Northern Gulf of Mexico Shelfwide Hypoxia Cruise

Two weeks ago, I was able to take part in the 6 day Northern Gulf of Mexico research cruise. This is its 31st year that it is going on and our third year taking part in it (see 1, 2). This year I was the lucky one to go instead of Dr. Thrash. This was my first official collection cruise so I was pretty excited to finally get out on a boat and put into practice everything I had learned while at the CMORE summer course.

Once again, our lab was working with Dr. Olivia Mason from Florida State University and her graduate student Lauren Gillies (@GilliesLE), who recently published a paper with Dr. Thrash from the 2013 research cruise: Archaeal enrichment in the hypoxic zone in the northern Gulf of Mexico. Congrats to them!

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Prepping the lab before the cruise starts

Though for the most part the set up and collection was the same as past years, this year I added a little twist to the game: Culturing.

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Our set up with the clean hood added for me to culture!

The cruise was a lot of fun and as usual I learned a ton about the Northern Gulf of Mexico and hypoxia. The main focus of the rest of the cruise was determining the size and nature of the 2015 “dead zone”. Dr. Rabalais (LUMCON) and her team worked countless hours to make sure all the data was collected and ready to be sent to NOAA, the EPA, and the public. This year we found that the dead zone was larger then scientists had predicted. This year’s dead zone extended over more than 6,400 square miles.

A map depicting the stations sampled, as created by Leslie Smith and Dr. Nancy Rabalais (LUMCON)
A map depicting the hypoxia measured in the nGOM, as created by Leslie Smith and Dr. Nancy Rabalais (LUMCON)

A few more pictures of me with some of the awesome graduate researchers (Mary Kate Rogener (@mkrogener) from Dr. Samantha Joye’s lab (UGA)) and Post Doc Ari Chelsky (Brian Roberts, LUMCON) also on board the RV Pelican.

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Sunset behind the RV Pelican
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Heading back to port at LUMCON in Cocodrie, LA
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Mary Kate working in her temporary anaerobic space
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Sometimes when you filter three depths in the Hypoxic waters you get three colors.
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Past years have been flat, this year we got some storms which was fun!
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Getting our sampling in before a squall moved through! It was blowing like stink out there but Lauren didn’t care
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Working in the hood to culture some microorganisms…Thanks for the picture Mary Kate
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Obligatory selfie
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The infamous C6C platform

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Keep an eye out for more publications from the Mason and Thrash groups on this exciting research area!


Shelfwide cruise roundup, for now

Nancy Rabalais’s team has been able to process some of the data and issued a press release on this year’s bottom water hypoxia. As I mentioned in the last post, the zone of hypoxia was actually two zones, which you can see below. The total estimated square mileage of bottom water at or below 2 mg/L dissolved oxygen was 5,052 square miles/14,785 square kilometers, which is almost three times larger than the goal proposed by the Mississippi River Gulf of Mexico Watershed Nutrient Task Force in 2001 and 2008.

Bottom water dissolved oxygen measured on the 2014 shelfwide cruise. Source: Nancy N. Rabalais, LUMCON, and R. Eugene Turner, LSU
Bottom water dissolved oxygen measured on the 2014 shelfwide cruise. Source: Nancy N. Rabalais, LUMCON, and R. Eugene Turner, LSU
Surface water chlorophyll a measured on the 2014 shelfwide cruise. Source: Nancy N. Rabalais, LUMCON and R. Eugene Turner, LSU
Surface water chlorophyll a measured on the 2014 shelfwide cruise. Source: Nancy N. Rabalais, LUMCON and R. Eugene Turner, LSU

I can provide some additional thoughts with pretty HD video to boot. The eastern stations, as seen in the chlorophyll map, were predominantly green water, with considerable phyotoplankton mass present in the water column. We could observe significant green-colored biomass both on the GF/D pre-filters and the 0.22 µm Sterivex filters. This is also what you see if you are actually in the water, and the video from the green-water CTD cast at station B6 confirms what was seen with the CTD instrumentation and the filters. Convenient, eh? There is dense, murky greenness at the surface. Deeper, the visibility improves as we get below the highest biomass concentration, but towards the bottom, where hypoxia was observed, we again see increased turbidity, but of a different sort. It’s much whiter than that at the surface. On the return trip, considerable marine snow can be seen (along with a jelly or two and other marine invertebrates).


The western stations, as you might imagine by looking at the surface chlorophyll data, were blue water, with very little phyotplankton mass compared to the eastern stations. The cast at station K3 shows beautiful blue water with high visibility (diver’s paradise), but as you descend, you again pick up the whitish turbidity at the bottom layer where hypoxia was observed.

Sterivex filters from this section were light pink, a phenomenon we observed last year as well. The 16S rRNA and metagenomic data will, among other things, help us uncover a bit more about the variant prokaryotic taxa seen in these contrasting zones of hypoxia.


