With the temperature teetering just below freezing, Jacob Perkinson diligently knocked ice and snow off concrete molds.

The Tandem Friends School senior could have enjoyed the snow day and stayed home like thousands of other area students, but he had work to do. The 17-year-old braved the frigid elements in order to keep his project's timetable on track.

Since last fall the Albemarle County resident has been making concrete reef balls that he hopes will help oysters make a comeback in the Chesapeake Bay. In June he plans to place 300 of the specially designed objects in the coastal waters off Smith Island.

The hope is that the cone-shaped balls will become home for oysters and, in so doing, will help reconstruct the once healthy oyster reefs. Jacob is working closely with Allied Concrete, which is donating all the materials and equipment. The Nature Conservancy is overseeing the project.

The Reef Ball Foundation is coordinating the effort and providing the expertise for creating the concrete objects, which look something like large, gray Wiffle balls. The foundation also will monitor the balls after they're in place.

"Every senior at Tandem does a senior project, so last spring I was looking around for an opportunity to do something," Jacob said as he took a break from his work.

"One of my friends' dad, Gus Lorber, was looking for a student to lead this project. It appealed to me, because I wanted to do something that would be hands-on.

"I also wanted to get involved with conservation, which is something I care about. Gus is the [president] of Allied Concrete, and he has given me all the concrete and material and has done everything for me."

A few times a week, Jacob refills the seven reef ball molds with concrete. It's a process that usually takes two or three hours to complete. Occasionally, he'll get a hand from classmates Matthew Jones and Katie Studholme, but for the most part he has been working alone.

This past summer Todd Barber, chairman and founder of the Reef Ball Foundation, drove up from his home in North Carolina to show Jacob how to make the balls. It isn't a difficult process, but the young conservationist learned that it does take some practice to master the operation.

"I have a concrete mix design which tells me the ingredients and all the proportions," Jacob said as he showed a visitor around his work area on the grounds of Tandem, where his father, Paul Perkinson, is the head of the school.

"I use gravel, sand, Portland cement and a few chemicals in the mix. The air compressor is used to fill the inflatable ball that goes in the middle of the mold to create a void. After the concrete sets up, I deflate the balls and pull them out.

"A lot of the ones I made in the beginning broke, because I filled them too high. That didn't leave enough space to get the ball out, so I had to break them open. Now that I've got the hang of it, that doesn't happen."

A lot of scientific thought has gone into the design of the reef balls Jacob is making. His are designed to help oysters, but reef balls come in many different sizes and shapes depending on how they're going to be used.

"The basic concept was that we wanted something that would be the base to form a natural reef," said Barber, who founded the nonprofit Reef Ball Foundation in 1993. "We came up with the designs based on all the criteria the different scientists who were working with us provided.

"Criteria such as not moving in a hurricane and using inert concrete so nothing would leech into the ocean. It had to be pH-neutralized so corals and oysters would grow on it. It had to create whirlpools to feed the corals and oysters better, and it had to have a certain percentage of void space to be able to house fish inside.

"And they had to have special surface textures to enhance the settlement and growth of hard corals and oysters. And we wanted something that if put in the water and left there long enough would become indistinguishable from a natural reef."

Barber's interest in helping re-establish reefs dates back to 1989. From the time he was old enough to put a scuba tank on his back, Barber has been an enthusiastic diver.

"My family would vacation in the Cayman Islands, and I started taking pictures of a little coral reef," Barber said during a recent telephone interview from his home in Greenville, N.C. "I did that every year to see how fast the coral grew.

"When I went back in 1989, I discovered that a hurricane had wiped it out. That [made me so angry] that I decided to do something about it.

"It took us about four years to develop something, and we got the first reef balls in the water in 1993. That same year I founded the foundation."

Barber and a paid staff of 100 employees, as well as countless volunteers like Jacob, have been hard at work ever since. To date the foundation has placed about a half million reef balls in waters around the world.

There are more than 4,000 reef ball projects under way around the globe. Although more than 55 countries are involved in the effort, coral reefs continue to die at an alarming rate.

"I've been working at this for 18 hours a day for the last 15 years without a vacation, because I'm passionate about what I'm doing," Barber said. "In that time, we've restored a little less than 1 percent of the reefs we've lost.

