“Very low levels” of Exxon Valdez oil threaten salmon and herring survival 25 years later

“Very low levels” of crude oil from the 1989 Exxon Valdez spill in Prince William Sound, Alaska, are a threat to the survival of herring and pink salmon that spawn in the region, according to a study released today by the US National Oceanic and Atmospheric Administration.

The study shows that embryonic salmon and herring exposed to very low levels of crude oil can develop hidden heart defects that compromise their later survival.

That means that the Exxon Valdez spill on March 24, 1989 may have had much greater impacts on spawning fish than previously recognized, according to the study published in  Nature’s online journal  Scientific Reports Very low embyronic crude oil exposures cause lasting defects in salmon and herring.

“These juvenile fish on the outside look completely normal, but their hearts are not functioning properly and that translates directly into reduced swimming ability and reduced survival,” said John Incardona, a research toxicologist at NOAA Fisheries’ Northwest Fisheries Science Center (NWFSC) in Seattle. “In terms of impacts to shore-spawning fish, the oil spill likely had a much bigger footprint than anyone realized.”

This is a juvenile pink salmon exposed to low levels of crude oil as an embryo. While these fish appear outwardly normal, they nevertheless developed heart defects that compromised their ability to swim. Fish that are less able to forage and avoid predators are much less likely to survive to adulthood. (NOAA)
This is a juvenile pink salmon exposed to low levels of crude oil as an embryo. While these fish appear outwardly normal, they nevertheless developed heart defects that compromised their ability to swim. Fish that are less able to forage and avoid predators are much less likely to survive to adulthood. (NOAA)

Previous research has shown that crude oil disrupts the contraction of the fish heart muscle cells. Embryonic fish exposed to trace levels of crude oil grow into juveniles with abnormal hearts and reduced cardiorespiratory function.

“With this very early impact on the heart, you end up with an animal that just can’t pump blood through its body as well, which means it can’t swim as well to capture food, form schools, or migrate,” said Mark Carls, toxicologist at the Alaska Fisheries Science Center. “Crude oil is changing basic physiology, or what makes a fish a fish.”

The research builds on earlier work by the Auke Bay Laboratories, part of NOAA Fisheries’ Alaska Fisheries Science Center, which found much reduced survival of pink salmon exposed as embryos to polycyclic aromatic hydrocarbons (PAH) from crude oil.

“Our findings are changing the picture in terms of assessing the risk and the potential impacts of oil spills,” said Nat Scholz, leader of the NWFSC’s ecotoxicology program and a coauthor of the new study. “We now know the developing fish heart is exquisitely sensitive to crude oil toxicity, and that subtle changes in heart formation can have delayed but important consequences for first-year survival, which in turn determines the long-term abundance of wild fish populations.”

The Exxon Valdez aground on Bligh Reef in Prince William Sound in May 1989. (NOAA)
The Exxon Valdez aground on Bligh Reef in Prince William Sound in March 1989. (NOAA)

The Exxon Valdez spill was the largest in U.S. history, with extensive oiling of shoreline spawning habitats for Pacific herring and pink salmon, the two most important commercial fish species in Prince William Sound.

Herring larvae sampled in proximity to oil were visibly abnormal, and mortality rates were higher for pink salmon embryos at oil spill sites than unaffected regions.

The herring fishery collapsed three to four years after the spill, when the herring spawned in oiled areas reached reproductive maturity.

The paper notes that the contribution of the spill to the herring population collapse, if any, was never determined and remains controversial.

Other studies, however, tend to confirm the findings, including heart problems for fish exposed to the Gulf of Mexico Deepwater Horizon spill and even fish exposed to naturally occurring oil seeps.

Oil spill caused unexpected lethal impact on herring, study shows

Gulf oil spill caused heart defects in fish embryos new study finds

The new findings suggest that the delayed effects of the spill may have been important contributors to the declines.

