Annelid worms have been essential to many of earth’s ecosystems since the Cambrian Explosion over 500 million years ago. Ancient worms burrowed in the sea floor, stirring up sediments, releasing oxygen, and opening up new habitats for complex animal life, changing marine ecosystems forever.
The Important Role of Marine Worms
Marine worms still burrow in sediments on the bottom of oceans and estuaries, they also cement themselves to rocks and coral reefs, build tubes, live on hydrothermal vents, and swim freely in the deep sea. Marine worms are essential to the health of the oceans. They play important ecological roles as decomposers, filter feeders, key predators, and an important food source for other marine organisms. Approximately 8,000 species have been described so far, but many new species are still being discovered. Watch this video to meet the diversity of worms living in the ocean.
On deep rocky reefs, some worms are builders, creating hard structures and tubes that provide habitat to crabs, snails, shrimp, and other worms. Other worms are decomposers on the ocean bottom, like bone-eating tubeworms that feed on whale bodies that sink to the bottom. At the bottom of the worm’s tube there is a sac with roots that secrete acid into the bone to dissolve it. Bacteria living with the worm digest the dissolved organic material, providing food for the worm.
Bacteria are also essential for hot vent worms which depend entirely on their symbiotic bacteria for food. The bacteria use chemicals like sulfur spewing from the vents to make organic compounds for the worm.
In the midwater some worms feed on marine snow which are sinking particles from the surface. Midwater worms like Peobius and Flota help cycle nutrients from the surface to the depths in their fecal pellets. And they concentrate carbon through those pellets, which sink faster than the marine snow they eat. Peobius uses mucus nets to catch particles of sinking organic matter as it drifts through the water column.
Other midwater worms are active predators, including the gossamer worm, Tomopteris. They are swift predators that prey on smaller midwater animals like arrowworms, tunicates and fish larvae, playing an important role in the midwater ecosystem.
