bioaccumulation and distribution

FISHERIES SCIENCE 2008; 74: 109–119 Bioaccumulation and distribution of trace elements in tissues of giant river prawn Macrobrachium rosenbergii (Decapoda: Palaemonidae) from South Vietnam Nguyen Phuc Cam TU,1 Nguyen Ngoc HA,2 Tokutaka IKEMOTO,2 Bui Cach TUYEN,3 Shinsuke TANABE2 AND Ichiro TAKEUCHI1* Department of Life Environment Conservation, Faculty of Agriculture, Ehime University, Matsuyama, Ehime 790-8566, 2Center for Marine Environmental Studies, Ehime University, Matsuyama, Ehime 790-8577, Japan; and 3Nong Lam University, Thu Duc District, Ho Chi Minh City, Vietnam ABSTRACT: Accumulation profiles of 22 trace elements in abdominal muscle, abdominal exoskeleton and the hepatopancreas of the giant river prawn Macrobrachium rosenbergii were analyzed The giant river prawn is an indigenous freshwater species from South Vietnam, and is cultured commercially and fished in the wild Samples were collected from Ho Chi Minh City and the surrounding area (SKEZ, South Key Economic Zone), and from the Mekong River Delta between 2003 and 2005 Highest accumulations of essential (Cu, Se and Mo) and toxic (As, Ag, Cd and Hg) elements were observed in hepatopancreatic tissue, except for Mn, Sr, Sn, Ba and V in the exoskeleton and Rb and Cs in muscle tissue Spatial differences showed concentrations of Cs and Pb in muscle and Sr in exoskeletons from the SKEZ were higher than those from the Mekong River Delta The opposite trend was observed for Cr, Se and Sb in muscle, Mo, Sb and Tl in exoskeleton, and Se, Hg, Mo, Cd, Sb, Tl and Bi in the hepatopancreas These differences in trace element concentrations in prawns likely reflect differences in industrialization and human activities between the two regions of South Vietnam KEY WORDS: exoskeleton, hepatopancreas, Macrobrachium rosenbergii, Mekong River Delta, muscle, trace elements, Vietnam INTRODUCTION Since the early 1990s, aquaculture in Vietnam has greatly expanded in total area of production and the number of target species cultured The level of management intensity has also increased Of the shrimp/prawn species cultured in South-East Asia, the black tiger shrimp Penaeus monodon is wellknown and has become commercially important to the region In Vietnam and throughout South and South-East Asia, the giant river prawn Macrobrachium rosenbergii is gaining importance as a target species in brackish and freshwater areas Macrobrachium rosenbergii is indigenous to South Vietnam, including the South Key Economic Zone (SKEZ) and the Mekong River Delta.1 *Corresponding author: Tel: 81-89-946-9899 Fax: 81-89-946-9899 Email: takeuchi@agr.ehime-u.ac.jp Received April 2007 Accepted 23 July 2007 doi:10.1111/j.1444-2906.2007.01474.x The SKEZ, including Ho Chi Minh City and seven surrounding provinces, is the most industrialized area of Vietnam, contributing up to one-third of Vietnam’s gross national product and approximately 40% of gross domestic product (GDP), of which Ho Chi Minh City accounted for 60–65% The GDP per capita of the SKEZ is double that of the Mekong River Delta The Mekong River Delta is a major agricultural production region of Vietnam contributing over 50 and 60% of the total national rice production and fishery exports, respectively.2,3 However, the rapid growth of urbanization, agriculture and industry in the southern region has also resulted in increased production and use of harmful substances such as certain trace elements.2,4,5 There is a possibility that elevated levels of trace elements could be harmful to exposed prawns, and that the elements may be transferred to higher trophic levels in the food web, including humans who consume the prawns © 2008 Japanese Society of Fisheries Science FISHERIES SCIENCE 110 The species M rosenbergii can be used to monitor the trace element pollution in the aquatic environment because they are omnivorous benthic animals6 that maintain their body in direct contact with the water and substrate of their environment, and they tend to accumulate metals in their tissues Previous studies have examined the accumulation of contaminants in tissues of a number of freshwater prawn species, and under different concentrations and times of exposure in the field (Cd, Cr, Cu, Hg, Ni, Pb and Zn in M nipponensis)7 and the laboratory (Cd and Pb in M rosenbergii;8 Cu, Cr and Zn in M malcolmsonii;9 Cd and Zn in M malcolmsonii;10 and Cu in M rosenbergii11) It has been shown that elements passively adsorbed onto the exoskeleton of a crustacean will contribute to the total body concentration of an element in the crustacean, and crustaceans can accumulate trace elements in hepatopancreatic and edible tissue (muscle).12 The present study was conducted to measure the specific accumulation of 22 trace elements in tissues of giant river prawns and to explore geographic variation of the elements in this commercially important species MATERIALS AND METHODS Sampling Wild-caught giant river prawns Macrobrachium rosenbergii were purchased directly from local fishers or from local small markets at the SKEZ (Ho Chi Minh City and Dong Nai) and the Mekong River Delta region (Can Tho, Dong Thap, Hau Giang and Tra Vinh) between September 2003 and April 2005 The locality of the prawns was verified NPC Tu et al prior to the purchases, and the fishers and stallholders were not informed that purchases would be made ahead of time At the markets, prawns were sampled from stallholders who bought from the fishers exploiting in river These markets were confirmed to be situated approximately 500– 1000 m from prawn catching areas Prawns were placed in polyethylene bags, transported to Japan, and