Deepwater Horizon, Gulf of Mexico, Oil Spill Research

During the summer of 2011, the group will participate on two research expeditions to the Gulf of Mexico to further explore the distribution and fate of oil in the deepwater sediments and to monitor the activity water column and benthic microorganisms.  These expeditions will provide another time point in the extensive time series data set we have accumulated pre- and post- Macondo Blowout.

Additionally, links to and PDFs of scientific papers pertaining to oil and gas degradation in the marine environment; information on various oil spills throughout the world and in US waters; links to websites of organizations and agencies with information pertaining to the Gulf of Mexico, various oil spills, and oil and gas degradation in the marine environment; etc., will be posted on a new research and resources page.  Some papers are already posted there.

Today I did a “Cover it live” chat with Erik Stokstad from Science Magazine discussing some of our recent findings related to the BP oil well Blowout.  For any of you who might be interested, you can replay the chat here.

Our papers related to our blowout work are starting to come out as well.  The first one was just published in Nature Geoscience last week. If you have problems accessing the article let me know.

Finally, I have received numerous questions lately and will be (slowly) answering them on the blog.

November 23, 2010: Seafloor “cold seeps” are areas where cool fluids from the deep subsurface are leaking out of the seafloor.  The temperature of these fluids is usually less than 20ºC.  Most methane-fueled or methane and oil fueled cold seeps share some common features, such as gas vents or bubble streams, gas hydrate mounds, microbial mats, and chemosynthetic animals and associated heterotrophic fauna. The biological and chemical diversity of these habitats is high.

Barite chimney (white) at a mud volcano.

On our current, we’ve been studying a different type of seep, places where super-salty brine, along with oil, gas, and fluidized mud, leak from the seafloor.  When we started this cruise, we knew of two varieties of brine seeps in the Gulf of Mexico: mud volcanoes and brine pools/lakes.  Mud volcanoes are characterized by high rates of fluid flow, higher temperature fluids (up to 40 ºC), and flow features like barite chimneys.  Mud volcanoes do not usually have dense chemosynthetic communities associated with them because the fluidized mud impedes their development.  Brine pools, lakes or basins are thought to have lower rates of fluid flux and these habitats often support development of dense chemosynthetic communities.

Bubbling mud pots along the shore of a brine pool

Our first ALVIN dive to GC246, a mud volcano site that had been imaged with JASON but never visited by a manned-deep ocean research submersible, revealed many surprises.  This site had a little bit of everything, but some things just should not have been there.  The seafloor around the site was dotted with mud pots and chimney structures.  The brine flowing from the mud pots collected into a small brine pool.  Upon close inspection, we realized the chimneys were not comprised of barite, rather they were sulfide chimneys.  Sulfide chimneys at a brine seep?  That’s pretty unusual.

Colorful sulfide chimney (about 7 cm wide and 15 cm tall).

This site was also unusual in that it was characterized by several different types of mineral crusts of varying color, red, white, orange (see image gallery below).  At first, we thought these were microbial mats, but upon closer inspection, we realized they were primarily mineral.  We did find lush microbial mats at this site, mainly white Beggiatoa, but most of the surface features were mineral crusts, which is strange.

Whispy Beggiatoa meadows along the edges of a mud volcano

A lot of work in the lab will be required before we can explain the features observed at this site but documenting the chemical composition of the lukewarm mud pot and brine pool fluids is where we’ll start.

Multicore tubes filled with red mud!

November 22, 2010: Every day at sea usually provides at least one surprise.The Orca Basin has provided us with quite a few big surprises, the most striking of which was the discovery of red and pink (!) sediments in the middle of the basin. In the Northern and Southern mini-basins, we collected cores of black, extremely sulfidic mud. When we sent the multiple-corer over the side in the central Orca Basin, we expected to retrieve something similar but much to our surprise, the mud recovered from the more shallow (2000 vs. 2200m) central basin was red (see image gallery below for more photos). Red and pink deep sea sediment…where in the world does that come from?

ALVIN group discussing options before the first Orca Basin dive

We don’t know so ALVIN dive 4650 aimed to explore this area in detail.  At this point, I have to give long overdue credit to the ALVIN group, particularly expedition leader Bruce Stickrott.  Without them, we would not be able to accomplish the amazing things we do!

