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June 17, 2010
Impact of Gulf oil spill on marine life is still uncertain
By SUSAN WEST
Chances
are remote that oil from the Deepwater Horizon spill in the Gulf of
Mexico would wash ashore in North Carolina, according to the state
Department of Crime and Public Safety.
If anything, beach-goers might see some tar balls on the beach, not a
smothering blanket of oil choking the life out of marshes and wildlife,
officials say.
But the consequences of the spill for marine life beneath the ocean
surface, something scientists say is difficult to assess, could flow
far beyond the Gulf.
“It’s sort of like waiting for a ticking time bomb to go off,” said
David Eggleston, professor of marine, earth and atmospheric sciences at
North Carolina State University.
“It could be a dud or a direct hit. We don’t know.”
For one thing, estimates of the amount of crude pouring into the Gulf
every day have steadily increased since the April 20 rig explosion,
from British Petroleum’s initial estimate of 1,000 barrels to an
estimate of as many as 60,000 barrels announced by government
scientists this week.
The rig explosion that killed 11 people and left a river of crude oil
gushing into the Gulf coincided with spawning season for many fish,
including migratory bluefin tuna, prized by commercial and recreational
fishermen on the Atlantic seaboard.
Early into the Gulf catastrophe, the Center for Biological Diversity
filed a petition to protect bluefin under the Endangered Species Act.
Eggleston said larvae are extremely sensitive to oil.
“The frontal boundaries where two water bodies meet tend to concentrate
larvae and also would concentrate oil by the same process,” he added.
Giant underwater plumes of oil droplets, as far as 3,300 feet below the
water surface and as far away as 142 miles from the spill site,
complicate the picture.
Naturally occurring bacteria feed on oil, but also deplete oxygen
needed by other inhabitants of the deep, potentially creating dead
zones devoid of animal life.
Some oil disperses naturally into the water column through wave action,
but British Petroleum has applied more than one million gallons of
chemicals to accelerate the process and reduce the amount of surface
oil.
Dispersing the oil could help reduce the threat to birds and other
animals that come into direct contact with surface water, but breaking
the oil into small particles could heighten the risk to marine life.
Although concentrations of oil-related chemicals in the plumes are low,
according to the National Oceanic and Atmospheric Administration, toxic
compounds that would be expected to evaporate from surface water have
instead spread through the ocean.
Small amounts of oil could impair immune systems and cause reproductive
problems in deep-water fish, such as sharks, swordfish, marlin,
snapper, grouper, and tunas.
Jellyfish, small fish, shrimp, crabs, and zooplankton that are dinner
for larger fish could be at risk too, posing a threat to the foundation
of the marine food chain.
“If toxics are incorporated into the food web, we’ll be dealing with
the consequences for years and years to come,” Eggleston said.
Another concern is that oil entering the Gulf Stream could contaminate
the Sargassum Sea and its rich beds of sargassum, a type of brown
seaweed that provides food and protection for young fish and sea
turtles.
Fish species found in sargassum mats include tuna, marlin, triggerfish, amberjack, and dolphin.
Eggleston said assessing the impact of the spill on underwater marine life will be complicated.
“Even with good information, say a bluefin larval index that goes back
20 years and data collected after the spill, it is difficult to assign
cause and effect,” he explained.
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