Whale Fall Ecosystems: A Deep Ocean Oasis

Whale fall is the darker aspect of Nature’s multifaceted beauty. Within nature’s complex systems, there are traditionally beautiful sights like flowers and forest, but there is also a darker beauty that is just as much a part of our world and that completes the life cycle of every living being – death and decomposition.

The interconnectivity of ecosystems is something that contemporary advocates of nature’s importance are very much aware of, and it is something that is tied directly to the life cycle of creatures, big and small. One of the most important animals on the planet, the whale, has a unique role to play after death for the organisms on the deep seafloor. The whale’s body, if it falls in the right place, is used and transformed after death into strikingly interesting and complex ecosystem. It can play host to up to five trophic levels of animals at a time, creating what some scientists and observers have deemed a “feast.”

Prior to thorough documentation of whale falls, it was believed that such biodiversity was exclusive to cold-seep sites and hydrothermal vents, where hydrogen sulfide and methane naturally seep through the sediment. However, it is now recognized that whale falls provide a unique opportunity for specialized animals from these environments to spread across the otherwise barren ocean floor.

The whale skeleton can support rich communities for years to decades, both as a hard substrate (or surface) for invertebrate colonization and as a source of sulfides from the decay of organic compounds of whale bones. A new food web level is formed in the bottom of the ocean in this way that gives food source and energy to other organisms.

What is a Whale Fall?

A whale fall is what happens after a whale dies and the carcass sinks to the bathyal or abyssal zones or a depth greater than 1,000 m or 3,300 ft.

Deceased whales do not float on the surface of the water as some lighter and smaller creatures might; they sink or “fall” to the bottom of the ocean floor. Once there, their bodies decompose, becoming an incredibly diverse habitat for the creatures who stumble upon them.

Animals come to eat the whale’s remains, to make new homes, and to hunt other smaller animals who have also been drawn to the whale fall. The whale makes something of a buffet for marine creatures of all sizes and appetites.

Whale falls were first discovered in 1854 after a new mussel species was found inside a piece of whale blubber. Approximately 100 years later, deep-sea trawlers were recovering more evidence of these unique ecosystems. One of the best studies of the events started in 1988 by researchers from the University of Hawaii. The scientists who worked on this project came to the incredible conclusion that one 40-ton whale carcass is equivalent to two thousand years’ worth of normal carbon.

Normally, creatures emend on smaller decomposing plants and animals falling from the surface for sustenance, known as “marine snow.” When a whale falls, it is cause for widespread celebration on the ocean floor.

One whale fall is equivalent to 1,000 years of marine snow.

Not every whale death is categorized as a “whale fall.” Some bodies fall to shallower depths where they are consumed much more quickly by scavengers. But full-grown whales at the right depths can play host to up to five trophic levels at a time, while smaller juvenile whales can only support around three.

Stages of a Whale Fall Ecosystem

Researchers have concluded that there are four distinct phases in a whale-fall ecosystem. These are as follows:

1. Mobile-Scavenger Stage: The flesh and soft tissues support the community of the scavengers. The first wave of organisms, scarves, hagfish, gigantic sleeper sharks, and larger crustaceans come to clean the carcass. Consumption is estimated to be around 88-132 pounds or 40-60 kilograms per day. It lasts from months to 1.5 years.
2. Enrichment-Opportunist Stage: In this stage, smaller organisms such as osedax worms (called the zombie worms) and crustaceans dig through the sediment to find bits of decomposing tissue and feed on the blubber. Animals also colonize bones. This stage lasts from months to 4.5 years.
3. Self-Fulfilling Stage: This stage is the longest. Bacteria consume the fat in the bones and produce hydrogen sulfide. This feeds the deep sea shellfish, mussels, clams, octopuses, and snails. That then powers other microscopic organisms. This stage is one of the longest, lasting between 50 to 100 years. The period makes studying these phenomena difficult.
4. Reef Stage: The final stage of the whale-fall ecosystem. The fat-depleted bones are fed on by suspension feeders.