 This image shows transient embryonic exposures to crude oil cause lasting reductions in the swimming speed of salmon and herring, months after additional juvenile growth in clean seawater. (NOAA)

This image shows transient embryonic exposures to crude oil cause lasting reductions in the swimming speed of salmon and herring, months after additional juvenile growth in clean seawater. (NOAA)

Scientists from the Northwest Fisheries Science Center and Alaska Fisheries Science Center temporarily exposed embryonic salmon and herring to low levels of crude oil from the North Slope of Alaska and found that both absorbed chemicals at similar concentrations in their tissues. The embryos were then transferred to clean seawater and raised as juvenile fish for seven to eight months.

Few of the exposed embryos were outwardly abnormal in any way. However, closer examination of the fish revealed subtle defects that could reduce their long-term survival.

Juvenile salmon exposed to oil grew more slowly, with those exposed to the highest concentrations growing the slowest. For salmon, early survival in the ocean is strongly influenced by juvenile growth, with smaller fish suffering higher loss to predators.

Scientists used swimming speed as a measure of cardiorespiratory performance and found that fish exposed to the highest concentrations of oil swam the slowest. Slower swimming is an indication of reduced aerobic capacity and cardiac output, and likely makes fish easier targets for predators.

Exposure to oil as embryos altered the structural development of the hearts of juvenile fish, potentially reducing their fitness and swimming ability. Poor swimming and cardiac fitness is also a factor in disease resistance.

Earlier studies on the ecosystem-scale crash of the Prince William Sound herring population  several years after the Exxon Valdez spill were based on higher levels of exposure to the oil. The new study shows that that cardiac injury occurs in normal-appearing fish that survive even lower level exposures.

The scientists reviewed data on measured oil concentrations in surface water samples collected in Prince William Sound after the oil spill and during the 1989 herring spawning season. Most of the 233 samples contained less oil than was believed to be toxic to herring at the time, based on visible gross developmental abnormalities. However, nearly all of the samples contained oil at or above concentrations shown in the new study to alter heart development.

If the Exxon Valdez spill impacted heart development among a large majority of fish that were spawned in proximity to oiled shorelines, the subsequent losses of juveniles to delayed mortality would have left fewer adults to join the population. Although not direct proof, this provides a plausible explanation for the collapse of the Prince William Sound herring stock four years later, when fish spawned during the oil spill would have matured.

The study concludes that the impacts of the Exxon Valdez spill on near shore spawning populations of fish are likely to have been considerably underestimated in terms of both the geographic extent of affected habitat and the lingering toxicity of low levels of oil. The findings will likely contribute to more accurate assessments of the impacts of future oil spills, Incardona said. “Now we have a much better idea of what we should be looking for,” he said.

That means, according to the study “that the impacts of the Exxon Valdez oil spill on populations of near shore spawning fish are likely to have been considerably underestimated, in term of both the geographic extent of affected habitats and the lingering toxicity of low levels of residual oil.”

The report calls for more studies of the sensitivity of the developing fish heart since the vulnerability “also has implications for other pollution sources in marine ecosystems, including increasing maritime vessel traffic and expanding land-based urban runoff.”

In 2013, the Northern Gateway Joint Review panel said this about the Exxon Valdez  oil spill.

Scientific studies after the Exxon Valdez spill indicated that the vast majority of species recovered following the spill and that functioning ecosystems, similar to those existing pre-spill, were established.

Species for which recovery is not fully apparent, such as Pacific herring, killer whales, and pigeon guillemots, appear to have been affected by other environmental factors or human influences not associated with the oil spill. Insufficient pre-spill baseline data on these species contributed to difficulties in determining the extent of spill effects.

Based on the evidence, the Panel finds that natural recovery of the aquatic environment after an oil spill is likely to be the primary recovery mechanism, particularly for marine spills. Both freshwater and marine ecosystem recovery is further mitigated where cleanup is possible, effective, and beneficial to the environment.

Natural processes that degrade oil would begin immediately following a spill. Although residual oil could remain buried in sediments for years, the Panel finds that toxicity associated with that oil would decline over time and would not cause widespread, long-term impacts.

