Environmental Monitoring and Assessment (2005) 104: 409–418 DOI: 10.1007/s10661-005-1681-x

c Springer 2005


ECOLOGICAL RISK ASSESSMENT OF ABANDONED SHRIMP PONDS IN SOUTHERN THAILAND PARICHART VISUTHISMAJARN1,∗ , BANJONG VITAYAVIRASUK1 , NIPA LEERAPHANTE2 and MONTE KIETPAWPAN1 1

Faculty of Environmental Management, Hat Yai, Songkhla, Thailand; 2 Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Songkhla, Thailand (∗ author for correspondence, e-mail: [email protected])

(Received 2 December 2003; accepted 2 June 2004)

Abstract. The potential ecological risks associated with contaminants from 15 abandoned shrimp ponds in southern Thailand were assessed at the screening level. Shrimp ponds reported as out of production for more than 2 years were selected as sampling sites. The assessment endpoint was identified as the protection of aquatic life from hazard of multiple agents or stressors in water or sediment from the ponds. The measurement endpoints were amount of toxic phytoplankton species, Yellow Head Viruses, SEMB viruses, oxytetracycline, cadmium, copper, and manganese. Data from field measurements and laboratory analyses obtained primarily from April to June 2003 were used in the risk analysis. The results showed that insignificant amounts of stressors were present, except for the metals. So, only concentration values of the metals were used in the calculation of hazard quotients (HQ) for risk characterization. The highest potential ecological risk characterized by the highest HQ value observed for each metal was 19 for manganese, 4.3 for cadmium, and 1.8 for copper. These findings indicated a need for further ecological risk assessment at a more detailed level to focus on the bioavailability and effects of metals from abandoned shrimp farms, with manganese the highest priority. Keywords: abandoned shrimp ponds, ecological risk assessment, hazard quotient

1. Introduction Following a boom in shrimp farming in Thailand during the 1980s, large areas of shrimp ponds have been abandoned over the past decade, either because shrimp disease has made production unviable or because changes in market prices have made farming unprofitable (World Bank, 1998). The total area of abandoned shrimp ponds in the country is unknown, but estimates for the area abandoned over the period 1990–1997 range from 4500 to 45 000 ha (MIDAS Agronomics, 1995; Lindberg and Nylander, 2001; Hossain and Lin, 2001; Bart et al., 2003). A wide variety of chemicals and biological products are applied during shrimp farming, some of which are persistent toxic chemicals that are likely to pose risks to adjacent ecosystems. The most commonly used types of product, in order of frequency of use by Thai shrimp farmers, are pesticides, disinfectants, microorganisms, feed additives, vitamins, antibiotics, fertilizers, and immunostimulants

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(Gr¨aslund et al., 2003). Although many investigations have studied the impacts of these substances on the environment (Flaherty and Karnjanakesorn, 1995; Dierberg and Kiattisimkul, 1996; World Bank, 1998; Gr¨aslund and Bengtsson, 2001; Boyd, 2002; Lindberg and Nylander, 2001; Gr¨aslund et al., 2003), there have been few reports on the impacts of shrimp ponds following their abandonment. Little to nothing is known about environmental effects and ecological risks related to abandoned shrimp ponds, even though considerable attention has been paid to the issue of pond abandonment in recent years. The objectives of this study were therefore: (1) to conduct an ecological risk assessment of abandoned shrimp ponds at the screening level, and (2) to provide guidance for further ecological risk assessment at the detailed level for abandoned shrimp ponds in southern Thailand.

2. Methods 2.1. S TUDY

SITES AND SITE DESCRIPTION

Fifteen abandoned shrimp pond sites, where continuous outbreaks of shrimp disease had been reported, were selected as sampling sites. Sampling sites were chosen on the basis of the research team’s judgment to represent a selection of locations, culture practices, and site histories that reflect shrimp farming trends in Thailand. The sampling sites were situated in three provinces in southern Thailand: Prachuap Kiri Khan (Figure 1), a major shrimp farming zone on the upper Southern coast of the Gulf of Thailand; Satun (Figure 2), a disturbed mangrove ecosystem area on the Andaman sea coast; and Songkhla (Figure 3), a former rice farming area adjacent to the Songkhla Lake lagoon system where paddy fields have been converted to shrimp ponds. 2.2. WATER

