From high above, the Aquarius Reef Base looked something like an alien anthill. A small army of divers had descended on the structure to take care of some daily maintenance tasks, and all six aquanauts were shuttling samples and equipment back and forth from reef to station. Eventually, this would grow exhausting. “The pinnacle, where we sample, seems to get further away each day, particularly when the current gets ripping,” wrote one aquanaut on the station’s blog. “But then we get to ride the current back in, ‘Finding Nemo’ style!”
The team’s main focus was the Xestospongia muta, a giant barrel sponge that thrives in both acidified and nonacidified microhabitats. By monitoring pH and CO2 levels around each sponge, and taking tissue samples for later analysis in the lab, they hope to determine if those sponges that live in acidified waters have a different protein makeup that helps them adapt to, and even thrive in, these regions.
Some sponges lived in the crevices where pH was low; others lived out on the open reef, where pH was closer to normal. Slattery wanted to see whether the crevice dwellers had any special adaptations that their open-reef-dwelling cousins lacked. “It’s just like humans and the common cold,” he explains. “Some people go through the whole season without getting sick at all, and then others catch every little bug that’s been flying around. We want to see if there’s the same type of natural variation in sponges responding to acidification.”
They also transplanted paired sponges—from acidified and nonacidified habitats—to sites facing additional stress, namely temperature increases. The idea was to see what impact prior exposures to low pH had on the organisms’ health, and also to see what effects these environmental changes had on physiology.
Lastly, the team took a detailed census of the flora and fauna in various microhabitats, especially the acidified crevices, and collected samples of all the species they could. Like the sponge tissue, these samples would be assessed for protein expression to see if similar organisms behaved differently when they were exposed to lower pH.