The gulfblog is back. Sorry it took me so long to do this update. The past couple of weeks have been the busiest and most demanding of my career. Everyone in the lab has been working feverishly to complete the analyses of samples collected on the Pelican and Walton Smith cruises. Those data sets are almost complete and I am now working to complete two manuscripts that I hope will be submitted by the end of June. Below I answer some of the questions that came in to the blog over the past two weeks. At the end, I talk about what our next research steps will be.
QUESTIONS POSED TO THE GULFBLOG
(1) Could you briefly define both, or distinguish between, DOM and CDOM?
Colored dissolved organic matter (CDOM) is a fraction of dissolved organic matter (DOM) that is “optically active” or “optically measurable”. Put simply, CDOM absorbs light. Oil is a type of CDOM. The light CDOM absorbs ranges from blue to ultraviolet so CDOM makes water appear greenish to yellow-green to brown (the color changes with increasing CDOM concentration).
(2) If you could gather dispersant concentration data from multiple water samples in the gulf, what question(s) would you try to answer with that information.
I can easily envision several ways to use dispersant concentration data. First, it would be useful to know how widespread – and at what concentration – the dispersants are present. Some forms of COREXIT contain dangerous components (e.g. 2-Butoxyethanol) and COREXIT is more toxic to some organisms than crude oil. COREXIT can be long-lived in the environment so we need to know the concentrations present around the Gulf – not just in the areas where it was applied; it will move around with the ocean currents. I have added the material safety data sheets (MSDS) for COREXIT 9500 and 9527 to the resources page of the blog. Read these for yourself to learn more about these products. Other questions—how do these dispersants impact microbial populations and microbial activity; are dispersants bioaccumulated, in other words, are they passed up to higher trophic levels?; are the dispersants toxic to key Gulf fishery species (shrimp, blue crap, tuna) and if so are some phases (larval, juvenile or adult) more sensitive than others?
(3) Relative to the daily flow and chemistry of the Mississippi River, how much larger and more toxic is the Deep Water spill?
While this could be an interesting mental exercise, comparing the Deepwater Horizon spill inputs to Mississippi River inputs is like comparing apples to grapefruits. They are nothing like one another: the average daily discharge of the Mississippi River is about 12,700 m3/s and the BP blowout discharge rate is <1 m3/s. Estimates of BP blowout flow rate are steadily improving, see the “Flow Rate Technical Group” reports (http://en.wikipedia.org/wiki/Deepwater_Horizon_oil_spill#Spill_flow_rateand http://www.deepwaterhorizonresponse.com/go/doc/2931/627011/ for more detail on this topic). The BP blowout fluid is comprised of oil, thermogenic gas, fluidized mud, produced water and perhaps brine and condensates. The dominant components of the BP blowout fluid are present in only trace amounts (oil) or at inconsequential levels (thermogenic gases or brine) in Mississippi River water.
(4) What is the background spill rate of all daily operations in the Gulf? (500 platforms leaking 1 barrel a day?)
Natural oil seepage in the Gulf of Mexico amounts to about 1000 barrels a day but this is spread across the ENTIRE Gulf of Mexico rather than being focused in a single area. The BP spill is at least 40 times (40,000 barrels a day) the natural seepage rate. At this time, it is unclear how much additional oil and/or gas is introduced into the Gulf of Mexico each day due to the routine development operations related to oil and gas extraction but most likely, this number is more comparable to the rate of natural seepage than to the flux resulting from a blowout at any water depth.
(5) Any update or news on oxygen depletion in the Gulf’s waters and whether this depletion is related to the oil spill?
I am still analyzing our data but I see a consistent trend of increased oxygen depletion in plume waters with distance from the leak site. Reports of oxygen depletion in other parts of the Gulf are coming in as well. Such patterns of oxygen depletion are unusual and require additional data (so more research cruises) and careful monitoring.
(6) Couldn’t purposeful mixing of surface and deep waters solve this oxygen depletion problem.
Maybe but maybe not… The deepwater plumes are at >1000m water depth. It is not straightforward to mix those waters with surface waters. Plus, do we really want to introduce the plume waters to the surface? They could contain dispersant. We know they contain a lot of gas and some oil. We do not know enough at this point to conclude that mixing of these plume waters with surface waters would do more good than bad. Again, we need more data.
(7) Given the toxic nature of the VOC, when the oil mess hits shores with the first storm of the upcoming season, how will this effect those living near shore? Specifically, a) well pollution given they likely have shallow wells or surface water for consumption. b) VOC is toxic to humans.
This is a complicated question and one that does not have a clear, straightforward answer. Certainly, having oil-laden seawater pushed inland by a storm surge is not a scenario anyone wants to see. Surface waters could be polluted and so could groundwaters. Some components of oil (volatile organic compounds or VOC) are toxic so the distribution of these compounds in the surface slicks would determine the magnitude of any storm-related problem. The VOC content of the surface slicks is something that is being tracked carefully and people living along the shoreline would be warned, as needed, if a storm comes through the region.