SAMPLING , FIELD MEASUREMENTS , AND LABORATORY ANALYSES

Temperature, pH, and conductivity of water from the abandoned ponds were measured in April 2003 using a mercury thermometer, pH meter (Orion 250A, USA), and a conductivity meter (WTW LF 320) . Water samples (80 mL) were collected from the ponds and stored in autoclaved bottles, kept at 4 ◦ C, and transported to the microbiological laboratory at the Songklanakarin Hospital, Hat Yai, Thailand, for identification and quantification of bacteria. 2.3. SEDIMENT

SAMPLING AND LABORATORY ANALYSES

Sediment samples were collected by taking cores at a depth of 10 cm with an 8-cm diameter coring device. Approximately 1 kg from the middle of each sample was put into a plastic bag using a plastic spoon, stored at 4 ◦ C, and transported to the

411

ECOLOGICAL RISK ASSESSMENT OF ABANDONED SHRIMP PONDS 650000

700000 900000

900000

600000

k1

c

k4

c

850000

c

k5 850000

k2 c k3

c Songk hla lake

k3cckk1245

cc

LEGEN D Songkhla GPS Point Province boundary Shrimp farm

750000

750000

c

800000

800000

Gulf of Thailand

700000

700000

N

8

0

8

600000

16 Kilo m eters 650000

700000

Figure 1. Sampling sites in Songkhla province.

laboratory. Sediment samples were dried in an oven at 50 ◦ C for 48 h. They were then grounded in an agate mortar and were sieved through a 200-mesh sieve. After homogenization, The samples were digested following the methodology of the U.S. EPA (1994). Concentrations of copper, cadmium, and manganese in solutions were determined using a graphite furnace atomic absorption spectrophotometer (VarianR Model GTA 100 SpectrAA-800, Varian, Australia). 2.4. P HYTOPLANKTON

SAMPLING AND IDENTIFICATION

Water samples of approximately 10 L were collected from each abandoned shrimp pond at a depth of 30–40 cm using a general-purpose plastic bucket. Water was filtered through a 20 µm plankton net and collected in a cod-end jar at the base

412

P. VISUTHISMAJARN ET AL. 600000

550000

s4

c

s3

c

s5

s2

c c

Andaman Sea

750000

750000

s1

800000

800000

c

700000

700000

cc c cc

MALAYSIA

Satun Tarutao Island

LEGEND

N

c 8

0

8

16 Kilometers

550000

GPS point Shrimp farm

600000

Figure 2. Sampling sites in Satun province.

of the net. The filtrate was transferred into a 500 mL labeled bottle containing 5% formalin. The preserved samples were transported at ambient temperature to the laboratory for species identification using a light microscope. Toxic phytoplankton species were identified using the keys of Lewmanomont et al. (1995) and Wongrat (1995). 2.5. B ENTHOS

SAMPLING AND IN REPLY TO IDENTIFICATION

Sediment samples of approximately 1 kg were collected from the bottom of each pond after digging to a depth of 15 cm using a spade. Samples were placed into a

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ECOLOGICAL RISK ASSESSMENT OF ABANDONED SHRIMP PONDS 650000

700000

Phetchaburi Gulf of Thailand

850000

80000

MYANMAR

c

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p4cp5 p3c p2 p1 Prachuap Kiri Khan

LEGEND GPS point Province boundary Shrimp farm Shrimp farm-mangrove Shrimp farm-swamp Shrimp farm-shrumb Shrimp farm/swamp Shrimp farm/shrunb Abandoned aquaculture farm

750000

750000

c

Chumphon

8

0

650000

8

16 Kilometers

700000

700000

N

700000

Figure 3. Sampling sites in Prachuap Kiri Khan province.

