Deep-sea communities are heavily limited by food, with a prime source of nutrients being marine snow, which is a term used to describe sinking organic matter. Whale falls, which are whale carcasses that sink to the seafloor, are valuable sources of nutrients in an otherwise nutrient-poor environment. A thirty-ton whale carcass, like one from a humpback whale, can transport organic matter two thousand times faster than the average fall of marine snow, as well as transport large amounts of carbon to the seafloor(Li, 2022). A single whale fall is able to support a deep-sea community for upwards of a hundred years due to their oil-rich skulls and thoracic vertebrae. The decomposition of a whale can also produce sulfidic conditions similar to hydrothermal vents, which can support methanogens and microbial mats. 

A whale fall off the coast of Monterey, CA, with octopuses and bone worms. Photo credit: OET/NOAA

Whales can also benefit deep-sea communities while alive. Many species of whale hunt in the deep sea, and while there, produce waste high in iron and other nutrients. This can be especially important in nutrient-poor regions, such as the Southern Ocean, where iron is the primary limiting nutrient for algae growth. 

Whaling decimated global whale populations. It is estimated that the current biomass of global whale populations is less than 25% of pre-whaling levels, with blue whale populations in the Southern Ocean being reduced by up to 99%(Pershing, 2010). Whale-falls are most common along whale migratory routes, which were also the routes whaling ships followed. This means that whales were removed from areas where whale-falls were the most frequent, and by extension, there were the most organisms reliant on whale-falls. It is estimated that 65-90% of whale falls have been reduced in the past 200 years, and that 3 million whales were killed during peak whaling years(Mingli, 2023). Up to half of the organisms dependent on whale-falls as a food source could have gone extinct in that time period(Li, 2022). 

Humpback whale distribution map in the North Atlantic Ocean. Photo Credit: NOAA 

Since whale-falls can also imitate the sulfidic conditions found at hydrothermal vents, it is also possible that the decline in whale populations caused a decline in deep-sea bacteria found at these environments. Some scientists theorize that whale-falls can act as islands of sorts between hydrothermal vents, allowing organisms to travel between vents and increase genetic diversity(Butman, 1995). The decrease in whale-falls likely resulted in habitat fragmentation between vents and narrowed the range of organisms common at hydrothermal vents. 

The removal of three million whales, as well as modern undoubtedly, had a substantial effect on deep-sea ecosystems. Fewer whales mean less nutrient transfer, carbon storage, and more habitat fragmentation of marine basin species. Without a solid understanding of what deep-sea communities were like before the peak of whaling, we will never fully know the impact that we have already had on deep-sea communities.