Identifying targets and making discoveries - AUV SENTRY

AT 42-05 | 26 November 2018

Identifying targets and making discoveries - AUV SENTRY 

Exploration and discovery in the deep ocean requires a lot of planning. The ocean accounts for 71% of Earth’s area. The deep ocean, defined loosely here as depths 1000m and greater, accounts for a disproportionate amount of the ocean volume yet most of this habitat is completely unexplored. Earth’s “inner space” is thus a frontier for discovery.

The entire ocean floor has been mapped (remotely) at a resolution of 5 km, meaning we can visualize features larger than 5 km (~3 miles). For context, this distance is just shy of double the length between the Lincoln Memorial and the Capital Building in Washington DC (~3 km or 1.9 miles). Imagine trying to navigate your way through a city if your map only contained landmark that more than 5 km in length! 

Only about 0.05% of the seafloor has been mapped using high-resolution sonar, meaning that for the vast majority of the deep sea, features less than 5 km in size are invisible. Thus, when working in the deep sea, a significant challenge stems arises from the lack of high-resolution maps. Such maps provide geological context and provide insight into potential chemical and biological characteristics to help target features/collections of interest. High-resolution mapping is thus a fundamentally important component of both science and exploration missions. 

So, how do we obtain high-resolution maps of the seafloor? Maps having better than 5km resolution can be obtained using shipboard multibeam sonar surveys. But, the highest resolution maps can only be obtained through near-bottom mapping and that is best done using autonomous underwater vehicles (AUVs). These AUVs are equipped sophisticated instrumentation and sensors that generate data that allow comprehensive habitat characterization. On this expedition, we are fortunate to have the AUV Sentry on board.

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The AUV Sentry is an asset of the National Deep Submergence Facility at Woods Hole Oceanographic Institution. Sentry is a flexible platform that comes with exceptional mapping capabilities and an impressive suite of chemical sensors. The vehicle is rated to 6,000 m (19,685 feet) making more than 90% of the deep ocean with its reach.

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Sentry has a multibeam sonar, a chirp subbottom profiler, and three high precision magnetometers for mapping. The vehicle also has a Seabird CTD (conductivity, temperature, depth) and a number of sensors including, optical backscatter, oxygen, and oxidation-reduction potential. Project specific sensors can be incorporated into the vehicle, as possible. Finally, the vehicle has a high quality digital still camera that allows it to collect images that can be stitched together to create photo mosaics.

The Sentry dives at night while the ALVIN dives during the day. The Sentry team generates maps that we use to plan and execute dives with the ALVIN as well as work in the water column. These maps help us hone our dive plan and more often than not, the maps identify new targets to explore and sample. The coordinated efforts of the ALVIN and Sentry teams accelerate our ability to explore these deep sea hydrothermally-impacted habitats.

Sentry data informs every aspect of our science. Sentry data also helps us identify targets for water column exploration. Combining the bathymetric data with the data from chemical sensors generates incredibly informative maps that show hotspots of fluid discharge. By programming the vehicle to do vertical as well as lateral profiling, we obtain a three dimensional representation of these dynamic environments. The data show how hydrothermal fluids propagate through the system at sites we know.

More importantly, we can discover new targets in new areas and plan future research around those finds. The area on the left of the image below remains unexplored but is clearly a worthy target. We plan to visit this site in February 2019, when we return to the Gulf of California.

Five. Thousand. Dives.

AT 42-05 | 25 November 2018  

Five. Thousand. Dives. 

The ALVIN is an incredible tool for doing deep ocean science. This versatile human occupied research vessel gives us eyes on the bottom and provides an unmatched perspective and appreciation for the habitat. ALVIN celebrated its 50th anniversary in 2014 and 25 November 2018 marked another incredible milestone: ALVIN dive 5000. So much history has been made in the ALVIN, I am so thrilled to be a part of dive 5000.

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As odd as it may sound, I feel at home in the ALVIN. I am always excited and eager to have the opportunity to dive. I find myself bubbling over with energy, wondering what we will see and imagining we will discover. I still find it incredible that diving to the bottom of the ocean is a part of my job.

