Seafloor Ecology Spring 2020

A crab and several different types of sponges inhabit this rock on Sur Ridge. Image © 2017 MBARI

MBARI Expedition #485

Expedition goal: Our cruise off the central California coast has several objectives related to two research themes in deep-sea ecology: 1) study the sponge and coral communities at Sur Ridge, and 2) revisit the “Octopus Garden” at the base of Davidson Seamount to study the fascinating biology of octopuses brooding there in warm hydrothermal springs.

Expedition dates: March 2 – 7, 2020

Ship: R/V Western Flyer

Research technology:  ROV Doc Ricketts, benthic respirometer systemdeep particle image velocimetry (DeepPIV), Deep Coral Cam

Expedition chief scientist: Jim Barry

Our primary goals focus on studies of deep-sea coral and sponge communities at Sur Ridge, a seamount about 60 kilometers (40 miles) off the coast of Monterey which rises to within 800-1,400 meters (2,600-4,600 feet) of the sea surface. This rocky ridge is rich with beautiful coral and sponge gardens containing centuries-old corals towering two-to-three meters tall like small oak trees, sponges one-to-two meters wide that may be even older, as well as a suite of fishes, sea stars, and other species that call these coral gardens home. The corals and sponges consume suspended plankton and drifting organic particles from currents sweeping over the ridge and must avoid being consumed by predators such as sea slugs and sea stars. We will be deploying a newly developed time lapse camera system, dubbed the Deep Coral Cam, to observe these communities over time, as well as other instruments including metabolic chambers and current meters. At the Octopus Garden, 3,200 meters (10,498 feet) below the surface, we will be measuring environmental conditions, deploying another time-lapse camera systems, and measuring metabolic rates of brooding octopus.

Updates from researchers on the R/V Western Flyer:

Saturday, March 7, 2020
Chris Lovera

The ROV is loaded and ready to distribute small logs along the seafloor at 500 meters (1,640 feet).

Fourteen years ago, Chief Scientist Jim Barry and Postdoctoral Fellow Craig McLain randomly distributed small logs throughout 500 square meters (5,381 square feet) of seafloor to look at the fate and development of wood-fall communities in the deep ocean. In November 2006, 36 pieces of acacia wood sewn into fine mesh bags were laid out on the seafloor at approximately 3,200 meters (10,498) deep off the coast of Monterey Bay. Five years later on October 2011, those logs were recovered and painstakingly picked of fauna that colonized and consumed them. Questions arose from that work, most curious among them were the surprising variability in number, timing, and type of species that arrived to live and dine on the logs—especially between logs separated by just a few meters.

On today’s final dive of our expedition series, MBARI’s Benthic Ecology Group, working with Janet Voight (Field Museum Investigative Research Center) and Julia Sigwart (Coastal and Marine Sciences Institute, University of California, Davis) are revisiting this work.

Even at nearly two miles deep, the navigating ability of the ROV allowed researchers to place wood at predetermined spots along these track lines with meter-level precision.

Late Friday evening, the ROV Doc Ricketts’ large drawer was neatly loaded with forty-one, 1’ x 4” x 4” sections of Douglas fir lumber. In a smaller drawer, the vehicle carried an acoustic beacon that will be placed on the bottom and used to relocate the experiment in the future. The 3,075-meter dive (10,088-feet) site out in the fan of Monterey Canyon is where mesh-wrapped fir blocks were laid out regularly along two axes on the seafloor, about 500 meters (1,640 feet) long, one heading east, one north.

Even at nearly two miles deep, the navigating ability of the ROV allowed researchers to place wood at predetermined spots along these track lines with meter-level precision. The gridded arrangement of this wood fall experiment may help us gain insight on the role that current direction plays at these depths and how it influences the possible episodic colonization of deep-sea animal larvae.

ROV pilots place each log at a predetermined location.

