A web-based resource on contaminant analysis techniques, organochlorine contaminant properties and sources, and the impact and extent of contamination on Blue Whales in the St. Lawrence seaway,
This resource has been produced for WhaleNet by Jason de Koning and Geoff Wild of the Metcalfe lab, in the ERS Department at Trent University, Canada
With the dawn of the industrial revolution, the nature of humankind's affect on the environment has been permanently changed. Our historical lack of understanding of the ecology has resulted in the release of large amounts of synthetic chemicals into the environment, producing a variety of detrimental effects throughout the biosphere--the extent of which are, still, not entirely known. The release of large amounts of pesticides into the air, soil, and watershed have particularly proven to be of major concern because of their toxic effects, their stability, and their tendancy to buildup in living organisms. PCBs, used widely in industrial applications since WWII, are also of major concern for similar reasons.
Historically speaking, the "Green revolutions" of the 60s gave birth to the modern chemical industry. New organochlorine pesticides synthesized in the lab have saved millions of lives by reducing disease vectors ('pests' which carry diseases affecting human beings), and have increased crop yields tremendously.
With the publication of Rachael Carson's "Silent Spring" in the late 60s, however, somewhat startling evidence was thrust into the public domain that serious effects of modern industrialization, the global proliferation of pesticides, and the transport of PCBs throughout the ecosphere were emerging--huge impacts on the health of fish and birds were most notable at this time.
It is now known that the combination of the long persistence and short and long term toxicity of these contaminants are of great biological and ecological significance--the very persistent and stable nature of organochlorines have become central and lasting problems associated with modern industrialization. Serious health effects including the promotion of cancer, and reduced reproductive success have additionally been associated with these contaminants.
The previously unimagined global accumulation and disposition of contaminants in the environment has become a problem of great urgency. In our efforts to ensure that we reduce both the effects of previous disturbances and the frequency and severity of future discharges, it is necessary to understand precisely what is being released, and whether or not it will have an impact on the environment.To vigourously pursue the regulation of discharges of hazardous substances, and the study of their environmental fate is therefore urgent; equally as important, is the study of the toxicity of such discharged substances, and the dynamics of their accumulation in trophic structures and in particular organisms and tissues.
In light of the strong evidence that exists, a sound ecology must be adopted to protect the sustainable habitability of our ecosystem, and to protect the wide biodiversity that we cherish. Technology must be re-engineered and applied responsibly to reverse, prevent, and study the impacts of pollution.
In this web-site, you will find information pertaining to our study of the buildup of such pollutants in Blue Whales of the St. Lawrence seaway. We present here new data from our study of organochlorine contaminants in blubber samples, obtained through a harmless biopsy technique, collected by the staff of the Mingan Island Cetacean Study (MICS) research station.
You will also find here an overview of some relevant information regarding contaminant dynamics in the environment--their fate and accumulation, the toxic effects of organochlorines on marine mammals, and in particular a discussion of common analytical techniques for quanitifying their presence in tissue samples.
Please forward any comments or questions to us by e-mail.
Sites of interest at Trent University:
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What are contaminants? Why is pollution so extensive?
Pollutants are commonly considered to be chemicals or substances which are present in our environment, because of the direct result of human activity or disturbance. Based on this broad definition, there are many types and classes of pollutants--each with their own properties and associated health affects.
This discussion will focus on the following classes, as well as the ability of some of these compounds to mimic natural reproductive hormones. The contaminants which we have tested for in blue whales, can be categorized as being either one of these, or some breakdown product of either.
Other websites discussing contaminants:
The PCB or poly-chlorinated biphenyl family of chemicals is comprised of 209 congeners or variants (numbered sequentially 1 through 209), differentiated based on the number and positioning of chlorine substitutions (see diagram below).
PCBs are artifically synthesized chemicals that have been created for industrial purposes, and are a type of organochlorine.
First manufactured in 1881, PCBs have been used primarily in electrical equipment -- transformers, capacitors, electromagnets, circuit breakers, switches, and voltage regulators have all used PCBs in the past. PCBs have also been used in heat transfer and hydraulic systems, and have even been used in industrial lubricants and household products.
PCBs were banned from use in household and industrial applications in the late 70s.
In 1981, 40% of all electrical equipment in the U.S. contained PCBs. Today, approximately 2100 tonnes of PCBs enter the environment every year--primarily from runoff, leaching from dumpsites, and combustion of plastics.
