5. oktober 2023 nyhet

By Pierre Blévin (Akvaplan-niva), Heli Routti (the Norwegian Polar Institute) and Anders Goksøyr (the University of Bergen)

Many pollutants are toxic and potentially harmful for marine life. Figuring out the pollutants’ effects on whales and polar bears is not easy. Traditional methods have limitations, but alternative research strategies are entering the laboratories.

Marine top predators such as killer whales and polar bears are exposed to high levels and complex cocktails of man-made chemicals. These cocktails include both “old” pollutants, which have been banned or restricted by international regulations for years already, and “new” pollutants, currently in use and continuously being released, sometimes as a replacement for already banned substances. The old pollutants, mainly persistent organic pollutants (POPs), are still found at high levels in marine mammals, as they remain intact in the environment for decades.

Exposed

Both the old and many of the new pollutants are toxic and thus potentially harmful for marine mammals’ health. They may disturb hormone and metabolic systems and can also act as immune suppressors. These physiological alterations may impair an individual’s survival and reproduction and ultimately jeopardise the future of some populations. For example, a recent study suggested that some killer whale populations are exposed to extremely high levels of polychlorinated biphenyls, a group of chemicals belonging to the old POPs, which may lead to a population collapse through disruption of metabolic and immune functions.

Female polar bear with cub observed under the midnight sun on the west coast of Svalbard. Photo: Pierre Blévin / Akvaplan-niva

Marine mammals are also exposed to additional stressors, including climate change, resource limitations, habitat loss, and human activities along the coast. Multiple stressors can often interact in complex and unexpected ways, making it difficult to study their combined effects. To date, our understanding of pollutant responses in marine mammals remains poor, and there is a lack of knowledge on the consequences when animals must cope with several stressors at the same time. Killer whales in Norwegian waters are the target of an intense whale tourism, and are thus exposed to artificial underwater noise and physical disturbances. The rapid decline of sea ice in the Barents Sea has led to drastic changes in polar bear habitat. Adverse health effects caused by pollutants, and potential stress related to climate change and tourism may thus interact, with possible combined effects associated with serious health consequences in these marine mammal species.

A dart fired from helicopter immobilised this female polar bear. Scientists are now ready to collect a biopsy sample. Photo: Magnus Andersen / Norwegian Polar Institute

Alternative approaches

Gathering knowledge about effects of pollutants in marine mammals is very challenging due to logistical and ethical constraints. Marine mammals are obviously inadmissible as experimental laboratory models. Most studies so far have tried to tackle the question with the correlative approach, where one investigates the relationships between tissue concentrations of pollutants and health parameters. But this approach is of limited value. In addition to usually being conducted on a restricted number of individuals, correlative studies do not provide any evidence for cause–effect relationships; nor do they allow us to decipher which cellular or physiological mechanisms are involved.

Photo: Once collected, the biopsy from the killer whale needs to be handled without delay. Each fragment will then be streamed to specific laboratory analyses. (Photo: Emma Vogel / UiT The Arctic University of Norway)

Over the last couple of years, several projects financed by the Fram Centre Hazardous Substances Flagship Programme have allowed our research group to develop valuable alternative approaches to overcome these hurdles. These molecular and cellular tools have helped us to understand which pollutants have potential to modulate important physiological processes like metabolism in marine mammals, and how they might achieve those effects. For example, how can a mixture of POPs affect the accumulation of fat in polar bear cells or the expression of genes in killer whale skin cells?

New projects SLICE and Marma-detox

The Research Council of Norway has awarded grants to two complementary research projects to deepen the knowledge on toxicological responses to multiple stressors in marine mammals. The project SLICE – Moving from field studies to ex vivo models for understanding and predicting toxicological responses to multiple stressors in marine mammals is headed by Pierre Blévin at Akvaplan-niva, and the project Marma-detox: Whales and polar bear in a petri dish: decoding marine mammal toxicology through in vitro and in silico approaches is headed by Anders Goksøyr at the University of Bergen. Both projects are being done in close collaboration with Heli Routti at the Norwegian Polar Institute, as well as other partners in Norway and abroad.

In SLICE and Marma-detox, we will establish tissue and cell cultures from selected marine mammal species such as polar bear, killer whale, and fin whale, to study molecular and cellular responses to pollutants and stress in these animals under controlled, experimental conditions. In practical terms, we will expose cells and tiny fragments of fat tissue to pollutants and/or stress hormones (to mimic the hormonal response under stressful conditions like climate change or whale tourism for example). We will then assess their toxicological responses, including gene expression and lipid metabolism, with advanced bioinformatic analyses. These are novel, cost effective and ethically sustainable approaches to test responses to pollutants and stress separately or simultaneously. These approaches are important steps forward to deepen our understanding of responses to multiple stressors in marine mammals. In SLICE, we will also run traditional correlative studies on a large number of individuals of killer whales and polar bears to compare the results from both approaches, and examine to which degree the responses observed in the lab reflect correlative field studies. In Marma-detox, the genomes of the marine mammal species will be scrutinised for information on gene sets related to contaminant response and susceptibility.

The fragment of killer whale tissue at the interface between skin and fat is used to establish cell cultures (the cells shown are fibroblasts). These cells will be further exposed to pollutants. Photo: Juni Bjørneset / Norwegian Polar Institute

As charismatic megafauna, polar bears and whales have a strong potential to raise environmental awareness. We have now entered in the United Nations Ocean Decade and both projects will strive to communicate their findings to a large audience including the scientific community, the public and relevant stakeholders. Knowledge generated by the projects will also be relevant to update the current "data deficient" and "vulnerable" conservation status of killer whales and polar bears in the International Union for Conservation of Nature’s Red List of Threatened Species.

SLICE and Marma-detox will involve an international research consortium distributed across five countries, as well as including several post-doctoral researchers, PhD candidates, and MSc students.

Additional info:

Relevant projects financed by the Fram Centre Hazardous Substances Flagship Programme:

Contaminant effects on energetics (led by Heli Routti / Norwegian Polar Institute)

Cellular responses to contaminant exposure in marine mammals from the Arctic (led by Heli Routti / Norwegian Polar Institute)

Giants of the ocean – affected by anthropogenic pollutants? (led by Heli Routti / Norwegian Polar Institute)

WhaleHealth – Contaminant levels and effects in killer (Orcinus orca) and humpback whales (Megaptera novaeangliae) present in Northern-Norway (led by Jenny Bytingsvik and Pierre Blévin / Akvaplan-niva)

The article has previously been published in Fram Forum: Polar bears and whales in the spotlight of toxicological studies - Framforum