Spending a week doing scientific research offshore in the northern Gulf of Mexico in May last year meant a lot of work and some interesting wildlife sightings for Kathryn E. Appler of the University of Texas Marine Science Institute. Above: Dolphins ride the swell pushed ahead of the R/V Pelican’s bow. Right: Marine sediment cores stand aboard the Pelican, ready for sectioning and sample preservation.
Explaining to your friends and family you are going on a cruise makes it sound like a vacation, including sleeping in till lunch, sunbathing by the pool or playing shuffleboard on deck. Instead, I boarded the Research Vessel Pelican only to be happily covered in seawater and mud.
This scientific cruise in May 2023 was one of several investigating the impact of the summer low oxygen (hypoxic) zones on microbes in the water column and marine sediments. Low dissolved oxygen can be lethal or instigate the relocation of several economically valuable macro-organisms (fish and shrimp).
These sites, including the northern Gulf of Mexico, are often called “dead zones” and are created by several factors, including nutrient pollution and increased stratification in the warmer summer months.
The composition of the microbial community can help us understand which microbes consume oxygen, potentially impacting the persistence of these hypoxic zones. Other microbes, including archaea and bacteria, can thrive and survive in low or no oxygen. Understanding microbial diversity and activity can help scientists understand and potentially mitigate these events.
Photos by Kathryn E. Appler
Long before hopping on board, cruise prep involved spending long hours collecting chemicals and calculating the number of gloves, tubes and pipette tips for sample preservation. Loading all our gear and personal belongings into a crammed Kia Sport, we began our two-day trek from Austin to Cocodrie, Louisiana. After securing all the delicate equipment onboard, we fell asleep, anticipating the beginning of our voyage.
Before dawn, geared up in orange safety vests, helmets and steel-toed boots, we headed to the multi-corer, consisting of a metal frame and several plastic tubes to collect sediment. Standing on the base to keep it level, we maneuvered it over the edge, stepping quickly back on the boat before it dropped about 20 meters out of sight. As the A-frame hit the bottom, the cables snapped back, and the cores (plastic tubes) snapped closed, collecting the mud. Then, the frame raised back up on deck as all the crew and researchers hustled to secure the swinging frame.
Kathryn E. Appler is a Ph.D. candidate at the University of Texas Marine Science Institute, describing the diversity in deep-sea hydrothermally-active sediments and unraveling the evolutionary and environmental roles of Asgard archaea.
When the multi-corer was secured, we released the tubes and began sectioning the cores for various research projects. Once the mud was onboard, the clock started to preserve as much as possible, rapidly scooping mud with sterile spatulas into pre-labeled tubes. We froze several vials immediately and kept the rest on ice before preservation, specifically to reduce the loss of DNA and RNA, which rapidly degrade.
After deploying the multi-corer once or twice, we spent the rest of the day in the wet lab, continuing preservation steps, labeling tubes and making notes about the sites. With the rocking, it was easy to get into a rhythm working at the bench, under the fume hood and on the deck. We repeated these steps at five sites.
After each successful sampling day, we joined another team of researchers to enjoy our temporary life at sea. This included fresh fish tacos and paella made by the incredible onboard chef, which rivaled any vacation cruise. We soaked up the sun and the spray from the waves on the bow, spotting dolphins, sharks and turtles. One rare sighting was a newborn dolphin with “fetal folds.” These are temporary marks from the mother’s rib cage that typically fade shortly after birth. After every day, we spent our nights watching the stars and passing oil rigs as we traveled to our next sampling station.
Returning to port, we safely secured our precious scientific cargo, packing our Kia Sport to the brim with coolers filled with mud. We said goodbye to the incredible crew and researchers with a night enjoying views of the bayou.
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