versión On-line ISSN 0717-9707
J. Chil. Chem. Soc. v.51 n.2 Concepción jun. 2006
J. Chil. Chem. Soc., 51, Nº 2 (2006) , pags: 901-904
MICROPOGONIAS MANNI AS A BIOINDICATOR FOR COPPER IN LAKE BUDI (IX REGION, CHILE)
JAIME TAPIA1*, EVELYN DURÁN1, FERNANDO PEÑA-CORTÉS2, ENRIQUE HAUENSTEIN2, CARLOS BERTRÁN3, ROBERTO SCHLATTER3, LUIS VARGAS-CHACOFF3 AND CLAUDIO JIMÉNEZ3.
1Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747 Talca, Chile.
This study determined the concentration of copper in the species Micropogonias manni, a fish found in Lake Budi, which is much consumed by the population of Puerto Dominguez, IX Region of Chile. The determinations were done by atomic absorption spectrometry with flame, taking into account the sex, weight and size of the species, and, as representative samples, liver and muscle tissue. The validation of the methodology was done by using certified reference material (fish muscle), The copper concentration found in the liver fluctuated between 3,1 - 323,4 µg g-1, while for muscle tissue it was between 0,7 - 27,0 µgg-1, dry weight. The maximum copper values found in muscle tissue, are greater than those found by other authors in various fish species. Statistical analysis showed that in muscle tissue, the sex, length and weight variables have no bearing on copper concentration; however, in the liver, the length and weight variables are significant.
Keywords: Lake Budi, Fish, Copper, Atomic absorption spectrometry.
During the last few years, there has been mounting interest in knowing the extent of the presence of chemical contaminants in aquatic systems, including heavy metals . However, the determination of the presence of traces of these metals, in different kinds of aquatic systems (marine, continental and estuarine) is complex, and there are many analytical problems that must be overcome in order to obtain reliable results . The majority of the concentration levels of heavy metals in water systems, are close to the detection limits of traditional analytical methods [3-4], therefore such methodologies must be optimized to increase the sensibility of conventional analytical techniques [5-6-7].
At present, studies related to heavy metal contamination in aquatic systems are focusing on the use of biological indicators [8-9-10-11-12], because they have the capacity to accumulate pollutants present in the aquatic medium, and their analysis provides an indirect estimation of the concentration of such substances in the immediate environment. Bioconcentration makes the detection of trace contaminants easier, and this has justified the use of organisms in monitoring programs [13-14].
Metals such as copper, zinc, cadmium, lead, and chromium, are of particular interest in this type of study, because they are toxic and persistent in aquatic organisms, when their concentration surpasses certain levels [11-15]. The incorporation of these metals into different aquatic ecosystems (e.g. lakes, rivers, estuaries), can result from the erosion of geological matrices, from atmospheric deposits, or through anthropogenic sources such as industrial or domestic effluents .
Fish can accumulate high concentrations of metals present in the water or in their food (zooplankton, phytoplankton) [17-18], thus increasing the concentration of certain metals or toxic compounds found in the surrounding medium; biomagnification is here understood to mean the increase in the concentration of contaminants along the food chains, in such a way that contaminants present in low concentrations and safe levels in organisms at the bottom of the chain (water, phytoplankton and zooplankton), are progressively accumulated till they reach harmful or lethal levels in organisms at the top of the chain . It must be remembered that fish are an important link in the food chain, since they are one of the principal sources of protein in human food consumption.
Copper is a heavy metal that over the last few years has been the object of several investigations concerning its concentration in fish samples [11-20-12], as has the part played by copper in fishes' metabolism, and also the toxic effects of this metal, when it surpasses certain levels of concentration .
The present investigation studied the copper content in the species Micropogonias manni, known as Huaiquil or Roncador, a fish native to Lake Budi, and consumed by the population of Puerto Dominguez (IX Region). The interest in determining the copper content in this species is based on the preliminary results of another study , which show a high level of this element in the fishes' sediments.
Lake Budi is located near the coast of Chile's IX Region. It is a special type of ecosystem, and due to its location, it receives some inflow of seawater. This inflow of water with a higher salt content, though it only happens on occasion, supports the existence of fauna with estuarine characteristics. These systems are characterized by very special internal dynamics of their chemical, physical, and biological variables, which to a large degree, are determined by four main components: the volume of water in tributary rivers and water run-off from the lake; inflow of seawater and tidewater; the type of rock making up the lake-bottom; and the movement of sediments and the atmosphere .
In this study, the determination of copper in the species Micropogonias manni is done on males and females, and also takes into account the length and weight of the species; liver and muscle tissue are used as representative samples.
