Seafloor Ecology Winter Expedition 2019

This type of bamboo coral, Keratoisis  sp., branches out into beautiful fan-like shapes. Bamboo corals are more abundant at Sur Ridge than at nearby Davidson Seamount. This coral is 1.6 meters wide, 1.5 meters tall, and thriving at 1,215 meters depth.

MBARI Expedition #481

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: December 13 – December 19, 2019

Ship: R/V Western Flyer

Research technology:  ROV Doc Ricketts, benthic respirometer systemdeep particle image velocimetry (DeepPIV), 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 ‘coral-cam’, to observe these communities over time, as well as other instruments including metabolic chambers and current meters. At the Octopus’s 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:

Tuesday, December 17, 2019
Steven Litvin

Wrapping up the cruise and the year:

It is the last day of the last research cruise of the R/V Western Flyer for 2019. We have had a busy and exciting four days exploring the depths of Sur Ridge and Davidson Seamount with the ROV Doc Ricketts. We have explored the Octopus Garden, measured the pumping and metabolic rates of deep-sea sponges, collected samples to better understand deep-sea food webs, and continued our work on the Deep-Sea Coral Observatory (DiSCO) project.

Our final day is a little different, no ROV today. Rather we spent our final hours on Sur Ridge re-deploying the sediment trap system we recovered on the first day and recovering the Benthic Respirometry System (BRS) and the new time-lapse camera system (nicknamed the “DiSCO photobooth”). This is big equipment! The sediment traps are connected to 500 meters of cable (that’s over 1,600 feet!) and the BRS and camera systems weigh hundreds of pounds. When recovered they have to be lifted from often rolling seas onto the Western Flyer. Working with the crew to get all this work done reminded me that all the amazing science and engineering that MBARI supports could not be accomplished without the incredible crew of the R/V Western Flyer and the other research vessels in MBARI’s fleet. From the captain to the cook, from the oilers and engineers to the mates and ROV pilots, these invaluable members of our community are the ones that make the science happen.

Happy Holidays and we look forward to reporting from our cruises in 2020!

Updates from researchers on the R/V Western Flyer:

Monday, December 16, 2019
Jim Barry

Taking the pulse of the Octopus Garden:

A small section of the Octopus Garden showing aggregations of octopus (Muusoctopus robustus). Nearly all are females on their nests. A single male is wandering across the foreground.

We were excited to send the ROV down 3,300 meters (just over two miles!) to the Octopus Garden, a site discovered a couple years ago where thousands of female octopuses nest in warm hydrothermal springs. As the ROV sank through surface waters we saw many pyrosomes again, but today there were many more sea butterflies (pteropods) flapping through the water filtering food. Soon they were gone and after nearly two hours, the ROV approached the bottom.

We positioned the oxygen/temperature sensor as close as possible to the octopuses to measure the temperature and oxygen levels of exhaled waters.

We found the Octopus Garden pretty quickly using the ROV “ultrashort baseline” navigation system.  There is no GPS underwater, so how do you know where the ROV is at any time? A sonic ping from the ship is sent down and once heard, the ROV pings back. Four receivers mounted on a pole dropped into the water during dives “hear” the ROV ping. The difference in the times the different receivers hear the ROV ping can be used to triangulate the position and depth of the ROV. It works great, at least under relatively calm seas.

Once we found the octopuses, we started to measure the temperature of the warm springs around the egg clusters. We wonder why they choose to nest in the springs, rather than in any rocky spot that seems suitable for laying eggs. We were also trying to measure the respiration rates of the octopuses by recording the oxygen concentration of their exhaled waters, compared to the oxygen in the water the octopus inhales. For each animal, we also measured their breathing rate—it varied from on to 11 per minute. We expect that in warmer water, the octopuses’ respiration rates and oxygen consumption will be higher. After this dive, we have quite a bit of video as well as oxygen and temperature measurements to process. Once that is complete, we may understand quite a bit more about any advantage these octopuses gain from nesting in cozy warm waters.

Measuring temperature in egg clusters.

Updates from researchers on the R/V Western Flyer:

Friday, December 13, 2019
Jim Barry

High densities of pyrosomes (colonial tunicates) in surface waters.

We dropped lines and headed out into the thick fog at just before 7:00 a.m. on this Friday the 13th. Hopefully the fog isn’t an omen of some sort. The Western Flyer headed for Sur Ridge, a rocky undersea ridge about 65 kilometers (40 miles) southwest of Moss Landing. The swell from a large North Pacific storm slowed our progress somewhat and we arrived as we finished lunch. We got to work with science operations right away. First, we deployed two  “free vehicles” over the stern and released them so that they sink to the bottom uncontrolled. They drift a bit in the currents, but typically sink straight to the bottom. One is a frame holding our benthic respiration system (BRS), which measures oxygen consumption by deep-sea animals. The second is a time-lapse camera, the “coral-cam,” a new part of our “coral observatory” we will use to observe deep-sea corals and sponges. We’re gathering the images to understand more about the pace of life in this deep-sea ecosystem, what species wander through, and how coral behavior and interactions with other species are related to oceanographic currents and food input from surface waters. The camera will capture an image every hour for a year.

We then launched the ROV and sent it toward the bottom. In surface waters we saw thousands of pyrosomes—tubular, pelagic colonial tunicates—more than I’ve noticed in 20 years of ROV diving. They make a living by filtering phytoplankton from the water, and can reach lengths over 10 meters (32 feet). These were about 15 centimeters (roughly six inches) long. Forty minutes later the ROV arrived at the bottom near 840 meters (~2,750 feet) depth, and we began working. First, we loaded the benthic respiration system with bamboo coral. Using the ROV manipulator arm, we collected small branches of bamboo corals (Isidella sp.) and placed them in chambers where oxygen consumption is measured. Next was the coral-cam. We found it using a navigation beacon it has to ping its location.

Deep-sea crab (Paralomis sp.) consuming a pyrosome.

We picked it up using the ROV and carried it to a rocky ledge where we plan to observe a group of corals and sponges. We connected its communications cable to the ROV so that we could adjust settings on the camera for the best image, made a few adjustments, and initiated its operation. We then disconnected and had the ROV head toward the surface. It will be exciting to see what happens in the coral communities over time. We also noticed many pyrosomes had sunk to the bottom. These pyrosomes are a food feast for a variety of seafloor species.  Several crabs were observed consuming them. Almost all deep-sea life depends upon organic debris sinking from the surface, but food fall events like these may be a rapid way for food to reach the deep sea.

MBARI Cruise Participants

Other Cruise Participants:

Chad King, Monterey Bay National Marina Sanctuary

Josh Lord and Morgan Weaver Lord, Moravian University

Amanda Kahn, Moss Landing Marina Labs

Erica Burton, National Oceanic and Atmospheric Administration