updated 10/20/2010 3:51:34 PM ET 2010-10-20T19:51:34

Six months after the Deepwater Horizon oil spill crisis began, the first expedition to send humans to the deep sea in areas within reach of the oil gusher is under way in the Gulf of Mexico.

Researchers are diving to the ocean floor aboard a two-person submarine to take data and samples from the massive forests of coral that thrive in the frigid, perpetual night of the deep Gulf waters.

One target is located just 40 miles from the site where the Deepwater Horizon oil rig exploded on April 20, and lies beneath the once-visible oil plume.

A group of independent scientists aboard the Arctic Sunrise, a Greenpeace vessel, sailed from Gulfport, Miss., on Oct. 14 and will explore areas as far as 3,280 feet down. Their primary tool is the cherry-red Deep Worker sub — a stubby vehicle that would look at home in a cartoon. The submarine is equipped to capture invaluable data on the deep ocean waters and the coral that lives and grows in the darkness.

Hey! Down here!
Deep-sea coral are less famous than their warm-water cousins, but far more pervasive, said mission participant Steven W. Ross, a professor at the University of North Carolina in Wilmington.

"There are more species of deep-sea coral," Ross told OurAmazingPlanet, "and they cover more area. Part of the reason is the deep sea is just bigger than the shallower water environment," said Ross, chief scientist on the expedition.

It's also harder to reach, which means that although this coral is everywhere, comparatively little is known about the corals that live on the Gulf's floor.

The main target of study is Lophelia pertusa, a species of cold-loving, branching coral found in almost every ocean in the world. The bone-white coral builds towering mounds in the deep ocean, and can live for hundreds, even thousands of years.

An expedition that used unmanned vehicles to take preliminary data and images of Lophelia pertusa colonies in the same area returned just weeks ago, and "we didn't see dying coral and dead fish lying on the bottom, so that's encouraging," Ross said.

"So far, there are no real obvious signs that the reefs are suffering, so we're cautiously optimistic that they've dodged a bullet," said Sandra Brooke, a coral biologist with the Marine Conservation Biology Institute who is on the ship surveying the area.

However, Ross cautioned that the lack of heart-wrenching photos of oil-blackened reefs doesn't mean the corals escaped unscathed.

Invisible killers
The damage to coral could be taking place on a less obvious level.

"One of the things that have been documented in other research is that oil can cause corals to abort their larvae," said Brooke, who specializes in coral reproduction.

This is the time of year when the coral should be spawning, and Brooke will be using the submersible to see if the waters are full of eggs and sperm, and to gather coral samples for closer study under a microscope in the lab.

"Given the timing of the reproductive cycle, they should be packed with eggs and sperm," Brooke said. "If there's nothing in there, then that's an indicator there's been some kind of impact."

Both Brooke and Ross said with little evidence of dramatic mortality, researchers are turning their focus to these less photogenic, yet possibly equally deadly effects of the oil spill. Stifled coral reproduction is just one of many possibilities.

"It may be their growth has been stunted," Brooke said. "Maybe the water column has been impacted and maybe they're starving, just like human populations after a disaster."

Brooke said that since Lophelia act as oases of life on the ocean floor, providing food and habitat to a host of creatures, damage to the coral could have far-reaching consequences.

The scientists said they plan to return to land toward the end of this week, and will have more concrete findings on the health of the coral later this year or in early 2011.

© 2012 OurAmazingPlanet. All rights reserved. More from OurAmazingPlanet.

