06 June 2010

Oil spill: What long term effects on our marine life?

What do authorities and experts say about the environmental impact of the oil spill?
Ghost crab on oil slick, seen on Tanah Merah on 27 May.

I've finally got a breather from field trips, and thought I should do a round-up of the spread of the oil slick and what was done to clean it up. Also how did the spill affect people and can it happen again?

Andrew Tan, CEO of NEA said on 28 May: "Thus far, the environmental impact has been minimal. We hope it will stay that way."

He added: "I understand the concerns of the environmental groups. On our part right now, the first priority we have is to make sure that the areas affected by the oil patches are cleaned up so that the public can continue to make use of these places."

The Malaysian Natural Resources and Envi­ronment Minister Datuk Douglas Uggah Embas said on 2 Jun that the oil spill "appears to have no lasting effect on the affected coastal areas". He said "Once the beach has been cleaned, there is no effect and no more odour of oil because the sea current is moving and there is clean water flowing in". Adding he could see the difference between one spot which had been cleaned up and the areas yet to be cleaned.

Professor Pavel Tkalich, an oceanographer at the Tropical Marine Science Institute, said on 27 May if the slick continues spreading, it could eventually reach the Southern Islands and even Pulau Ubin and Pulau Tekong over the next few days. 'The slick will move back and forth and can gradually spread beyond to the southern islands in the next four days.' He added that environmental damage to corals and mangroves in these parts would be unavoidable, but unlikely to be significant.

Peter Ng, director, Raffles Museum of Biodiversity Research, said on 30 May: "In the short term, some animals will die. We have not seen mass kills but I'm sure some are affected". The breathing of fishes, for example, will be affected if their gills are coated with oil. "(In the) longer term, the oil will affect the animals and plants in different ways. It may reduce the reproduction, it may reduce the growth rate, it might reduce their strength. And that has long-term implications."

While the scale of the pollution was 'minor', he cautioned that any amount could upset the fragile ecosystem in Chek Jawa. With most of the oil patches along the wetlands cleaned up yesterday evening, he said the next step will be to monitor the long-term effects of the pollution. As this is the first major pollution in the area, it is unclear how the ecosystem there will react.

Prof Ng and his team of researchers have been working closely with NParks to monitor the situation at the nature area. "The authorities have already done what there is to be done... At this stage, the system has to self-recover," he said. "If we don't let too much oil hit it, the chances of recovery are not too bad."

What are some of the possible effects on marine life?

from Effects of the spill may linger for years by Grace Chua Straits Times 31 May 10;
Marine biologist Prof Chou Loke Ming explains that when oil slicks hit, they prevent corals from getting enough sunlight, cut off oxygen by coating plants and fish gills, and harbour volatile organic compounds that can poison marine life.

If most of the oil is removed, the impact from poisons and a lack of oxygen can be reduced, Professor Chou said, but spraying dispersant chemicals can break up the oil into smaller droplets which can sink to the bottom and affect marine life deeper in the sea.

In the longer term, how long will shores take to recover? Marine life may take three to four years, depending on the severity of the impact, Prof Chou said.

Commenting on how long oil from a spill lingers in the environment, climate expert Michael Totten, of international non-governmental organisation Conservation International, said that would depend on the type of oil, location, currents and weather conditions. For instance, more than 98 tonnes of oil from the 1989 Exxon Valdez spill off Alaska still lingers in the sands of Prince William Sound, as the remote area was hard for clean-up teams to reach.

More information about impact of oil spills on marine life from other reports

From Lessons from the Exxon Valdez disaster
Yereth Rosen and Peter Henderson, PlanetArk 7 May 10;
The crude began changing as it hit the water, releasing benzene and other pungent chemicals into the air, the start of a months-long process of transforming from a light liquid to a tarry gunk that would cling to more than a thousand miles of beaches in southern Alaska.

By one estimate, about 21,000 gallons of oil still linger on some of Alaska's beaches, often in the form of dark brown globs just beneath the rocks.

There are still some experts who argue that the aggressive cleanup following the Exxon Valdez spill proved more harmful than the oil itself. That continuing debate points to how conflicts among various groups looking to make things right can end up hampering cleanup efforts.

