A recent study led by our lab, published in the Journal of Animal Ecology, highlights the surprising ability of so-called sessile or sedentary marine animals to actively adjust their buoyancy and travel with the ocean currents.
Field surveys conducted in two regions of Atlantic Canada in different years revealed that the local sea cucumber species (Cucumaria frondosa) could tumble of the seafloor at speeds of 30 to 55 meters per minute. Trials conducted in the lab demonstrated that overcrowding, low salinity, and high turbidity prompted a sudden intake of water by the critters. This bloating favoured neutral buoyancy and the balloon-shaped individuals just detached and drifted away.
Another species (Holothuria scabra) was investigated along the coast of Madagascar. Similar buoyancy adjustment was detected in sea ranching facilities, where floating sea cucumbers jumped the fences and drifted at sea, aided by changing tides.
These findings resonate with anecdotal sightings of ballooned or tumbling sea cucumbers, sea star, soft corals, and sea anemones, among others, calling for a revision of the locomotor capacity of so-called "sedentary" benthic animals, with implications for worldwide management and conservation of comercially and ecologically significant species.