stored in a deep freezer at -20°C until chemical analysis Sampling locations were noted and individual body weights of prawns were measured (Table and Fig 1) Chemical analyses To analyze tissue-specific concentrations of trace elements, M rosenbergii were dissected and tissues of abdominal muscle, the abdominal exoskeleton and the hepatopancreas were carefully separated from other body organs Trace element concentrations were analyzed based on the procedure described by Kubota et al.13 and Nam et al.14 Tissue samples were dried for 12 h at 80°C About 0.2 g of the sample was digested in mL of concentrated HNO3 in a microwave system for 30 Levels of 19 trace elements (V, Cr, Mn, Co, Cu, Zn, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Tl, Pb and Bi) were analyzed with an inductively coupled plasma–mass spectrometer (ICP-MS) (HP-4500, Hewlett-Packard, Avondale, PA, USA) Matrix effects and instrument drift in the ICP-MS measurements were corrected using an internal standard method with yttrium as the internal standard Concentrations of Hg and Se were determined using a cold vapor atomic absorption spectrometer (AA680, Shimadzu, Kyoto, Japan; Model HG-3000 Table Sampling locations and biometry of giant river prawn Macrobrachium rosenbergii from South Vietnam Location Site Bien Hoa, Dong Nai Site District 9, Ho Chi Minh City Site District 2, Ho Chi Minh City Site Can Tho City, Can Tho Site Cao Lanh, Dong Thap Site Phung Hiep, Hau Giang Site Cau Ngang, Tra Vinh † n Weight† (g) River 58.7 Ϯ 31.0 106°51.578′ Local small market 62.5 Ϯ 44.3 10°47.049′ 106°45.288′ Local small market 126.8 Ϯ 76.9 12 Sep 2003 10°01.843′ 105°45.904′ Local small market 23.8 Ϯ 2.1 19 Apr 2005 10°24.331′ 105°41.387′ River 43.5 Ϯ 19.3 29 Aug 2004 09°48.281′ 105°49.252′ Local small market 29.2 Ϯ 3.4 21 Apr 2005 09°47.510′ 106°27.177′ Local small market 55.1 Ϯ 18.1 Date Latitude Longitude 16 Apr 2005 10°52.056′ 106°49.894′ 17 Apr 2005 10°47.005′ 17 Apr 2005 mean Ϯ standard deviation © 2008 Japanese Society of Fisheries Science Remarks Trace elements of Macrobrachium of Vietnam FISHERIES SCIENCE 111 Fig Map showing sampling locations (Sites 1–6) of Macrobrachium rosenbergii in the South Key Economic Zone (SKEZ) and Mekong River Delta, South Vietnam cold vapor system, Sanso, Tsukuba, Japan) and a hydride generation atomic absorption spectrometer (Model HFS-3 hydride system, Hitachi, Tokyo, Japan), respectively For As analysis, samples were digested with an acid mixture (HNO3–H2SO4– HClO4 = 1:1:2) and determined by a hydride generation atomic absorption spectrometer (HVG-1 hydride system, Shimadzu) Accuracies of the methods were assessed using certified reference material DORM-2 (National Research Council of Canada) in triplicate, and recoveries of all the elements ranged from 87 to 111% of the certified values All data were expressed on a dry weight basis (mg/g dry wt) Statistical analyses One-half of the value of the respective limit of detection was substituted for those values below the limit of detection and used in statistical analysis.15 Data were tested for goodness-of-fit to a normal distribution with Kolmogorov–Smirnov’s one-sample test Because concentrations of some trace elements did not follow a normal distribution, non-parametric tests were alternatively used to compare between different groups A Wilcoxon signed ranks test was used to detect betweentissue differences in trace element concentrations Spearman’s rank correlation coefficient was used to measure the strength of the association between elements in tissues For testing geographic differences, log-transformed data were analyzed using one-way analysis of covariance (ancova) with body weight as the covariate P < 0.05 was considered to indicate statistical significance These statistical analyses were executed by the program SPSS v10.05 (SPSS, Chicago, IL, USA) RESULTS Tissue-specific distribution of trace elements Trace element concentrations in abdominal muscle, abdominal exoskeleton and hepatopancreas of M rosenbergii are shown in Tables 2–4, respectively Zinc and Cu, both essential nutrients, had considerably higher concentrations in all tissues analyzed in M rosenbergii, ranging from 9.71 mg/g Cu in muscle (from Site 4) and 6.01 mg/g Zn in the exoskeleton (Site 2) to 17 500 mg/g Cu (Site 3) and 141 mg/g Zn (Site 6) in the hepatopancreas Chromium levels ranged from 0.10 mg/g in muscle (from Site 3) to 2.3 mg/g in the hepatopancreas (Site 1) Concentrations of Mn varied from the lowest level of 0.987 mg/g in muscle (Site 3) to a high level of 734 mg/g in the exoskeleton (Site 4) The range of Co levels was from 0.013 mg/g in muscle (Site 3) to 1.2 mg/g in exoskeleton (Site 2) For Se and Mo, of all tissues analyzed, the hepatopancreas had the highest levels of accumulation Concentrations of nonessential elements in M rosenbergii varied widely across tissues Levels of In, Sb, Pb and Bi were low and undetectable in some samples A significant level of variation in Cd concentrations among tissues was observed in M rosenbergii Cadmium levels in muscle, exoskeleton and hepatopancreas of M rosenbergii were 0.048 Ϯ 0.065 mg/g, 0.031 Ϯ 0.044 mg/g and 13.5 Ϯ 14.7 mg/g, respectively Similarly, the highest concentrations of Ag (2.4 Ϯ 3.6 mg/g, from Site 3) were found in the hepatopancreas Particularly, the exoskeleton contained the highest Sr levels (1670 Ϯ 909 mg/g) among the tissues, which was about 300 times higher than that of muscle with the lowest concentration (5.58 Ϯ 3.71 mg/g) © 2008 Japanese Society of Fisheries Science © 2008 Japanese Society of Fisheries Science Cr Mn [...]... 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