hink of reefs
as rain forests of the seafloor.
Like the towering trees of the rain forest, reefs support an
extraordinary diversity of species. Like trees of the rain forest,
they often take centuries to mature. And like the rain forests, they
are in peril.
Pollution, temperature change, dredging, ship groundings,
commercial fishing, even recreational diving — all have wreaked
havoc on reefs.
Artificial reefs can't eradicate the causes of reef destruction,
but by adding structure to the seafloor, they provide shelter for
fish and a place for plants and coral to grow.
They also divert anglers and divers from fragile natural systems
by providing new destinations for sport. An artificial reef
fashioned in the shape of the Southern Cross that serves as a
snorkeling trail has eased traffic and reduced damage to
Austrailia's Great Barrier Reef.
Artificial reefs are not
a new concept, but only in the past 20 years have they become
friends of the marine environment. The first artificial reefs were
made from tires, appliances, sunken ships, junked cars, culverts and
rain forests, the world's coral reefs are in
Many do more harm than good. Tires wash ashore. Appliances, cars
and ships leak harmful chemicals. Heavy objects damage natural reefs
as currents toss and turn them over the seafloor. Today, only
concrete and heavy-gauge steel are allowed in most U.S. waters.
Deliberately sunk ships must be thoroughly cleaned before they are
left to drown.
Structures are now being designed specially as artificial reefs,
and stable, non-toxic concrete is the material of choice. The
ReefBall, created by Florida diver Todd Barber, is a squat, concrete
dome with lots of holes. The structure comes in eight sizes, the
smallest of which is about the size of a basketball.
The holes in the concrete provide cover for fish and marine
invertebrates. The rough sides allow plants and coral to cling to
the concrete. According to Barber, the ReefBall needs only a few
years in the ocean to be fully shrouded in sea growth. The ReefBall
also sits still on the seafloor, as most of its weight is
concentrated at its base.
Barber's company, the ReefBall Development Group, has planted
50,000 units around the world since 1993. The company sponsors reef
restoration eco-tours will even mix your ashes into an "Eternal
Reef" ball if your will stipulates it.
California to restore kelp beds have shown that even simple concrete
rubble can provide the right foundation. "We've found the bed has to
be at least 10 hectares (24.7 acres) for the kelp to persist," says
Dennis Bedford of the California Department of Fish and Game. "The
rubble piles have to low-relief. We found high peaks of rubble
concentrate kelp eating fish and inhibit kelp growth."
Development Group has planted 50,000 ReefBalls on the world's
seafloors since 1993.
Kelp will start to form on rubble piles within a year. In 15
years, an entire community will likely flourish.
Although artificial reefs no longer pollute or wash up on shore,
a troubling question remains: Do reefs increase fish populations or
make them easier prey for anglers?
Marine officials say artificial reefs provide more habitat and
increase fish populations. They also allow that angling harvests are
on the rise, effectively canceling the population growth.
"In some cases fish seem to prefer artificial reefs to
lower-relief natural reefs nearby, but they're moving into a baited
trap, because anglers know where the artificial reefs are," says Jon
Dodril of the Florida Division of Marine Fisheries.
Building mitigating artificial reefs when real reefs are damaged
doesn't address problems of pollution, nutrient runoff and
over-exploitation of the oceans, he adds.
"Artificial reefs are a
good management tool," says Dodril, "but you have to clearly
establish your goals when you construct a reef. You can't increase
fish numbers and creating a fishing spot. You have to choose one or
officials say artificial reefs provide more habitat and
increase fish populations. They also allow that angling
harvests are on the rise, effectively canceling the population