Dolphins are the sentinels of pollution in Brazil

In Guanabara Bay in Southeastern Brazil, Guiana dolphins are highly contaminated by PCBs. Tissue samples taken from the cetaceans showed PCB concentrations that are among the highest in the world, according to a study conducted by researchers from Brazil and Liège who were concerned about the health of Guanabara Bay’s 12 millions residents.

Known for its beaches, sun, music, carnival, and tropical forests, Brazil is a major tourist attraction. But while Europeans still see Brazil as a land of unspoilt nature, this emerging nation has actually undergone extensive industrial development. And industrialisation unfortunately brings its share of pollution. The South-eastern part of Brazil has been particularly affected. This is where the city of Rio de Janeiro is located, on the shores of the great Guanabara Bay. The Bay stretches inland 30 kilometres from the coast and is almost as wide, with 150 km of beaches and a 1 km-wide mouth. Within the Bay there are no less than 130 islands, which contribute to its image as paradise on earth.

But appearances can be deceiving, for Guanabara Bay is far from idyllic given its high pollution levels. The small population of Guiana dolphins (Sotalia guianensis) that live in the Bay are suffering the consequences. These were the findings of researchers Krishna Das (The University of Liège’s Oceanography Laboratory), Gauthier Eppe (CART – the University of Liège’s Centre for Analytical Research and Technology), and Paulo Dorneles (Université Fédérale de Rio de Janeiro and a Visiting Professor at ULg in January 2014) in an article that will soon be published - and is already available online  - in the journal Science of The Total Environment (1).

Marine mammals, victims of bioMAGNIFICATION

"All of the land-based contaminants resulting from industrialisation in the region can be found in the marine environment," explains Krishna Das, a FRS-FNRS Research Associate at the University of Liège’s Oceanography Laboratory – MARE Research Centre. "Cetaceans are at the top of the food chain and thus accumulate all these contaminants," the scientist explains. In fact, the higher up you go in the food chain, the more toxic substances are consumed and stored. This is called biomagnification. For example, if an planktonic organism ingests one unit of a toxic substance, a small fish that eats 10 of these organisms absorbs 10 units of this toxic substance. And when the biggest fish eats 10 of these little fish, it accumulates 100 units of toxic substances, and so on. Since cetaceans are at the top of the marine food web, they are particularly affected by this problem.

As part of a collaborative project between ULg and several Brazilian research teams, the scientists wanted to check on the dolphins in Guanabara Bay and the surrounding area. They analysed concentrations of three pollutants in three cetacean species. “We looked for the presence of PCBs (Polychlorinated biphenyls), PCDDs (polychlorinated dibenzo-p-dioxins) and PCDFs (polychlorinated dibenzofurans) in Guiana dolphins, Rough-toothed dolphins, and False killer whales," says Krishna Das. The first species lives mainly on the coast, while the other two live in more open waters. "Guiana dolphins live inside the Bay and never leave it. Although Rough-toothed dolphins live outside the Bay, individuals of the species often come inside the Bay to feed," adds Krishna Das.

The multiple harmful effects of PCBs

The three kinds of pollutants have a very similar chemical composition and were selected because they originate in industrial processes. "Even though PCBs have been banned in Brazilian production since the 1980s, many items containing PCBs are still in circulation today," explains Krishna Das. "My Brazilian colleagues speculate that there is a black market for PCBs to repair these items when they break down." PCBs were used extensively from 1930 to 1970, since they are very good electrical insulators and have excellent dielectric and heat-conducting properties. But they cause a number of health problems, which led authorities in a number of countries to ban the substance and conduct tests for concentration levels in food for humans and animals. "In general these pollutants affect the immune system, the endocrine system, the nervous system, and to top it all off they are also carcinogenic," warns Krishna Das. "In marine mammals the suspected effects are mainly immune suppression. As a result, animals contract diseases more easily, and their endocrine systems are disrupted.” Scientists believe that the high pollutant concentrations in tissues of Guiana dolphins from Guanabara Bay may be hampering the reproductive success of these animal population.

These effects have also been noticed among humans, and more and more studies have shown the impact of PCBs on metabolic and functional disorders associated with obesity.

Record levels of contamination

The blubber and liver samples that Krishna Das, Gauthier Eppe, and Paulo Dorneles tested were collected from animals that were stranded or incidentally captured in fishing nets, according to international protocols. "For our analyses, we extracted the lipids from these samples, since the pollutants we were looking for are lipophilic,” says Krishna Das. "In order to do this, we ground the tissue and extracted the lipid phase using organic solvents. After purifying this fat fraction, we used gas chromatography and mass spectrometry techniques to separate and quantify the target molecules.” These analyses were mainly conducted at ULg and in Spain. “I remember when Paulo arrived at the Centre for Analytical Research and Technology with the samples. They were so contaminated that Gauthier Eppe and his colleagues were worried that the dolphin samples would contaminate their entire system!" And for good reason: the results showed that the samples from Guiana dolphins living in Guanabara Bay contained concentrations of PCBs that were among the highest in the world! “The Bay is connected to the Atlantic Ocean, but water renewal is very slow since the mouth is so narrow,” explains Krishna Das. “Since the water is stagnant, pollutants are not washed out to sea.” In the 1990s, there were more than 100 Guiana dolphins in Guanabara Bay. Only 40 remain today.

If these findings about marine mammals are sad and worrisome, what about the health of the 12 million men, women, and children who live on the Bay and eat its fish every day?

The need for awareness

“Guiana dolphins are the sentinels of pollution in Guanabara Bay. This type of study could bring awareness to the issue, and thus attract the attention of policymakers, and may help to bring about changes in regards to environmental protection,” says Krishna Das. In the near future, the researchers are planning to continue their study by examining contamination levels in the Bay’s fish, and study the way pollutants are exported beyond the Bay via fish movements. “We would like to quantify this flow of pollutants. We also want to better understand the Bay's food web, using stable isotopes of carbon and nitrogen. This is the subject of a parallel study whose results were just published in the journal Ecological Indicators," adds the scientist. The researchers would also like to examine the human health impact of the high levels of pollution in Guanabara Bay, in collaboration with the medical community. “People need to become aware of the problem,” insists Krishna Das. 

And finally, this Belgian-Brazilian collaboration could even give rise to a new method for examining contamination levels in marine mammals. “Brazil is a tropical country and the carcasses of stranded animals decay very quickly. It can therefore be hard to obtain good quality samples, particularly for histopathology studies, or for biomarker research,” explains Krishna Das. “But bones remain well-preserved for much longer, and pollutants tend to reduce bone density. Paulo Dorneles and his colleagues therefore decided to develop a method to quantify bone density, and to compare this density to pollutants that have already been analysed,” says the researcher.

(1)  Dorneles PR, Sanz P, Eppe G, Azevedo AF, Bertozzi CP, Martínez MA, Secchi ER, Barbosa LA, Cremer M, Alonso MB, Torres JP, Lailson-Brito J, Malm O, Eljarrat E, Barceló D, Das K. High accumulation of PCDD, PCDF, and PCB congeners in marine mammals from Brazil: A serious PCB problem. Science of The Total Environment. Volumes 463–464, 1 October 2013, Pages 309–318