The most abundant colonizers found in previous wood fall studies are boring clams in the family Xylophagaidae. Xylophaga are deep-water relatives of shallower, wooden-boat-fouling clams with the misplaced moniker, shipworm. Teredinidae, the shipworm family, are the termites of the sea. They can wreak havoc on wooden structures submerged in saltwater—ships, docks, and pier pilings. Xylophaga, their smaller deep-sea cousin, also excavates holes in wood, slowly burrowing by the movement of its foot and hard bivalve shell over time. The hollowed-out homes they make while feeding eventually become their wooden caskets. They grow as they bore and the small settlement opening at the wood’s surface eventually turns into a passageway they can no longer escape through. These small encapsulated “ecosystem engineers” of the deep sea contribute to the organic matter that surrounds wood falls and enhances food availability for other animals in the community. A halo of life composed of bacteria, fungi, and a diverse assemblage of deep-sea invertebrates grows up in, on, and around the wood. Yet, our previous study oddly found that some logs even in close proximity can show little to no signs of colonization. We will return to this site in a few years to take video, retrieve some lumber to sample, and see if this latest experiment helps answer some of our questions about how, when, and where these deep-sea animals colonize deep-sea wood falls.

The Benthic Ecology Group and ROV pilots gather around the ROV Doc Ricketts for a team photo.

Updates from researchers on the R/V Western Flyer:

Friday, March 6, 2020
Gregory Bongey

Should you ever find yourself as a marine science student in your fifth year of a master’s program, your first, second, and third priorities are to defend your thesis as soon as possible. Unless of course, you receive an unexpected opportunity to join MBARI on a deep-sea research cruise. In that case, practicality can wait.

Gregory Bongey, a graduate student at Moss Landing Marine Labs, joined the Benthic Ecology Group aboard the Western Flyer. Read about his experience here.

Updates from researchers on the R/V Western Flyer:

Thursday, March 5, 2020
Andrew DeVogelaere

Today we split the science team to run ROV operations while preparing to relaunch our large, physical oceanography mooring. That allowed us to have an extra exploration dive at Davidson Seamount today. There is always a special excitement about exploration dives because we get to view areas that no human eyes have ever seen before, with the potential of making exciting new discoveries.

We decided to dive in the southwest section of Davidson Seamount, starting at 3,200 meters (10,500 feet) deep. This is one of the deepest areas of the Monterey Bay National Marine Sanctuary, and the sediment looked somewhat tropical in the lights of the ROV, lighter in color and more “fluffy” than other areas that we frequent. We immediately came across large gouges in the seafloor—over one to two meters (five to six feet) long, 18 centimeters (seven inches) deep—with sediment piled up along the edges. Some of these features were “fresh,” with sharp edges, while others seemed older, with smooth delineations. The control room was abuzz with hypotheses on what could create such features, and we investigated online scientific literature. In the end, we believe it’s likely that beaked whales are feeding in the area, carving the gouges as they pin large fish to the seafloor. Giant cusk-eels, over four feet long, are common in this area along with grenadier fishes, which have been found in the stomachs of beached beaked whales. Sperm, fin, blue, and humpback whales are often seen above Davidson Seamount, and now it seems that the rarely-seen beaked whales (they have a low profile and dive for long periods of time) also use this marine protected area.

This newly-explored area is also home to large sea spiders, sea stars the size of bucket lids, and the ghost-like, high-fin lizardfish. When small rocks were present along the muddy seafloor, black corals and sponges often took advantage of them for living space. We also came across a spectacular, stepped, mud cliff, over 30 meters (100 feet) tall. Sadly, even at this remote location, we observed the impact of humans—a small pile of assorted metal objects.

When we reached the volcanic edge of Davidson Seamount, black corals and tall, straight bamboo corals were present, but not abundant. In fact, the rocky area was surprisingly devoid of sea life. We came across one octopus that we thought might be a continuation of the octopus garden on a southern bank of Davidson Seamount, but it was a lone individual of a different species and was not brooding eggs.

Later, on the muddy bottom, we came across a favorite species of ours, the pom pom anemone, and a surprising amount of kelp that managed to drift down to 3,050 meters (10,000 feet), 128 kilometers (80 miles) from shore. As we ended our dive, we took water samples to analyze for environmental DNA. We can compare DNA left behind by organisms living in the area to a catalogue to let us know what lives in this area that we may have missed with our remotely operated vehicle. What a wonderful and memorable way to spend a day!

Updates from researchers on the R/V Western Flyer:

Wednesday, March 4, 2020
Steven Litvin

After two days working at Davidson Seamount it was time to return to Sur Ridge to find the Deep Coral Cam we dropped off on the first day of the cruise and move it to the spot where it will spend the next nine months. Before heading to Sur Ridge, we steamed back to Monterey to pick up Paul McGill and Alana Sherman, two of the engineers working on the Deep-Sea Coral Observatory (DiSCO) project and who lead the development of the Deep Coral Cam. We don’t bring the Western Flyer back into port to swap crew; instead, we send an inflatable skiff to shore. It is a ton of fun speeding along the water to meet the Western Flyer then being lifted by crane onto the deck. Definitely a unique way to get on a ship!

