WaterWords-Deep Sea

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Keep up to speed with the latest USGS deep-sea research cruise with this seafloor syntax.

From October 7 to November 7, the U.S. Geological Survey, the National Oceanic and Atmospheric Administration (NOAA), and the Global Foundation for Ocean Exploration (GFOE) are exploring deep-sea corals, sponges, and fish habitat off the U.S. West Coast. While the expedition is underway, let us serve as your terminology tour guides to the unusual and sometimes hard-to-pronounce words that dwell in the depths of deep-ocean science.

red squat-lobster (Eumunida picta)

The bright red squat-lobster (Eumunida picta) is often seen among the live coral colonies, with their arms raised to grab anything edible that passes by.

(Credit: NOAA-OER Florida Deep Corals. Image courtesy of Brooke et al. 2005, NOAA-OER Florida Deep Corals.)

The WaterWord:  Deep Sea  

Definition: The deep-sea refers to the part of the ocean below 200 meters (650 ft), which marks the point at which sunlight begins to fade. Though sunlight can technically penetrate down to 1,000 meters (3,280 ft), 200 meters (650 ft) marks the depth at which photosynthesis can no longer occur. 

Etymology: Deep – from the Old English deop meaning "having considerable extension downward;" Sea - Old English  of Germanic origin meaning "sheet of water, sea, lake, pool”

Use/Significance in the Earth Science Community: Even though the deep sea covers more than 60% of our planet, only an estimated 5% of the seafloor has been explored. What we do know is that deep-sea habitats are as varied and complex as those on land and host a diversity of natural resources, including deep-sea corals and associated fish habitats, and mineral and petroleum resources that have the potential to serve as an energy source.


We collected this Cerianthid with the ROV.

(Credit: Deepwater Canyons 2012 Expeditions, NOAA-OER/BOEM. Deepwater Canyons 2012 Expeditions, NOAA-OER/BOEM)

U.S. Geological Survey Use: USGS brings together multidisciplinary scientific expertise to better understand deep-sea resources and habitats. Expeditions like the EXPRESS 2019 cruise help provide the information necessary for effective conservation and management of these understudied ecosystems and to understand and document seafloor hazards and natural resources that impact human health, safety, and the economy.

Next WaterWord: Remotely Operated Vehicle

Keep up with the deep-sea findings on the Cruise Log and social media: Facebook and Twitter.