Related

25th anniversary of Exxon Valdez disaster looms over Northern Gateway dispute

How oil spills kill fish: new study points to cardiac arrest; possible implications for humans

Oil spills kill fish. That’s well known. Now scientists say they have found out why oil spills kill adult fish. The chemicals in the oil often trigger an irregular heartbeat and cardiac arrest.

A joint study by Stanford University and the US National Atmospheric and Oceanic Administration have discovered that crude oil interferes with fish heart cells. The toxic consequence is a slowed heart rate, reduced cardiac contractility and irregular heartbeats that can lead to cardiac arrest and sudden cardiac death.

The study was published Feb. 14, 2014 in the prestigious international journal Science and unveiled at the convention of the American Association for the Advancement of Science in Chicago.

The study is part of the ongoing Natural Resource Damage Assessment of the April 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

Scientists have known for some time that crude oil is known to be “cardiotoxic” to developing fish. Until now, the mechanisms underlying the harmful effects were unclear.

Exxon Valdez

Studies going back to the Exxon Valdez oil spill in Alaska in 1989 have shown that exposure to crude oil-derived chemicals disrupt cardiac function and impairs development in larval fishes. The studies have described a syndrome of embryonic heart failure, bradycardia (slow heart beat), arrhythmias (irregular heartbeats) and edema in exposed fish embryos.

After the Gulf of Mexico spill, studies began on young fish in the aftermath of the Deepwater Horizon spill. The two science teams wanted to find out how oil specifically impacts heart cells.

Crude oil is a complex mixture of chemicals, some of which are known to be toxic to marine animals.

Past research focused on “polycyclic aromatic hydrocarbons” (PAHs), which can also be found in coal tar, creosote, air pollution and stormwater runoff from land. In the aftermath of an oil spill, the studies show PAHs can persist for many years in marine habitats and cause a variety of adverse environmental effects.

The scientists found that oil interferes with cardiac cell excitability, contraction and relaxation – vital processes for normal beat-to-beat contraction and pacing of the heart.

Low concentrations of crude

The study shows that very low concentrations of crude oil disrupt the specialized ion channel pores – where molecules flow in and out of the heart cells – that control heart rate and contraction in the cardiac muscle cell. This cyclical signalling pathway in cells throughout the heart is what propels blood out of the pump on every beat. The protein components of the signalling pathway are highly conserved in the hearts of most animals, including humans.

The researchers found that oil blocks the potassium channels distributed in heart cell membranes, increasing the time to restart the heart on every beat. This prolongs the normal cardiac action potential, and ultimately slows the heartbeat. The potassium ion channel impacted in the tuna is responsible for restarting the heart muscle cell contraction cycle after every beat, and is highly conserved throughout vertebrates, raising the possibility that animals as diverse as tuna, turtles and dolphins might be affected similarly by crude oil exposure. Oil also resulted in arrhythmias in some ventricular cells.

“The ability of a heart cell to beat depends on its capacity to move essential ions like potassium and calcium into and out of the cells quickly.” said Barbara Block, a professor of marine sciences at Stanford. She said, “We have discovered that crude oil interferes with this vital signalling process essential for our heart cells to function properly.”

Nat Scholz, leader of the Ecotoxicology Program at NOAA’s Northwest Fisheries Science Center in Seattle said.”We’ve known from NOAA research over the past two decades that crude oil is toxic to the developing hearts of fish embryos and larvae, but haven’t understood precisely why.”

Long term problems in fish hearts

He added: “These new findings more clearly define petroleum-derived chemical threats to fish and other species in coastal and ocean habitats, with implications that extend beyond oil spills to other sources of pollution such as land-based urban stormwater runoff.”

The new study also calls attention to a previously under appreciated risk to wildlife and humans, particularly from exposure to cardioactive PAHs that can also exist when there are high levels of air pollution.

“When we see these kinds of acute effects at the cardiac cell level,” Block said, “it is not surprising that chronic exposure to oil from spills such as the Deepwater Horizon can lead to long-term problems in fish hearts.”

