diving in bathyscaphe Trieste II (DSV-1) on 19 February 1977. The skeleton of the carcass, which was completely devoid of organic tissue, remained intact and collapsed flat on the seafloor. The submersible recovered a jawbone and phalanges. The whale was considered to be a gray whale based on the size of the bones and the skeleton, the lack of teeth and its location west of Santa Catalina. The first whale-fall ecosystem, which included a chemoautotrophic assemblage living on the anaerobic breakdown of organic material in whale bones, was discovered by a team of scientists led by University of Hawaii oceanographer Craig Smith in 1987. The DSV Alvin observed the remains using scanning sonar at in the Catalina Basin and collected the first photographic images and samples of animals and microbes from this remarkable community. Many other whale falls have since been found by more researchers and deep-sea explorers as well as naval submarines. The increase in detection is largely due to the use of cutting-edge side-scan sonar which can minutely examine the ocean floor for large aggregations of matter. A 2022 study identified 45 known natural whale falls, 38 implanted ones, and 78 fossil ones with most in the Pacific but a significant number, particularly of fossil ones in the Atlantic. Ecology Whale falls are distributed heterogeneously throughout space and time, with a concentration along migration routes. There is much faunal overlap in these whale falls across oceans. Mussels and vesicomyid clams belong to groups that harbor chemosynthetic bacteria, which can draw energy from inorganic chemicals, such as sulfur. Before their presence was discovered at whale falls, the only known habitats of these groups were sunken wood and hydrothermal vents. Similarly, lucinid clams were previously only known to inhabit carbon seeps and anoxic seafloor sediments. Osedax, a genus of deep-sea polychaete worms, act as ecosystem engineers by excreting acid to erode whale bones and absorbing the nutrients trapped within. This enhances biodiversity in the deep sea by increasing the water diffusion into the matrix of bones and facilitating colonization of the bone matrix by rarer species. Osedax have more dramatic effects in juvenile skeletons, which are not as well-calcified as adult skeletons. At whale fall sites it is common to see between three and five trophic levels present, with two main nutritional sources constituting the base of the food web. Adult whale carcasses can house up to five trophic levels,