Today for dive 5000, Andreas Teske and I will be exploring sites in the Guaymas Basin. ALVIN working at the bottom is a very efficient and impressive – if not jaw dropping – thing to be a part of. I find myself awed when the pilot pulls off a circus maneuver to get precisely the sample we needed.

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What is it like to dive and work in the ALVIN? In a word, it is intense. We embark on a dive with a long list of tasks to complete and samples to collect. Dive plans are always ambitious because we have to make the most out of every sampling opportunity on the bottom. The work we do at the seafloor involves using ALVIN’s robotic arms to collect samples and deploy instruments. It is an incredible operation to witness and getting to the point of sampling is a complicated process (see Sentry ‘mapping the bottom’ blog for context).

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Today’s dive was incredible. Not because it was dive 5000, but because it was a discovery-filled, jaw-left-agape ALVIN experience. I still cannot believe what we saw today. We worked a part of the Cathedral site that we have studied before and that area was stunning enough. And then we went exploring and it was beyond fantastic.

We saw a sonar reflection and headed towards it. What we found there was a massive flange with numerous venting chimneys surrounded by a large field of Riftia and microbial mats.

The terraces were amazing. Mineral towers rose from the base in a variety of shapes and forms. Three large discharge points were clear and even more visible upon close inspection. It was a sight to see. We sampled four types of discharge chimneys on this dive. Consolidated sediments that were saturated with oil. Oil saturated metal sulfide chimneys and cleaner metal sulfide chimneys from the terrace site.

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Fluid discharge from the mound generated shimmering water that obscured the features behind it. In one of the images, I realized later that an octopus was hidden behind the shimmering water. Do you see it? So many things are only visible in the pictures we shoot from ALVIN well after the dive. Often, I see something significant some time later.

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Given the significance of Alvin dive 5000, we took several pictures commemorating the event at the bottom of the Guaymas Basin. We took this picture at the edge of the terrace, where the Riftia field began. I have never seen so many Riftia – the field went on as far down the fissure as we could see.

After the dive, we had a celebration on the surface. ALVIN once again delivered a bountiful collection of animal, rock, and microbiological samples. It was an incredible day.

Dive 5000 dive team disembarks from ALVIN (L to R): Mandy Joye, Danik Forsman (ALVIN pilot), Andreas Teske (picture by Rebecca Rutstein).

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Dive 5000 dive team in front of ALVIN with signed 5000 logo (L to R): Andreas Teske, Danik Forsman (ALVIN pilot), Mandy Joye (picture by Rebecca Rutstein)

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STEAMing at the seabed...

AT 42-05 | 20 November 2018

STEAMing at the seabed…

The deep sea is such a magical place. I am always in awe of my surroundings. When I look through the ALVIN viewport and take in the dramatic beauty of these deep seascapes, my jaw is often agape. Still, I sometimes have a hard time effectively conveying the stunning majesty of these sites to others. One way to effectively communicate the beauty and dynamic of these sites to others is to work with artists. I am thrilled that an incredible artist, Rebecca Rutstein, joined us on this expedition.

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Rebecca shares my love of the ocean and is particularly fascinated by the deep sea. This expedition marks the fifth time she has sailed as an ‘artist at sea’ and this ALVIN dive marks her first visit a hydrothermal seafloor ecosystem.

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Rebecca and I met at a National Academy of Sciences Keck Futures Initiative workshop on “Ocean Memory”. She was subsequently awarded the Delta Visiting Chair for Global Understanding at the University of Georgia (UGA) and is the first artist to receive the award. She and I are collaborating on a project focused on Guaymas Basin and Rebecca already produced a number of Guaymas-themed works that went on exhibit in the UGA Museum of Art November 1st. Her exhibit will be on display for a year.