The study used captive populations of bluefin and yellowfin tuna at the Tuna Research and Conservation Center, a collaborative facility operated by Stanford and the Monterey Bay Aquarium. That meant the research team was able to directly observe the effects of crude oil samples collected from the Gulf of Mexico on living fish heart cells.

“The protein ion channels we observe in the tuna heart cells are similar to what we would find in any vertebrate heart and provide evidence as to how petroleum products may be negatively impacting cardiac function in a wide variety of animals,” she said. “This raises the possibility that exposure to environmental PAHs in many animals – including humans – could lead to cardiac arrhythmias and bradycardia, or slowing of the heart.”

Tuna spawning

The Deepwater Horizon disaster released over 4 million barrels of crude oil during the peak spawning time for the Atlantic bluefin tuna in the spring of 2010. Electronic tagging and fisheries catch data indicate that Atlantic bluefin spawn in the area where the Deepwater Horizon drilling rig collapsed, raising the possibility that eggs and larvae, which float near the surface waters, were exposed to oil.

Blue fin tuna
An Atlantic bluefin tuna ( ©Gilbert Van Ryckevorsel/TAG A Giant/Courtesy Standford University)

The spill occurred in the major spawning ground of the western Atlantic population of bluefin tuna in the Gulf of Mexico. The most recent stock assessment, conducted in 2012, estimated the spawning population of the bluefin tuna to be at only 36 percent of the 1970 baseline population. Additionally, many other pelagic fishes were also likely to have spawned in oiled habitats, including yellowfin tuna, blue marlin and swordfish.

Block and her team bathed isolated cardiac cells from the tuna in low dose crude oil concentrations similar to what fish in early life stages may have encountered in the surface waters where they were spawned after the April 2010 oil spill in the Gulf of Mexico.

They measured the heart cells’ response to record how ions flowed into and out of the heart cells to identify the specific proteins in the excitation-contraction pathway that were affected by crude oil chemical components.

Fabien Brette, a research associate in Block’s lab and lead author on the study said the scientists looked at the function of healthy heart cells in a laboratory dish and then used a microscope to measure how the cells responded when crude oil was introduced.

“The normal sequence and synchronous contraction of the heart requires rapid activation in a coordinated way of the heart cells,” Block said. “Like detectives, we dissected this process using laboratory physiological techniques to ask where oil was impacting this vital mechanism.”

Related: Oil spill caused “unexpected lethal impact” on herring, study shows

 

Oil spill dangers can linger for 40 years, report shows

Genivar report
Cover of Genivar tanker report (Transport Canada)

The Genivar report for Transport Canada on oil spills say that some persistent effects can last for more than 40 years, based on a study of a spill in Cape Cod, Massachusetts. The report  notes that persistent sub-surface oil is still a problem at Prince William Sound, site of the Exxon Valdez disaster in 1989.

On long-term effects, Genivar reports: “The ingestion of contaminated food (such as oiled mussels), may represent the most important exposure pathway for aquatic fauna during a chronic
phase. Chronic exposure to contaminated sediments is also important for fauna or
vegetation.”

 

 

 

It goes on to stay that “large-scale oil spills might have considerable long-term
consequences on social structure and public health, interfering with traditions and
causing cultural disruptions.”

It appears that in the case of an oil-spill, time may heal some wounds, but not all of them, at least if time is considered within human lifetimes and the lifetimes of other species.

Ecological recovery is measured by how quickly individuals and populations of
species return to pre-spill conditions. It is determined by factors such as oil type,
exposure duration, water temperature, degree of weathering, spill response and the
individual and species-specific life history traits. In most environmental habitats,
recovery is completed within 2-10 years after a spill event, but in some exceptional
cases, such as in salt marshes, effects may be measurable for decades after the
event.

In the case of the Exxon Valdez oil spill in Prince William Sound… in 1989, the persistence of sub-surface oil in sediments and its chronic exposure continues to affect some of the wildlife through delayed population reductions, indirect effects and trophic interactions 20 years beyond the acute phase of the spill.