2-mm mesh sieve and washed with pond water to wash out the sediment prior to its fixation in a plastic bottle containing 5% formalin. In the laboratory organisms were transferred to 70% methyl alcohol for sorting, identification to the family level, and counting at a later date. 2.6. S AMPLING

AND IDENTIFICATION OF CRABS

Crabs living in the ponds under study were captured and kept alive in an openair plastic basket. They were transported to the laboratory for isolation and

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identification of Yellow Head Virus and Systemic Ectodermal and Mesodermal Baculovirus (SEMBV) by using the polymerase chain reaction (PCR) technique. 2.7. Q UALITY

CONTROL

A rigorous quality control program was implemented including duplicate samples and certified reference materials of heavy metals in sediment (National Research Council of Canada). Accuracy were in a range from 91.4–109.7% with coefficient of variation less than 10%. Glasswares used in the analysis of metal concentrations were washed in a neutral detergent and then immersed for 24 h in a bath of 10% nitric acid solution. Between each washing step and at the end of the procedure the glassware was rinsed with double distilled, de-ionized water. Quantitation of oxytetracycline residues was performed at a certified laboratory of Department of Fishery in Songkhla using a HPLC (Oka et al., 1985). 2.8. E COLOGICAL

RISK ASSESSMENT METHODOLOGY

The methodology of Hill et al. (2000) for ecological risk assessment at the screening-level and the methodology specified in the ecological risk assessment guidelines proposed by the U.S. EPA (1996) were followed. The assessment methodology consisted of three steps: problem formulation, risk analysis, and risk characterization. 3. Results and Discussion 3.1. P ROBLEM

FORMULATION

The endpoint addressed in the assessment was the protection of aquatic organisms from deleterious effects of antibiotics, toxic metals, biological toxins, and pathogens retained in the abandoned shrimp ponds. The measurement endpoints consisted of a number of stressors: oxytetracycline, cadmium, copper, and manganese in sediments; toxic phytoplankton species; and Yellow Head Virus and SEMB virus in crabs. 3.2. R ISK

ANALYSIS

3.2.1. Exposure Pathways and Potential Receptors The release of stressors and pond contaminants can occasionally be discharged to the surrounding environment from abandoned shrimp ponds through runoff, erosion, flooding, or discharge of contaminated groundwater. Contaminants might also be adsorbed or precipitated in sediments, in which case they would be expected to remain in the ponds. Sediment contaminants are directly available to benthic organisms and bottom feeders; and, for chemicals that biomagnify,

ECOLOGICAL RISK ASSESSMENT OF ABANDONED SHRIMP PONDS

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are indirectly available to piscivores (fish-eaters), aquatic insectivores (insecteaters), and higher predators through food chain exposures. Sediment contaminants are less likely to be transported by mass flow (erosion). Dissolved contaminants are directly available to aquatic organisms. Plants and animals that are most likely to be affected by contaminants that do not biomagnify (chromium and copper) include benthic invertebrates and the embryos and fingerlings of freshwater fish and amphibians. Animals that are most likely to be affected by contaminants that biomagnify (if any) include piscivores (such as birds) and consumers of aquatic invertebrates such as fishes and crabs. The results of laboratory analyses showed that only copper, cadmium, and manganese were likely to pose ecological risks in the abandoned shrimp ponds studied. This finding is related with the past, significantly higher concentrations of major seawater elements (Ca, Mg, K and Na) were found in abandoned pond soils as compared with active ones at almost all soil depths. Concentration for the Ca, Mg, K, and Na of 1.3–3.4 times, 1.4–2.1 times, 7.0–30.0 times and 1.2–6.3 times greater respectively (Towatana et al., 2002). 3.2.2. Risk Calculation/Exposure Estimates Hazard quotient (HQ) values were used to represent the potential risk to aquatic life. The HQ values were calculated by dividing the concentrations of cadmium, copper, and manganese by their associated benchmark sediment quality guideline values (U.S. EPA, 2003). If the maximum concentration of a metal found at the site exceeds the screening benchmark guideline value (HQ > 1), the risks cannot be considered negligible and there is a need to consider them further in a detailed-level ecological risk assessment (Hill et al., 2000). 3.3. RISK

CHARACTERIZATION

Table I shows the HQ values calculated for each study site. The highest ecological risk from copper exposure was found at Site 3 in Satun. HQ values suggested that moderate potential ecological risks from copper exposure were likely for the majority of sites (80%) in Satun. The highest potential ecological risk from cadmium exposure was found at Site 3 in Prachuap Kiri Khan, and a high-potential ecological risk from cadmium exposure was also found at Site 4 in Songkhla. A relatively highpotential ecological risk from cadmium exposure was found at Site 1 in Satun. By far the highest potential ecological risks came from manganese exposure, with high HQ values found at all sites in Prachuap Kiri Khan (HQ = 2.8 − 19) and at Site 1 in Satun. Copper and its compounds have high acute and chronic toxicity to aquatic life. Acute toxic effects may include death of animals, birds, fishes, and plants. Chronic toxic effects may include shortened life span, reproductive problems, lower fertility, and changes in appearance or behavior (Hall et al., 1998). Cadmium is a nonessential element that can be both carcinogenic and toxic to aquatic organisms (Wright