Photos: Month 4

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  1. The Blue Dolphin, left, and the HOS Centerline, the ships supplying the mud for the static kill operation on the Helix Q4000, are seen delivering mud through hoses at the site of the Deepwater Horizon Oil Spill in the Gulf of Mexico, off the coast of Louisiana, on Aug. 3, 2010. In the background is the Development Driller III, which is drilling the primary relief well. (Gerald Herbert / AP) Back to slideshow navigation
  2. Eddie Forsythe and Don Rorabough dump a box of blue crabs onto a sorting table at B.K. Seafood in Yscloskey, La., on Aug. 3, 2010. The crabs were caught by fisherman Garet Mones. Commercial and recreational fishing has resumed, with some restrictions in areas that were closed by the Deepwater Horizon oil spill. (Chuck Cook / AP) Back to slideshow navigation
  3. Sea turtle hatchlings that emerged from eggs gathered on the northern Gulf Coast of Florida are released at Playalinda Beach on the Canaveral National Seashore near Titusville, Fla., on Aug. 2, 2010. The sea turtles were born at a Kennedy Space Center incubation site, where thousands of eggs collected from Florida and Alabama beaches along the Gulf of Mexico have been sent. (Craig Rubadoux / Florida Today via AP) Back to slideshow navigation
  4. A crab, covered with oil, walks along an oil absorbent boom near roso-cane reeds at the South Pass of the Mississippi River in Plaquemines Parish, Louisiana on Aug. 1, 2010. BP is testing the well to see if it can withstand a "static kill" which would close the well permanently. (Pool / Reuters) Back to slideshow navigation
  5. A boat motors through a sunset oil sheen off East Grand Terre Island, where the Gulf of Mexico meets Barataria Bay on the La. coast, on the evening of July 31. (Gerald Herbert / AP) Back to slideshow navigation
  6. Oil approaches a line of barges and boom positioned to protect East Grand Terre Island, partially seen at top right, on July 31. (Gerald Herbert / AP) Back to slideshow navigation
  7. Oil from the Deepwater Horizon oil spill is seen near an unprotected island in the Gulf of Mexico near Timbalier Bay, off the coast of Louisiana on Wednesday, July 28. (Gerald Herbert / AP) Back to slideshow navigation
  8. Greenpeace activists stand outside a BP gas station in London, England, on July 27 after they put up a fence to cut off access. Several dozen BP stations in London were temporarily shut down to protest the Gulf spill. (Leon Neal / AFP - Getty Images) Back to slideshow navigation
  9. James Wilson sells T-shirts to those arriving in Grand Isle, La., for the music festival Island Aid 2010 on July 24. (Dave Martin / AP) Back to slideshow navigation
  10. Activists covered in food coloring made to look like oil protest BP's Gulf oil spill in Mexico City on July 22. The sign at far left reads in Spanish "Petroleum kills animals." (Alexandre Meneghini / AP) Back to slideshow navigation
  11. People in Lafayette, La., wear "Keep Drilling" tee shirts at the "Rally for Economic Survival" opposing the federal ban on deepwater drilling in the Gulf of Mexico on Wednesday, July 21. Supporters at the rally want President Obama to lift the moratorium immediately to protect Louisiana's jobs and economy. (Ann Heisenfelt / EPA) Back to slideshow navigation
  12. A flock of white ibis lift off from marsh grass on Dry Bread Island in St. Bernard Parish, La., July 21. Crews found about 130 dead birds and 15 live birds affected by oil from the Deepwater Horizon oil spill on July 19 in the eastern part of the parish behind the Chandeleur Islands. (Patrick Semansky / AP) Back to slideshow navigation
  13. Kenneth Feinberg, administrator of the BP Oil Spill Victim Compensation Fund testifies during a hearing before the House Judiciary Committee on July 21 in Washington, D.C. The hearing was to examine the claim process for victims of the Gulf Coast oil spill. (Alex Wong / Getty Images) Back to slideshow navigation
  14. An American white pelican has its wings checked during a physical examination at Brookfield Zoo’s Animal Hospital by Michael Adkesson and Michael O’Neill on July 21. The bird, along with four other pelicans, was rescued from the Gulf Coast oil spill and will be placed on permanent exhibit at the zoo. (Jim Schulz / Chicago Zoological Society via AP) Back to slideshow navigation
  15. Native people of the Gwich'in Nation form a human banner on the banks of the Porcupine River near Ft. Yukon, Alaska July 21, in regard to the BP oil spill with a message to protect the Arctic National Wildlife Refuge from oil development. The images include a Porcupine caribou antler and a threatened Yukon River Salmon. (Camila Roy / Spectral Q via Reuters) Back to slideshow navigation
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  1. Image:
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    Above: Slideshow (15) Oil spill disaster in the Gulf - Month 4
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