Arctic Ringed Seals Face a Double Threat From Warming and Contaminants

A single exceptionally warm year can have a major impact on the wellbeing of Arctic animals. New research indicates that Arctic ringed seals face two connected dangers: climate-related nutritional strain and the accumulation of dangerous contaminants in their bodies.

Led by Simon Fraser University, the study found that warmer conditions may alter the seals’ food supply and, at the same time, reduce their ability to eliminate toxic chemicals.

Increasing temperatures and diminishing sea ice are also making it more difficult for the seals to obtain nutritious prey.

This combined pressure may endanger the seals themselves, as well as the broader Arctic ecosystem and the communities that rely on it.

Why Arctic ringed seals matter

Arctic ringed seals are a key part of the northern food web. They feed on small marine animals and fish.

In turn, bigger predators including polar bears prey on ringed seals. Inuit communities likewise depend on them for food security and cultural practices.

“Ringed seals are a crucial link between invertebrates, fish and apex predators, and they are a cornerstone of northern food systems,” said study senior author Tanya Brown.

“We’ve found that warmer conditions can change what they feed on, which changes their contaminant exposure, and that can affect their overall health and survival.”

Health issues in ringed seals can therefore have consequences throughout the Arctic food chain.

Examining ringed seal health

The researchers studied 38 Arctic ringed seals from Saglek Bay and surrounding fjords in Northern Labrador. Blood, blubber and liver samples were gathered from 2009 to 2011.

Saglek Bay is recognised as a hotspot for polychlorinated biphenyls, or PCBs. The toxic substances originated from a military radar station dating from the Cold War era in the region.

The scientists additionally screened for mercury, DDTs and chlordane. DDTs are man-made insecticides, while chlordane was formerly applied as a pesticide against termites.

Although many of these substances have now been prohibited internationally, they can persist in the environment for decades.

Liver samples from each of the three years contained high concentrations of PCBs, mercury, DDTs and chlordane. These compounds can trigger oxidative stress.

Oxidative stress harms cells and is associated with inflammation, reduced immunity, long-term illness and reproductive difficulties.

Malnutrition signs during a warm year

The year 2010 was particularly notable. Sea-surface temperatures that year were 5.5 degrees Celsius above normal, while Arctic sea-ice levels were also low.

Blood and blubber collected in 2010 revealed distinct indications of malnutrition. The seals had reduced levels of omega 3 and omega 6 fatty acids, both essential to health. Their saturated fat levels rose and their blubber layers grew thinner.

Blubber does more than act as body fat: it provides an energy reserve and keeps seals warm in freezing water. A reduced blubber layer offers less insulation against cold and stores less energy.

“We saw that just one year of unusually warm temperatures and reduced ice is enough to change what these seals are eating and how their bodies process nutrients,” said Anaïs Remili, postdoctoral fellow and lead author of the study.

Warmer waters probably altered the fish and other prey available to the seals. As a result of this dietary change, they had less access to nutrient-rich food.

How contaminants accumulate

Many of the hazardous chemicals detected in the seals are persistent contaminants, meaning they degrade extremely slowly. Atmospheric and ocean currents can transport them vast distances, including to isolated parts of the Arctic.

The chemicals are also lipophilic, or fat-loving. In marine mammals, they are stored in blubber.

For seals with thick, healthy blubber, much of the contamination remains contained within the fat tissue. Problems arise once seals begin to lose weight.

“Thinner, nutritionally stressed seals redistribute the contaminants they had stored in their blubber back into the bloodstream, which then circulates through their entire system,” said Remili.

“Even though our 2011 samples showed the seals generally rebounded from the malnutrition, we know that any future nutritional stress may compound the impacts of longer-term damage from oxidative stress.”

Put simply, when seals use up fat in difficult periods, toxins held in that fat return to the bloodstream. The process carries harmful chemicals to essential organs.

Climate change may worsen the pressure

Climate change is already transforming the Arctic. Sea ice is vanishing more quickly, ocean temperatures are climbing, and marine food webs are changing.

As ice recedes and water temperatures increase, seals may have to travel further or dive deeper to find food. Shifts in ocean currents may also transport additional global pollutants into Arctic waters.

For years, communities along the Labrador coast have voiced concerns about the effects of warming and contamination on wildlife and human health. Ringed seals remain central to Inuit food systems and culture.

“Healthy seal populations are essential for food security and cultural continuity,” Brown noted.

Safeguarding Arctic ecosystems will demand firm action on climate change alongside tighter restrictions on persistent global pollutants. Ringed seals act as sentinels of the North, reflecting the health of the waters, ice and food webs on which they rely.

A decline in their health indicates strain across the whole Arctic system, bringing repercussions that extend through wildlife, communities and the wider climate.