The discovery was made by biogeochemist Dr Rainer Amon while the Arctic Sunrise carried out four transects  of the Gulf of Mexico. The scientists and crew of the Greenpeace vessel deployed Amon’s sampling equipment to analyze the levels of dissolved oxygen in the water column – a clear marker for bacterial degradation of oil and gas , and to take seawater samples from several points in the water column.
“From the measurements we’ve taken,” said Dr Amon, “we see clear signs of oxygen deficiency on a large transect starting at the Macondo wellhead, all the way 300 miles to the west. How much of oil and gas components are still in the water is something that we need to now investigate in the laboratory”.
The levels of dissolved oxygen did not fall as low as Dr Amon would expect if a major portion of the oil and gas had been consumed in these waters, suggesting that the petrochemicals, have not “gone away” as has been claimed by the government, and that between three and four million barrels of oil still remain unaccounted for following the disaster.
“What we want to do,” explained Dr Amon, “is to come up with a mass balance of how much oil was put in the water column, the sediment surface. When we’ve analyzed all the samples we’ve collected for our work and that of our colleagues, we hope to come up with a pretty good estimate of how much of the oil and gas was put into the system - hopefully we can then come up with good ideas of where that missing oil and gas has gone.”
A colleague of Dr Amon’s also on board the Arctic Sunrise, benthic ecologist Cliff Nunnally, carried out a separate survey on the effects of the oil released into the benthic environment, by taking sediment samples from the ocean floor at depths of over 4300ft (1300m) just 4.5 nautical miles (8km) from the site of the disaster .
The samples retrieved – some of which contained visible amounts of oil with a strong odor - will be used to investigate the ecological status of the benthic environment and will be compared to base-line data collected by the scientists earlier this decade. This will provide a clear understanding of the effects of the massive quantities of oil released onto the benthos of the Gulf of Mexico.
Greenpeace has sent also sent a sample of this oily sediment to an independent lab for analysis, for fingerprinting to Deepwater Horizon disaster, and to check for presence of dispersants.
The Arctic Sunrise is on a three-month research expedition to investigate the environmental impacts of the Gulf oil spill, during which it has welcomed on board scientists from several US academic institutions in the Gulf of Mexico, and provided a platform for independent research.
“Despite everything that BP and the government would like us to think, the truth is, the oil spill's impact is not ‘over’”, said Greenpeace US research director Kert Davies. “Scientists know better, fishermen know better, the people of the Gulf and certainly the clean up crews endlessly picking up tar balls know better. The government and BP need to be honest with everyone about the extent of the damage, admit what they do not know and prevent this from ever happening again."
In October, the Arctic Sunrise will be working with Steve Ross of University of North Carolina Wilmington and Sandra Brooke of the Oregon Institute of Marine Biology and Marine Conservation Biology Institute using a submersible to dive to the floor the Gulf of Mexico, where they will study the effects of the oil disaster on coral reef habitats and marine communities.
NOTES TO EDITORS
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 Four transects were carried out at locations west of the spill site, investigating what is thought to have been a major trajectory for the deepwater plumes of oil and gas.
 The CTD probe lowered from the Arctic Sunrise into the Gulf measures physical parameters on its descent through the water column. CDT stands for conductivity (from which salinity is determined), temperature and depth (measured as pressure). The particular model used by Dr Amon also contains a fluorometer and dissolved oxygen probe. The latter is now a key tool in locating the fate of petrochemicals in the gulf; any metabolic activity resulting from bacterial degradation of the oil and gas consumes oxygen, and as oxygen transport at depth is very slow, this consumption results in a marked reduction in the dissolved oxygen levels for a considerable time period.
Once the probe reaches maximum depth, back on ship, the scientists carefully observe the graphs produced in real time, for evidence of dissolved oxygen anomalies. As the CTD returns the surface, water sampling bottles are triggered at the depths considered most interesting based on the graphs. Once recovered these samples are probed and analyzed for a range of parameters. Back in the laboratory, the scientists will study the influence or oil and gas determining the amount of metabolised hydrocarbons in each sample by looking at the ratio of carbon isotopes in the dissolved inorganic carbon (the products of metabolism), genetic studies will examine shifts in the bacterial community composition, and two techniques will be used to determine the levels of PAHs (polycyclic aromatic hydrocarbons) present.
 Nunnally took samples of the seafloor at locations south, west and east of the deepwater horizon spill site using a “box core” – a large metal device that samples the top two feet of sediment.
Scientists from a range of disciplines will analyze the sediments gathered:
Chemists will determine the abundance of different elements, isotopes, ions and compounds both to characterize the composition of the cores and to determine the levels of oil and oil derived carbon they contain.
Geologists will determine the physical nature of sediment.
Biologists will then work on three levels studying the bacteria, meiofauna (particularly the nematodes), and macrofauna present. They will determine the community composition and abundance of the life that dwells in the benthos at these depths and will compare the results to baseline data to gain understanding into the disturbance to the ecosystem caused by the massive influx of oil.
Dr Rainer Amon
Associate Professor, Department of Marine Sciences, Texas A&M University, at Galveston, and Department of Oceanography at Texas A&M University, at College Station
In June 2010, Dr Amon was on board the NSF vessel RV Cape Hatteras, tracing the movement of subsurface oil plume near to the Deepwater Horizon site. This time out, he will be studying the extent, composition and impacts of the oil and gas that has remained in the Gulf’s deep water, by gauging dissolved oxygen levels and stable carbon isotopes of dissolved inorganic carbon as a way to locate areas affected by the oil spill.
Dr. Amon holds a Ph.D. in marine sciences from the University of Texas and a Masters in Zoology from University of Vienna. After his Ph.D. Dr. Amon spent eight years as a researcher at the Alfred Wegener Institute in Germany before accepting his position at TAMUG in 2003. He has worked extensively in the Arctic, using organic matter from Russian rivers flowing into the Arctic Ocean, to trace pollution, the movement of water masses, and other environmental changes. Amon has participated in numerous research expeditions to the Amazon River and the Arctic Ocean during his career. More locally, Amon is a co-investigator to study the growth of E coli in Houston bayous by combining geochemistry with molecular ecology, a multiyear study funded by the Texas Commission for Environmental Quality.
Clifton C Nunnally, Phd. Student in Oceanography, Texas A&M, at Galveston
Nunnally’s focus on board the Arctic Sunrise is on the sediment communities close to the Deepwater Horizon disaster site, where he will investigate whether oil has reached the bottom, and if it has, to examine the how it has affected the biota – such as marine invertebrates.
With a Bachelors Degree in Science from Abilene Christian University (1998) and a Masters from Texas A&M University (2003), Nunnally’s work has centered on two large oceanographic studies: the Deep Gulf of Mexico Benthos (DGoMB) project which was a initial survey of deep-water habitats prior to the expansion of oil and gas exploration on the Northern Gulf of Mexico continental slope, and the physical and biological processes behind the Gulf of Mexico ‘Dead Zone’. Clifton Nunnally also spends each summer at Alice Cover Research Station located near Simpson Bay in Prince William Sound, Alaska, where he focuses on benthic invertebrates such as clams and starfish, which sea otters feed on.
Dave Walsh, Greenpeace Media Officer on board the Arctic Sunrise, , +31 20 712 2616
Molly Dorozenski, Greenpeace Media Officer in New York, , +1 917-864-3724