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WINTER 2014
C
oral reefs are the world’s largest biological
constructions and are among the most
beautiful ecosystems on Earth. They host a
huge portion of the ocean’s biodiversity and
are enormously valuable to humans both for tourism and
the sustenance of coastal populations. They are the result
of slow but progressive hard-coral growth, which over
decades or centuries leads to established reefs.
Even in nutrient-poor waters, coral reefs can be
miraculously productive. The corals grow through the
activity of tiny algae, which live within the corals’ tissues
and photosynthesize the sun’s light. The corals protect
the algae and supply them with ammonium; the algae
in turn release sugars and other organic nutrients that
the corals use for food. These microscopic, pigmented
algae, known as zooxanthellae, also confer color to the
hard corals of the reef. The symbiosis with these algae
is obligatory for tropical stony corals. If the algae die or
are ejected from the corals (a phenomenon known as
coral bleaching), the corals die almost immediately and,
in most cases, without any chance of recovery. The loss
of these algal symbionts means the loss of the engine
that produces the corals’ food, and the corals become
immediately vulnerable.
REEFS AT RISK FROM SUNSCREENS
Many factors threaten corals, including physical damage
from anchoring, fishing with explosives, excess heating
of the ocean’s surface and pollution. Somewhat recently,
a new emergency has been added to the list of the top-
10 threats to coral reefs around the globe: sunscreens.
Scientific investigations conducted at several reefs
around the world — in the Caribbean, Fiji, the Red Sea
and the Coral Triangle — indicate that the effects are
almost immediate and generally lead to coral death
within 48 hours.
Approximately 30 percent of the sunscreen that
has been spread on a person’s skin is released into the
environment when the person enters the water. Even
a single drop of a sunscreen containing problematic
chemical filters and preservatives, which are present in
more than 99 percent of the products available on the
market, can provoke bleaching and kill the coral.
Most commercially available sun-care products are
harmful to corals, and the effect is not dose-dependent.
The sunscreens activate viral infections that are generally
latent, similar to the mechanism by which herpes appears
on humans’ lips (cold sores) in the presence of ultraviolet
(UV) light. It is an on/off mechanism determined by the
compounds contained in the sunscreens.
THE NEED FOR LEGISLATION
Unfortunately, adequate legislation is lacking in most
countries, including the U.S. Before sunscreens can be
sold, they must be shown to be dermatologically safe
and to have an actual ability to protect the skin from
UV light, but they are not subject to any environmental
regulations. A notable exception to the lack of
restrictions is in Mexico, where the use of sunscreens
is banned in the cenotes (limestone caverns), which are
popular with tourists.
BE WARY OF “SAFE” SUNSCREENS
A research team at the Polytechnic University of
Marche in Ancona, Italy, tested several sunscreens,
and all had significant impacts on marine life. Especially
concerning are products that claim to be safe for
corals because they are biodegradable. These products
confound consumers by suggesting that biodegradable
is equivalent to environmentally friendly, but this is not
the case. Even products that degrade rapidly in seawater
remain in the system long enough to kill any corals
they come in contact with. This was exactly the case
with one product the team tested, and it’s one of many
B Y R O B E R T O D A N O V A R O , P H . D .
Sunscreens Linked
to Coral Bleaching
WATER PLANET
STEPHEN FRINK