Exploration of Whale Falls

Whale falls have been explored through the use of deep-sea robotic devices starting in the 1970s. In 1977 the first abyssal whale fall was discovered by the US Navy. Since then, numerous whale falls have motored using submersibles and ROVs, or remotely operated underwater vehicles. They have helped scientists learn about patterns of ecological succession. This term refers to the process of change in the structure of species in a community over time. The time scale can be decades or millions of years.

In February 2002, MBARI researchers Robert Vrijenhoek and Shana Goffredi discovered a recent whale fall while exploring the outer part of Monterey Canyon using MBARI’s remotely operated vehicle, Tiburon.

In a 2019 expedition, researchers found a whale fall at a depth of 10,623 feet near Davidson Seamount within NOAA’s Monterey Bay National Marine Sanctuary.

Why are Whale Falls Important?

Whale falls, the final resting places of these leviathans, are more than just dramatic features on the ocean floor; they are pivotal to the health and complexity of deep-sea ecosystems. These natural phenomena are a crucial nutrient source that contributes to biodiversity, scientific research, and carbon sequestration, underscoring their integral role in marine and global environmental processes.

A Crucial Source of Nutrients

Wang reported in 2021 that the deep-sea environment has long been considered to be low-energy, nutrient-poor because the organic inputs are achieved by only a small amount of carbon produced by photosynthesis. However, there are some local areas with high microbial biomass and activity in the deep-sea, in which whale fall is like an “oasis” in the “ocean desert” and has become an important geographical station for the evolution and development of life in extreme deep-sea environments.

Biodiversity Hotspots

Whale falls are crucial for increasing biodiversity in nutrient-poor deep-sea areas. They serve as temporary ecosystems, supporting unique communities that include specialized species, such as bone-eating worms, clams, and sleeper sharks, that are not found elsewhere.

Whilst otherwise these areas would have remained barren at such great depths, whale falls create an incredible source of nutrients for a variety of creatures. In the bathyal and abyssal zones, which categorize a whale fall, the carcasses create complex local ecosystems. Deep-sea organisms can feed on the body for decades afterward. In the seafloor of the North Pacific, whale fall supports the survival of at least 12,490 organisms of 43 species, contributing to the prosperity of deep-sea life.

Scientific Research

Whale falls have become important sites for scientific research, offering insights into the resilience and adaptability of life in harsh environments. Studies of these unique ecosystems can inform our understanding of biodegradation processes and the limits of life on Earth, which has implications for understanding potential ecosystems on other planets.

Carbon Sequestration

Whale carcasses contribute to carbon sequestration by transporting carbon from the ocean surface to the deep sea, a process known as the “whale pump.” This helps mitigate the atmospheric concentration of carbon dioxide to a small extent, which is significant in the context of climate change.

The Effects of Whale Hunting

Unsurprisingly, the whale hunting industry has had an impact on the creation of these important ecosystems. With more whales being removed from the oceans and less breeding, the number of whale falls has also been reduced. Scientists are just beginning to understand the effects that the overhunting of whales is having on deep-sea organisms, but they believe that it’s not insignificant.

The removal of large whales from the sea could, some scientists predict, remove 30% of the overall biomass of the deep sea. The amount of carbon sequestered by the oceans is also decreased due to whale hunting.

Whales are an undeniably important part of all marine ecosystems and the broader system that affects all living things, whether they dwell on land or under the sea. A healthy, balanced ocean means that humanity has the best possible chance of maintaining a healthy society. Scientists agree that only when humankind learns to live alongside the rest of the natural world, rather than in opposition to it, will the earth truly be balanced.

Other Types of Falls

Whales are by far the largest animals in the ocean, but there are some others that scientists have also spent time researching that could provide a similar habitat for deep sea creatures. Although it would be a much less extensive one.

For example, a whale shark carcass was discovered alongside three mobile ray carcasses. These four carcasses did provide some manner of sustenance for the scavengers around them, such as the hagfish, but the bodies had not progressed past the first stage, the “mobile-scavenger stage”.

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