Poisoned bodies, dangerous blobs and dissolving snail shells: the threats facing the killer whale family J pod read like a horror film.

The resident orcas of British Columbia's South Coast have no natural enemies, but the toxins in their environment are creating unnatural threats that could wipe out the entire population of the Salish Sea's top predator, scientists say.

J pod is one of three orca families that belong to the endangered southern resident group. They are among the most-studied whales in the world and scientists say pollutants in the ocean, and the water itself, could be what's killing them.

A CBC podcast, Killers: J pod on the brink, hosted by Gloria Macarenko, examines the range of threats facing B.C.'s southern resident killer whales.

Peter Ross, vice-president of research at Ocean Wise and a marine mammal toxicologist, says the southern residents are the marine mammals most contaminated by polychlorinated biphenyls (PCB) on the planet.

Research suggests global killer whale populations could collapse in as little as 30 to 50 years because of exposure to PCBs.

The carcinogens are banned in Canada, but PCBs linger in the ocean for a long time and whales accumulate the toxin in their body tissue. A female killer whale can live up to 70 years — and the longer a whale lives, and the more contaminated salmon they feast on, the more PCBs they store in their bodies.

In a report released in February 2018, Fisheries and Ocean Canada said B.C.'s resident killer whale population is on a trajectory to disappear, unless further efforts are taken. (Elaine Thompson/Associated Press)

"They affect normal development, the immune system, reproductive health and brain development," says Ross, who said the dangerous chemicals can also be passed on to calves through their mothers' milk.

Ross says PCB levels in southern residents are likely causing hormonal and reproductive problems — and for the endangered orcas, every birth, and death, matters.

The southern resident population is reported to be at a 30-year low and their mortality rate is high — around 50 per cent of babies die in their first year.

J 32, an 18-year-old juvenile resident orca dead on a beach near Courtenay, B.C. in 2014. A necropsy revealed the female whale was malnourished and pregnant when she died. (CBC)

But PCBs aren't the only contaminant threatening J pod's survival.

Microplastics — anything smaller than five millimetres made of synthetic petrochemical or plant-based plastic material — are a relatively new threat and research on their impact is just beginning.

Scientists do know microplastics can be mistaken for food by zooplankton, tiny organisms at the bottom of the food chain. Lab evidence shows that eating plastic can kill or reduce these organisms, which are a key food for chinook salmon — J pod's primary food source.

Chinook salmon make up more than 98 per cent of the diet of southern resident killer whales. (Vancouver Aquarium/NOAA/Jamie Lusch)

Attack of the killer blob

The fragile food chain is also threatened by temperature changes in the ocean.

In 2015 and 2016 a large mass of water at least 2 C warmer than normal, nicknamed "the blob," loitered in the Pacific Ocean and wreaked havoc on the ecosystem.

According to Brian Hunt, biological oceanographer at the University of British Columbia, in 2016 B.C. had the warmest surface waters on record, and there were "substantially reduced growth rates of juvenile salmon during that year."

Scientists also noticed large numbers of zookplanton in the blob that are normally found off northern California, not Canada. Salmon rely on zooplankton for food, but the ones found in the warmer waters have much less nutrition.

"Changing ocean conditions are impacting the foundations of the ocean ecosystems and the plankton communities that support the food webs," explained Hunt.

An orca consumes a wild salmon (Centre for Whale Research)

Souring seas and sea butterflies

The ocean isn't just getting warmer, it's also getting increasingly acidic.

The oceans absorb about 30 per cent of carbon dioxide produced by humans, the United Nations says.

Since 1997, the oceans have absorbed man-made heat energy equivalent to a Hiroshima-style bomb being exploded every second for 75 straight years, according to a 2016 study published in Nature Climate Change.

This CO2 intake is changing the chemistry of the water and this is having a ripple-effect on the food chain.

Pteropods, which inhabit the top 200 metres of ocean waters, are a key source of food for other marine animals. (Nina Bednarsek )

Salmon off the South Coast munch on pteropods, which are swimming sea snails that live at the surface of the ocean and float freely on the current in a fashion that has earned them the name sea butterflies.

These salmon snacks have shells made of calcium carbonate and the acidity of the ocean is now dissolving those shells, endangering this integral food source.

The snails can repair their shells, but the energy they use to do so exhausts them and can lead to premature death.

Marine researcher Iria Giminez tests a water sample at her lab on Quadra Island. (Catherine Rolfsen)

Iria Gimenez, researcher at the Hakai Institute , studies the impact of ocean acidification in the Salish Sea. At her lab on Quadra Island, she tests a sample of water that measures 428.2 for CO2.

"That's basically 400 parts per million,' said Giminez, who explained the number would have been closer to 270 before the Industrial Revolution.

Those numbers will keep rising as more carbon is pumped into the atmosphere, risking more changes to the ecosystem.

Killers: J pod on the brink is a CBC British Columbia original podcast about the southern resident killer whales, hosted by Gloria Macarenko. You can get it now for free at CBC Podcasts.