Skip to main content

Planet Postcard: Life at the Bottom

Photo of an Annelid
Courtesy of NOAA Ocean Exploration and Research

To most of us, the bottom of the ocean is as mysterious and enigmatic as deep space. When we do get a glimpse into this secret world, it can be a bit frightening. Creatures that resemble Hollywood monsters often come to mind. But amongst the formidable, also lies the beautiful, the unique, and the curious. For every lurking cusk-eel, there’s an adorably plump synallactidae sea cucumber.

Whether you’ve ever noticed it or not, the bottom of water bodies, such as the ocean, is teeming with life known as benthos. These aquatic creatures live on, in, or near the bottom of water bodies. So, whether you’re sailing on the open ocean or kayaking around the lake down the road, you’re floating above an underwater universe made up of benthos!

Browsing Benthos

They may have started at the bottom, but now they’re here in NOAA’s Benthic Deepwater Animal Identification Guide. Images collected by the 2015 Deep Discoverer dives around the Hawaiian Archipelago and Johnston Atoll provide a virtual treasure chest of benthic animals. From Annelids to Zoantharians, the Benthic Identification Guide gives you a glimpse into the often unseen world of deep-sea creatures.

But, these photographs are more than just pretty pictures. They serve a very important purpose in scientific discovery and classification. The Benthic Identification Guide serves as a landing page for scientists around the world to classify or even identify benthic animals. Having a worldwide network of scientists lending their knowledge of benthic creatures ensures that the images and data collected are identified and classified accurately.

In some cases, scientists were able to identify previously unknown animals. There were many new species or genus (a group of species that are closely related) discovered on this dive—too many to list here. But, several new species include a seastar, red coral, and white coral. The white coral was recently named Crypthelia kelleyi. Likewise, the adorably prickly squat lobster is a new genera of the family Chirostylidae.

Photos of newly discovered benthos

New benthos were discovered by explorers during a 2015 Deep Discover Dive. Several are pictured here from top left; seastar in the genus Pythonaster, red coral in the genus Swiftia, white coral named Crypthelia kelleyi, and squat lobster in the family Chirostylidae. Courtesy of NOAA Ocean Exploration and Research.

Scientists have collected over 13 specimens of deep-water coral over the past year. A Smithsonian scientist that specializes in these and other families of coral recently identified that nine of these specimens are new in some form; eight being a new species and one being a new genus.

While all of these Latin scientific names may not mean much to the average person, they symbolize important advances in scientific discovery and the future of deep-ocean exploration. Future and current dives will only bring more new discoveries to the surface, giving scientists and the public a better understanding of our underwater ecosystem.

What are Benthos?

Most benthos are spineless bottom feeders. That may sound harsh, but many benthos are indeed invertebrates, which lack a backbone. Creatures like sea stars are a great example of an invertebrate benthic species. With about 2,000 species of sea stars living in the ocean, these charismatic critters are widely known for having five arms, but species with 10, 20, and even 40 arms exist.

Though benthos feeding habits differ, many filter feed, which entails sieving food particles or small organisms from the ocean. Others eat the bottom sediments, graze on kelp, eat carrion, or hunt other animals. Sunlight cannot usually reach below 200 feet in the ocean, which prevents many food sources from growing on the deep seafloor. Benthic animals in the deep ocean have to rely primarily on food particles that rain down from higher up in the ocean. A good portion of this “food rain” is eaten by animals higher up, leaving the deep-sea benthic creatures with what little remains.

The diversity of life is much higher at the bottom of water bodies primarily because the bottom offers many more types of habitats that organisms can adapt to. Research indicates that the diversity of species living in the deep-sea may rival the species richness found in tropical coral reefs.

While it’s natural to assume that few lifeforms could withstand the harsh, frigid habitat of the deep ocean, benthic organisms are well adapted to this environment, living and thriving in the cold dark waters. These animals adapt by having low metabolic rates, living and working at a slower speed than organisms in warmer waters. Some species of squat lobsters, such as Munidopsidae, live at depths of 1,000–5,000 meters (.62-3.1 miles) in the ocean. They can be found in seamounts, canyons, and next to deep-sea hydrothermal vents.

To cope with the vast darkness, many benthic creatures create their own light. Bioluminescence, a colorful, chemical glow that can be turned on and off, serves several purposes. Many species of benthos flash colors and patterns to communicate with their own kind. Hunters use bioluminescence to search out prey, and the hunted use this light to ward off or confuse predators. Other creatures, unable to create their own light, borrow it from those who can. Known as fluorescence, they absorb the light from other organisms and reemit it as a different color.

As water depth increases, so does water pressure. Over most of the deep seafloor, benthic animals must withstand thousands of pounds of water pressure across their entire bodies. These animals avoid the pressure by filling their tissues and internal cavities with water instead of gas.

Global Impact

Benthic animals aren’t just resting on their laurels all day—they serve a crucial role in the underwater ecosystem. Fish species such as haddock, catfish, and most flatfishes eat benthos. Many benthic animals sieve the ocean floor and scavenge on dead organisms, essentially cleaning it up. Feeders and active diggers regularly move the bottom sediments, increasing the oxygen content and overall productivity, much like earthworms on land.

Though the deep ocean region benthos call home is remote, its impact is far reaching. Researchers hope that the survival strategies used by deep-sea benthic animals to cope with environmental extremes may one day be adapted to improve human health and life. Scientists already use bioluminescent and fluorescent chemicals found in some benthic animals as genetic markers in medical research. Other enzymes, genes, and compounds that allow animals to function despite crushing pressure and freezing cold are under investigation for use in new medicines, industrial processes, and toxic waste cleanup.

Science Goes Deep

Some benthic animals reside as deep in the ocean as 5,000 to 6,000 meters. That’s the equivalent to 13 Empire State Buildings stacked on top of each other. So how do we learn more about these creatures when they seem inaccessible to humans?

While an actual scientist may not be able to dive to these depths in person, a remotely operated vehicle (ROV) certainly can. NOAA’s research ship, the Okeanos Explorer, explores our largely unknown ocean for the purpose of discovering and learning more about sea life, such as benthic animals. The Okeanos Explorer is home to the Deep Discoverer ROV, which can dive to depths of nearly 4 miles and withstand pressures almost 600 times that at sea level. This ROV provides scientists with high-quality imagery and environmental data that give valuable insights into complex underwater ecosystems.

Related News