It then goes on to stay that

Four decades after the oil spill In Wild Harbor (USA), Spartina alterniflora beds had a reduced stem density and biomass and mussels in oiled locations showed decreased growth and filtration rates.

According to a Boston Globe story, published at the time of the Deepwater Horizon oil leak in the Gulf of Mexico, in 2010, the Wild Harbor, an oil barge ran aground near Cape Cod in September, 1969, spilling 200,000 gallons of fuel, some of which is still there.

The Boston Globe story noted:

Today, Wild Harbor looks much like any other Cape Cod marsh, but the oil below the surface affects its resiliency. Fiddler crabs normally burrow deep down, funneling oxygen to the roots of marsh grass. Here, they stop digging when they reach the oil, turn sideways, and burrow back to the surface. They also act “drunk’’ from the oil they ingest, and predators can catch them more easily, research shows.

The Woods Hole Oceanographic Institute has been studying the Wild Harbor spill for the past 40 years.

At a recent conference, Dr. John Teal updated scientists on the “multi-decadal effects” of the Wild Harbor spill. According a blog on the conference:

At the time of the 1969 spill, lobsters, clams, and fish died by the thousands, but most people believed the harm would be temporary, reflecting the conventional wisdom of the time. Barge owners and oil industry experts even told residents that most of the oil would evaporate and any damage would only be short-lived. However, researchers at WHOI were not so sure and immediately began cataloging species and tracking where the oil was and kept at it for years. The researchers understood that the immediate, short term effects of oil pollution were already obvious and fairly well-understood, but that everyone was rather ignorant about the long-term and low-level effects of an oil spill….

Beginning three to five years after the spill, marsh grasses and marsh animals were again occupying most of the oiled area. An observer unfamiliar with Wild Harbor would not have been able to visually detect the oiled areas after just 10 years, and by the second decade after the spill, the marsh’s appearance had returned to normal. However, the WHOI researchers pointed out that for more than a decade after the spill, an oil sheen still appeared on the surface of the water when mud from the most heavily oiled parts of the marsh was disturbed….

In 2007, WHOI researchers documented that a substantial amount of moderately degraded petroleum still remained within the sediment and along eroding creek banks of the marsh oiled in 1969. They also demonstrated that the ribbed mussels that inhabit the oiled salt marsh, and are exposed to the oil, exhibited slower growth rates, shorter mean shell lengths, lower condition indices, and decreased filtration rates even when placed in a healthy marsh. Researchers have also documented detrimental effects of the 1969 oil spill on the salt marsh plants themselves.

 

Related Oil Spill on the Wild Harbor Marsh by John M. Teal and Kathryn A. Burns
The Genivar report goes on to note:

Long-term effects on the population in the aquatic environment (especially on mobile fauna) are especially difficult to confirm. Benthic [bottom dwelling] invertebrates may be more at risk than fish species due to the fact that more or less sessile organisms are likely to suffer higher initial rates of mortality and exhibit long recovery times as a result of
exposure to oil-saturated habitats.

Nearshore demersal [bottom-dwelling] fish can also suffer from long-term chronic exposure, as indicated in masked greenlings and crescent gunnels by biomarkers on hydrocarbons 10 years after the Exxon Valdez spill. Mortality in sea ducks and sea turtles due to chronic exposure was also reported many years after the spill and other results indicate that effects on cetacean populations can last beyond 20 years after the acute exposure phase.

As for the recovery of the economy after a spill, Genivar notes it is based “on the time required for effected industries to be fully restored to pre-spill conditions.

The length of time required is influenced by the duration of the aquatic area closures (e.g. commercial fisheries, recreational fisheries), the public perceptions on seafood safety and the perceived effects of the aesthetic quality of the environment. Even after the full ecological recovery of the aquatic resources, fisheries can be far from reestablished, as is still the case for herring fisheries in the Exxon Valdez spill area…

As reviewed by Genivar, negative perceptions associated with the quality of fishery products, even for fisheries that have not been contaminated and also for regions not directly affected by the spill, can be far more important than the direct economic losses. This also holds true for the tourism sector and all other related spinoff sectors.

