Journal of Dairy & Veterinary Sciences
The environment of the Bahía Blanca estuary is
considered a hot spot in terms of pollution. Bioindicators should have
the ability to react relatively fast to certain pollutants and
environmental disturbances. Therefore, an exploratory study was carried
out determining and quantifying the concentrations of cadmium (Cd),
chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) in the muscle and
liver of Mustelus schmitti narrownose smooth-hound and were compared
with the values obtained from their respective helminth assemblies. In
most of the fishes analyzed, the concentration of heavy metals was
higher in the infra communities of cestodes compared to the host. Our
results position the cestodes as efficient sentinel species of pollution
by bioaccumulating higher concentrations of heavy metals than the host
tissues, thus behaving in excellent early warnings of environmental
pollution, more real than quantifications in sediments, in water and
fish
Keywords: Heavy metals; Bioaccumulation; Sentinels parasites
Introduction
The estuary of Bahía Blanca (39° 03′44 ″ S 62° 04′00
″ W) is an adequate environment to develop pollution studies,
considering that it is an area that includes urban centers, several
industrial parks and deep-water ports. All the effluents are discharged
with different degrees of pretreatment, so they generate different
impacts on the ecosystem. In environmental monitoring to detect heavy
metals, organisms are often used as bioindicators, which have the
ability to react relatively fast to certain toxic products and
environmental disturbances. Some of these organisms, such as parasites,
may be highly sensitive to brief exposures, poorly detected in water,
sediment or fish [1-5]. Our previous studies in the estuary have focused
on evaluating the parasitism of fish in the time scale to be able to
compare and analyze them as effect indicators altering some parasites
population parameter such as prevalence and abundance or causing
symptoms in their hosts in response to environmental disturbances
[6-10]. The narrownose smooth-hound Mustelus schmitti Springer, 1939 is a
resident fish of the estuary of Bahía Blanca and third in importance as
a fishing resource. Based on the fact that some parasites, such as
cestodes,
have the ability to absorb and accumulate more chemicals than their host
tissues [11].
The objective of the present study was to analyze
whether a higher concentration of metals in the parasites respect to
their host was applicable in the cestodes- narrownose smooth-hound model
and to evaluate if these helminths possess ecotoxicological value and
could be used in the study area as early bioindicators of anthropic
impact. Therefore, an exploratory study was carried out in order to
determine and quantify the cadmium (Cd), chromium (Cr), copper (Cu),
lead (Pb) and zinc (Zn) concentrations in the muscle and liver of the
narrownose smooth-hound and compared with the values obtained from their
respective cestode assemblages (Dollfusiella sp., Orygmatobothrium
schmittii, Calliobothrium australis and Symcallio sp.) The samples were
analyzed by Inductive Coupling Plasma Atomic Emission Spectrometer
(ICP-AES, LANAQUI-CERZOS-CONICET-UNS). The values were compared with the
limit values allowed by the European Union for fish meat.
Results and Discussion
In most of the fishes analyzed, the concentration of
heavy metals was higher in the infra communities of cestodes compared
to each host. The parasites concentrated 270 times more Cadmium than the
fish muscle. For this metal, the standards established in the liver and
those of the parasites were exceeding the limits established
by the European Union for muscle or liver. Chromium
was bioconcentrated in the cestodes two times more than the
muscle and six times more than the liver. Copper was accumulated
with values 65 times more than muscle and up to four times more
than in the liver. Lead had values 48 times more in helminths than
both muscle and liver of fishes. For this metal in most dosages,
the concentration measured in parasites exceeded the limit value
established by the European Union. Zinc bioaccumulated in parasites
seven times more than muscle and four times more than liver.
Only in one case the Zinc concentration was three times higher in
the liver than in parasites.
The environment of the Bahía Blanca estuary is considered
a hot spot in terms of pollution and is included among the most
eutrophic coastal ecosystems known [12]. Also, since many years
it have been reported high concentrations of heavy metals and
pesticides in water and sediments [13,14]. The combined effect
of these pollutants, plus the sewage discharge, the industrial effluents
of petrochemical origins, and the overheated water from
a thermoelectric power station (620MW) all of them represent a
growing threat to the environment. These increase in anthropogenic
activity around estuaries, coupled with the persistence of
heavy metals, their high toxicity, strong tendency to bioaccumulate,
and non-degradability [15], usually affect water. As negative
effects it could change the trofic web in the aquatic fauna, eliminate
the spawning and larval recruitment sites and a potential
decrease in diversity, affecting all the ecosystem [16,17]. That is
why the need to choose of efficient bioindicators in the evaluation
of the quality of the environment [18].
Conclusion
The estuary of Bahía Blanca is one of the most important in
Argentina, having the main deep-water port system in the country.
Although fish species can be used as efficient and useful bioindicators,
our results position cestodes parasites as sentinel species of
contamination for the fact that reported higher concentrations of
heavy metals than their hosts. This would avoid possible underestimations
in pollution levels by being quantified only in sediments,
in water and in fish.
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