83% of the variance respectively, and are moderately influenced by E. coli and ammonical-nitrogen in water. In comparison with some international standards of marine water quality for fish cultivation (Table 3), the water qualities at both sampling sites generally complied with the Australian and New Zealand Environment Conservation Council: Water Quality Guidelines (ANZECC, 2000), the ASEAN Marine Environmental Quality Criteria (AMWQC, 1999), the Water Quality Objectives issued by Hong Kong Government (HKSAR, 2014), Taiwan Environmental Protection Administration (TEPA, 2014) and California Environmental Protection Agency (CEPA, 2014).
Table 1 Physio-chemical properties of water sampled in two sites. Average value indicated by ⁄ is significantly different according to T-test at 5% level. Within the same row of each parameter at the same site, means with the same letter are not significantly different according to Duncan’s Multiple Range test at 5% level. Site
Sampling Temperature point (°C)
Average (±SD)
pH
Average (±SD)
Conductivity Average (ms/cm) (±SD)
Victoria Harbour (VH)
VH1 VH2 VH3 VH4 VH5 VH6
22.03 ± 0.08a 22.13 ± 0.02a 22.51 ± 0.08a 22.54 ± 0.07a 22.68 ± 0.03a 22.46 ± 0.05a
22.3 ± 0.25 8.24 ± 0.08a 8.25 ± 0.02a 8.24 ± 0.02a 8.23 ± 0.04a 8.24 ± 0.05a
7.86 ± 0.07a 57.4 ± 0.20a 47.7 ± 0.24a 47.0 ± 0.49a 47.1 ± 0.26a 47.2 ± 0.23a
8.17 ± 0.15 81.7 ± 0.51a 74.7 ± 0.13b 77.1 ± 0.14b 88.4 ± 0.16b 76.1 ± 0.27b
47.3 ± 0.32a 30.8 ± 0.18a 30.9 ± 0.16a 30.5 ± 0.14a 30.6 ± 0.12a 30.7 ± 0.10a
48.9 ± 4.14 90.1 ± 0.28a
22.39 ± 0.05a 22.43 ± 0.05a 22.30 ± 0.04a 22.79 ± 0.06a 23.74 ± 0.04a 23.37 ± 0.06a
22.8 ± 0.59 8.16 ± 0.03a 8.15 ± 0.04a 8.16 ± 0.09a 8.15 ± 0.01a 8.09 ± 0.05a
8.23 ± 0.02a 47.2 ± 0.14a 46.0 ± 0.04a 47.0 ± 0.23a 47.1 ± 0.25a 49.9 ± 0.23a
8.15 ± 0.04 58.2 ± 0.19ab 69.3 ± 0.06a 63.7 ± 0.19a 42.9 ± 0.13c 66.3 ± 0.10a
47.1 ± 0.16a 30.6 ± 0.03a 29.8 ± 0.25a 30.4 ± 0.05a 30.4 ± 0.09a 29.8 ± 0.03a
47.3 ± 1.31 57.7 ± 0.39ab 59.6 ± 9.38⁄ 30.6 ± 0.13a 30.2 ± 0.37
Ma Wan (MW) MW1 MW2 MW3 MW4 MW5 MW6
Dissolved Oxygen (%)
Average (±SD)
Salinity (ppt)
81.3 ± 6.57
30.7 ± 0.07a 30.7 ± 0.14
Site
Sampling point
Phosphatephosphorus (mg/L)
Average (±SD)
Ammonicalnitrogen (mg/L)
Average (±SD)
BOD (mg/L)
Average (±SD)
E. coli (CFU/ 100 ml)
Victoria Harbour (VH)
VH1 VH2 VH3 VH4 VH5 VH6
0.03 ± 0.01a 0.05 ± 0.02a 0.02 ± 0.01a 0.04 ± 0.01a 0.03 ± 0.01a 0.05 ± 0.01a
0.03 ± 0.012 0.31 ± 0.06a 0.29 ± 0.05a 0.38 ± 0.04a 0.41 ± 0.04a 0.28 ± 0.05a
0.37 ± 0.05a 3.58 ± 0.24a 4.45 ± 0.05a 3.74 ± 0.14a 3.62 ± 0.08a 4.79 ± 0.14a
0.34 ± 0.05 120 ± 4.12b 135 ± 3.08b 210 ± 4.23a 185 ± 2.32b 240 ± 5.42a
3.56 ± 0.30a
3.95 ± 0.52
85 ± 3.03c
Ma Wan (MW)
MW1 MW2 MW3 MW4 MW5 MW6
0.02 ± 0.01b 0.06 ± 0.02a 0.03 ± 0.01b 0.04 ± 0.01b 0.02 ± 0.01b 0.05 ± 0.01b
0.03 ± 0.016 0.31 ± 0.02a 0.29 ± 0.03a 0.35 ± 0.04a 0.43 ± 0.02a 0.39 ± 0.03a
0.38 ± 0.01a 3.64 ± 0.18a 4.49 ± 0.05a 3.77 ± 0.08a 3.31 ± 0.15a 3.91 ± 0.07a
0.35 ± 0.05 320 ± 3.84b 395 ± 5.03b 255 ± 1.34c 590 ± 3.45b 740 ± 4.53a
4.12 ± 0.14a
3.87 ± 0.41
490 ± 4.65b
Average (±SD)
Average (±SD) 162.5 ± 58.8
465 ± 179.9⁄
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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Table 2 Rotated component matrix. Component
Water temperature pH DO EC Salanity PO4 NH4–N BOD E. coli Eigenvalue Contribution (%)
Eigenvalues 1
2
3
0.065 0.095 0.701 0.172 0.154 0.210 0.497 0.330 0.625 1.69 24.12
0.478 0.415 0.337 0.257 0.232 0.133 0.571 0.039 0.387 1.22 19.11
0.388 0.256 0.097 0.026 0.274 0.382 0.287 0.022 0.194 1.04 16.83
Table 3 Comparison of present data with standards. Parameters
Present study
Standard
Reference
pH
7.77–7.95
DO (%)
42.6–90.1
EC (ms/cm) Salinity (ppt) Phosphate-phosphorus (mg/L) Ammonical-nitrogen (mg/L) BOD (mg/L) E. coli (CFU/100 ml)
46.0–57.4 29.8–30.9 0.02–0.06
6–9 6.5–8.5 54% 44% 55–60 33–37 0.05–0.06
ANZECC (2000) AMWQC (1999) ANZECC (2000) AMWQC (1999) ANZECC (2000) CEPA (2014) ANZECC (2000)
0.28–0.43 3.32–4.79 85–740
0.21 2–6 610
HKSAR (2014) TEPA (2014) HKSAR (2014)
