Dr. Jim Barry (MBARI) has a novel idea: one way to sequester, or trap, a source of CO2 might include sinking sources of cellulose that are normally burned on land, like this corn bale.

Crabby Test Subjects

After an early morning "jigging" for Humboldt squid with a Hopkins Marine Station (Stanford University) Ph.D. student and my Monterey Bay National Marine Sanctuary colleagues, the first order of business was to retrieve an instrument called a "benthic respirometer." This car-sized contraption was placed at a mind-boggling depth of 10,500 feet (3,200 meters) just two months ago by MBARI's Dr. Jim Barry.

In October, galtheid crabs (squat lobsters) were placed into respiration chambers by the ROV. Every four hours, the oxygen levels are dropped at varying rates before being flushed with fresh seawater. These numerous intervals give an average respiration rate for the crabs, which served as a baseline for the addition of seawater with a higher than normal amount of carbon dioxide (CO2), which was pumped from bags on the respirometer.

The benthic respirometer sitting on the aft deck after it surfaced from 10,500 feet. The cylinders on the bottom are the respiration chambers that contained the galtheid crabs. The red box contained the bags of seawater enriched with CO2.

This experiment tested the crabs’ tolerance to high CO2 levels, extrapolating what is currently taking place in the world’s oceans. Each year, about 1/4th of our CO2 emissions are absorbed through the sea surface.  That extra CO2 reacts with ocean waters to make the oceans more acidic. Deep-sea animals cannot tolerate a rapid rise in pH, and they will be among the first to suffer dire consequences if humans don’t take steps to abate CO2 emissions over the next few decades.

Corny Research

“Doc Ricketts” only dove once today, to a site where Dr. Barry sunk a large “corn bale” in 2009. A corn bale is what is left from a corn plant after the ear of corn is harvested. This cellulose material is bound into a large (4 x4x8’) bale and is normally burned for disposal. Of course, burning this material puts more CO2 into the atmosphere, so Dr. Barry had an intriguing thought. Since there are very few deep-sea animals that can digest cellulose, why not sink a large corn bale as a way to “sequester” CO2, or prevent it from ever entering the atmosphere or ocean chemistry? It may sound crazy, but any idea to stymie climate change is worthy of exploration.

This bale sat almost two miles below the ocean surface, so it took more than two hours for the ROV to reach bottom. The talented ROV pilots had a difficult mid-water current to deal with, which was pulling on the umbilical, or the line that connects the ROV to the R/V Western Flyer. While compensating for this “pull,” the pilots sampled sediment around the bale, collected some galtheid crabs that were crawling all over this bale, and used an instrument called the “hokey pokey” to measure oxygen levels outside and inside the corn bale.

A galtheid crab sits on top of a corn bale, 10,500 feet deep.

According to Dr. Barry, these crabs actually can digest some of the corn bale, since their gut contains bacteria that produce cellulase, an enzyme that can break down cellulose. Now, while these crabs certainly aren’t adapted to corn bales thrown into the ocean by humans, there are occasional sources of cellulose, such as logs that were pushed out to sea by storms. That’s happened for millennia.

Crushed Cups

We almost forgot a tradition with these deep dives. Using Sharpies, visiting crew typically adorn styrofoam cups with names, designs, patterns, dates, etc. The incredible pressure more than 10,000 feet down crushed our cups to the size of a large thimble. It’s quite amazing to see the transformation, and it makes a nice gift or conversation piece for the office desk.

Once again, the day bid us adieu with another fiery sunset, followed by the first “green flash” that I have ever witnessed. Tomorrow, we explore a prominent submarine geologic feature called “Sur Ridge.”

— Chad

Yes, it's another photo of a sunset. They keep getting better, and besides, a "green flash" followed.

P.S.: “Popular Science” featured this expedition in its December 13 edition of PopSci.com.

Wandering Around Manhattan in the Dark

Without the constraints of a “to-do” list, we made two dives on Sur Ridge, a moderate-sized bump on the seafloor, about 28 miles offshore of Point Sur, CA. There have only been a couple of dives on this feature by a geologist about 10 years ago, but not in this area. We were the first humans ever to see this part of the seafloor. This feature is about 11 miles long and 3 miles wide, or about the size of Manhattan Island.

Now, the ROV only can see about 15 feet wide and might travel only a mile in a day. Think about it. It’s as if someone lowered you by helicopter into Manhattan, in total darkness. You turn on your flashlight and go about a mile forward. Now, tell me you can surmise what the entire island looks like? Most likely you didn’t see Wall Street, or Madison Square Garden, Rockefeller Center, maybe not even Central Park or even a Chinese restaurant, yet those exist on Manhattan, and you would’ve never know it after even a few “dives.” This is why scientists need to conduct many, many dives in an area to even begin to have an idea of what the ecology might be like.

An Unexpected Treasure

Today was a perfect example of how different an area can be from one end to the other.