Surprisingly, not much has changed in the technology of cleaning up oil spills, and research on what to do is dominated by "gray literature" funded by either oil companies or environmental organizations that makes some experts wary.

Cleaning up oil is tough at the beginning and gets harder every day. The first job is to contain a spill, a nearly impossible task in the real world.

On the water, booms which absorb and contain spills on relatively calm seas can be used to herd it into big pools that can be sucked up or burned. Chemical dispersants which separate crude into fine droplets can be sprayed from ships and planes. Rusty-colored oil 'mousse' is formed where dispersants mixed into the water by waves are breaking down the oil.

Above all, the oil needs to be kept off shore, which over time is the most difficult thing to do. When oil hits land it's often for a short visit -- dropping off a sheen and then moving with the tides up or down the shoreline. Eventually though, the oil ages, becoming a tar -- like a blob that gloms onto a surface and won't let go.

That's fine on a hard-packed sandy beach, which is the best place for an oil spill, since a careful lift of a thin layer of sand can get rid of most of the problem. But in marshes, new and old oil can spread thin and deep with a ferocity that makes any cleanup counterproductive -- boots kill more than the oil.

The threats to wildlife are legion. Fish eggs in water and turtle eggs on land can be fouled by oil. Growing fish mutate, otters and whales swimming through oil can get sick or suffocate from the fumes or oil coating their breathing passages. Petroleum fouls feathers, and small sea creatures can ingest chemicals and die.

How that affects the environment is still being studied. Do tiny sea creatures eat the tiny droplets of oil, creating a food chain timebomb in the way that mercury levels concentrate in bigger fish? Researchers say they don't know or disagree.

In the Exxon Valdez disaster, the main plan was to float the oil off the beaches. Since oil floats, flooded beaches would shed the oil, which could be caught at the waterline. The main problem was that by this time the oil was tar, stuck to rock, and wasn't going to move that easily.

"This stuff became much more difficult to deal with plastered on the rocks than it was the first few days. and that is what led us to deal with it with the hot water," NOAA's Robinson remembers, describing the decision to rely heavily on high pressure hot water to wash the rocky beaches.

"The aggressiveness of the cleanup in the end contributed to more damage than the oil did," he believes. Nine strips of beach were left untouched as an experiment, and those nine beaches look better today than the swept ones, where whatever was alive was cooked to death in superhot water.

That is not to say a white sand beach is easy to clean. The key to such an effort is to wait until all the oil has arrived, skim it and a little sand off with a shovel, and be done. But oil moves with tides, so the perfect time to clean is a moving target. Volunteers can easily dig too deep, or not deep enough. Heavy equipment works faster but can damage the beach. And so a simple one-two exercise can become a seemingly endless process that is repeated until there is no beach left.

Exxon also put fertilizer on beaches far and wide, calculating that naturally existing microbes that eat naturally seeping hydrocarbons would multiply with the fertilizer and munch up the oil, which many said was indeed the case.

Oil still lingers on some Alaska beaches, in surprisingly fresh condition. NOAA estimates that about 21,000 gallons of oil are buried in beaches. "There's more oil out there, in larger quantities and in a more toxic state, than we thought there would be," said Craig Tillery, Deputy Attorney General of Alaska.
From Oil Cleanup Chemicals Worry Environment Watchdogs
Deborah Zabarenko, PlanetArk 5 May 10;
Oil-dispersing chemicals used to clean up the vast BP spill in the Gulf of Mexico carry their own environmental risks, making a toxic soup that could endanger marine creatures even as it keeps the slick from reaching the vulnerable coast, wildlife watchdogs say.

The use of dispersants could be a trade-off between potential short-term harm to offshore wildlife and possible long-term damage to coastal wildlife habitat if the oil slick were to reach land.

So-called dispersants work on an oil spill as dishwashing detergent works on a greasy skillet: they break up oil into tiny droplets that sink below the water's surface where naturally occurring bacteria consume them. Without dispersants, oil stays on the water's surface, where bacteria can't get at them.