Except the dissolved oxygen (DO), all measured parameters between the two sampling sites fell into comparable ranges. The possible reason would be there is strong natural flow and most water movement is tidal. Due to this large movement, the channel is a good settlement basin for the pollutants either brought from upstream or by the flood tides. In addition, the minimal water exchange process also increases the self-cleaning power of the channel. The water qualities of two sites were similar due to the prohibition of pollutants loaded into the habitat set by Hong Kong law. Besides, algal blooms, sewage effluents and all fish feed and fish wastes disposed directly are three major environmental impacts resulting from low DO found in mariculture farm. Such low DO waters do not cause impacts during high tide due to dilution effect. However, impact was significant in low tide. This is because as DO levels in the marine habitat can fluctuate greatly with the amount of bacteria present in the site, Therefore, when DO declines below threshold levels, which vary depending upon the species, mobile animals must move to waters with higher DO; immobile species often perish. If the concentration of DO fall further, many species will often become stressed and immobile species may die (hypoxia). A second condition, known as anoxia, occurs when the water becomes totally depleted of oxygen and results in the death of any organism that requires oxygen for survival. Such indicator is important because DO affects the growth, survival, distribution, behaviour and physiology of fish. By comparing the current seawater temperature with the report (HKEPD, 2013), the current temperature was higher than in the past. Anthropogenic activities or global warming have significant impacts on marine environment by increasing seawater temperature. The study was in line with Al-Rashidi et al. (2009) that the seawater temperature in Kuwait Bay has increased by an average 0.6 °C per decade, about three times higher than the global average rate reported by the Intergovernmental Panel on Climate Change (IPCC). Seawater temperature is one of the key indicators that
affect directly the marine fauna and flora and alter its life (Mann and Lazier, 2005). High seawater temperature weakens the immune system of low-tolerance fishes and creates unfavorable conditions making potential events of massive Fishkill (AlMarzouk et al., 2005). In recent years, multivariate analyses such as cluster and principal components analysis have been widely applied to evaluate the temporal and spatial characteristics of water quality. Several studies (Singh et al., 2005; Ozbay et al., 2009; Kamble and Vijay, 2011; Yab et al., 2011) have classified the monitoring stations based on selected water quality parameters to determine and identify the stations affected most by pollution in a water system. Principal Components Analysis (PCA) has been widely applied to reduce the amount of water data and summarise the statistical correlations among water quality parameters, with a minimal loss of the original information (Helena et al., 2000). PCA, as the multivariate analytical tool, is used to reduce a set of original variables and to extract a small number of latent factors (principal components, PCs) for analysing relationships among the observed variables (Mahmud et al., 2007). By comparing the water quality parameters by PCA, a significant difference of E. coli levels was found in water between two sampling sites, although the water current is high in the study site. Since the currents at two sites were not similar, the results obtained truly reflecting the effect of fish culture towards water quality in two sites. Therefore, it may pose hazard to human’s health as human contact with and consumption of fishes presents hazards from a range of bacterial zoonotic infections, contamination of fishes and fish products with E. coli is a widespread concern in food handling and hygiene practices, and E. coli have been linked to foodborne illness, with fishes or fish products likely serving as a vehicle (Piérard et al., 1999; Terajima et al., 1999; McCoy et al., 2011). The other possible reasons for the elevation of E. coli present in water may be subjected to change the sediment properties over time in reclamation project, leading to causing algal bloom occurred around the mariculture (Sadally et al., 2014). In the early 1940s, fish farming was introduced in Hong Kong turning a vast amount of arable lands into mariculture in New Territories. The transformation of potential high yielding variety nutrients and into mariculture increased the yield of both cultivations and simultaneously deteriorated the water quality nearby the fish farm. Therefore, prolonged ‘‘contamination’’ caused by mariculture accelerates leaching base materials and alter sediment quality and rapidly depletes marine water quality because it delivered high volume of organic matter, inorganic effluents and toxic chemicals to the ecosystem that result in hypernitrification and eutrophication (Martínez-Córdova et al., 2014). As a results, oxygen depletion in water leads to grow in E. coli and poor feeding of fish, starvation, reduced growth and more fish mortality, either directly or indirectly. Since the