Coastal First Nations launch election commercial with Exxon Valdez radio call

Coastal First Nations have launched a commercial aimed at the British Columbia electorate, using the call from the Exxon Valedez to US Coast Guard Valdez traffic control saying that the tanker had run aground.

 

The commercial makes the connection between the Exxon Valdez disaster and the possibility of a tanker disaster on the British Columbia coast if the Enbridge Northern Gateway project goes ahead.

According to the Vancouver Sun, Paul Simon personally approved the use of the song Sounds of Silence in the commercial.

The BC New Democrats, who are leading the polls have said they oppose Northern Gateway. The ruling BC Liberals have set out five conditions that must be met if the project is to go ahead.

US calls for study that could relax double-hulled oil tanker regulations, citing costs to build, energy consumption

The United States Department of Transportation Maritime Administration has issued a call for a study that is calling into question the future of double-hulled oil tankers.

On August 6, 2012 the Maritime Administration, also known as MARAD, issued a “solicitation” for a study on the Safety, Economic and, Environmental Issues of Double Hulls.

In the call for the study, MARAD says:

Following the Exxon Valdez disaster, the passing of the Oil Pollution Act of 1990 (OPA 90) led to the requirement to replace single hull petroleum tankers with double hull tank vessels sailing in U.S. waters. This requirement was soon adopted by the International Maritime Organization (IMO) and became a worldwide regulation. This means that, today, tank vessels worldwide are carrying thousands of extra tons of steel in order to meet the double hull requirements.

Though these double hulls reduce the threat of oil pollution as a result of grounding, they significantly increase the amount of energy needed to propel a vessel and increase the amount of air pollution into the atmosphere. As a result, the maritime industry’s carbon footprint and criteria pollutant emissions are increased.
In addition to the need to burn more fuel, it is acknowledged that double hulls can cause several other problems which will be detailed in this study.

Here in Canada, Enbridge Northern Gateway and its supporters, in briefings on maritime and tanker safety on the west coast of British Columbia, have always said that the changes following the Exxon Valdez disaster in Prince William Sound and the subsequent US Oil Pollution Act as almost guaranteeing that such a disaster could not happen again.

Now it appears that some people in the U.S. Department of Transportation may be worried that increased use of double-hulled tankers will cost too much. There’s also the apparent question of balancing the carbon footprint of increased emissions from tankers with the danger from a hydrocarbon spill.

The request for the study was covered by tanker industry sites such as Marine Link but only surfaced in major media on Sunday, when The National, an English-language newspaper in Abu Dhabi broke the story, “US maritime agency considers overhaul of oil-spill regulation”

Reporter David Black notes:

In July last year, the IMO adopted binding regulations to limit the expected gas emissions increase by reducing fuel consumption of ships by as much as 15 million tonnes in 2020, a 14 per cent reduction, and by 2050, by as much as 1,013 million tonnes. This will lead to savings in fuel costs for the shipping industry of up to US$200 billion a year, says the IMO.

Black says that the US agency seems “to suggest by abandoning the additional weight of double hulls the savings would increase and pollution be cut further, adding “On the other hand, since the introduction of double hulls, pollution from major oil spills has been reduced to practically zero.”

The National story says even the tanker industry itself is worried about the move, quoting the the international tanker owners’ organization.

“We have noted reports about Marad’s intended study on tanker double hulls but, except for what we gather from press articles, we have little knowledge on the reasoning behind this,” said Bill Box, Intertanko’s senior manager for external relations.
“From our members’ experience, double-hull designs have evolved into safe and reliable ships with an excellent safety and pollution prevention record. We might provide comments when such a study would be released by Marad.”

 

The requirements for the double-hull study, as posted by the US government are:

1. The Contractor shall conduct an assessment of the history in the evolvement of “The Double Hull Rules”.

2. The Contractor shall conduct the assessment of any rules that are being proposed in bodies such as the IMO, U.S. Congress and other such bodies’ worldwide as they relate to additional hulls for environmental reasons.