PCBs are referred to as hydrophobic contaminants; this means, effectively, that they are not soluable in water. PCBs, however, are very soluble in lipid or fat (ie. they are lipophilic). Because of these properties, there is the potential for PCBs to readily bioaccumulate in the fatty tissues of many organisms.
PCBs have been found to be present in every living animal that has been examined.
Because different PCB congeners break down differently in the environment, and because they are metabolized differently in organisms, the substances that we find and test for are rarely the same as what has been released into the environment.
PCBs are known to suppress the immune system, promote cancer, and to interfere with other important biological systems in animals.
Additionally, PCBs are believed to have the ability to trick the endocrine system of many animals, mimicking estrogen--the female hormone responsible for the development of sexual characteristics. Evidence suggests that this endocrine modulating behaviour may be 'feminizing' males of many different species--resulting in decreased reproductive fitness, and endangering the future of many species (potentially including ours).
A major problem with PCBs, and other organochlorine contaminants, is that they are quite persistent in the environment. This means that they do not break down quickly in the environment, but they tend to stay unchanged over relatively long periods of time. PCBs in the watershed tend to accumulate in fish and marine mammals (such as whales) as a result, or to settle to the bottom.
Spectacular fish kills were reported as early as the 60s in Carson's "Silent Spring", when major disturbances of river sediment in heavily PCB-contaminated areas re-introduced these contaminants into the 'living space' of various organisms.
As mentioned above, one of the biggest sources for PCB release into the environment, currently, is from runoff and leeching. Because PCBs are relatively inert and stable, they can stay in river or lake sediment for a long time--where they will cause few problems. Disturbance of the sediment layer, however, results in rapid re-exposure into the watershed.
In organisms such as the blue whales which we examine here, an analogous phenomenon of re-exposure occurs. When the blue whales of the St. Lawrence migrate in order to reproduce, they eat very little and live off of their substantial fat stores. PCBs and other lipophillic contaminants, however, are associated with fatty tissues--therefore
As fat is broken down for energy, the associated PCBs and contaminants are re-released into the organism.
It is suspected that this phenomenon has far reaching implications for the health of such animals.
Before the chemical revolutions of the last 50 years, most pesiticides were inorganic compounds. In the 60s, however, DDT was invented. DDT (dichlorodiphenyltricholoroethane) is still considered one of the most effective and cheapest insecticides, and has enjoyed widespread global usage following WWII until the early 70s.
A simple structure diagram for DDT. (See our contaminants page for an animated 3D structure!)
DDT was banned in 1972 in North America, but is still widely used in China, and many developing countries. The problem of bioaccumulation of DDT is very similar to the same problem with PCBs--because of DDTs lipid-water partitioning behaviour, it readily bioaccumulates in organisms' fatty tissues.
DDT has been linked to reproductive failure in mammals, and to decreased reproductive fitness of may birds. DDT has been furthur linked to tumour promotion in some organisms.
Some of these effects come from evidence suggestiong that DDT has endocrine disrupting potential--causing it to behave like a so-called 'environmental estrogen' in many organisms.
Click here to learn more about the contaminants that we have tested for.
Click here to learn about contaminant analysis.
The Blue Whale (Balaenoptera musculus)
Blue whales are the largest mammal ever known to have lived on Earth.
They average 23 to 32 metres in length and usually weigh between 80 and 130 metric tonnes. The head of a blue whale comprises about one quarter of its length. As its name suggests, the blue whale is generally blue-gray in colour, although it may appear mottled with light gray or white patches. On its underside it is lightly coloured and has many pleated grooves. Seemingly strange, the blue whaleís underside commonly appears yellow. The yellow colour is due to a film of algae that accumulates there (blue whales are sometimes called ësulfur bottomsí as a result). Blue whales have been found that are older than 100 years.
Distribution and sociality
The blue whale is found in most of the worldís oceans, but usually remains well offshore. It only enters more inland waters, like the Gulf of St. Lawrence, where plankton is abundant. During the summer months the blue whaleís range shifts toward the poles. Generally, blue whales can be found among packs of ice in the Arctic and Antarctic, as well as in some less extreme clines like the Gulf of St. Lawrence. When the ice of winter makes feeding at the poles difficult, blue whales migrate toward the equator. The whales which we have studied are believed to feed princibly in the Gulf of St. Lawrence and North Atlantic areas.
Blue whales feed almost exclusively on euphausiids or krill -- a type of planktonic crustacean. The stomach of some individuals have been found to contain as much as five million krill (about 2 US tons). Estimates of food intake suggest a daily diet of 3 or 4 tons.