After we picked up the engineers it was time to head off to Sur Ridge. We loaded up the ROV Doc Ricketts with an acoustic Doppler current profiler (ADCP) and two Nortek Aquadopps, instruments used to measure currents and flow around the corals and sponges we will image with the Deep Coral Cam. Flow, food, and habitat are thought to be major factors determining where we see deep-water corals and sponges, so ADCPs and Aquadopps are an important part of the DiSCO project.

As the Doc Ricketts decended 1,200 meters (4,000 feet) to the bottom of Sur Ridge, we decided where to place the Deep Coral Cam. Of course the site would have to have coral, but the bottom also needed to be relatively flat and not too rocky, plus have room for the Deep Coral Cam—which is three meters (10 feet) tall and almost as wide—and the ROV. We scouted three of the our “marked” sites— coral habitats we have monitored over time—then decided on “The Rock”, a giant boulder covered in corals and sponges. Thanks to the acoustic transponder on the Deep Coral- Cam, which allows us to pinpoint the position of the equipment underwater, we quickly located the camera, lifted it with ROV, and moved it to “The Rock”. We positioned the Deep Coral Cam in front of a scenic collection of animals, including large bubble gum corals, a Picasso sponge, and a bamboo coral. Once the ROV pilots carefully plugged the Deep Coral Cam into the ROV the engineers sprang into action, tilting the camera (housed in a titanium sphere) to best capture the corals and sponges and adjusting the exposure and the ISO to get the sharpest images.  After the camera was in position, we unplugged it from the ROV, placed the ADCP and the Aquadopps nearby, and the ROV headed back up to the surface.

Over the next nine months the Deep Coral Cam will take one picture every hour. This collection of almost 7,000 pictures will give us information on how coral and sponges interact with the environment and the other animals sharing their habitat over time. We are excited as to what these pictures will show since there is little known about day-to-day changes in coral and sponge ecosystems.

Updates from researchers on the R/V Western Flyer:

Tuesday, March 3, 2020
Amanda Kahn

Ready to deploy the sediment traps. These sediment traps will remain on the seafloor until December, collecting marine snow that rains down from the ocean’s surface.

Today was a mixed day of deploying and recovering moorings along with an ROV dive. In the morning, the sediment trap mooring we recovered yesterday was redeployed at the top of Sur Ridge. The sediment traps will remain there until December, collecting marine snow that rains down from the ocean’s surface. Corals and sponges are thought to grow well on bumps and ridges like Sur Ridge because deep currents around these structures continually sweep in new water filled with marine snow created by plankton blooms above, delivering abundant food. The sediment traps show us how much marine snow falls at different times of the year, and how much of that marine snow makes it to the depths of Sur Ridge.

Still, there is a lot we don’t know about what sponges and corals need to thrive. In many parts of the ocean, we see habitat that visually appears like it should be excellent coral/sponge habitat. It’s cold, dark, has rocky hard surfaces to attach to, and has similar currents to what we see at Sur Ridge. But there are not corals and sponges growing into the remarkable communities we see at Sur Ridge. To understand what makes Sur Ridge a particularly good place for a coral or sponge to live and grow, another mooring was deployed today: the McClane Profiler.

Prepping the McClane Profiler for deployment.

The profiler measures temperature, depth, and salinity (conductivity). There are also sensors to measure oxygen, water clarity (turbidity), current speed and direction, and to detect elements of sinking plankton in the water using fluorescence and CDOM (colored dissolved organic matter), which can tell us something about the food quality and quantity arriving to Sur Ridge. The profiler takes these measurements while traveling up and down a mooring line, so it gives us a view of water column properties across 500 meters (1,600 feet) of depth! It was deployed at the top of Sur Ridge, and surveyed from 950 meters to 450 meters (3,100 – 1,500 feet).

