This South Dakota Mines Research Blog article is
based on a press release from
the California Academy of Sciences published here.
On April
20, 2010, the Deepwater Horizon (DWH) petroleum drilling rig exploded off the
coast of Louisiana, resulting in the world’s worst oil spill in history with
more than 4 million barrels of oil released into the Gulf of Mexico. Though the
short-term impact of the oil spill on local wildlife was widely researched
among scientists and discussed in the media, there has been relatively little
research on the long-term effects of the disaster.
Laurie Anderson, Ph.D, professor and head of the Department of Geology and Geological
Engineering at South Dakota Mines, collected Eastern Oysters from the Gulf
Coast. A second set of oysters was collected from the Chesapeake Bay area that
were unaffected by the Deepwater Horizon oil spill.
“We were able to collect live specimens of
common coastal species of snails, mussels, and oysters after the spill but
prior to landfall of the spill throughout coastal Louisiana and Dauphin Island,
Ala.,” says Anderson.
Anderson
joined other researchers from the California Academy of Sciences, Nova Southeastern University (NSU) and Kent State
University in a new paper published in PLOS ONE. The team of
researchers show that the Eastern Oysters from the
Gulf Coast have significantly higher rates of metaplasia—a condition that can
cause debilitating tissue abnormalities—than those from a region unaffected by the
DWH oil spill, even several years after the event, raising concerns about the
health of the economically and ecologically important species.
“It’s
worrying to find such a high incidence of metaplasia,” says study author and the
California Academy of Sciences Curator of Invertebrate Zoology and Geology Peter Roopnarine, Ph.D. “Eastern Oysters are not only a major link in the ecosystem’s food
chain, they are also ecosystem engineers, forming oyster reefs that shelter
other organisms and protect coastal areas from storm surges.”
Metaplasia
is a reversible condition where some of an organism’s differentiated cells
change type due to stress from the environment. Since differentiated cells have
specialized roles, like how the cells in our gut facilitate nutrient uptake,
changing into a different type can inhibit the organism’s overall health.
“In
humans, metaplasia is commonly found in lung cells exposed to the extreme
stress of cigarette smoke,” says lead author and NSU professor Deanne Roopnarine, DPM. “When my brother Peter mentioned he was researching the impact of
the Deepwater Horizon oil spill on oysters, I wondered whether they might show
signs of metaplasia or other histological impacts and ultimately joined the
project.”
The
oysters collected by Anderson were sent to Professor
Deanne Roopnarine and her undergraduate lab students, who spent months shucking
them, sectioning out their internal tissues, fixing the tissues to slides and
staining the slides to compare the cellular structures between Eastern oysters
from the Gulf Coast and those from Chesapeake Bay that
were unaffected by the DWH oil spill.
The
researchers found that oysters from the Gulf of Mexico study sites had
significantly higher rates of metaplasia along their digestive and respiratory
tracts than those from Chesapeake Bay, including oysters sampled as late as
2013, three years after the DWH oil spill.
“The
differences we found between the oysters was devastating,” Professor Deanne
Roopnarine says. “Those from Chesapeake Bay had beautiful ciliated gills, which
they use to help filter food particles, while some from the Gulf Coast had no
cilia at all. When I saw that I thought, how are these animals feeding and
surviving?”
One
theory for how the oysters might be surviving is that they have adapted to live
with metaplasia and other impacts from the petroleum extraction industry, which
has been operating in the region for nearly a century.
Without
tissue samples from Eastern oysters prior to the DWH oil spill, however, the
researchers say there is insufficient baseline data to determine whether or not
the rates of metaplasia in Gulf Coast populations were directly affected by the
event.
“Detecting
the direct effects of the DWH spill would be difficult, even with pre-spill
specimens, as both the spill and the recovery response, such as the large-scale
release of freshwater into coastal areas, were environmental stressors for the
oysters,” Anderson says.
The
research team hopes that their results inspire deeper, longer-term monitoring
efforts for Eastern oysters and other important but often overlooked species
along the Gulf Coast that could be negatively impacted by continued oil spills
in the region, like those being reported in the aftermath of Hurricane Ida.
“As long
as we continue extracting petroleum from our planet’s oceans, we will continue
to expose coastal ecosystems to contamination,” Curator Peter Roopnarine says.
“Hopefully this study and its samples—which are now stored in the Academy’s
scientific collections for future researchers to use—will lead to a better
understanding of how oil spills are directly impacting those communities.”