Seafloor Ecology Expedition 2019

Bubblegum coral and elongate goiter sponge at Sur Ridge

MBARI Expedition #462

Expedition goal: Our cruise off the central California coast has several objectives related to three research themes in deep-sea ecology: 1) study the sponge and coral communities at Sur Ridge, 2) revisit a corn stover sunk to 3,200 meters depth in 2009 and sample the colonizing communities, and 3) begin a wood-fall experiment to see how species colonize these ephemeral sources in the deep sea.

Expedition dates: April 19 – April 24, 2019

Ship: R/V Western Flyer

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

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 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.

Some of the questions we have about the Sur Ridge sponge and coral communities include: Why are corals and sponges thriving on some parts of the ridge but sparse in others? Is this difference attributed to food and feeding success, predators, and/or competition with their neighbors? How vulnerable are sponges and corals to human activities like climate change, which is now penetrating the depths of the ocean? To begin answering these questions, we plan various activities for each day, such as deploying current meters, sediment traps (funnel shaped traps that capture sinking debris), and other sensors to measure water flow and suspended material that influence the type and abundance of food sweeping over the ridge and past corals.  We will also be measuring respiration rates of sponges and corals using novel sensors and instruments, tagging corals to monitor growth, and measuring rates of predation by sea stars—the deep-sea corals nemesis.

Our second goal is to revisit a large bale of corn stover (essentially a hay bale) that we sunk to a depth of 3,200 meters (10,500 feet) in 2009. We wanted to test one notion for deep-sea carbon sequestration that could mitigate climate warming by storing carbon in the deep-sea rather than allowing it to be emitted to the atmosphere. One idea for deep-sea carbon sequestration is to gather up crop residue (stalks, husks, and other plant material, package it, and sink it in the deep ocean where it will remain for many centuries, rather than allowing it to degrade in the soil and ultimately release COinto the atmosphere. This peculiar idea was suggested years ago and, in preparing for a cruise in 2009, we decided to sink one corn bale to test this notion. We’ll revisit the bale on this cruise to probe it with sensors to measure its rate of decay, giving us some idea of how long its carbon will remain in the deep sea before eventually making its way back to the atmosphere.

Our third goal for the cruise is to initiate an experiment measuring the diversity of animals that colonize wood falls in the deep sea. Logs and other woody debris are carried to the sea by rivers and eventually sink, some to great ocean depths. These wood falls can be a bonanza for some organisms living in the food-poor abyss. Wood-fall organisms—perhaps most notably wood-boring clams, are notorious for their damage to wooden ships, but several related species live in the deep ocean. Some are wood-fall specialists and are found nowhere else, while others are opportunists that use any food source they can find. Our experiment will place small wood falls, 10 x 10 x 45.5 centimeter wood blocks (4 x 4 x 18 inch wood blocks), on the seafloor across an area the size of 10 football fields to see if the assemblage of organisms (clams, snails, crustaceans, worms, etc.) that colonize each block are related to the distance between blocks. This will help us understand if larvae drifting over the seafloor may sense a wood fall or if the colonization process is more random. From this and similar experiments, we are building an understanding of how food limitation and the challenging conditions in the deep sea have shaped the evolution of species and their abilities to exploit ephemeral “food falls” (wood, whales, or anything in between).

Updates from researchers on the R/V Western Flyer:

Wednesday, April 24, 2019
Postdoctoral Fellow Amanda Kahn

Studying the connection deep-sea sponges create between microbes in the water column and seafloor communities.

Deep-sea animals have so many different adaptations to find food because food is scarce in deep water.  Deep-sea sponges are common at Sur Ridge and grow to over a meter (3.3 feet) tall!  Sponges are filter feeders that specialize in eating bacteria, which are too small for most other animals to eat. By eating them, sponges turn some of the bacteria into sponge tissue and excrete the rest as clumps that make them large enough for other animals to eat. In a way, sponges create oases in the deep ocean.

To figure out how large an effect sponges have, we deployed a suite of instruments to study the water around sponges. Combined, the three sampling methods described below will teach us the role of sponges as consumers and transformers of microbes at Sur Ridge. These kinds of careful physiology measurements will supplement the mapping and observational work that the Deep Coral and Sponge Observatory at Sur Ridge will aim to target.

When we found a sponge to study, we first used the DeepPIV, developed by Principal Engineer Kakani Katija in MBARI’s Bioinspiration Lab, to shine a sheet of laser light across the sponge. The laser sheet illuminates particles moving in the water, which can be analyzed on a computer to assess water motion and speed. The DeepPIV allows us to measure the rate that sponges are moving water through their filter-feeding system, which allows us to calculate the volume of water processed by deep-sea sponges—it can be substantial! A shallower species of sponge was estimated to pump about 900 times its own body volume each day.

After we finished measuring the pumping rate using the DeepPIV, we used a FireSting oxygen sensor to measure the amount of oxygen each sponge is removing from the water. Measuring the respiration rate shows how hard the sponges are working to filter feed. The FireSting came as a piece of electronics with a sensor that couldn’t get wet. Postdoctoral Fellow Amanda Kahn and Senior Research Technician Chris Lovera coordinated with several MBARI staff including David French, Dale Graves, and several ROV pilots, to make the instrument waterproof, to allow its electronics to interface with the ROV, and to design it in a way that it could be handled by the manipulator arms of the ROV.

