What can whales tell us about pollution in Antarctica?

We found long-banned pesticides and industrial pollutants in the blubber of humpback whales from Antarctica, suggesting these contaminants accumulate in Antarctic food webs. The pollution levels however were the some of the lowest measured in the world for these whales. Good news for the whales!

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Our study on humpback whales from Antarctica just got published in Environmental Pollution and it is my first publication as a first author. Here is an explanation of the study in a non-academic way with our main findings. If you have any questions, you can reach me at the bottom of the post.

Toxic chemicals in our oceans

Chemical pollution has been affecting our oceans’ health. In particular, a type of man-made chemicals called “persistent organic pollutants” (POPs) include long-banned industrial chemicals like PCBs and pesticides like DDT. These contaminants are persistent, meaning that even decades after their ban, they still circulate in the atmosphere and end up in Antarctica. Because these chemicals associate with lipids, they accumulate throughout the food chain and affect the health of marine mammals.

Humpback whales are the sentinels of Antarctica’s health

Humpback whales in the Southern Hemisphere are the sentinels of the Southern Ocean’s health. They carry useful information from their feeding zones all around Antarctica. Since persistent organic pollutants accumulate in food webs, Humpback whales can give us a representation of which contaminants reach Antarctica and accumulate in Antarctic food webs. We just need to measure these chemicals in their blubber, where they are the most abundant.

The goal of our research was to determine southern humpback whales’ feeding habits and measure their contaminant levels to help us measure pollution in Antarctica. To do so, we used samples of about 150 whales we sampled in both Ecuador and Mozambique, where they breed after they complete their migration.

Long-banned pesticides in southern whales

Even though the concentrations were low, we discovered whales from Ecuador had higher DDT concentrations. DDT is a harmful pesticide that was used for agriculture and was banned decades ago. These Ecuador whales feed close to South America in the Antarctic Peninsula. We know countries in South America still use DDT in vector control (to eradicate insects that carry diseases). As a result, through the atmospheric and oceanic currents, pesticides used in South America end up in Antarctica.

The pesticide we found in the highest concentration is called hexachlorobenzene: a fungicide used in wheat agriculture was banned decades ago as well. This chemical is very volatile, like most persistent organic pollutants, and travels through the atmosphere to redeposit in Antarctica. 

Good news for recovering humpback whale populations

We found that whales breeding in Ecuador and Mozambique feed on Antarctic krill in different zones around Antarctica. The main contaminants we found were pesticides. However, whales from our study actually had some of the lowest contaminant concentrations ever measured in humpback whales. Pollutant levels were low, so they are not a direct threat to the whales’ health. This is good news for southern humpback whales populations since they are still recovering from industrial whaling.

Do you want more details?

For more information, you can read our just published peer-reviewed paper in Environmental Pollution.

Remili et al., 2020

If you wish to know how exactly we did our analyses, let me know so I can write about it. Also, if you wish to obtain the free-access version (so you do not have to pay to read the study), let me know and I will send it to you right away.

Do not hesitate to share the good news everywhere!

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Make sure to read our post on the threats baleen whales face today.