Dozens of bodies discovered off the coast of Los Angeles have scientists baffled.
This article is Hakai Magazine.
Recently, two scientific expeditions have made some surprising discoveries on the ocean floor off the coast of Los Angeles. First, they found thousands of naval weapons. Second, researchers discovered whale remains. Seven whale skeletons were identified in the dark depths, bringing the total to more than 60 whales. This phenomenon is known as a “whale fall.”
Eric Terrill and Sophia Merrifield, oceanographers at Scripps Institution of Oceanography at the University of California, San Diego, who led the 2021 and 2023 expeditions, set out to assess waste littering the 135-square-mile ocean floor surrounding the San Pedro Basin. The area, twice the size of Washington, DC, and centered about 15 miles offshore, was used as an industrial waste dump in the early to mid-1900s. Many of the objects uncovered during the expedition turned out to be barrels containing the banned pesticide DDT and its toxic by-products.
Prior to this effort, scientists had found only about 50 whale carcasses in the world’s oceans since a Deep Sea Navy ship found the first one off Santa Catalina Island near Los Angeles in 1977. When these large marine mammals die and sink, they form biological oases on the resource-poor sea floor, providing nutrition and habitat for a wide range of organisms, from scavengers hagfish and sharks to microbes, mussels, clams, worms, nematodes, crabs and jellyfish.
The whale carcasses include gray, blue, humpback, fin, sperm and minke whales, according to Greg Rouse, a marine biologist at Scripps Institution of Oceanography who collaborated on the expedition. The skeleton count is “three to five times higher than I would expect based on regional calculations,” said Craig Smith, professor emeritus of oceanography at the University of Hawaii at Manoa, who led the first whale carcass survey expedition in the late 1980s but was not directly involved in the current expedition. Smith has published estimates of how many whale carcasses might be found in various locations, including off the west coast of North America. These estimates are based in part on the assumption that whale carcasses last an average of 12 years before disintegrating or being covered by sediment. But even if they survive for 70 years, “it still doesn’t reach the densities we’re seeing in the San Pedro Basin,” Smith said.
One possible explanation is that it’s simply “the highest-resolution survey ever done in an area of this size,” Smith says. Similar high-resolution surveys will need to be conducted elsewhere to understand the typical number of whale carcasses in the ocean. A lack of oxygen in the water also likely plays a role in the number of intact skeletons. The basin’s deep valley drops 2,600 feet down and is surrounded by rock beds that prevent mixing with more oxygen-rich water. That leaves a low-oxygen zone where the microbes and biological processes that break down whale bones proceed very slowly, Smith says. For example, when Terrill and his colleagues used an underwater autonomous vehicle to collect photos, videos and other data from the seven carcasses in 2023, they found no bone-eating worms (red creatures with feathery gills most commonly found on whale carcasses) covering the bones. Another factor in the high number of visible whale carcasses may be that there are no rivers draining into the nearby ocean, so there is less influx of sediment to hide sunken objects.
While the researchers think it’s unlikely that toxic waste or weapons dumped here caused the whales’ deaths, the area has heavy shipping traffic, and more whales may die here from ship strikes than elsewhere. Two of the busiest ports in the U.S., Los Angeles and Long Beach, California, are just northeast of the study site, and shipping lanes stretch throughout the region. Meanwhile, thousands of gray whales migrate here every year, and blue whales feed here regularly, says John Calambokidis, a marine biologist with the Washington-based nonprofit Cascadia Research Collective.
The Scripps researchers plan to eventually return to the ocean with a remotely operated vehicle to gather more photos and video of the whale’s fall, which may help them determine what species was inside the dead whale and reveal signs of trauma from the ship strike. Smith and Rouse also hope to take bone samples from the whale’s skeleton to determine what caused the whale’s death and learn more about its life cycle.
The mass whale carcass provides a concentrated opportunity to learn more about the food webs that these bounty creatures support and the life that depends on them. It may also reveal more about the role the decomposing whales play in the ocean’s carbon and nutrient cycles. If they survive for decades outside of this area, “it would change the whole oceanography picture,” says Rouse, because it would mean these giant whales are transporting and sequestering more carbon to the seafloor than previously thought.