Why are sea cucumbers especially common in the deepest ocean trenches?

Sea cucumbers (class Holothuroidea) are remarkably successful in the deepest ocean trenches, where they can constitute more than 90 percent of the total weight of living organisms. While the specific physiological reasons for their dominance at these extreme depths remain a subject of ongoing scientific investigation, their success is linked to their specialized feeding habits and biological adaptations.1

Many sea cucumbers are deposit feeders that actively swallow large quantities of mud and sand to extract organic nutrients. This method of feeding allows them to thrive in environments where they can process the sediment found on the deep-sea floor. By turning over vast amounts of surface sediment, they play a critical role in altering the physical and chemical composition of the seafloor. Additionally, some species have evolved to be highly adaptable, with certain deep-water forms capable of swimming, and others demonstrating the ability to survive across significant depth ranges—in some cases from approximately 37 to over 5,000 meters. They are the only echinoderms known to reach depths of 10,000 meters or more.2345