Coral Sponges and Our Eco-Future

Lindsey Deignan, a fourth-year Ph.D. student in marine biology, is demystifying the ocean floor. In collaboration with advisor Joseph Pawlik, as well as fellow graduate students, Deignan has uncovered new information about underwater ecosystems, by actually living among them.

Most of Deignan's fieldwork occurs in the Florida Keys, specifically Key Largo, where she has deployed twice as an aquanaut, living for 10 days inside Aquarius, a submerged research station roughly the size of a school bus. Her primary focus is coral reefs and the organisms that occupy them.

"Coral is a living organism," Deignan explains, "but corals are dying, at drastic rates. It's possible that even in my lifetime, a coral reef as we imagine it, as we know it, will no longer exist." CoralSpongesDeignan

As coral dies, it leaves behind its skeleton: a reef of calcium carbonate, which in turn draws microbes, sea urchins, small fish and, especially fascinating to Deignan, marine sponges.

"Sponges are important because, in the Caribbean in particular, they're one of the most dominant organisms on coral reefs," Deignan said. "Sponges are also a lot more diverse than coral, and a lot less is known about them."

In addition to cycling nutrients through the water column, which is how they feed, sponges can become a food source for fish, sea turtles and other invertebrates, as well as a habitat for small fish and crabs. They are also the subject of ongoing pharmaceutical research for cancer treatments.

"There are thousands of species, and they're always discovering more," Deignan reports. Not only do they provide valuable information through their own processes, sponges are key indicators of the state of the overall ecosystem.

Hence, Deignan's multiple forays underwater to study the organism. Typically, through a scuba dive, a scientist can remain underwater for no longer than an hour before rorced to resurface; deployment as an aquanaut, on the other hand, makes it possible to explore the ocean for upwards of eight hours a day.

"The number one benefit that you get from being under there is time spent on the reef," Deignan shares "You get at least a month's worth of work done in a weeK--you get to live underwater and look out the window at night to see fish swimming by."