Whale Falls: How a Whale's Death Feeds the Deep Sea

When a large whale dies in the open ocean, it may sink miles to the seafloor. There its body becomes a feast that can last for decades. Scientists call this a whale fall. This article explains how it works.

What is a whale fall?

The body of a dead whale on the deep seafloor. A 2003 review by marine ecologists Craig Smith and Amy Baco says that falls of large whales, which weigh 30 to 160 tons, deliver huge pulses of food to the deep-sea floor. Smith says that a single whale fall can deliver as much food as the small particles that normally drift down over a period of 100 to 2,000 years, depending on location. Ocean Conservancy describes it as a food oasis in a deep-sea desert.

How was it discovered?

By accident, then by experiment. Scientific American reports that in 1987 researchers found a whale skeleton on the seafloor that appeared to have been dead for years, covered in worms, clams, snails, and patches of microbes. To learn how these communities work and how long they last, Smith’s team began in 1992 and sank three gray whales over six years, visiting them regularly until 2000. They also revisited the original skeleton and another found in 1995. Groups in Sweden, Japan, and Monterey, California, later ran similar experiments.

What are the stages?

Three, according to Smith and Baco, and they overlap.

• The mobile scavenger stage. Large scavengers such as sleeper sharks, hagfish, and rat-tail fish remove soft tissue at a high rate, about 40 to 60 kilograms a day. Scientific American says this feast can last up to two years, depending on the size of the whale.
• The enrichment opportunist stage. Worms and other small animals feed on the organically enriched sediment around the bones. This stage lasts up to two years.
• The sulfophilic stage. Microbes break down oils in the bones, which supports a community of sulfur-loving (“sulfophilic”) animals and microbes. For a large whale this stage can last up to 50 years, and perhaps a century, Scientific American reports.

Some researchers describe a fourth, “reef” stage, but no whale fall has been watched long enough to confirm it. That idea is still a hypothesis.

What are bone-eating worms?

Worms of the genus Osedax, whose name means “bone devourer.” In the interview, Smith describes them as worms with no gut or anus that bore into whale bones. They have a red, palm-tree-like crown that sticks out to take up oxygen. About 35 species have been identified, and the first was described in 2003.

Why does it matter?

Whale falls may act as stepping stones. Scientific American says Smith’s team suggested in 1989 that whale skeletons might help animals spread between other deep-sea communities that live on chemical energy, such as those around hydrothermal vents.

Where can I learn more?

For death on land, see What Happens to a Dead Animal in Nature?. For what scientists learn from human bodies, see Body Farms. For returning a body to nature, see Green and Natural Burial.