We recovered the profiler in the afternoon, after the ROV dive had concluded for the day. The ROV dive shared the goal of observing the conditions that make life at Sur Ridge so abundant. Acoustic Doppler current profilers (ADCPs) that had been deployed since December were recovered and new ones redeployed to measure water currents among and above the corals. We also collected water samples from sponges, which will help us understand how much food they eat and how much food they have in the water around them. The samples were collected using a small pump with a nozzle that could be inserted near where we wanted to sample, then pumping water slowly into IV bags. In addition, we collected samples for future stable isotope analyses on corals, sponges, crabs, snails, sea stars, squat lobsters, and other seafloor animals to determine who eats whom in the complex Sur Ridge food web.

ROV Doc Ricketts holding onto an ADCP.

Finally, we collected water samples at different depths and different locations around Sur Ridge that will be analyzed for environmental DNA (eDNA). The eDNA profiles are assessed over time to study changes in coral and sponge communities at Sur Ridge, and to test the limits and capabilities of this method of remote detection.

It was a full, busy day and the team worked together until late into the evening to process samples and record all of the great science from the day.

Updates from researchers on the R/V Western Flyer:

Monday, March 2, 2020
Andrew DeVogelaere

After months of preparation and a full day of loading equipment, the crew boarded R/V Western Flyer at 4:00 a.m. Our main destination for the research cruise is Sur Ridge and its dense forests of deep-sea corals and sponges. Sur Ridge is located 45 kilometers (28 miles) west of Point Sur, near the center of the Monterey Bay National Marine Sanctuary (MBNMS), and four hours from our home port of Moss Landing, California. Chief Scientist Jim Barry is leading a team from MBARI, MBNMS, and Moss Landing Marine Labs to continue to build on a deep-sea coral observatory. This research incudes placing instruments that measure currents and assess food availability, while also making visual observations with ROV Doc Ricketts. We want to learn what it takes for deep-sea corals to survive and thrive for hundreds to thousands of years, and what their role is in this spectacular deep-sea ecosystem. Formal plans were set aside for day one of the six-day cruise, as the rough weather dictated that we would not be launching the Doc Ricketts; however, we could make good use of our time by deploying and retrieving equipment.

Gearing up to deploy the Deep Coral Cam.

MBARI engineers and scientists have developed the Deep Coral Cam to record what happens to and around corals over longer periods of time. The Deep Coral Cam takes an image at intervals that we select, and then thousands of images can be viewed in sequence as a movie or individually. Our initial, brief effort with the coral-cam showed exciting potential as we could see fishes “sitting” near corals and sponges while sea stars (some known predators on corals) roam the area and corals sway with changing currents. Today we successfully launched the Deep Coral Cam, and will be adjusting its position to best view coral communities when we are able to visit it with the Doc Ricketts.

We were also able to retrieve two particle traps today. These cone-shaped instruments collect marine snow, pieces of organic matter that float down from the sea surface and midwater areas. Marine snow moves carbon into the deep sea, and is a source of food for many animals, including deep-sea corals. The particle traps switch collecting chambers every three days (or as often as we chose) so we can assess changes in marine snowfall through time. One cone was positioned 15 meters (16.4 feet) and the second cone was 550 meters (1,804 feet) above the seafloor, with a current meter placed in between the two cones.

Crew recovers two particle traps.

After being in place for three months, the particle trap mooring was retrieved by sending a sound signal to a release mechanism above the anchor so floats can lift all of the line and instruments to the surface. We can’t use Styrofoam floats at 1,200 meters (3,937 feet) because they would be crushed by the pressure, so our floats are made of glass balls, the size of bowling balls, encased in shockproof plastic containers. Getting the mooring on deck safely took a carefully orchestrated team of a winch operator, deckhands, and scientists, all wearing safety helmets, life jackets, and steel-toed boots.

After the particle samples were stored and the equipment properly lashed down on deck, activities moved into the dry lab. Plans are being made to re-deploy the particle traps and to select ROV dive locations for tomorrow. The captain decided to bring the Western Flyer closer to shore for the night, just off of Pebble Beach Golf Course, to avoid larger ocean swells and high winds. Today was a success, and were all excited for a new adventure tomorrow.

MBARI Cruise Participants

Other Cruise Participants:

Erica Burton, National Oceanic and Atmospheric Administration

Andrew DeVogelaere and Chad King, Monterey Bay National Marina Sanctuary

Tom Guilderson, Lawrence Livermore National Laboratory

Amanda Kahn, Moss Landing Marina Labs

Eve Pugsley, University of California, Santa Cruz