A killer whale’s tale: Protect critical habitats by addressing scrubber washwater from ships


Killer whales are both iconic in pop culture—you’ve probably seen them in movies, at amusement parks, and, if you’re lucky, in the wild—and cultural symbols for North America’s Pacific Northwest. They’re also crucial top predators in their ecosystem and in serious trouble. The resident killer whales (RKWs) off Canada’s Pacific coast have quite low population numbers—only 71 Southern RKWs and 309 Northern RKWs remain. To help protect them, Fisheries and Oceans Canada established areas of protection and recovery called critical habitats within British Columbia’s straits and waterways. This makes it illegal to destroy any habitat within those boundaries, and in December 2018, Canada expanded the initial critical habitat area to include Southwest Vancouver Island and western Dixon Entrance. This is shown in Figure 1.

The expansion made the area of critical habitat 2.5 times its original size. It’s a great step for conservation, but the expanded area is one of heavy ship traffic where vessels tend to bottleneck before entering the busy shipping channel of the Strait of Juan de Fuca. What pollution is being expelled by these ships and what are the risks for RKWs?

Figure 1
Figure 1. The previous critical habitat of RKWs (yellow) and the 2018 expanded areas (purple) with ship traffic patterns.

One kind of pollution comes from exhaust gas cleaning systems, more commonly known as scrubbers. These are a cheaper way for ships to continue using heavy fuel oil, the cheap, viscous oil leftover from the distilling process, after January 1, 2020. This is because scrubbers reduce ships’ air emissions of sulfur oxides (SOx) enough to meet the International Maritime Organization’s (IMO) global sulfur limit, which took effect at the start of this year. The mechanics of how scrubbers work is explained in detail in our prior report that considered the RKW habitat, and here we focus on open-loop scrubbers and hybrid scrubbers running in open-loop mode. Essentially, with these scrubbers, seawater is taken in, sprayed over the exhaust fumes so it traps pollutants, and then discharged back into the ocean in one continuous loop. In other words, the air pollution is traded for water pollution. Does that washwater get treated or cleaned before being dumped back into the ocean? Often not. In 2017, at the European Sustainable Shipping Forum, a survey given to the group found that it was not common practice to use water treatment options in open-loop mode.

Unfortunately, these open-loop scrubbers are popular. According to the classification society DNV GL, open-loop scrubbers are 80% of the current market, and hybrid or closed-loop scrubbers are another 19%. As for what’s in the post-scrubbed washwater being continuously dumped into the ocean as the engine runs, polycyclic aromatic hydrocarbons (PAHs), heavy metals, nitrates, and acidity are listed by the IMO’s Marine Environment Protection Committee (Resolution MEPC.259(68)) as pollutants that are to be monitored under their guidelines of discharge criteria for scrubber washwater while in use. What does it mean when ships using open-loop scrubbers can be assumed to be discharging acidic, polluted water with little to no treatment of the contaminants into the ocean? Well, it’s not good for anyone, and especially not for the RKWs that have no choice but to swim, eat, and survive in those waters while already being among the most polluted animals on Earth.

Moreover, components of scrubber washwater like heavy metals and PAHs are known to persist in a marine environment—i.e., once they’re there it is hard for them to biodegrade. When these pollutants are absorbed by marine life, typically from diet, they are stored in their fat reserves and then forcibly metabolized when the whale taps into its reserves in times of need like starvation or pregnancy. This is a problem: PAHs can interfere with and damage DNA, and that is known to cause cancer. Studies of belugas, cetaceans similar to killer whales, have shown that high PAH concentrations corresponded to higher rates of intestinal cancers. Additionally, heavy metals can accumulate in the liver, bone marrow, and kidneys of marine mammalsreproductive dysfunction and these metals can suppress their immune systems, making them more susceptible to disease.

While these singled-out components are potentially damaging to RKWs, what of the cocktail of pollutants that are collectively being dispelled in washwater? Although no studies of the impacts of scrubber washwater on RKWs specifically have been done, there is already evidence of increased mortality of zooplankton, the foundation of all marine food chains, when exposed.

Just how much washwater are we talking about? Using the 2017 Automatic Identification System ship traffic data and 2017 scrubber-equipped ships we designated in our earlier report, we examined how much scrubber washwater is being released in the expanded designated habitat as compared to the 2017 boundaries. Expanding the critical habitat by 2.5 times brings the amount of discharge from 3.3 million tonnes (Mt) to 5.1 Mt, a 55% increase (see Figure 2). These results are not surprising, but still paint a grim picture of what the RKWs face. And we know that 90% of this is coming from cruise ships.

Figure 2
Figure 2. 2017 scrubber discharge in tonnes.

According to Canada’s Species at Risk Act, a critical habitat is supposed to consider features such as prey availability, beneficial acoustic environment, and ideal water quality. An area with busy ship traffic, including ships known to have scrubbers, isn’t exactly “ideal water quality” material. Current water quality trackers, both inside and outside of the critical habitats we’re talking about, are already indicating high PAH and heavy metal concentrations in sediment and shellfish in high ship traffic areas.

As it stands now, toxic scrubber washwater is being dumped into these protected areas with apparent disregard for the health and safety of this iconic species of RKWs. Additionally, without policy requiring closed-loop or zero-discharge operations, the use of open-loop or hybrid scrubbers releasing washwater is expected to grow, and we now know it’s in areas of recovery efforts for the RKWs, in amounts that should be of concern for one of the most polluted animals on Earth. Canada can ban scrubber discharges in the protected areas and should consider doing so as quickly as possible, especially as cruise ships are currently not sailing. And luckily, there’s a way forward to address the scrubber issue on the global level. In our second blog post on this topic, my colleague, Dr. Bryan Comer, lays out a four-step plan for phasing out scrubbers.