I am always excited when I climb the ladder down into the ALVIN. You never know what you will see and experience during a dive but you can be assured that you will see something you have never seen before (at least once). But, this dive is different – working with an artist has changed the way I see and think about things. The marriage of STEM (STEM=science, technology, engineering and mathematics) and art gives rise to STEAM. On dive 4994, Rebecca and I explored incredible areas around Cathedral Hill, deployed some new instruments, and observed amazing geology and biology. When we landed on the seaflloor and looked out the viewport, we saw a set of chimneys surrounded by Beggiatoa mats and some others that were covered in tubeworms as well as mats.

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On the seafloor, mats serve as a bulls eye, marking areas where energy-rich hot fluids discharge from the seafloor.

In Guaymas, the Beggiatoa mats are prolific – thick, widespread and colorful. I have blogged about Beggiatoa mats often but the mats in Guaymas are special. They are thick, expansive and full of metabolic surprises.

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The sharp edges of the mat demarcate changes in thermal and, hence, geochemical regimes. Similarly, the transition between colors – orange to white and/or yellow – likely reflects shifts in reduced sulfide concentration and flux. Sometimes, the mats have surprising topography that generates flow regimes that accentuate fluid flow. The biology we observe tells us a lot about the chemistry.

The Beggiatoa are large bacteria – visible to the naked eye and when viewed through a microscope, they resemble orange spaghetti.

These mats grow laterally along the seafloor and vertically upwards along the hydrothermal chimneys.

They take advantage of sulfide fluxes wherever they can get them and their colonization of geological features creates a magical patchwork of colors and topography along the seabed.

One of the highlights of the dive for Rebecca was seeing a hydrothermal chimney colonized by both Beggiatoa and Riftia.

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Riftia are giant tubeworms that ‘farm’ sulfide-oxidizing bacteria in an internal compartment called a trophosome. The bacterial symbionts in Riftia oxidize hydrogen sulfide, just like Beggiatoa, and they use this energy to fuel their metabolism and growth. Some portion of this production is siphoned off by the animal to support its own grown. These chemosymbiotic associations are common at hydrothermal vents and at cold seeps.

After a very successful dive, we returned to the surface full of energy and ideas and motivation. I am excited to see what art Rebecca generates based on the incredible things she witnessed during this dive!

Hot Stuff

AT 42-05 | 18 November 2018

Hot stuff

Hydrothermal environments are dynamic; things change often and they change fast. Understanding how microbial populations and activity are shaped by thermal and chemical gradients is one of our primary research objectives here in Guaymas Basin. These extreme habitats are an ideal place to search for new microorganisms and new metabolisms and to probe the temperature limits of life. Opportunities for discovery abound.

Alvin Dive 4991 was UGA PhD student Andy Montgomery’s first dive.

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We visited Cathedral Hill, a site that has been sampled before and one we know well. We landed a bit to the NE of the previous sampling area and found ourselves surrounded by beautiful small (1.5m) hydrothermal spires and even more small vents along the seafloor. Colorful Beggiatoa microbial mats carpeted the seabed around areas of hydrothermal seepage.

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This environment may seem simply beautiful, but it is extreme and challenging for the organisms that live here. We inserted a heat flow probe into the seabed using the ALVIN’s Schilling manipulator.

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Beneath the orange Beggiatoa mat, temperatures reached 67ºC at 25cm and were 99ºC at 50 cm beneath the mat (see the dark blue line and sensor T9 data on the temperature log figure). Life thrives along these extreme thermal gradients.

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Hydrothermal fluids moving through the sediments generate steep thermal gradients. These fluids are also enriched in reduced chemicals that provide metabolic fuel – for example, hydrogen sulfide, methane, and ammonium – for the microbial communities that live there. The colorful Beggiatoa mats oxidize hydrogen sulfide to sulfate and this sulfate provides metabolic fuel by other microorganisms that live in association with the Beggiatoa. Numerous feedbacks between elemental cycles exist, creating puzzles involving energy flows and metabolic exchanges for the science team to ponder and resolve.

Despite the harsh conditions along the seabed in Guaymas Basin we often see fish, eels and even octopus. We spotted a shy octopus watching us from a distance during this dive.