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TABLE I Hazard quotients (HQs) of sediments from abandoned shrimp ponds and sediment quality guideline values for cadmium and copper HQ Province

Site

Cadmium

Songkhla

1

0.2

0.8

0.9

2

0.2

1.2

0.8

3

0.1

0.9

0.8

4

3.9

0.9

0.6

5

0.9

0.7

0.5

Satun

Prachuap Khiri Khan

Copper

Manganese

1

2.6

0.9

1.3

2

0.2

1.2

0.7

3

0.7

1.8

0.9

4

0.3

1.2

0.6

5

0.9

1.5

0.4

1

0.7

1.2

2.8

2

0.3

0.5

6.9

3

4.3

0.4

6.5

4

1.1

0.8

15.3

5

0.7

Threshold effect level∗

0.676

Probable effect level∗

4.21

Discharge multimedia environmental

0.3

1.2 18.7 108 2.4

19.0 – – 104

goal (DMEG) for solid waste ∗

U.S. EPA (1997).

and Welbourn, 1994). According to Hall et al. (1998), cadmium can increase cell volume, lipid relative volume, and vacuole relative volume in algae. Cadmium has been shown to adversely affect several enzyme systems in fish, such as those systems involved with neurotransmission, intermediary metabolism, and mixed-function oxidase/antioxidant activity (Hall et al., 1998). Manganese affects fish by destroying gill epithelium causing respiratory difficulties and suffocation; accumulating in internal organs; and causing lesions on gills, liver, spleen and kidneys (Grizzle, 1981). Exposure to manganese impairs growth and increases mortality (Stubblefield et al., 1997). 3.4. C ONCLUSION Potential risks from contaminants in abandoned shrimp ponds can be ranked in order of severity for the locations in Prachuap Khiri Khan > Satun > Songkhla,

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and for the stressors as Manganese > Cadmium > Copper. The findings of this study, together with evidence that abandoned shrimp ponds provide habitat for birds such as stilts and egrets (Lindberg and Nylender, 2001) suggests a need to determine doses of toxic metals from shrimp ponds for animals at higher trophic levels, including birds. A direct approach to assessing impacts of metals from sediment on birds would be to collect birds from the field for blood sample analysis in order to determine whether metals are bioaccumulating. The biological impacts arising from abandoned shrimp ponds should be considered significant if higher levels of biological organizations are affected by substances originating from abandoned ponds. Further studies should also investigate additional factors such as water hardness and alkalinity, which are known to be important factors influencing copper toxicity. 4. Acknowledgements This project was financially supported by the National Research Center for Environmental and Hazardous Waste Management, through Research Fund Grant No. NRC-EHWM/2003-001. References Bart, A., Steven R.B. and Diana J.S.: 2003, ‘A Study of Aquaculture Browfields: Abandoned and Converted Shrimp Ponds in Thailand’, in: H. S. Egna and C. Craven, (eds), Pond Dynamics/ Aquaculture Collaborative Research Support Program: Tenth Work Plan, Oregon State University, OR, U.S.A. Boyd, C.E.: 2002, Chemical and Biological Amendments Used in Shrimp Farming, Report prepared under the World Bank, NACA, WWF and FAO Consortium Program on Shrimp Farming and Environment. Changna, S.: 2003, Personal Communication, March 12, 2003, Provincial Fisheries Station of Prachuap Kiri Khan, Muang District, Prachuap Kiri Khan, Thailand. Dierberg, Forrest E. and Kiattisimikul, W.: 1996, ‘Issues, impacts, and implications of shrimp aquaculture in Thailand’, Environ. Manage. 20(5), 649–666. Flaherty, M. and Kanjanakesorn, C.: 1995, ‘Marine shrimp aquaculture and natural resource degradation in Thailand’, Environ. Manage. 19(1), 27–37. Gr¨aslund, S. and Bengtsson, B.E.: 2001, ‘Chemicals and biological products used in South-East Asian shrimp farming, and their potential impact on the environment – A Review’, Sci. Total Environ. 280, 93–131. Gr¨aslund, S., Holmstr¨om, K. and Wahlstr¨om A.: 2003, ‘A field survey of chemicals and biological products used in shrimp farming’, Marine Pollut. Bull. 46, 81–90. Grizzle, J.M.: 1981, ‘Effect of hypolimnetic discharge on fish health below a reservoir’, Trans. Am. Fish. Soc. 110, 29–43. Hall, L.W., Scott, M.C. and Killen, W.D.: 1998, ‘Ecological risk assessment of copper and cadmium in surface water of chesapeake bay watershed’, Environ. Toxicol. Chem. 17(6), 1172–1189. Hill, R.A., Chapman, P.M., Mann, G.S. and Lawrence G.S.: 2000, ‘Level of detail in ecological risk assessment’, Marine Pollut. Bull. 40, 471–477.