Finally, for the first time on this trip, we used a new instrument designed by MBARI Mechanical Engineer Larry Bird to collect samples of the water after it passes through the sponge’s filter system. The water can be compared with surrounding water to determine how much bacteria the sponge ate from the water, and any other changes that have been made to the water chemistry.

As a bonus to doing this work, some of the measurements require us to wait several minutes. During that time, we can zoom in on the vibrant, diverse community of animals that live on and around sponges.

Updates from researchers on the R/V Western Flyer:

Monday, April 22, 2019
Senior Research Technician Susan von Thun

Octopus Garden

When MBARI and MBNMS researchers were onboard the E/V Nautilus last year they had the opportunity to check out a spot near Davidson Seamount.  They found something so surprising and intriguing that we revisited the same site on this expedition. On the seafloor, in cracks and crevices on the edge of this underwater mountain made of ancient lava, they saw octopuses—not hundreds, but thousands of octopuses—sitting on their eggs! When an animal protects its eggs, we call it brooding. This was the first time scientists have ever seen such a large aggregation of brooding octopuses anywhere in the world.

On last year’s dive, the scientists were able to get a first look. Just last month, MBNMS researchers joined Woods Hole Oceanographic Institution (WHOI) on the R/V Atlantis and visited the site again and were even able to collect some eggs and measure the water temperature. Now, with ROV Doc Ricketts, we had the opportunity for a short dive on the site as we headed to Sur Ridge from Station M (off Southern California).

What is creating this oasis in the deep sea? On the Atlantis expedition, the team measured the water temperature in the crevices where the octopuses lived and found that it is nine degrees Celsius (48 degrees Fahrenheit) warmer. It seems that the warm water is what brings the octopuses to the area, but why? Do the eggs develop more quickly at higher temperatures? Why is warm water seeping out of the seafloor here? These are all questions we are hoping to answer with continued research at the site. MBNMS Research Coordinator Andrew DeVogelaere, says they plan to return with E/V Nautilus again in October and hope to continue to answer some of these questions.

Below is a video showing the octopus garden on NOAA’s E/V Nautilus.

Updates from researchers on the R/V Western Flyer:

Sunday, April 21, 2019
Senior Scientist Jim Barry

Deep-sea coral observatory

Along with the sanctuary and other collaborators, studies of deep-sea coral and sponge communities at Sur Ridge are becoming a focal area for collaborative deep-sea research around Monterey Bay.  As one element of this partnership, MBARI is initiating a “Deep-Sea Coral Observatory” to help understand various processes that influence the biodiversity, productivity, and vulnerabilities of species inhabiting the coral ecosystem at Sur Ridge. The observatory includes a suite of instruments including current meters that will characterize the flow patterns across the ridge and sediment traps to measure the composition and abundance of sinking organic debris from surface waters. This debris is the major food resource for these deep-water communities. Time-lapse cameras will document changes in the biodiversity of key study sites, and traditional and new sensors will document changes in some physical parameters (pH, O2, temperature, salinity, and chlorophyll) and, we hope, the reproductive and biological condition of corals under observation. Expeditions to the ridge will be used for a variety of focused studies and experiments to understand the growth, survival, and sensitivity of corals to competitors, predators, and human activities, including climate change.

You can bet that we stand to learn quite a bit about the hidden lives of deep-sea coral communities, from the importance of food sinking from above to their vulnerability to changes in ocean conditions associated with climate change.

Updates from researchers on the R/V Western Flyer:

Saturday, April 20, 2019
Senior Scientist Jim Barry

Deep-sea coral discovery

Unlike shallow water coral reefs that are accessible in most tropical reef areas, deep-sea corals are typically remote and inaccessible due to their great depth, often hundreds to thousands of meters beneath the surface, as well as far from shore. So, even though deep-sea coral ecosystems occur in deep rocky habitats across the world ocean, most are rarely seen by humans. A few years ago, scientists Andrew DeVogelaere from the Monterey Bay National Marine Sanctuary (MBNMS) and I discovered thriving and diverse deep-sea coral and sponge communities only 64 kilometers (40 miles) from Moss Landing on the Central California coast at a site called Sur Ridge, a discovery resulting from a bet between these two friends.

For years we worked together on various projects and had long speculated about the type of seafloor biological communities we might find at Sur Ridge. Although there had been no sampling of the ridge, Andrew thought there might be some deep-sea corals, but I thought the ridge was likely to be covered in mud, preventing corals from thriving there. A few years ago, we were on a cruise to study ecological changes associated with a sunken shipping container that had fallen from a ship during a storm and found by chance during an ROV survey by my research team. After several days of ROV dives to study the container, we had an extra day of ship time and decided to explore Sur Ridge­—to settle the bet, but more importantly, to learn something about another region of the Monterey Bay National Marine Sanctuary.

Using the best maps available at the time, we chose the steepest section of the ridge to start, hoping there was some exposed rock formations. Watching the video monitors as the ROV landed on a muddy bottom in 1,250 meters (4,101 feet) water depth, it initially looked like the corals were absent. But when the ROV moved toward the steep slope, the ROV ran, almost literally, into a rock wall—covered with colorful corals and sponges. Happily, DeVogelaere won the bet, but we all win due to the relative ease in studying this special site. Surveys over the past few years have led to Sur Ridge being designated as a Sanctuary Ecologically Significant Area (SESA).

MBARI Cruise Participants

Other Cruise Participants:

Presley Adamson, Monterey Bay Aquarium; Erica Burton and Andrew DeVogelaere, Monterey Bay National Marina Sanctuary; Eve Pugsley, University California, Santa Cruz.