As we headed towards the bottom, we passed through several different interfaces with thick brine fog; each layer was distinct, the most shallow had swimming amphipods, the next two deeper, anoxic layers were simply microbial wonderlands.  When we finally reached the seafloor, the surface was orange/brown, typical of sediments coated by iron-oxyhydroxides (we think…lab experiments are required to  clarify this) but with pink sediment below.

Orange/brown, iron-rich terrace; at the lower edge a brine flow was visible.

When we collected sediment cores at this location, we saw that the thin surficial brown layer covered, yes, the hot pink layer sampled in the multiple core samples. We drove up the ridge, which was strangely enough, terraced, and at the edges of these terraces, there appeared to be brine flows: dark, reduced patches where if one looked closely, you could see the shimmering produced when fluids of different densities mix. This is one of the many reasons I love ALVIN: there is no substitute for seeing these things with your own eyes. It’s so different from looking at the video feed from an ROV. There is no replacement for “being there” and seeing things live, even if it’s cramped, cold and you’re looking through a tiny viewport.

Pink (!) sediment collected from the sponge garden

We collected sediment and brine fluid samples as we traversed up the ridge and were amazed the entire time by the pervasive pink sediment underlying the orange/brown surface layer. The pink sediments had the consistency of freshly mixed, but not yet firmed, jello, and were quite a challenge to sample. But our pilot Bruce is an ace at coring and we got some great cores.

Once we moved further up the slope, we entered the sponge garden area. Here, sponges are abundant on the seafloor and the sediment is still pink. We saw at least five or six different species of glass sponges and each was spectacularly beautiful.  I’ve posted more images of sponges in the gallery below.

Our hypothesis is that the pink color is due to some pigment that the dominant microorganism carries. It will be exciting to tease apart this pink microbial mystery.

November 19, 2010:  The Orca Basin occupies a large (~150 km²) depression (roughly SE  to NW) along the continental slope in the Northern Gulf of

Multibeam mosaic of Orca Basin bathymetry (map is oriented NW, lower left corner, to SE, upper right corner). Purple reflects deeper depths.

Mexico.  At the basin bottom, a hypersaline brine (260‰, about 7 times the salinity of seawater) fills depressions below roughly 2200m.  There are two deep depressions, one to the north and another to the south end of the basin (the dark purple colors on the map above) are the focus of our work here.  We will also sample in the middle of the basin, where it is less deep but where previous studies documented active brine flows.

The brine layer is about 250m thick and it derives from dissolution of Jurassic age salt that underlies and surrounds the basin.  This basin is very different from the other brine lakes/pools and mud volcanoes we are studying because brine seeps from the canyon walls into the basin rather than venting up through the seafloor.  The  Orca basin could be more similar to brine basins in the Mediterranean than to mud volcanos and upward-advection-derived brine lakes and pools in the Gulf of Mexico.   We aim to make this comparison.

CTD profile through the southern mini-basin of the Orca Basin

Very little is known about the microbiology of the Orca brine or overlying seawater.  The strong geochemical gradients in the basin are certain to drive significant and dramatic changes in microbial community composition and microbial activity.  Over about 150m of depth, the salinity increases from that of normal seawater (about 35 PSU) to over 250 PSU.  Over the same depth interval, temperature increases slightly (from 4 to 5 ºC) and dissolved oxygen concentrations decrease to zero.  The halocline (salnity increase) and oxycline (oxygen concentration decrease) are separated by about 75m.  We were very surprised to observe that the concentration of colored dissolved organic matter increased by over 10 fold over this range, meaning that there is potentially a lot of microbial fuel (dissolved organic matter) in the brine.

The halocline was visibly thick with microbial life.  We collected samples across the halocline and oxycline using the ALVIN-mounted brine sampler and

Dense microbial life along the halocline of the Orca Basin

the CTD-rosette and are currently analyzing gas concentrations, chemical composition, and conducting rate assays to evaluate how microbial processes very over the various interfaces.  We are sampling at three sites in the Orca Basin, the Northern sub-basin, the Southern sub-basin, and the middle, most shallow, sub-basin.  We are also collecting sediments from these sites to characterize sediment biogeochemistry and microbiology.  More on that tomorrow…

November 17, 2010:  When fluids seep out of the seafloor, they provide chemical substrates to fuel both microbial and macro-biological communities.  Even hyper-salty brine seeps are “oases” of life along the seafloor.  While the salt content of some seafloor brines can create challenges for macro-organisms, microbial life thrives in brines.