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Hossain, Z. and Lin, C.K.: 2001, Diversified Uses of Abandoned Shrimp Ponds—A Case Study in the Upper Gulf of Thailand, ITCZM Monograph. No 5, School of Environmental Resources, and Development, Asian Institute of Technology, Pathumthani, Thailand, pp. 1–23. Lewmanomont, K., Wongrat, L., and Supranwanid, C.: 1995, Algae in Thailand, Office of Environmental Policy and Planning, Ministry of Natural Resources and Environment, Bangkok, Thailand. Lindberg, T. and Nylander, A.: 2001, Strategic Environmental Assessment on Shrimp Farms in the Southeast of Thailand, Minor Field Studies No. 176, International Office, Swedish University of Agricultural Sciences, Uppsala, Sweden. MIDAS Agronomics: 1995, Pre-investment study for a coastal resources management program in Thailand, Interim Report. Prepared for the World Bank, Washington, DC, by MIDAS Agronomics Company, Bangkok, Thailand. Oka, H., Matsumoto, H. and Uno, K.: 1985, ‘Improvement of chemical analysis of antibiotics. VIII application of prepared c18 cartridge for the analysis of tetracycline residue in animal liver’, J. Chromatogr. 325, 265–274. Stevenson, N.J.: 1997, ‘Disused shrimp ponds: Options for redevelopment of mangrove’, Coastal Manage. 25(4), 423–425. Stubblefield, W.A., Brinkman, S.F., Davies, P.H., Garrison, T.D., Hockett, J.R. and McIntyre, M.W.: 1997, ‘Effects of water hardness on the toxicity of manganese to developing brown trout (Salmo trutta)’, Environ. Toxicol. Chem. 16(10), 2082–2089. Towatana, P., Voradaj, C., and Panapitukkul, N.: 2002, ‘Changes in soil properties of abandoned shrimp ponds in southern Thailand’, Environ. Monit. Assess. 74, 45–65. U.S. EPA (United States Environmental Protection Agency): 1994, Methods for the Determination of Metals in Environmental Samples Supplement I, EPA 600/R-94/111, Environmental Monitoring System Laboratory, Office of Research and Development, OH, U.S.A. U.S. EPA: 1996, Proposed Guideline for Ecological Risk Assessment, EPA/630/R-95/002B, Office of Research and Development, the United States Environmental Protection Agency, WA, U.S.A. U.S. EPA: 1997, The Incidence and Severity of Sediment Contamination in Surface Waters of the United States, Vol. 1: National Sediment Quality Survey, EPA 823-R-97-006, Office of Science and Technology, the United States Environmental Protection Agency, WA, U.S.A. USEPA (United State Environmental Protection Agency): 2003, Contaminated Sediments: Sediment Quality Guidelines. http://www.epa.gov/watersciences/cs/guidelines. Wongrat, L.: 1995, Phytoplankton, Department of Fishery, Biology Faculty of Fishery, Kasetsart University, Bangkok, Thailand. World Bank: 1998, ‘Shrimp Farming and the Environment: Can Shrimp Farming Be Undertaken Sustainably?’, Word Bank Report. Prepared for the World Bank by Erik, H. and Ulf, W., KPMG Centre for Aquaculture and Fisheries, Bergen, Norway. Wright, D.A. and Welbourn, P.M.: 1994, ‘Cadmium in aquatic environment: A review of ecological, physiological and toxicological effects of biota’, Environ. Rev. 2, 187–214.