(8) Some sources speak of a very severe limit on what is reported? Do you have any comment on this aspect?
I can only speak for myself -- I have never been told “what to say”. I believe everyone wants to be clear and as certain [as is scientifically possible] before results are presented to the public. Some information/data is required for the “Natural Resource Damage Assessment” (NRDA for short) and because those materials will be used in litigation at a later time, they may not be released to the public. I know everyone is starved for information but the reason things are coming out slowly is that we want to be certain and clear about what we say.
(9) Can a chemical fingerprint of the oil really be accurate when the same has traveled for weeks mixed with dispersants through tens of miles of water and a 5000' pressure gradient with multiple thermal layers and biological degradation?
Oil is a complex mixture that contains gasolines, C15+ saturated and aromatic compounds, waxes and asphaltenes. The relative abundance of these different fractions, along with their hydrogen and carbon isotopic composition, generates a unique molecular fingerprint for oil from a given reservoir. Another chemical component of oil that contributes to it’s “fingerprint” is its sulfur content. Chemically fingerprinting weathered oil is more difficult but the combination of relative fraction abundance, carbon and hydrogen isotopic composition, and sulfur content provides a powerful combination that can identify the source reservoir.
(10) Is a plume map of concentrations being developed? Are single plumes traceable from the well head out 40+ miles?
We were able to trace the Southwest plume out 20+ miles. The Northeast plume is traceable for 30+ miles. So, yes these features can be tracked quite far from the source.
(11) I saw on the blog that you could dirty a cloth significantly by flowing the plume water through it; what kind of concentrations are you encountering?
We don’t have the data yet so do not yet know the concentrations of oil in the subsurface.
(12) What types of oily water are we actually seeing? Seems that 99% of the press coverage involves surface conditions, but the potential for environomental problems like 99% below the surface.
The subsurface environmental consequences of the plumes, such as oxygen depletion, are as (or more) likely to be driven by the gas content than by the oil content. Because gas is rapidly oxidized by aerobic microorganisms, gas consumption can drive oxygen depletion. The slicks at the surface are supported by continuous flow from the riser pipe to the surface. The subsurface plumes are similarly linked to flow from the riser pipe. Probably there is dispersant in surface waters and in plume waters. The surface oil would form surface “sheen” without application of dispersant—when the oil thins and spreads on the surface, it forms “sheen”.
(13) Will you publish your cruise analysis on your blog?
General results will be summarized on the blog. When papers are published, I’ll post links to the PDFs so that people can obtain them if desired.
(14) What is the sampling regime for phytoplankton, zooplankton, ichthyoplankton, invert larvae?
Our focus is microbiology, basically the components of the foodweb smaller than most phytoplankton or zooplankton. Other groups are working on these components of the pelagic and coastal ocean food web.
(15) Are you tied into SLOCUM Gliders from Mote and Rutgers?
There are several groups using gliders in the Gulf (Rutgers, WHOI, the Navy and iRobot). I’m not directly involved with this but I’m following their results on line.
(16) How is the oil spill affecting the normal Mississippi River dead zone?
It’s unlikely that the BP spill will impact the distribution of the seasonal hypoxic zone around the mouth of the Mississippi River.
(17) Have you seen any evidence of other sources of oil such as might indicate fractures in the sea floor near to the site of the wellhead explosion?
No, we have not seen any evidence of fractures in the seafloor near the riser pipe.
(18) I’m doing some analysis for the iRobot data we collected and I could use a little guidance. How is the CDOM relative signal calculated in the plot shown on the Gulfblog (2010/05/station34b_watermark.jpg)?
The CDOM signal in this plot is calibrated so that the relative signal intensity can be converted to mg/m3 relative to standard units of quinone sulfate, the compound frequently used as an oil standard for CDOM fluorometers.
(19) Will your testing tells us anything about the presence of polycyclic aromatic hydrocarbons?
Yes, we’ll know the concentration of PAHs once the hydrocarbon analyses are completed.
(20) Are attempts being made to remover the plume from the water? Is there a practical method to do this?
Right now, no there are not plans to do this. Practically speaking, this will be very difficult.
(21) Where can I find data on shoreline VOC content?
Check here http://www.deepwaterhorizonresponse.com/go/doc/2931/542539/ or search the deepwaterhorizon.response website to find up-to-date information. The EPA is charged with monitoring air quality in regions impacted by the spill.
We’re hoping to have all our time-sensitive laboratory analyses completed within the next two weeks. Some analyses related to microbial composition will require a few months. We are setting up experiments this week to evaluate the response of the microbial community to changes in oil and gas concentration. These experiments will last for about two months. In the meantime, I’m starting to write papers describing various aspects of the data set. We’ll be heading back out to the Gulf for additional research cruises in July, August/September and November. Things are going to get busier and I don’t expect things to slow down any time soon.
WEEKLY PRESS CONFERENCE.
In addition to the blog, I will be conducting a weekly press conference to keep people informed of our results. The media advisory for the weekly press conferences is available on the resources page of the blog.