The problem, according to Jackie Savitz, a senior scientist at the marine environmental group Oceana, is that the dispersants themselves can be toxic to wildlife. Dispersants can also enhance oil's toxicity in the dispersion process.
From Concerns Up and Down the Food Chain
Leslie Kaufman New York Times 5 May 10;
The water surface is the temporary home for the eggs of dozens of species of fish and shellfish, whose offspring spend their earliest days floating along currents — the very layer where most of the oil settles.

There, the effects can be devastating, studies from previous spills show, like whales so drugged and disoriented by noxious petroleum fumes that they can drown, and tiny translucent organisms whose bodies are literally burned from the inside out as the sun heats the fuel they have ingested.

“Unfortunately, we’ve had a lot of experience in how oil affects marine life, ecosystems, coastal communities, and fisheries,” said Christopher Mann, with the marine program of the nonprofit Pew Environment Group. “The iconic images of oiled seabirds are just the tip of the iceberg, because oil spills affect life up and down the food chain.”

Fill a jar with plankton from the local waters in the spring and it will typically contain the larvae of 80 species. All the eggs and hatchlings are surface dwellers, with almost no ability to swim away from the slick.

“Eggs and larvae that dwell near the sea surface are especially vulnerable,” said Jeffrey Short, Pacific research director for Oceana, a nonprofit organization that works for marine preservation.

The components of crude oil, he added, can produce developmental deformities at low concentrations, and “any such deformities are ultimately lethal to organisms in the wild.”

Even normal feeding might expose sea creatures to harm from the spill: sea grass and other vegetation covered in oil are ingested by fish that are then eaten by bigger fish and finally by manatees or other marine species. It is this food-chain effect that worries Larry Schweiger of the National Wildlife Federation.

“It is not a question of whether all these species will be affected now. It is when,” he said.
From Wildlife still exposed to Exxon Valdez oil 20 years after
Wiley-Blackwell EurekAlert 14 Apr 10;
Scientists in Alaska have discovered that lingering oil from the 1989 Exxon Valdez spill is still being eaten by some wildlife more than 20 years after the disaster.

"Our research has shown that oil remaining in the area, particularly in inter-tidal areas, was encountered and ingested by some near-shore animals."
From Why coastal oil spills can pollute for decades: study
Marlowe Hood Yahoo News 17 Jan 10;
Up to now, experts puzzled over why remnants of the 11 million gallons of crude that fouled some 1,300 kilometers (750 miles) of Alaskan coastline have persisted for so long.

At first it seemed that nature, with some help from technology, would soon wash away one of the worst environmental disasters in history. But within a decade it became apparent that the rate at which the oil was disappearing had dramatically slowed, from 70 percent per year to about four percent. Today, it is estimated that some 20,000 gallons remain.

Michael Boufadel and Hailong Li of Temple University in Philadelphia, Pennsylvania wanted to find out why this oil was not been broken down through biodegradation and weathering, as had been widely predicted.

Collecting field data and running computer simulations, they found the key lay in the fact that affected beaches consisted of two layers, each with different properties. The geographically variable impact of rising and falling water tables also played a critical role.

Oil was temporarily stored in the porous upper layer, slowing the rate at which it was subject to weathering. This is an environment lacking the kind of nutrients needed by oil-eating micro-organisms to thrive further protected the fossil fuel.

The second layer, while composed largely of the same materials, was far less porous: on average, water moved through the top layer 1,000 times faster.

When the water level from declining tides fell below the interface between the two layers, oil seeped from the upper to the lower stratum, especially where there was little or no freshwater discharge to compensate. "Once the oil entered the lower layer, it became entrapped by capillary forces and persisted," the authors said.

Because of the even lower oxygen content in the sub-stratum, the crude was not degraded and has remained suspended.

The study also said that oil tends to linger on gravel beaches more than on sandy ones.

More related reports
  • Oil, risk and technology: Choices we need to make William Jackson, BBC Green Room 18 May 10: raising deep questions about our addiction to oil. Compensation may be paid for immediate damages - but what about the wider environmental harm?
  • Significant global oil spills Reuters 5 Jun 10; a selection of some of the most significant oil spills, including marine leaks, pipeline leaks and oil dumping, in terms of severity and size across the globe.

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