Gas bubbles venting from a mud volcano

At the venting center of a brine flow, numerous bubbles of gas and drops of oil are apparent in the water column.  At some sites, these vents may occupy a small area (2 x 2 m) while at others, the vents occupy large  areas (50 m long x 3 m wide faults where bubbles explode from the subsurface).  Along with dissolved gases, the venting fluids deliver nutrients (mainly nitrogen and bioactive trace metals) and dissolved organic carbon to the seafloor; these materials can fuel microbial processes that further promote growth and proliferation of macro-biological communities.

Away from the main vent, brine flowing along the seafloor can look rather strange, often there is a lighter colored, ropey structure to the brine flows, and because they are dense, they flow down slope (see image gallery below).  The areas adjacent to brine lakes or pools is often home to diverse animal life, ranging from tube worm bushes, mussels, holothurians (sea cucumbers), heart urchins, clams, pogonophorans and microbial mats to various other invertebrates (see image gallery below).

Dense mussel beds along the edge of a brine flow

We are collected brine and sediment samples from around various animal habitats to evaluate how variations in geochemistry and microbial activity alter the animal habitats.  Some might find the diversity of animal life around these brine seeps  shocking.  Microbial mats are abundant (1st image gallery below).  Meadows of holothurians (better known as “sea cucumbers”) and heart urchins are abundant along the edges of brine lakes and pools (2nd and 3rd image gallery below).  Mussel beds are home to a diverse variety of associated fauna including fish, crabs, invertebrate worms and snails (4th image in the gallery).

We’re moving next to the Orca Basin, which promises to be one of the most interesting sites we visit during this cruise!

Hard sonar reflection (yellow) created by vigorous gas bubble discharge (GB425 mud volcano)

November 15, 2010:  On of the most significant challenges faced when working at areas with active fluid venting is to quantify the fluid flux rate from the deep reservoirs to the overlying water column.  A primary objective of this project is to link microbial community composition and activity to differences in fluid chemistryand fluid flux, so we have to quantify the fluid flux and evaluate whether, and if so how, the flux changes over time. To the eye, fluid fluxes at these sites appear high:  this image shows the strong (yellow) sonar reflection of gas bubbles being released along a fault line at the GB425 mud volcano. The wall of bubbles was about 50 meters long and about 3 meters wide (see image gallery below to view the bubble wall).

Rick Peterson and Rich Viso (CCU) preparing samples for radium analysis

To achieve our objective, we are characterizing the fluid’s geochemistry and using a suite of inert tracers, including temperature, salt content, radon concentration, and radium isotopes, to independently estimate and verify the rates of fluid flux.  Temperature and salt content are conservative tracers and we measure these parameters in the brines using a conductivity-temperature sensor, which we lower carefully through the fluid.

To evaluate change in fluxes over time, we deploy logging temperature sensors in the brine so that we can evaluate an annual record of temperature in the fluid and in the overlying seawater.   Rick Peterson and Rich Viso (both from Coastal Carolina University) are quantifying concentrations of radon and radium in the venting fluids and overlying in the water column to help constrain fluid fluxes.  The data they are generating is an essential component of the information required to constrain fluid fluxes at the study sites.

When temperature and salt are combined with radon and radium, two excellent inert tracers of deeply sourced fluid input, we expect to be able to constrain fluid fluxes quite well.  Quantifying the flux is complicated because we must know the chemical signature of the deep “end-member” fluid and to do this, we use the brine sampler to sample the deepest parts of actively venting sites (see image gallery below of  brine sampler intake penetrating into the deep brine).

Multibeam seismic image of a mud volcano; the hotter colors are more shallow, showing how the mud volcano rises from the seafloor

The features we are studying are dramatic, as shown in this multibeam seismic mosaic of an active mud volcano, the so-called “Hot Site”, produced by Rich Viso (Coastal Carolina University).   The combination of seafloor mapping, sampling brine fluids and the overlying water column, and the holistic suite of geochemical tracer being applied will allow us to obtain the “flux” data necessary to link habitat parameters and habitat change to microbial community dynamics.

Kirsten Habicht (U Southern Denmark) having a cold water bath after her first ALVIN dive

November 13, 2010:  Every cruise on board the R/V Atlantis with the DSV ALVIN has one thing in common – amazing discoveries and fun initiation rituals.