principal source of oxygen in water is atmospheric air and photosynthetic planktons. Obtaining sufficient oxygen is a greater problem for aquatic organisms than terrestrial ones during eutrophication. The data obtained from the study of water quality in two sites was compared with the water quality guideline to protect the aquatic life (i.e., ANZECC, AMEQC, HKEPD, TEPA, and CEPA). Water quality guideline is very useful to screen sediment contamination by comparing water contaminant concentration with the corresponding quality guideline, provide useful tools for screening sediment chemical data to identify pollutants of concern and prioritise problem sites. According to the results, the water quality in VH was similar to the date pressed in the marine water quality report issued by HKEPD (2013). Before the sewage diversion, nutrients were an impact issue in Victoria Harbour. Algal bloom in these waters was occurred throughout the year. Starting in December 2002, the majority of sewage effluent which was discharged into
Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
H.M. Leung et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
Victoria Harbour was collected via the Strategic Sewage Disposal Scheme (SSDS) deep tunnel to Stonecutters Island sewage treatment plant (SCISTP) and discharged into waters after chemically enhanced primary treatment. Therefore, DO in the water is likely to improve and the concentration of nutrients was decreased in marine water. The implementation of environmental policy and sediment treatment greatly improved the water quality to remedy ecological degradation in the past as evidenced by the present study. Water quality at the two sites studied complied with international standards; nevertheless, regular studies of water pollutant levels is recommended to monitor the impacts of MW and other FCZs to waters in Hong Kong and the relationship between fish consumption and their levels in human bodies, is necessary to improve and update information on the water quality in mariculture in order to establish a framework for their proper management and control in future. Therefore, in order to keep the water quality of Hong Kong Waters, continue with the enforcement control of all waste water discharges and the rectification of illegal discharges of foul water to the harbour is needed. Acknowledgement The authors thank KW Sin, HC Fung, WH Chan, HH Cheung for technical support. References Al-Marzouk, A., Duremedz, R., Yuasa, K., Al-zenki, S., Al-Gharabally, H., Munday, B., 2005. Fish kill of Mullet Liza klunzingeri in Kuwait Bay: The role of Streptococcus agalactiae and the influence of temperature. In: Walker, P., Lester, R., Bondad-Reantaso, M.G. (Eds.), Diseases in Asian Aquaculture V. Fish Health Section, Asian Fisheries Society, Manila, pp. 143–153. Al-Rashidi, T.B., El-Gamily, H.I., Amos, C.L., Rakha, K.A., 2009. Sea surface temperature trends in Kuwait Bay, Arabian Gulf. Nat. Hazards 50, 73–82. AMWQC, 1999. ASEAN Marine Environmental Quality Criteria. ANZECC, 2000. Water Quality Guidelines. Australian and New Zealand Environment Conservation Council. Bronmark, C., Hansson, L.A., 2005. The Biology of Lakes and Ponds. Oxford University Press, Oxford, p. 285. CEPA, 2014. Califormia State Water Resources Control Board. Cheung, K.C., Leung, H.M., Wong, M.H., 2008. Metal concentrations of common freshwater and marine fish from the Pearl River Delta, South China. Arch. Environ. Contam. Toxicol. 54, 705–715. Davenport, Y., 1993. Responses of the Blennius pholis to fluctuating salinities. Mar. Eco. Progr. Ser. 1, 101–107. Delince, G., 1992. The Ecology of the Fish Pond Ecosystem with Special Reference to Africa. Kluwer Academic Publishers, London, p. 230. Dickman, M.D., Leung, K.M.C., 1998. Mercury and organochlorine exposure from fish consumption in Hong Kong. Chemosphere 37, 991–1015. Ding, J., Ge, X., Casey, B., 2014. ‘‘Blue competition’’ in China: Current situation and challenges. Mar. Policy 44, 351–359. Garizi, A.Z., Sheikh, V., Sadoddin, A., 2011. Assessment of seasonal variations of chemical characteristics in surface water using multivariate statistical methods. Int. J. Environ. Sci. Technol. 8, 581–592. Gyawali, S., Techato, K., Yuangyai, C., Monprapusson, S., 2012. Evaluation of surface water-quality using multivariate statistical technique: a case study of U-tapao river basin, Thailand. KMITL Sci. Technol. J. 12, 7–20.
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Please cite this article in press as: Leung, H.M., et al. Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.01.028
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