Blue whales, like all balaenopterid whales, are filter-feeders. They feed by taking a huge volume of water into their mouths and passing it through their baleen. The baleen is a set of plates in the whaleís mouth which act as a sort of sieve to keep the krill in the mouth while allowing the water to drain out. The grooves along the underside allow the mouth to expand many times it normal size, and let the blue whale filter as much as 1000 US tons of water and food at a time.
Most of the contaminants such as PCBs and pesticides that whales accumulate, are ingested in their food.
Immediately below is a graph of the amount of a contaminant in a typical whale, throughout its lifetime. The initial peak represents contaminant offloading from this animal's mother, via milk. PCBs and pesticides are typically associate with fat, and since milk is necessarily high in fat (especially in marine mammals), the neonate receives large amounts of these contaminants when weaning. Once the calf is weaned its uptake slows, allowing some of the contaminants to be disposed of. Also discussed below, this profile represents accumulation in males or non-reproductive females only.
Breeding takes place during the winter, while the blue whales are in the more equatorial reaches of their range. Female blue whales reach sexual maturity at about age 7. They carry their young for 10 or 11 months (the gestation period), and nurse for another 6 or 7 months. When born, calves are 7 to 8 metres long and their length roughly doubles during the period of nursing. Female blue whales will not breed while nursing, and so about two years occur between successive pregnancies. When nursing, a calf typically gains 90kg per day!
As mentioned above, contaminant accumulation by calves occurs very rapidly, because the mother's milk is very high in fat--which is necessary to help the infant increase its fat stores and grow rapidly.
As is discussed elsewhere, contaminants such as PCBs are associated with lipid, and accumulate in fat tissues. Therefore, when a mother is weaning a calf, she is unloading a large amount of her contaminant burden onto the neonate. This is represented in the figure below, and represents a contaminant accumulation profile for a typical female.
As is evident from this graph, in the first few years of life, contaminant levels climb rapidly due to uptake from milk. As the infant is weaned, uptake slows and contaminant levels lower because of growth dilution. In males (as can be seen in the first figure) contaminants then accumulate throughout the rest of the animals life--but in females, each time she reproduces, her contaminant burden is drastically lowered.
The blue whale was at one time one of the most hunted of the baleen whales. By 1968, 338 000 blue whales had been killed, and whale biologists feared that the whale would become extinct. It has been estimated that a mere 3% of the former population remains. The Atlantic stock of blue whales was reduced by Canadian and Norweigen whaling efforts into the early 20th century. Similar whaling activities in Alaskan waters likely reduced the blue whale numbers in the Pacific. Antarctic populations of blue whales, too, have declined. The number of blue whales in the Gulf of St. Lawrence has previously been estimated at 60 to 100 individuals, but more recent estimates show that this number is really about 200. Optimistic news for the blue whale conservation effort has come from the North Pacific, which suggests that blue whale stocks here are rebounding.
The blue whale is considered an endangered species under the US Endangered Species Act (1973) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Since 1966, the International Whaling Commission (IWC) has prohibited all hunting of the blue whale, and it lists all blue whale stocks as protected. Also, the blue whales within Canada's 200 mile fisheries zone (including the Gulf of St. Lawrence) are protected against hunting under Canadian Whaling Regulations (which prohibit all forms of commercial whaling).
For further reading on blue whale biology, refer to the following publications:
Bask. Y. 1993. "Blue Whale Population May Be Increasing Off California." Science, vol. 260: p. 28.
Mansfield, A. W. 1985. "Status of the Blue Whale, Balaenoptera musculus, in Canada." Canadian Field Naturalist, vol. 99: pp. 417-420.
Tershy, B. R. 1992. "Body Size, Diet, Habitat Use, and Social Behaviour of Balaenoptera Whales in the Gulf of California." Journal of Mammology, vol. 73: pp. 477-486.
Walker, E. P., F. Warnick, S. E. Hamlet, K. I. Lange, M. A. Davis, H. E. Uible, and P. F. Wright. 1964. Mammals of the World, vol. 2. Johns Hopkins Press, Baltimore.
Yochem, P. K., and S. Leatherwood. 1985. "Blue Whale Balaenoptera musculus (Linnaeus, 1758)." In: S. H. Ridgeway, and R. Harrison (eds.). Handbook of Marine Mammals, vol. 3. publisher? pp. 193-240.
Or have a look at some of these web sites:
Click here to learn about blubber biopsies.
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Copyright 1997, ERS Department, Trent University. All rights reserved.
by Geoff Wild and Jason de Koning