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D I VE SLATE
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WINTER 2016
S
ome effects of marine pollution are visible,
such as the plastic garbage that often
litters reefs and beaches. Other effects are
similarly obvious, such as the brimstone
stench of a nearshore dead zone caused by
sewage and fertilizer runoff. Unfortunately,
marine pollution goes even further than most people
can easily witness, and these less-apparent aspects of
pollution have elusive but far-reaching consequences.
I first came to understand the significance of
sunscreen lotion in marine pollution during an
investigation into
declining coral reefs in
the U.S. Virgin Islands. A
local resident complained
to my investigative team
about an oily, iridescent
sheen on the surface of
the water that lingered
after the mass of tourists
had gone home; it was
supposedly caused by
sunscreen washing off
the swimmers. “Swimmer
pollution” threatens coral
reefs across the world, from the Gulf of Aqaba in the
Red Sea to the shores of Playa Hermosa, Costa Rica,
and almost everywhere in the Caribbean. Anywhere
humans get into the water on or near a reef is a
potential avenue for contamination.
Besides washing off swimmers’ skin and into the
water, sunscreen can get into the sea by other means.
Many sunscreen ingredients are readily absorbed
through the skin. Oxybenzone, one of the most
common ultraviolet-blocking chemicals in sunscreen,
for example, can be detected in urine within 30 minutes
of application. When you flush the toilet or wash off
sunscreen in the shower, chemicals from the lotion
enter the sewer. For towns near coral reefs and without
sophisticated sewage treatment and management
systems, this pollution is rather inevitable. (There
is an etymological argument that the word “sewer”
comes from the old English word “sea ward,” in which
household and municipal waste was channeled out of
villages and towns toward the sea or other bodies of
water.) Any coral reef near significant human habitation
is potentially vulnerable to a plume of pollution.
Sunscreen lotions do not threaten every single
coral reef in the world.
Sunscreen and other
personal care products,
however, do threaten
the coral reefs that are
most important to people
— those that are focal
points of tourism as well
as fringing reefs that are
critical for protecting
coasts from erosion.
And they threaten
the capacity of local
subsistence fisherman to
access the abundance of food that healthy nearshore
reefs once provided. Not only does intense sunscreen
pollution threaten the survival of these reefs, but it also
can prevent the recovery and restoration of already-
degraded reefs.
ECOTOXICOLOGY OF SUNSCREEN LOTIONS
AND THEIR INGREDIENTS
In October 2015 my colleagues and I examined the
toxicological effects of oxybenzone on coral larvae.
1
We found that oxybenzone induces coral bleaching
by lowering the temperature at which corals will
SUNSCREEN POLLUTION
By Craig Downs, Ph.D.
A SERIOUS AND INCREASINGLY CLEAR THREAT TO CORAL
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SUNSCREEN POLLUTION
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TWENTY-TWO ANCIENT SHIPWRECKS FOUND
IN GREECE
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TRINIDAD’S LEATHERBACKS
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DAN MEMBER PROFILE
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CALENDAR OF EVENTS, EDUCATION SPOTLIGHT
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TRAVEL SMARTER
STEPHEN FRINK