As we prepared to hit the water, the dive master told our small group that if we wanted to spot big game like a stingray or a whale shark, we’d probably have to look up, toward the sunlight.
Then he led us into the Caribbean off Puerto Rico’s south coast to the La Parguera Wall on my first deep-water dive.
The wall is a sharp plunge from about 60 feet to depths of more than 1,500 feet. Recreational scuba divers like me never go below 40 meters (130 feet). This dive, several years ago, took me within a few meters of that limit.
Light and pressure change rapidly as you descend. Every 10 meters, or 33 feet, adds the weight of one atmosphere to the pressure your body experiences. So it takes twice as much air to fill your lungs at 10 meters compared to what you need at the surface, three times as much at 20 meters, and five times as much at 40 meters. The deeper you go, the faster you exhaust your air supply — and the more quickly your body absorbs potentially dangerous levels of nitrogen. Deep dives are brief dives.
Clear, shallow tropical waters, like my favorite dive spots off Key Largo, Fla., are alive with bright colors. But water absorbs light, and it absorbs the short wavelengths first. So as you go deeper the reds disappear, then the yellows, then the greens, until finally all that is left is the deep blues and the deeper violets. It is no surprise that La Parguera is famous for its black coral. Corals have no need for bright colors in an environment where those colors are invisible.
At 121 feet I hovered a few feet off the wall, looking first at the dim spot of sunlight far above, and then down into the blackness. There is no physical barrier preventing a diver from trying to explore beyond the limits. You can fly a plane just so high before gravity and the plane’s limited lift stop you. But you can, if you choose, venture into the void below. If you quickly change your mind you can return to the surface, though you will be risking a horrible case of the bends. Beyond a certain point, the relentlessly increasing pressure of the water will crush the buoyancy out of your flotation vest, sending you in an uncontrolled plunge to a rapid death.
Nitrogen narcosis, the “rapture of the deep,” can set in unpredictably on deep dives. This is one reason to never dive alone. My head was clear, however, as I momentarily pondered the abyss before turning my attention back to the wall alongside me, the dive group in front of me and the fish schooling above. It was like flying high in the atmosphere, getting close enough to sense the proximity of outer space without entering it.
I have been thinking about my first deep dive lately as I read about the Deepwater Horizon drilling debacle in the Gulf of Mexico.
The runaway oil well sits in 5,000 feet (more than 1,500 meters) of water. At that depth the water pressure is more than 150 atmospheres, the temperature hovers just above freezing, and everything is pitch-black except where remote-controlled equipment provides tiny pinpricks of light. There is very little life down there, and the creatures that do live there — adapted to their exotic environment — almost never come in contact with surface-dwellers. An endless rain of dead organic matter filters down from the bright, warm shallow layers.
We have been hearing predictions of imminent environmental disaster for the past month. Not much has happened yet, though there certainly is enough gooey sludge floating on the surface to make a big mess, especially in the sensitive tidelands of south Louisiana near the spill.
Mostly, however, the blowout has become a giant and uncontrolled science experiment. It appears that much, perhaps most, of the spilled oil has been entrained in layers of tiny droplets far below the sea surface. We don’t know where it is going to go, we don’t know whether it will stay at those depths or will eventually rise to the surface, we don’t know how much will be consumed by tiny organisms (crude oil is an organic substance that eventually decomposes naturally), and we don’t know how much and what sorts of environmental damage it may do. We may, however, be far better off having the oil stay in the black, cold, lifeless depths, if that is what it ultimately does. The environmental damage may not be proportional to the amount of oil spilled, thanks to the fact that the spill is happening in such a desolate place.
Government scientists reported last week that a small portion of the spill near the surface had reached the Gulf’s loop current, which can be considered the headwaters of the Gulf Stream. Environmentalists fear that the current will carry damaging amounts of oil to my favorite diving spots in the Keys and onward to the tourist-crowded beaches of South Florida.
I hope not, and I doubt that anything very significant will come of this scare.
The Florida marine environment is hardly pristine to begin with. There was great excitement when tar balls were found near Key West last week, until lab reports proved the tar balls did not come from the Gulf oil spill. More likely they are detritus from passing ships. The reefs off Fort Lauderdale are littered with old tires (placed there in a harebrained 1970s scheme to improve fishing!), and the Keys waters are full of old wrecks. I have personally picked up lumps of coal from an 1890s shipwreck near Key Largo. The fragile undersea environment faces a lot of threats, but I don’t think the fatal blow will come from an oil well hundreds of miles away and thousands of feet below.
The Deepwater Horizon accident will be litigated and studied for years, or more likely decades. It will clearly do significant harm even if we cannot yet know what, where or how bad the damage will be. It is going to constrain and delay undersea oil development. Yet, more than anything else, it may educate us about a strange, otherworldly place that we have scarcely visited, and which most of us can only safely imagine from a depth of 40 meters or less.
May 26, 2010 - 12:15 pm
We’ve learned a lot about the long term environmental effects of disastrous oil spills. Unfortunately, it doesn’t make the headlines. Thirty years ago an oil spill in Mexico’s Campeche Sound released 3.3 million barrels of oil over a 10 month period. It appeared to be a doomsday event. The first year was devastating for wildlife including malformations in their offspring. But scientists were taken by surprise when two years later the marine environment had recovered (including the shrimp industry), thanks to oil eating microbes.