Krill: the planet's smallest influencers?

It was late March 2024, and the Antarctic summer was nearing its end. Just a few days earlier, I was on the Sylvia Earle, a small expedition ship that had departed from Ushuaia and crossed the infamous Drake Passage, the body of water separating South America from the white continent. 

The undeniable visual acknowledgement that the Antarctic winter was coming presented itself to us in the form of the sea ice of the Weddell Sea pushing north, and surrounding the tiny landmass in front of us, Paulet Island. The island was a prominent location on the expedition cruise that I had joined, due mainly to the incredible survival story of a Swedish scientist, Otto von Nordenskjöld, who led a Swedish expedition here in 1901. 

Our planned expedition cruise, 'Deep Weddell Sea Following the Nordenskjöld', was not to be. With sea ice blocking our path into the Weddell Sea, the expedition leader had no choice but to make a new plan. I was disappointed to be unable to return to the Weddell Sea, the land of floating ice, where I had spent a month onboard the Agulhas II. This vessel was the South African ice breaker that, in 2022, was part of the Endurance 22 expedition that located the wreck of Sir Ernest Shackleton’s Endurance. This is how expedition travel works, though, and such uncertainty can be powerful and exhilarating when commanded by nature. On our new course, we were to head southwest to the dramatic landscape and rich wildlife of the Antarctic Peninsula.

I was outside on deck, taking in the southern ocean's cold and often unrelenting wind as gigantic, majestically crafted icebergs passed the ship. The snow-capped mountains of the South Shetland islands came into view, but something else diverted the attention of everyone on deck, crew and guests alike. It was a spectacle of nature in front of our eyes and we had the best seats in the house. 

This was a frenzy like nothing I'd ever seen. More whales than I could count, lunging, spy hopping and filter feeding in every direction, whilst an armada of chinstrap penguins soared above and under the waves like black and white torpedos. Why was there so much wildlife activity in one place?

A colour change in the water, a moving murkiness, started to connect the dots. It was feeding time and the dish of the day was krill. 

Krill are a relatively small crustacean, growing up to about 6cm in length and weighing, on average, around one gram. But despite being petit, they pack a critical punch. This is because they are the primary food source for penguins, seals, whales and other marine life populations. Estimates of how much krill these species consume are hard to quantify. An average crabeater seal, for example, consumes around 11,000 a day and a single Adelie penguin, 1,200. A blue whale consumes as many as 3 million a day.

Species like humpback and blue whales migrate to the Antarctic from warmer waters every year to feast on this essential prey. Essentially, anything that doesn't rely on krill to survive in Antarctica eats something that does. With that sort of demand, an abundance of krill is always needed. The reported hundreds of millions of krill are estimated to collectively weigh more than 400 million tonnes, roughly the same as all humans on the planet. 

Back on board the Sylvia Earle we witnessed true nature at play. The important food source for many of the continent's natural visitors was being banqueted on by awe-inspiring marine life in a spectacular display. It was a real pinch-me moment, easily compared, I imagine, with that of a BBC David Attenborough film crew. 

However, what seemed like an abundance of food for the wildlife we were watching is under extreme threat due to climate change, rising ocean temperatures and acidification. Still, the krill fishing industry, which is exponentially decreasing the stock of krill in the region, is already facing a decline.

Anyone who has had the privilege of seeing the wildlife of the dream-like polar regions, in the flesh or on screen, will attest to the unfathomable idea and tragedy of such incredible, fascinating wildlife losing their primary source of sustenance. 

However, other worrying consequences directly affect us humans, too. Antarctic krill feed on phytoplankton, a single-celled marine plant that absorbs carbon dioxide during its development. Krill then transfer this carbon through their faeces and shed their exoskeletons to the ocean floor, where it can be stored away. This is a perfect example of nature’s great balancing act, prolonging the prosperity of the planet and its ecosystems. That is, of course, when human activity doesn’t get in the way. 

A recent international study reported that krill can remove 12 billion tonnes of carbon each year from the earth's atmosphere. We all know the importance of reducing our carbon emissions, but finding methods to remove what is already there is one of our time's most significant technological challenges. Yet here, krill are doing it to unprecedented levels under our noses. When it comes to krill the human race has a lot to be thankful for. 

Fast forward to a few evenings later, and during a citizen science seabird survey on the observation deck, I spotted something I didn't expect to see on the horizon: ship lights. 

It is not an uncommon or strange sight to see in the Antarctic Peninsula, even though operators do a very efficient job of avoiding being in the same spots as others to minimising impact and maintain the feeling of being remote. But considering we were the last expedition ships in Antarctica by a good few days, and no research ships were showing on the radar, seeing other vessels was unexpected.

I lowered my binoculars to get the attention of two of the ship's expedition team. I asked Linda, a naturalist from the Netherlands and the expedition medic, and Peter, a PhD biologist and retired lecturer from the US if they knew what sort of ships they might be. After peering through their binoculars, the concern on their wildly experienced faces spoke a thousand words. They were fishing trawlers and the intended catch was, you guessed it, krill. 

As we got closer, two large trawlers turned into three, then three into four. Suddenly, we didn't feel so alone anymore. 

The immediate concern was if these vessels were registered, or were taking advantage of most other ships having left for the season to sneak in and bag a haul of the lucrative catch. 

A visit to the bridge confirmed these were permitted trawlers, assumed to follow regulations and quotas. Despite this confirmation, it raised the question of why they were here in the first place. Why krill? And crucially, why should we care? 

The existence of such a large, lucrative industry in such a remote part of the world is only sometimes widely spoken about outside of the concerned parties.

Krill is a typical food used in salmon farms and aquarium fish food, krill oil, Omega-3 tablets, and supplements. In some cultures, humans eat krill as a source of protein, a practice started in the 19th century based on krill being previously described (falsely, I’ll add) as limitless food stock. 

But do we need it? Considering the importance of krill in carbon capture, they play a crucial role in the marine ecosystem. Indeed, alternatives to their properties can be found elsewhere, outside of this incredibly influential species. The answer is yes, but as with many questions like this, a complicated yes. 

The krill-based industry is growing around 12-15% yearly as the demand for krill-based health products against heart disease, high blood pressure and depression, increases. However, the krill population is already in decline due to climate change and the retreating or reduced formation of sea ice, which is where the algae and plankton that the krill feed on, are found.

Despite regulations or catch limits, the threat to many of the Antarctic wildlife species that depend on krill is a very real one, and many are calling for stricter rules, the widening of marine protected areas or the complete ban of krill fishing in Antarctic waters. 

This experience shared by those on the Sylvia Earle alongside an accompanying lecture by the expedition team on the subject later that evening, fired up the activist in everyone on board. Discussions around the tables of the ship's restaurant that night focused primarily on the topic. For many of the guests, a display of activism came with many choosing not to eat fish that evening. As simple or optimistic as that sounds, it represents something much bigger. That is the power of experience to change our perspective and decisions. The combination of exposure to such incredible wildlife and the understanding of the factors threatening it produced immediate action. Buying or eating products that contain krill and contribute to reducing this significant food stock felt out of the question. Our experience resulted in us vowing to spread the message as Antarctic Ambassadors and pay careful attention to products containing krill so we can choose alternatives. 

Another example of one of the long-lasting impacts of expedition travel to areas like the polar regions. I do not doubt that others on the Sylvia Earle who shared that experience have also returned and told this story. I've found that passion for communicating these stories, in particular, is sent into overdrive when partnered with the exposure and experience of expedition travel.