3. The Contractor shall assess all the relevant safety issues related to double hulls for each class of vessel. E.g. Double bottoms are difficult and expensive to maintain and can result in corrosion problems. Unchecked corrosion in older double hull vessels can lead to cargo leakage into a double bottom and the buildup of dangerous vapor which could cause an explosion under certain conditions. The Contractor will obtain data from appropriate organizations which details the issues in double bottoms on older vessels including cracking, leakage, and the potential for vapor buildup.

4. The contractor shall conduct a complete economic study of the consequences of Double Hulls. E.g. they significantly add to the construction cost of vessels. They result in the loss of cargo space which also adds to the carbon footprint since an additional vessel(s) is needed to carry the same cargo tonnage.

5. The contractor shall assess the complete consequences of the carbon footprint of designing, constructing, maintaining and operating vessels with double hulls. E.g. Apart from the extra propulsive forces and fuel needed, the carbon footprint of double hull maintenance is substantially increased.

6. The Contractor shall prepare a report on the results of the project. The report shall be grammatically correct and must be professionally written to a high level of competence in the English language. The report must clearly specify the safety, economic and environmental issues details above.

 

Micro organisms played key roles in Exxon Valdez, BP cleanup: study

Environment Link

A study by the U.S. Lawrence Berkeley National Laboratory is reporting that microbes, mostly  bacteria, but also archaea (single cell organisms without a cell nucleus) and fungi, played key roles in mitigating both the Exxon Valdez oil spill in Alaska and the  BP Deep Ocean Horizon disaster in the Gulf of Mexico.

In a news release, Terry Hazen, microbial
ecologist with the Lawrence Berkeley National Laboratory (Berkeley Lab) says, “Responders to future oil spills would do well to mobilize as rapidly as
possible to determine both natural and enhanced microbial degradation
and what the best possible approach will be to minimize the risk and
impact of the spill on the environment.”

Hazen, who leads the Ecology Department and Center for Environmental
Biotechnology at Berkeley Lab’s Earth Sciences Division and  has studied
microbial activity at both spill sites, published the paper with colleagues in Environmental Science & Technology. The paper is titled “Oil biodegradation and bioremediation: A tale of the two worst spills in U. S. history.”

The authors say that hydrocarbons have been leaking into the marine environment for millions of years and so “a large and diverse number of microorganisms, including bacteria, archaea and fungi, have evolved the ability to utilize these petroleum hydrocarbons as sources of food and energy for growth.”

Such microorganisms are only a small part of a pre-spill microbial community in any given ecosystem. Hazen says in both the Exxon Valdez and the BP Deepwater Horizon spills, the surge in the presence of crude oil sparked a sudden and dramatic surge in the presence of oil-degrading microorganisms that began to feed on the spilled oil.

“In the case of the Exxon Valdez spill, nitrogen fertilizers were applied to speed up the rates of oil biodegradation,” Hazen says. “In the case of the BP Deepwater Horizon spill, dispersants, such as Corexit 9500, were used to increase the available surface area and, thus, potentially increase the rates of biodegradation,” he says.

According to the study, within a few weeks of the spill, about 25 to 30 per cent of the total
hydrocarbon in the oil originally stranded on Prince William Sound
shorelines had been degraded and by 1992, the length of shoreline still
containing any significant amount of oil was 6.4 miles, or about
1.3 per cent of the shoreline originally oiled in 1989.

Microorganisms also played a similar role in the Gulf of Mexico Deep Ocean Horizon disaster, despite major differences in the temperature, environment, ocean depth and length and type of spill, the study says.  Hazen and his research group were able to determine that indigenous
microbes, including a previously unknown species, degraded the oil plume
to virtually undetectable levels within a few weeks after the damaged
wellhead was sealed.

The study concludes that decisions as to whether to rely upon microbial oil biodegradation or whether to apply fertilizers, dispersants, detergents and/or/other chemicals used in environmental cleanup efforts, should be driven by risk and not just the presence of detectable hydrocarbons.

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