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Lower pH harms
By Susan Milius
By midcentury, growing acidification of
the world’s oceans may undermine sexual reproduction in elkhorn coral badly
enough to halve the supply of youngsters
settling down to build reef.
Acidification, which happens as
increasing levels of atmospheric carbon
dioxide dissolve in the ocean and form
acid, is expected to threaten reefs worldwide in coming decades. In lab tests with
seawater modified to reflect conditions
expected later this century, sperm of the
elkhorn coral, Acropora palmata,
fertilized eggs 13 percent less often on average
compared with sperm in today’s seawater,
says Rebecca Albright of the University
of Miami. At low sperm concentrations,
which Albright suspects more realistically model life in the sea, fertilization
success fell by as much as 64 percent.
Even when fertilization was successful,
Elkhorn corals release their sperm and
eggs at night. Coral fertilization could
decline as seawater pH drops.
the resulting larvae had more trouble
getting established on a reef, Albright
and her colleagues report online November 8 in the Proceedings of the National
Academy of Sciences.
Since the beginning of the industrial
revolution, global seawater has dropped
from about 8. 2 on the pH scale to between
about 8.05 and 8. 1. Each unit on the scale
reflects a shift in acid concentration by a
power of 10, so the effect to date has been
about a 30 percent increase in acid level.
For the tests, Albright and her colleagues bubbled carbon dioxide gas into
natural seawater to mimic the predicted
ocean chemistry of a world where emissions have driven atmospheric carbon
dioxide from the current concentration of about 387 parts per million up to
560 ppm, an increase that could occur by
midcentury if emissions are not abated.
She and her colleagues also tested a
case of atmospheric carbon dioxide levels
reaching about 800 ppm by 2100. Elkhorn coral fertilization and settlement
suffered even more at those concentrations. The pH change could reduce the
supply of established youngsters on a
reef by 73 percent, the researchers say.
Sexual reproduction is not the only
way corals expand. Individuals can clone
themselves, but sex maintains the genetic
diversity that researchers hope will help
corals cope with a disrupted environment.
“It is a big deal if you lose sexual
reproduction, even in species with very
effective means of reproducing asexually,” says ecologist Steve Gaines of the
University of California, Santa Barbara,
because in corals and most other invertebrates the sexually produced offspring
are the ones that colonize new places.
BPA passes easily through the skin
finding may explain high levels of chemical seen in cashiers
By Janet Raloff
Bisphenol A readily passes through skin,
scientists report. The finding suggests
handling store receipts could be a significant source of exposure to the chemical,
which has been linked to health concerns.
A majority of thermal receipt papers
employ BPA in their heat-sensitive color-change coating (SN: 8/28/10, p. 5), a
powdery substance that can rub off.
In the new study, toxicologist Daniel
Zalko of the French National Institute for
Agricultural Research in Toulouse and
colleagues collected pig ears minutes
after slaughter. The researchers then
applied various amounts of BPA to the
pig skin. The lowest concentration deliv-
ered a dose of BPA in the ballpark of
what could rub off onto a person’s skin
from handling receipt paper, Zalko says.
The findings, posted online October
27 in Chemosphere, are “unequivocal in
showing that yes, BPA can go through
human skin,” says Frederick vom Saal
of the University of Missouri-Columbia.
They may also explain another finding:
Among nearly 400 pregnant Cincinnati-area women, cashiers had the highest
BPA concentrations in their urine, scientists report in an upcoming issue of
Environmental Health Perspectives.
Because BPA can’t be seen or smelled,
consumers have had no way to identify
receipt paper with the chemical. That
should change soon. On November 8,
Wisconsin-based Appleton Paper — the
sole source of BPA-free U.S. thermal-receipt paper — began embedding tiny
red fibers to mark its paper.
Evan D’alEssanDro/rsMas, Univ. of MiaMi