In 2006, MBNMS and MBARI made many dives on the Davidson Seamount, an extinct underwater volcano that last erupted 9 million years ago. Davidson is much, much larger than Sur Ridge at 26 miles long and 8 miles wide. Its elevation is comparable to the Sierra Nevada Mountains at 8,000 feet tall, yet its summit is still 4,000 feet below the surface. Beautiful, rare, and slow-growing corals were found all over the seamount, but primarily near the summit. Why?

Corals are suspension feeders; the colony uses its individual polyps to grab particles of food out of the water. Since higher water flow means more food, corals are found on peaks, ridges, and areas of sharp slope change, as water is generally flowing faster up these features, bringing food with it.

So, we targeted high slope and ridged areas in the northern part of Sur Ridge. Although we had high expectations for this dive, what we saw blew our socks off. Corals immediately appeared on the screen, and following the ridge up to the summit, the volcanic rock was just covered with individuals of the majestic Bubblegum coral that rivaled the size of those found on Davidson Seamount. The diversity and density far exceeded our collective predictions, and they were continuous up the side of the ridge, a 300 meter change in elevation!

Large bubblegum corals growing on the northern side of Sur Ridge.

Everyone in the control room that wasn’t driving the ROV were either snapping photos, annotating the live map, taking digital frame grabs, or writing down data wildly. I think I saw a few people drool, too. It was observation like these that catalyzed the addition of the Davidson Seamount to the Monterey Bay National Marine Sanctuary in 2009, which protects the seamount, and its long-lived corals, from being disturbed in any way.

The Surprises Keep Coming

One of the tough decisions with exploration is “where to go next?” Although we probably could’ve found more large and diverse corals in the northern section of Sur Ridge, the decision was made to pick up the ROV and travel about 6 miles south. Again, we targeted an area with the sharpest rise in elevation, in hopes the observations would be similar to dive one.

They were not.

We were presented with a rising landscape, but oddly, most of the rock seemed to be sedimentary, and not igneous like in dive one. We saw mudstone and other relatively fragile rock broken up into shards and clumps, collapsed downslope or below outcrops. Very little to no coral. Why? These long-lived, slow-growing corals need a solid substrate upon which to grow on, and fragile mudstone doesn’t suffice. Despite the few small corals we did see, the dive was still informative, maybe not as “sexy” as the prolific corals from dive one. Personally, I found the geology fascinating, and the sponge density was still quite high.

Sedimentary rock formations at Sur Ridge.

Conspicuous Clams

Funny how sometimes the mundane can surprise you. There was just about an hour left in the dive, cruising south along the top of the ridge, when Dr. Jim Barry noticed a small white oval shape in the corner of the screen. I happened to be operating the ROV camera at the time, so I panned and zoomed to the object in question, and it appeared to be a clamshell. What’s a clam doing on Sur Ridge?

Well, that’s the reason why Dr. Barry recognized that small object in a sea of small objects. He’s a bit of an expert on vesicomyid clams, which is a special family of clams that have formed a symbiotic relationship with chemosynthetic bacteria that live inside its gut. It’s a complex chain of events, but essentially, these bacteria convert sulfides into energy for the clam. These sulfides only come from three known sources in the ocean (thus far): cold seeps, hydrothermal vents, and whale falls. Cold seeps area areas where fluid methane escapes through fissures in the rock.

Bacteria living within the sediment at cold seeps or colonies that digest whale bones use methane as their energy source to convert sulfates into sulfides, which are then in turn used by the symbiotic bacteria. Symbiotic bacteria near hydrothermal vents, on the other hand, use hydrogen sulfide that is coming directly out of the vent. There are no hydrothermal vents on this part of the coast, and although there are clams on whale falls, they are of a different species. That means a cold seep was near, so the hunt was on.

Vesicomyid clams half-buried within a "cold seep" on Sur Ridge.

Dr. Barry surmised that the clamshell just rolled downhill, and he was right, we traveled a bit up the slope and found several live clams half-buried in the sediment. The pilot then noticed four additional clusters of clams to the left, and it left Dr. Barry befuddled. He never would have expected cold seeps on this ridge. But, there they were, as plain as day. A somewhat giddy Dr. Barry requested a few clams be taken as samples so that he can verify their species, and there were several species within these clusters. This is a very exciting and important find.

One Last Treat

As our dive drew to a conclusion, it had one more spoil to throw our way, I noticed a small dark purple glob floating in the shadows and called it out. The ROV pilots oriented the vehicle in that direction to enable camera zoom. As I enlarged the creature, one pilot blurted out, “baby vamp!” Indeed, it was a juvenile vampire squid (Vampyroteuthis infernalis). No wonder these are made into stuffed animals.

A juvenile vampire squid (Vampyroteuthis infernalis) just a few meters above Sur Ridge.

Tomorrow is the last day of this extraordinary research cruise. Who knows what tomorrow will bring?

— Chad