Area of the study
The present study was carried out in Lake Budi (38° 52´ S, 73° 18´ W), which consists of a coastal lake system sporadically connected to the sea; it begins approximately one mile south of the estuary of the Imperial River, in a meandering channel which sporadically unites Budi Lake with the sea, from the end of autumn (approximately in the month of May) till the beginning of spring (September or October). Its tributary rivers are the Budi, Temo, Allipén, Comué, Bolleco, and Botapulli, which are the gateways for the anthropic intervention that has taken place in the watershed over the last decade. Figure 1 shows the geographic location of Lake Budi.
Taking of samples
The taking of samples was done on two monitoring campaigns at Lake Budi; the first was in July (winter), and the second in October (spring) of the year 2004. The samples were obtained at the lakeside, by purchasing the fish from local residents whose livelihood is the capture and sale of Micropogonias manni, in the town of Puerto Dominguez in the IX Region.
The samples were measured and weighed on site. The measurements were taken with a plastic measuring tape graduated in centimetres, to determine the total length of each sample. Weight was determined with a field balance graduated in grams. The fish were gutted and their sex was determined, and plastic bags were used to obtain part of their muscle and liver tissue, which were immediately frozen in pretreated plastic containers, and labelled for subsequent chemical treatment.
The reactive used were of high purity (Suprapure, Merck, Darmstadt, Germany). The cleanliness of the material was paramount for obtaining an optimum analytical result. Plastic and glass materials were washed with non-ionic detergent and abundant de-ionized water; subsequently, a solution of nitric acid was used for treatment (HNO3) 10 % v/v for 48 hours, and then rinsed 3 times in double-distilled water.
The liver and muscle tissue samples were lyophilized till a steady weight was obtained; using a Labconco lyophilizer. The samples were then homogenized and kept in pre-treated plastic containers till the corresponding analysis.
For digestion, 1.0 g of the sample was weighed and 10 ml. of Suprapur Nitric Acid was added. Subsequently the samples were dried to almost total dryness with constant agitation under vapour/gas extraction equipment, and the use of a heating element graduated to 90oC. The resulting solution was filtered and washed with double-distilled water, giving a final volume of 25 ml. in a pre-treated volumetric container. The analyses were done in duplicates, with their respective blank solutions.
The determinations were done by atomic absorption spectrometry under flame (air/acetylene), and using a Unicam model 969 spectrophotometer, with a deuterium background corrector.
Validation of the methodology
The validation of the analytical methodology was carried out using certified DOLT-1 reference material (fish muscle), from the National Research Council of Canada (NRC) Chemistry Division. The validation results are shown in Table 1.
RESULTS AND DISCUSSION
In order to determine the relation between the different variables involved (copper content in muscle and liver, sex, length, and weight), an 0,05 ANCOVA was used (covariance analysis). In the first part, the sex of the fish was used as the categoric variable, the length and weight were used as covariables, and the copper content in muscle was used as dependent variable. In a second part, a similar analysis was carried out, but the dependent variable was copper content in the liver.
On the basis of the results, it was shown that for copper content in muscle, neither the sex, length or weight of the fish have a bearing on its concentration: copper concentration in muscle showed no significant differences in relation to the variables studied. However, when the liver is chosen as the dependent variable, the situation is different, because the length and weight variables do show a relation to the copper concentration; but sex does not have a bearing on this accumulation.
Table 2 shows the copper concentrations in representative samples of liver and muscle tissue of Micropogonias manni, collected in Budi Lake (IX Region, Chile). The samples numbered a total of 50 (25 male and 25 female). The analyses were carried out with a replica, taking into account the length and weight of each fish.
The results showed that the concentration of copper in the liver of males varied between 3,1 and 323,4 µg g-1, while for females it fluctuated between 10,5 and 140,3 µg g-1, dry weight. The results showed that for both sexes, concentrations of copper were higher in the liver than in the muscle tissues, except for sample N° 17 (Table 2), which showed a certain similarity of concentrations, 3,1 ± 0,6 and 3,9 ± 0,6 µg g-1 in liver and muscle tissue, respectively.
Bibliographic references report that in some Turkish lakes (Tokat), the range of copper concentrations found in other fish species varies between 1,0 and 4,1 µg g-1 in samples of muscle tissue, which is a lower maximum value than that found in Lake Budi, which reached 27,0 µg g-1. Other studies [11-12], show than in fish samples from the Northeastern Atlantic, copper concentrations vary from 0,10 - 0,97 µg g-1 and in the Northeaster Mediterranean Sea, they varied from 0,04 to 5,43 µg g-1. There were no data reported concerning the concentration of copper in fish livers.
The authors of this study are grateful for the financial support of FONDECYT Project 1030861, Integrated Analysis of the Coastal Rim of the IX Region, Proposals and Criteria for the Ecological Planning of the Wetlands.
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