Descending to a depth of 278 feet, the remotely operated vehicle (ROV) Mohawk arrives at a brilliant reef. Butterflyfish, wrasses, and grouper weave through coral bouquets of orange Swiftia exserta, white Muricea pendula, and purple Thesea nivea. Wrapped around the bright assortment of corals are basket stars and feather stars, latched onto branches for protection and access to nutrient-filled ocean currents. A barracuda jets by, appearing as a blur to scientists excitedly watching through glowing video screens at the surface. From the control room they direct the ROV pilot to a robust and extensively branching S. exserta — an ideal sample to represent the healthy coral population. While one ROV pilot keeps the machine positioned near the sample, another manipulates a mechanical arm with a joystick. Carefully extended, the arm collects a small portion of the coral and loads it into one of several storage compartments. The specimen has a long journey ahead — approximately 1,200 miles from the bottom of the Gulf of Mexico to the Smithsonian National Museum of Natural History in Washington, DC.
Scientists are collecting corals to better understand deep seafloor ecosystems of the Gulf of Mexico and to help protect these sensitive habitats. The 2010 Deepwater Horizon oil spill, which released approximately 134 million gallons of oil into the Gulf over 87 days, devastated seafloor organisms. S. exserta was one of the most impacted coral species. Scientists knew that recovery could be accelerated by human intervention, but they had a limited understanding of the role S. exserta and other corals played in the broader ecology of the Gulf. Dr. Heather Shull is part of a team at the Smithsonian working to fill that knowledge gap. “When we collect coral samples,” says Shull, “we learn about how seafloor communities are connected and which organisms, large and small, make their homes on these corals. All of this information helps us to know how these communities may react to changes in their environment.” Her efforts are a part of many Mesophotic and Deep Benthic Communities (MDBC) restoration projects, which restore seafloor ecosystems in the Gulf that were injured by the Deepwater Horizon oil spill.
MDBC projects are led by the National Oceanic and Atmospheric Administration (NOAA) and the Department of the Interior. The MDBC field season, from March to October, is planned a year in advance, when expedition schedules are determined by matching restoration priorities with vessel availability, and filling each voyage with experts to complete mission objectives. This is how Shull found herself aboard NOAA Ship Pisces with 12 other experts working alongside the ship’s crew. Each has unique expertise: in addition to coral biologists, there are scientists that study fish, hydrographers that map out the ocean floor, and oceanographers that study water chemistry. They use a wide assortment of instruments and tools to explore and understand deep sea environments. Key to collecting corals is the Mohawk, or “Mo-Mo,” as its pilots from the University of North Carolina Wilmington Undersea Vehicles Program (UNCW UVP) affectionately refer to it. This remotely operated vehicle, owned by the National Marine Sanctuary Foundation, navigates the seafloor while being piloted from the surface, allowing scientists to observe and collect samples. After collecting the branch of S. exserta, the machine spent six more hours gathering specimens from a previously unexplored area of the world.
After a successful mission, the Mohawk bursts out of a swell. The ship crew and ROV team are wrestling against the wind and the waves as they pull the machine from the deep in a carefully coordinated operation. Harnessed to the stern, the crew is focused on guiding the swaying machine, weighing 640 pounds, away from the rocking ship as it is adeptly lowered onto the deck by a crane operator. Despite the back and forth tumult, the Mohawk lands safely aboard. As the overflowing collection bins are opened, the biologists are greeted by a diverse assortment of colorful creatures. The bright orange branch of S. exserta is accompanied by several other coral fragments, packed alongside sponges, anemones, worms, and many other animals found at the seafloor. Some species were inadvertently transported to the surface, hitching a ride on a coral branch or a crustacean’s shell. These “hitchhikers” can include tendrilled basket stars, microscopic shrimp, and other organisms that call these surfaces home. With today’s ample catch, the scientists will be busy for hours. Each individual organism will be meticulously cataloged and processed in the ship’s wet lab, a critical step in documenting seafloor habitats.