2014 Shelfwide cruising update 4

Well, that’s all folks. We’re headed home. We only found isolated pockets of hypoxia found a smaller coastal patch of hypoxia west of the F line. We searched western transects all the way to the P line, which is off the map I posted below in the first update. All in all, Lauren and I collected over 100 samples. It’s going to be an exciting dataset, for sure. I’ll update the blog with higher quality images when I get back, and look for some cool CTD cast videos, brought to you by Mike Henson’s GoPro.



2014 Shelfwide cruising update 3

We’ve finished the H transect and are motoring westward to I. As of now, we have observed no hypoxia west of the F line. However Nancy and Gene have described situations in the past where the hypoxia is discontinuous. We will know soon enough. The last couple days have been very calm, with almost glassy seas. It hasn’t been terribly hot either, so all in all, it’s a pretty ideal situation for sampling. Lauren and I have filtered 3-12 liters from the surface and the oxygen minimum at over 35 sites so far. This will be combined with lots of additional metadata being collected via the CTD and other researchers on board.






2014 Shelfwide cruising update 2

This morning we’re transiting from the E to the F line. As of now we’ve found stratification and bottom water hypoxia (dissolved oxygen < 2 mg/L) at almost all stations from A, B, and C 6 shoreward, and D' and D 3, E 2A shoreward. Which is many more stations than at this point on the cruise last year. It's not hard to see why. Surface water has been filled with phytoplankton blooms (I've taken to calling it shelfwide Gatorade, because of the green color) and some of my GoPro recordings of our CTD casts (I'll post video when I get back to shore) show marine snow raining down. This is yummy yummy candy for aerobic heterotrophs that will respire the carbon, and in doing so, draw down the dissolved oxygen (DO) in the water. This process will have been going for some time to reduce bottom water DO to hypoxic levels. I'll keep you posted!





2014 Shelfwide cruising update 1

Saturday night we shoved off in the R/V Pelican from LUMCON a little after midnight, as per the usual shelfwide cruise routine. We motored eastward through the night and arrived at the southwest pass of the Mississippi River Sunday morning, one of its several engineered mouths. After collecting samples through the salinity gradient a little upriver, we turned around and proceeded immediately to the A’ line. We finished the A’ line last night as I went off shift and Lauren took over and this morning. The A line was sampled through the night more exhaustively, including multiple casts per site and box cores. We’re running 12 hour shifts, 7-7. I’m on in the day and my night counterpart is Lauren Gilles (@GillesLE), a PhD student in Olivia Mason’s (@OUMasonJar) lab who was also my partner in crime last year. We’re significantly ramping up our sampling frequency and this year collecting from multiple depths at each site as well. Right now we’re transiting to the B line. For more information on the shelfwide cruise, head over to the site on the topic.







Platform dive 1 to service LUMCON hypoxia SONDEs

Yesterday I did my checkout dive with LUMCON’s dive safety officer Lora Pride. I’m working on getting certified for scientific diving, according to the AAUS standards, in support of some of our lab research goals. As part of the check out, we serviced a set of SONDEs that are mounted on the leg of an oil platform at the station we refer to as C6C. There are SONDEs at three depths (2.4 m, 10.7 m, 19 m) collecting real-time dissolved oxygen, temperature, conductivity, turbidity and fluorescence measurements (for a diagram click HERE). These SONDEs need to be changed out on a monthly basis (roughly), allowing for weather considerations. Yesterday we exchanged all three SONDEs on the platform for new ones, requiring us to dive in with calibrated units, remove the old ones, clear off the biofouling on the mounts, and install the new ones in the freshly cleaned mounts. I brought my camera along and documented some of this. The boat ride out is about an hour (at between 20-40!! kts- a much more exciting ride than the Pelican), on a 26′ Boston Whaler, one of LUMCONs small boats. I also collected water for inoculating a new HTC experiment.

A beautiful day for diving. Our whaler ready to go.
Closeup of our whaler with dive tanks visible.
Busy day at C6C with supply boats and helicopters buzzing around.
The section of the platform where our gear is mounted. The closest pylon has the moored SONDEs
Station C6C, with supply boat visible.
Getting a secondary calibration measurement of water temp/DO with a handheld YSI probe. The bottom water was certainly hypoxic, with DO < 0.5 mg/L.
DSO Lora Pride
A thoroughly encrusted SONDE
Lora cleaning a SONDE mount
Blurry photo of a new SONDE going in
A little gobi poking out of a barnacle shell. I missed the focus on this guy, but it gives a good idea of the life on the platform leg.
More of the sea life on the platform leg
Coming home
Part of our decaying coastline. What was perfectly green marsh a year ago is now dying. LA coastline is disappearing at a rate of one football field per hour. 

UPDATE (7/3/14): I’ve had some questions about the coastline decay mentioned in the final caption. There is a lot of information out there, but here’s a link to the Department of the Interior’s page on Louisiana’s coastline, and a link to a recent LA Times article detailing the various legal maneuvers between the State of Louisiana, the oil companies, and other interested parties.