Each day begins around 6:30, with final checks of the sub and ultimately loading the science observers of the day into the ALVIN (Melitza Crespo is shown below).  We have several scientists who’ve never been in ALVIN before and for them there is a special treat upon returning to the surface, you can look forward to a bath in lots of 4ºC water.  Brrrr.  There’s even a special throne where one sits while receiving this special treat (shown here is Dr. Kirsten Habicht’s initiation from two days ago).

Melitza Crespo (UGA) getting ready to enter the ALVIN.

We are working at depths around 500-2000m.  It takes about half an hour to go 500m so two hours to descend 2000m.  Once you’re on the bottom, you have about 5 hours of time to collect samples.  Then, the sub returns to the surface and is picked up by the ship.

We spent our first four dives working in the Alaminos Canyon area and saw some unbelievable features on the bottom.  We built a special sampler, we’re working on a name for the gadget but for now it is “BAFS” (Brine Anoxic Fluid Samper) [shown below] that we use to sample targeted (specific) brine layers.  The reel allows us to lower an intake hose to a specific depth and then we use a pump to introduce brine sample into the chamber.  We can collect 12 brine samples at a time and when the sub returns to the surface, we take the bottles off the sub and move them to the cold room for sampling [shown below].  The bottles keep the brine from heating up and keep the samples from losing the dissolved gas on the way up.

Everyone spends a lot of time in the cold room processing sediment and brine samples (see below) but it’s worth it because, eventually, you get a close-up view of the seafloor in your own ALVIN dive in addition to the fantastic data on these unique habitats.

The Alaminos Canyon “Red Crater” stands out as the most spectacular site we’ve visited so far.  The red (iron) minerals present at the seafloor are not stable at surface pressures and rapidly degrade.  We’re eager to get them home to see what they are made of.

November 12, 2010:

DSV ALVIN in front of the R/V Atlantis (courtesy WHOI)

On November 8th, we sailed from Galveston Texas on board the R/V Atlantis which carried the Deep Submergence Vessel (DSV) ALVIN, t he ALVIN crew, the Ship’s crew, and 21 researchers from across the globe.

This collaborative project involves scientists from the University of Georgia, the University of North Carolina at Chapel Hill, Florida State University, Harvard University, the University of Bremen (Germany), the University of Southern Denmark, and the University of Minnesota.

Samantha Joye about to climb on board ALVIN

Our task over the next three weeks is to explore and describe the microbiology and biogeochemistry of deep seafloor hypersaline habitats.  We all enjoy sailing on the Atlantis and working with the crew of the ship and the DSV ALVIN.  Seeing the bottom of the ocean — things no one has seen before, riding around in a small metal ball beneath a mile or more of water …it’s an indescribable experience.

Astounding out-of-this-world hypersaline habitats litter the seafloor in the Gulf of Mexico.  Our project — the Gulf of Mexico Hypersaline Ecosystem Microbial Observatory — is funded by the National Science Foundation.  Hypersaline environments are abundant in the Gulf because salt underlies much of the sediment along the Northern Gulf and over time this salt dissolves and leaks slowly (brine pools/lakes) or is violently ejected (mud volcanoes) from the sea floor.   The range of hypersaline habitats is large and we learn something new on almost every dive.

As with our previous cruises of late, everyone is putting in long hours and working extremely hard.  Because we’re working in very deep environments (>2000m water depth), we will spend a lot of time working in a 4ºC cold room, processing samples retrieved from the seafloor.

Samantha Joye and Vladimir Samarkin working in the 4ºC cold room

We’ll be crisscrossing the lower and upper slope studyinghypersaline mud volcanoes and brine pools and lakes for about three weeks, and then we head back to the Macondo wellhead region to visit the bottom in ALVIN.   We will spend a week mapping and sampling oil on the seafloor. The first two sites we visited are in Alaminos Canyon (AC), a deep canyon (2300 m water depth) that cuts into the Sigsbee

Samantha Joye typing away during the descent to AC601.

Escarpment.  At this depth, it takes about 1.5 hours to reach the bottom in ALVIN, so we work on the way down (well, sometimes we sleep on the way down and very often on the way up!).

