Dive 02: Blake Ridge

Date: June 15, 2018
Location: Lat: 31.94937883°, Lon: -75.52429803°
Dive Depth Range:: 3,356 - 3,436 meters (11,010 - 11,273 feet)
Midwater Transects Depths: 300, 500, 600, 700, and 800 meters (984, 1,640, 1,968, 2,297, and 2,625 feet)

Location of NOAA Ship Okeanos Explorer on June 15, 2018. Download larger version (jpg, 502 KB).

3D view of the planned ROV track for Dive 02 shown as orange line. The background represents the seafloor depth color-coded with slope in degrees. The warmer the color, the steeper the slope. The red area shown is approximately nine degrees slope.

Three-dimensional view of the planned ROV track for Dive 02 shown as an orange line. The background represents the seafloor depth color-coded with slope in degrees; the warmer the color, the steeper the slope. The red area shown is a slope of approximately nine degrees. Download larger version (jpg, 2.6 MB).

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Dive 02: Water Column Waltz

On June 15, our team explored an unknown feature at the foot of the Blake Ridge and then, after finishing exploration of the seafloor, we conducted midwater transects. While we saw a few corals and sponges on the seafloor today, the most exciting observations by far were the animals observed in the water column! The water column is the largest biome on Earth and yet we know so little about its inhabitants.

Some of the highlights from today’s dive were documenting a sergestid shrimp with long antennae that help to increase the area around which the animal can sense, and a beautiful Medusa jellyfish (Solmissus sp.) with its tentacles extended. The most surprising of today’s observations was a quick visit by a swordfish. And of course, our team was very excited to see a cirrate octopus on #octopusfriday!

Video courtesy of the NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018. Download larger version (mp4, 19.7 MB).

Today was the second dive of the expedition, at a site on Blake Ridge. As an unexplored area with relatively high slope and the potential to be habitat suitable for corals and sponges, this site was proposed to help with NOAA's Southeast Deep Coral Initiative objectives of understanding the distribution of sensitive species, including coral and sponges, in the area. This region was first mapped during the U.S. Extended Continental Shelf Project, which provided excellent bathymetry data. The dive location was selected by reviewing the multibeam backscatter collected during this initiative. Backscatter data can indicate the type of seafloor substrate, with high-intensity backscatter generally indicating harder substrates and low-intensity backscatter indicating soft substrates. When planning the dive, the science and mapping teams looked for this high-intensity backscatter as it often indicates areas of hard substrate that can provide suitable habitat for coral and sponge species. While this location at the foot of the Blake Ridge was completely unexplored prior to today’s dive, an Alvin submersible dive along the Blake Ridge in the early 1990s documented an unexpectedly high abundance of sponges and corals, demonstrating that this region could support these types of communities.

The remotely operated vehicle (ROV) Deep Discoverer was on the seafloor for about four hours from 14:36:41 to 18:29:00 UTC. During the dive, the ROV moved upwards along a nine-degree slope on Blake Ridge. The dive began at 3,406 meters (11,175 feet) and the ROV traveled up the slope, then turned and followed the slope edge until the dive’s end at around 3,356 meters (11,010 feet) depth. While scientists expected to see exposed hard substrate because of high backscatter returns, they mostly found only occasional outcrops of rock. It is highly likely that more rock is just below the sediment drape, but we did not have a way to physically measure the depth of sediment over bedrock. This dive had a high diversity of sponges on the outcrops of rock; however, it yielded fewer coral species than expected. Other organisms of note during the dive were holothurians (sea cucumbers), brittle stars, other species of sea stars, squat lobsters, and rattail deep-sea fish. Stay tuned for the dive summary for a detailed list of the species and substrates observed. The ROV made four sponge collections, a single rock collection, and a collection of a small stalked bryozoan and a colonial tunicate. Sediments were collected during one of the biology sample collections. A highlight of note was that at 3,404 meters (11,167 feet), the ROV documented a feather star that might be a new depth record in the Atlantic Ocean for this species.

Midwater exploration dive transects were conducted during the ascent at five distinct depths: 800, 700, 600, 500, and 300 meters (984, 1,640, 1,968, 2,297, and 2,625 feet). As the midwater is one of the largest and least explored biomes on the planet, the team surveys for 10 minutes at consistent depths throughout the water column to help create a census of what is there and to allow for comparisons with other locations. There were various organisms throughout the water column, with the 300-meter depth mostly comprised of chaetognaths (arrow worms). With the water column transects complete, the ROV headed back to the surface and NOAA Ship Okeanos Explorer is headed to the next dive location for tomorrow at a site named "Giant Bedforms."

This feather star of family Antedonidae was imaged around 3,404 meters (11,167 feet) during the second dive at Blake Ridge of the Windows to the Deep 2018 expedition. This might be a new depth record for the Atlantic Ocean. Image courtesy of the NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018. Download larger version (jpg, 1.2 MB).

A sea star imaged feeding on stalked bryozoan during the second dive of this expedition at Blake Ridge. This behavior was recorded at about 3,388 meters (11,116 feet). Image courtesy of the NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018. Download larger version (jpg, 982 KB).