NEW ORLEANS (AP) — A study on possible
effects of the 2010 BP oil spill indicates dispersants may have killed
plankton — some
of the ocean's tiniest plants and creatures — and disrupted the
food chain in the Gulf of Mexico, one of the nation's richest
seafood grounds.
Scientists who read the study said it points toward major future effects of the spill. One called its findings scary.
For the study, Alabama researchers pumped water from Mobile Bay into 53-gallon drums, then added oil, dispersant or both in
proportions found during the oil spill to simulate the spill's effects on microscopic water-life in the bay.
Over more than 12 weeks in 2010, BP's well
spewed nearly 200 million gallons of oil into the Gulf of Mexico. The
company used
more than 1.8 million gallons of dispersants — more than 770,000
gallons of it at the oil's source on the ocean floor — to
break up the oil into tiny droplets. Earlier research hadn't found
significant problems for the environment and marine life,
but dispersants had never before been used a mile underwater or in
such large amounts.
The researchers found that, within days, the
numbers of plant-like phytoplankton and ciliates — plankton that use
hairlike
cilia to move — increased under an oil slick. But they dropped
significantly in the drums with dispersant or dispersed oil,
while the numbers of bacteria increased. The study was published
Tuesday in PLoS ONE, one of the peer-reviewed journals in
the online Public Library of Science.
"In those tanks, all of the energy seems to get trapped in the bacterial side. There were lots of bacteria left but no bigger
things. It's like the middle part of the food web is taken away," said lead researcher Alice Ortmann of the University of
South Alabama and Dauphin Island Sea Lab.
Microbes are too small for fish to eat. Ciliates, on the other hand, "graze" on microbes. Phytoplankton and cilates both get
eaten by larger zooplankton, which are fodder for tiny crustaceans that, in turn, get eaten by small fish.
Brian Crother, a biology professor at Southeastern Louisiana University, called the findings scary, though limited because
the experiments spanned only five days. "If these guys are on the money, they have pointed to something really disastrous
happening in the Gulf," he said.
The study was extremely well done, said
Michael Crosby, senior vice president for research at Mote Marine
Laboratory in Sarasota,
Fla. "You've got to look at the impact on the ecosystem as a
whole, rather than individual species," he said.
It is also, he said, more evidence for what
he has thought all along: that the Gulf of Mexico's food web is in
danger. "If
you go a couple steps beyond their findings, I think we're going
to see these things happening and it's going to take years
for them to be seen," he said.
Ortmann said she and her colleagues, including scientists at Auburn University, were surprised that dispersant alone had such
a big effect on plankton.
Carbon is a basic part of most life on earth, and an earlier study at Dauphin Island Sea Lab found that plankton quickly gulped
down oil from the spill.
Crother said the new study makes clear that
the damage to plankton was from dispersant, not oil. "These guys have
shown ...
that the carbon available from that dispersant is not easily
utilized for energy at the bottom of the food chain," he said.
Still, other research indicates that "fish did very well in 2010," Ortmann said. There's no indication that the food web was
completely disrupted, but it might have been interrupted in certain areas, she said.
More research is being done to try to understand the spill's actual impact, she said.
Crosby noted that some environmental effects weren't seen for years after the tanker Exxon Valdez hit a reef and broke open
off Alaska in 1989, causing what was then the nation's largest spill, 11 million gallons.
The late 1980s had been marked by record
commercial harvests of herring, but by 1993, the number of spawning
adults had dropped
by three-quarters. Disease, ocean changes, contaminants,
competition from other fish and increasing numbers of humpback whales
are being studied as possible reasons that the species has never
recovered.
"The herring population in Prince William Sound didn't collapse until four years after the Exxon Valdez," Crosby said. "It
has never recovered. Never."