How tagging whales can help us understand ocean pollution

Whale with arrow

At 5 mm or smaller, microplastics are barely visible to the naked eye. But if you seek them out, these tiny particles can be found almost everywhere: along seafloors, entangled in corals, and even frozen in arctic ice. In the Mediterranean, where microplastics have accumulated abundantly, WWF scientists are now analyzing traces of plastic they find in whales to understand the strain that rising pollution is putting on our oceans and marine species—and what can be done to stem the plastic tide.



The Pelagos Sanctuary is a stretch of sea between France, Monaco, Italy, and the island of Sardinia. It is the largest marine protected area in the Mediterranean. WWF-France helped create the sanctuary—and the Cap Cetacés project—in 2000. Both aim to protect the region’s unique concentration of 18 cetacean species from pollution and maritime traffic.

While larger plastic debris kills millions of marine animals each year, WWF’s research shows that species from zooplankton to whales ingest microplastics, which can clog digestive tracts and alter feeding behavior, affecting growth and reproduction. As microplastics are metabolized, they release harmful chemicals, which have been linked to adverse health outcomes in whales.

Every year, many tons of microplastics wind up in the semi-enclosed Mediterranean Sea—the result of poor waste management, excessive plastics use, and mass tourism. In response, WWF is pushing for governments and businesses to develop better waste management systems, ban single-use plastics, and adopt legally binding targets to eliminate plastic waste by 2030. 



Since 2016, Cap Cetacés has collected and biopsied tissue samples from about 200 fin, pilot, and sperm whales in the Pelagos Sanctuary. Their findings? The sanctuary’s whales have abnormal levels of various toxic chemicals, proof that dangerous contaminants can make their way from polluted water to plankton and on up the food chain—even to humans.

SKIN Skin samples help researchers determine a whale’s gender and genetic makeup. This allows them to map out relationships among whales and track population size.

BLUBBER A whale’s body stores toxins in the blubber under its skin, so scientists analyze this fatty layer to ascertain its chemical contamination levels. The blubber also reveals a whale’s pregnancy status, which provides vital clues to how toxins affect fertility.

Whale biopsy sample

How do WWF scientists collect whale tissue samples?

  1. Special biopsy arrows are fitted with small titanium cylinders. When an arrow is deployed, the cylinder removes a small piece of skin and fat from the whale.
  2. After the arrow falls out, small buoys affixed to the shaft keep it afloat until it’s retrieved from the water.

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