First, specimens are individually photographed with a unique identification tag before preparation for future analyses. Documenting the appearance of each organism early is important: removed from the conditions of their natural environment, the appearance of these creatures will begin to change, and chemicals used for preservation will further degrade their colors. The S. exerta specimen, still vibrant, is photographed and then cut, providing two smaller pieces that get flash frozen with liquid nitrogen. Dry freezing the samples preserves the tissue for future genetic and isotopic analyses. The primary sample, that will eventually end up in Washington D.C., is stored in ethanol and kept at room temperature, while sub-samples are placed in the wet lab’s freezer. They will embark on a separate journey after leaving the Gulf. Working through specimens in this manner keeps the biologists busy for hours.
On this MDBC expedition, the team onboard NOAA Ship Pisces collected samples at seven different locations. In addition to exploring the depths with the Mohawk, there were around-the-clock scientific operations that kept the crew busy: the seafloor was imaged with an autonomous underwater vehicle, the depth and roughness of the seafloor was determined using multibeam echosounder surveys, and environmental conditions were documented by collecting water quality data. Not a moment went by without data being collected.
Needless to say, after 14 days at sea, each member of the crew was exhausted, but Shull’s job was far from complete. Every specimen needed to be prepared for shipment to the Smithsonian Museum Support Center in Maryland. To make sure the samples were not damaged on their journey, they were individually double bagged and heat-sealed before being gently packed into boxes. The last 24 hours aboard NOAA Ship Pisces were as bustling as ever, with the scientific crew preparing hundreds of specimens for their long journey ahead.
Only 36 hours after reaching port in Pascagoula, Mississippi, the branch of S. exserta arrives at the Smithsonian Museum Support Center. Here, wonders and relics from the farthest reaches of the globe are brought together and carefully organized on rows of seemingly endless shelves. The Invertebrate Zoology (IZ) collection is where corals and other deep sea creatures are processed. In this massive scientific repository there are approximately 50 million specimens, accounting for a third of all National Museum of Natural History holdings.
Once the S. exerta arrives, it is immediately unpacked and stabilized alongside other cruise specimens. Every specimen collected by the Mohawk is carefully cataloged with all of its collection data and given a unique museum number. Then it is transferred to an appropriate taxonomic expert who gives the specimen the most accurate scientific identification possible. They examine the specimens’ physical features, analyzing every inch of the coral, from the way its arms branch to its surface texture. Little is known about many of these marine species, so identification often involves sequencing a portion of the sample’s genome to better understand how it is related to other species. Shull notes that this can sometimes lead to novel findings: “We are discovering new species every year and learning about the community of organisms on the ocean floor in the process.”
Around the same time, the other samples taken from the same S. exserta branch are at Lehigh University in Pennsylvania and at a United States Geological Survey (USGS) laboratory in Florida. At Lehigh, genetic material is being analyzed to learn how this individual coral sample is related to other S. exserta populations across the Gulf of Mexico. At the USGS lab, tissue is being dried, ground up, and then shipped to UC Davis for isotopic analyses, to help scientists understand where S. exserta gets nutrients essential for life.
Back at the Smithsonian, Shull prints an archival label for the positively identified branch of S. exserta. According to Shull, “we want to preserve this specimen so that it can continue to be studied and add scientific value, often in ways that we can’t predict when we first collect it.” Every aspect of the archival process is designed to provide future scientists flexibility when looking up this particular specimen. The label uses ink that won’t fade with time, and includes the biological classification of S. exserta (Family Plexauridae, subphylum Anthozoa, phylum Cnidaria). It also indicates the precise coordinates and depth at which the sample was collected while describing that it was collected with an ROV. Most importantly, it includes a unique specimen number for the museum catalog.
The S. exserta sample, now called USNM IZ 1717497, is placed in a special airtight container with its label, preserved indefinitely in the Invertebrate Zoology collection. This is where Shull stores the sample away for future reference. While the sample helps guide restoration in the Gulf of Mexico today, there’s no telling when, or why, a scientist may need to look up this sample in the future. Future researchers will be able to use all the collection data. The information is inventoried in the NOAA Institutional Repository, and permanent archiving will help answer future research questions without requiring another trip into the field. Perhaps one day there will be a new coral disease spreading through the Gulf. Or maybe there will be habitat loss for many marine organisms due to warming waters. Whatever the case may be, this sample of S exserta will exist as a permanent physical record of the coral community in the Gulf of Mexico. It joins a far reaching collection of specimens that serve as a snapshot of an ever changing planet.