ALVIN's map track (green) around the edge of the AC601 brine lake

Our first study site,  AC601, is an inactive brine lake.  We mapped the AC601 brine lake perimeter with ALVIN (picture, to the left).  This place is unlike anything you could even imagine – it’s a large feature (about 100m in diameter), and it’s deep (20m).  Within the lake floats barite (a mineral comprised of barium and sulfate) icebergs and along its edge, is a 1-

Edge of the AC601 brine lake showing "Barite Beach"

2 meter wide ‘barite beach’ (picture to the lower right).  Beyond this, one sees a variety of animals, mussels, urchins, holothurians, and numerous other invertebrates.   The brine in the lake is three times more salty than seawater, yet it is teeming with microbial life.  Even though the sediments become salty just beneath the surface, they harbor diverse microbial and animal communities.  So, while these brines are certainly “extreme” environments, they provide habitat to diverse forms of life from microbes, to urchins, to worms and even fish!

View of the "Red Crater" from the Pilot's window (the things sticking up in front are the tube cores we use to sample sediment

The second AC site we visited today, the “Red Crater”, is an active mud/brine volcano (picture to right).  The Red Crater could just as well be exist on the surface of Mars.  The red color comes, we believe, from iron minerals that precipitate when the brine reacts with overlying seawater.  The white material in the pictures is a combination of barite and elemental sulfur (picture lower left).  This is truly one of the most bizarre and amazing places I’ve ever seen.

Red (iron rich) and white (barite, elemental sulfur) precipitate as the upwardly flowing reduced brine mixes with ambient seawater. the surfa

We have our final dive to the AC region tomorrow, and then we head to Garden Banks in search of vigorously venting mud volcanoes!

September 5th, 2010:  Sometimes, I get a feeling that the day is going to offer some surprises.  This morning, I had a feeling.

We’ve spent a lot of time in the Southwest quadrant over the past two weeks searching for oil and gas.  We’ve seen mostly weak signals.  The sediments at the sites we visited during that time were oxidized and did not contain a lot of gas or oil.

Looking through the hole created by a burrow in far field control sediments (credit: Melitza Crespo)

Until we sampled at a site about 20 miles offshore from Mississippi, we did not see oil along the seafloor.  At that station, we saw a thin layer (couple of mm) of what looked like sedimented oil.  We won’t know the oil content (or source) until we do detailed analyses after the cruise but oil has a distinct feel and this sediment felt oily.  We got a glimpse of what we had expected to see.

Today, at a site about 16 nautical miles from the wellhead, we dropped the multicorer into a valley.   When the instrument returned from the bottom, it contained something we had not seen before: a layer of flocculent, sedimented material that was cm’s thick.  The top, apparently recent layer, contained some fraction of oil.

A layer of oil on a sediment core (from a site NE of the wellhead)

At a natural oil seep, the entire sediment column is saturated with oil.  Cores of sediment collected from natural seeps are oil-stained top to bottom and often the water overlying the sediment core has a thick (mm to cm) layer of crude oil floating at the top.  Natural oil seep sediments are distinctive.  The photos of cores shown from GC185 here are extreme examples (they are VERY oily!) but the point is that the entire sediment column is oil stained at a natural seep.  At the site we visited today, the oil obviously came from the top (down from the water column) not the bottom (up from a deep reservoir).

Oily sediments from a natural Gulf of Mexico cold seep, Green Canyon 185.

What we found today is not a natural seep.

We collected control sediments in a region to the south east of the wellhead that was never overlain by the blowout oil slick.  Those sediments consisted of fine grained sediment mixed with calcareous ooze.  There was no hint of oil in the control sediments.

The near shore sediments contained grayish muddy clay and a thin layer of orange-brown oil at the  surface.

The sediments we collected today were similar at the bottom — gray muddy clay — but the upper few cm consisted of oil floc — we call it “oil aggregate snow”, because it settled down to the water column to the seafloor just like snow falls from the sky to the ground.

Close up of the oil floc/sediment interface (L) and zooming in to see a chunk of oil snow (middle) and then zooming in more to see the oil aggregates (R, small dark brown/black spots).

We will determine how much oil is in this layer and evaluate the rates of microbial metabolism in the sediments when we return to UGA.  We want to know whether and how much of this material lies along the seafloor at other sites.  So, tomorrow, we will go to a site about 12 nautical miles northwest of the wellhead and run a full station there.  We’ll see what the sediments look like there and with that knowledge, we’ll decide where to go next.