Creatures in this underwater forest could save lives
DAUPHIN ISLAND, Ala. — It was 6 a.m. at the dock on a Tuesday in December, and the weather did not look promising. Fog hovered over the water, and the engine of the Research Vessel E.O. Wilson rumbled.
Our ship disappeared into the mist, and by 7:30 the crew, a team of biologists, chemists and microbiologists, reached its destination. The sun lounged on obsidian water, masking a secret world where land and sea swap places, and past, present and future collide. This is the underwater forest. Its unusual residents, shipworms and related marine organisms, could serve as incubators of unexpected medicines, churning out new lifesaving formulas and compounds that may not be found anywhere else on the planet. But first the group of scientists had to manage to dive 60 feet beneath the ocean’s surface to recover their unusual subjects, a task made more challenging by three days of uncooperative weather.
“Underwater forest” is not a metaphor — this is a not a coral reef or a sea grass bed that resembles surface woodlands but bona fide trees with roots and leaves. For thousands of years, this cypress grove — about two football fields long and 5 feet wide — lay silent, preserved within an oxygen-less tomb of sand and sediment. Then came Ivan.
In 2004, the hurricane, Category 5 before making landfall, ripped through the Gulf of Mexico, with winds up to 140 mph kicking up 90-foot waves. Ivan scooped up nearly 10 feet of sand from the seabed, awakening the sleeping forest beneath.
Now the forest whispers secrets of the gulf’s past environment and climate, and hints at its future. Few have seen it, and those who have intentionally keep its precise location secret. But they entrusted this group of scientists, led by Dan Distel, a shipworm marine biologist and director of the Ocean Genome Legacy Center at Northeastern University, with the highly guarded coordinates for the day’s expedition.
With a grant from the National Oceanographic and Atmospheric Administration, this group aboard the E.O. Wilson was the first to explore, document and study the shipworms and other marine xylophiles that moved into the forest when it emerged.
Shipworms, the scientists say, are critical for drug discovery.
A Place Like No Other
The forest was once a swamp about 100 miles inland. Its bald cypress trees, and their buttressed trunks as big as cars, supported a diversity of terrestrial life. But now it shelters grouper, red snapper, mantis shrimp, crabs, anemones and other sea dwellers. And for shipworms, it’s an all-you-caneat buffet.
“This is sort of like a wooden whale fall,” Margo Haygood, a molecular biologist at the University of Utah, said before the trip; a whale fall is a dead whale that sinks to the seafloor. Life erupts around it.
Haygood has studied giant shipworms in mangroves in the Philippines with Distel. But they have never seen anything like this. No one has.
The sunken forest is larger, farther from shore and older than anything remotely like it. And as novel habitats and money for drug discovery dwindle, and with antibiotic resistance, new diseases, infections and age-related illnesses rising, the research team thinks it has everything to uncover new drugs.
Like wildflowers after a fire, diversity blooms as new habitats are established. In the early stages of settlement, when everything is still fighting for space, territory disputes kick up a lot of chemistry. And while sifting through it all, Haygood thinks there’s a better chance for finding nontoxic new drugs that work well.
Shipworms appear to be good drugmakers, and while studying them elsewhere, the team has discovered compounds that are now making their way through the early stages of drug development.
Their pharmaceutical talent might be explained by bacteria living in their gills, which send enzymes to the gut to help shipworms break down wood. Somehow, this process also leaves the gut nearly sterile, suggesting antibiotics might be at play. And Haygood says that any compounds they find have already gone through millions of years of pre-screening in the bodies of evolving shipworms. This makes them likely to be less toxic to humans than drugs that are whipped up in a lab.
Each species, they have found, has a distinct and different set of bacterial partners, or symbionts. In their view, every unstudied species, every specimen, is potentially an unopened treasure chest of unimagined chemical combinations. And a site like the underwater forest might be concealing millions of unknown bacteria.
Sailors named shipworms, which burrow into and devour wooden ships and dikes. But they are not worms; rather, they are elongated clams that grind into wood with microscopic teeth, and digest the wood with the help of symbiotic bacteria living in their cells.
Pholadidae, which resemble white grapes, are shipworms’ younger cousins. Somewhere during their evolution, pholadidae lost the symbiotic bacteria in their cells, along with their ability to consume wood. But shipworm-associated bacteria that potentially contain additional pharmaceutical gold could hitchhike on their bodies.
Then there are the bryozoans, a phylum of animals all its own. Bryozoans attach to wood but don’t eat it. Some colonies resemble gummy-ish lichens, but on closer inspection are woven squares. Each square, often smaller than the tip of a pin, is an individual animal. Its bacterial symbionts produce chemical defenses that protect the animal’s soft body and larvae. Some of these toxins and other compounds could be helpful in treating Alzheimer’s, cancer, HIV or pain.