"We're still losing, but I'm an eternal optimist. I really believe through technology and continued smarts, we'll be able to think our way through this as long as we get enough people to understand what the problem is.

"I think the word is getting out, and developed countries like the United States are becoming more and more aware of how important reefs are to the environment. But the poorer the country is, the less likely they're going to know about this or do anything about it, because they're more worried about things like feeding their kids than they are about the oceans."

Barber said all the coral reefs in the world would fit into a space the size of South Carolina. The 43-year-old said that in his lifetime we have lost 30 percent of them.

Coral reefs play vital roles in the ecosystem by creating buffers, which keep beaches in place and give fish and other marine life like oysters a place to live. Barber said if all the reefs in the world died, we would lose about half the species on Earth.

Coral reefs also serve as one of nature's sentinels, giving early warning that something in the ecosystem is going awry. In this case, the imprint of human civilization is largely to blame.

Many people picture coral reefs as simply picturesque rock-like formations on the ocean floor. In fact, corals are living animals that when born are able to swim in order to find suitable fixtures to attach themselves to.

Once permanently affixed, corals develop a skeleton. These easily can be damaged by a careless diver, but changes in their environment appear to be causing the greatest damage.

"Corals are basically used to very stable conditions, constant temperatures, no pollution," Barber said. "Whenever there's a change, the corals are the first to die, because they're so sensitive to change.

"If you take a map of human population [density] and overlay it on top of all the reefs of the world, wherever there's more people your reefs are in much higher danger and have gone extinct much faster.

"Wherever there are very few people, the reefs are still in pretty good shape. What I often tell people is that reefs are allergic to humans."

The loss of oysters in the Chesapeake Bay is partly due to a virus called vibrio vulnificus. The Virginia Institute of Marine Science is involved in an effort to repopulate the bay with oysters that are immune to the virus.

Bringing healthy populations of oysters back to the bay shouldn't just be a concern to people who harvest and eat them. Oysters serve as wonderful filtering systems in polluted water and are a necessary component in the effort to save the bay.

One bright light in all the gloom is the fact that corals and oysters love to adhere themselves to concrete. Scientists haven't figured out exactly why this is the case, but they have some theories.

"There seems to be something about the calcium and the silica in the concrete that attracts marine life and gives it a good base structure," Lorber said. "Right now the Virginia Institute of Marine Science is using smaller versions of the reef balls in tanks to raise oysters that are resistant to the vibrio virus.

"We're hoping they will put some of them into the system that Jake is going to be putting into place off Smith Island. One of the things I really like about this project is the synergy that's involved.

"You have school kids like Jake building these things. Government agencies get involved, because they usually have the land and the ability to give permits. And then you have an organization like the Reef Ball Foundation that coordinates things and will monitor the projects once they're in place."

The foundation's Web site has more than 50,000 pages of information on reef-related topics. It also has a wealth of photographs that follow the progress of reefs after they're in place.

"One of the most important aspects of the foundation is education," Barber said. "Sometimes the act of building a reef is much more important than the reef itself, because people learn to protect them.

"Only 2 percent of us ever bother to put on a mask and snorkel and get in the water to look at this kind of stuff. So it's that 2 percent who have to tell the rest of us what's going on down there.

"If we were burning down all our trees like we have killed the corals, everybody would be screaming about it, because everybody would see it. But not that many people see the corals and so education is really important so people understand what's happening and how quickly we are depleting this resource."

Because the foundation posts all the results it gets from projects on their Web site, be they good or bad, Jacob will be able to keep an eye on his project for years to come. He was thinking of the future as he warmed up with a well-deserved cup of hot chocolate.

"I hope what I'm doing will make a small difference," Jacob said as he looked at the pile of reef balls he has made so far. "But more importantly, they'll be monitored to see how much they help.

"That research will help further our knowledge about the most effective ways to restore oyster habitat. This is a relatively new method for providing them with a new habitat.

"A lot of the research that's going to be done on reef balls will be done on projects like mine. My hope is that someone will continue this project next year."

Follow Jacob's project and find more information on reef balls at www. reefball.org.