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Some animals – squid! – are attracted to the lights and curious and they often come up to the submarine to check it out. Others pretend to be invisible and sit still, hoping not to be noticed. This octopus fell into the latter category.

During the last part of our dive, something strange, something that was out of place. At the base of a chimney, a large white object caught my eye. It took me a moment to realize what it was … a large plastic seed bag. Yes, we found plastic trash at the bottom of the ocean in a beautiful hydrothermal vent field. This painful reminder underscores the reach of plastic pollution, which reaches the depths of the ocean basins and spoils sites like this. We need to be better stewards of the ocean and we all need to dial back our use of plastics.

 

Back to the Seafloor

AT 42-05 | 17 November 2018

Exploring the Guaymas Basin, Gulf of California

The Gulf of California is an active young ocean undergoing early phases of rifting, seafloor spreading, and hydrothermal imprinting. The hot, thick organic rich sediments, hydrothermal spires, and other geological oddities found at the seabed in the Gulf of California offer ideal locales to study extremophiles and search for novel microorganisms and metabolisms. On this expedition, our work will focus on the Guaymas Basin, located in the central area of the Gulf of California. The next two weeks are sure to be filled with beautiful, mesmerizing, and stunning seafloor scenes.

The UGA group – me along with Post Doc Guang-Chao Zhuang, PhD students Andy Montgomery, Hannah Choi, and Rachael Karns – left Athens before the crack of dawn. We met up with artist-extraordinaire Rebecca Rutstein at the Atlanta airport and boarded our flight to Hermosillo, Mexico. It was a long (18 hour) travel day. The next morning we met another UGA PhD student, Tito Peña-Montenegro, who arrived before us and together, we traveled to the port of Guaymas where we boarded the R/V Atlantis.

The R/V Atlantis, operated by Woods Hole Oceanographic Institution, is one of the most sophisticated sea-going research vessels in the world. The Atlantis is also home to the world’s most famous research submersible, the ALVIN. We loaded our gear onto the ship and spent much of the next 24 hours setting up the labs and preparing for our work. On this expedition we will be deploying in situ instrumentation at the seabed, collecting bottom water, sediments and rock samples using ALVIN, and sampling the water column – searching for hydrothermal plumes – using the CTD/Niskin rosette. Over the coming weeks, I will share stories about these aspects of our work.

Today (Saturday November 17th) will be the first dive of this expedition. We will be visiting Cathedral Hill, an area of extensive microbial mats and mounds that we have visited and sampled before. Why go back?? Well, in hydrothermal areas, the forces of nature interact dramatically and dynamically: geological fluxes drive chemistry and biology, biology creates it’s own geology and physics also plays a role. This means that things change, often in surprising ways. It is unlikely that things will be the same as before; instead it is very likely that things will be different. Changing flux regimes and pulsed perturbation are common in hydrothermal areas. While some organisms thrive in hydrothermal areas by being able to tolerate extreme conditions, others thrive by being able tolerate changing conditions and perturbation. Today, we will have a look and see how Cathedral Hill and a site nearby – Rebecca’s Roost – look now, compared to the last time we were here in 2016. 

Joining me in the ALVIN today is Andy Montgomery, a PhD student in my research group; this will be Andy’s first ALVIN dive. Andy studies chemoautotrophic microorganisms. Yes, chemoautotrophic is a mouth full but this term refers to microorganisms that use chemical processes (“chemo”, for example, microbes that oxidize ammonium, hydrogen, or carbon monoxide) to generate energy for growth. These microbes obtain their structural carbon from carbon dioxide (they convert carbon dioxide into biomass). In other words, Andy studies primary producers that live in the dark at the bottom of the ocean using nifty metabolisms that take advantage of the high fluxes of ammonium, hydrogen, carbon monoxide and methane. It is sure to be an incredible dive day followed about 24 hours of non-stop sample processing.

By the end of the expedition, we are sure to be a bit sleep-deprived. But, all the hard work and long hours are worth it. I’m excited about seeing new things, developing new ideas, and am sure that, by the end, I will be even more fired up to return for more sampling in February.