Failed dive attempt at C6C

Last week we sailed on the R/V Acadiana to C6C to de-winterize the SONDE attachments only to be stymied by a jack-up rig and increasingly bad sea state. We sailed for three hours, and when we arrived, the water was calm enough to dive, so we suited up. With the first team of divers literally standing on the transom to jump in, a jack-up rig radioed for us to wait so they could post up near our dive site. We waited for two hours on station (incidentally, we could have completed everything we needed to do in that time), with 10-15 kt wind on the water for the duration, and when the first team finally splashed, the sea state was trash. Dive Safety Officer Lora Pride called it all off. These things happen. But there were some good photos, and a video of the scene out there at C6C before we got stopped, so I thought I’d post them. We’ll be out again soon.

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The R/V Acadiana poised for action at dawn
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The LUMCON docks at 0 dark 30.
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Heading out, with an old friend coming in – the R/V Pelican returning to LUMCON
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Breakfast on the ship- a major perk of the Acadiana!

Here you’ll see some video of one of the many service helicopters that land on the rig and some of us getting ready on the back of the Acadiana. The sea state is relatively calm at this point, so it would have been perfect timing to dive.

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Back at the dock, our dive flags still flying. We’ll get ’em next time

 

Platform dive number 3 at Pelto-6.

Last Saturday (12/5/14) we trucked out to Pelto-6, an unmanned platform near C6C, for more training dives and practice with underwater sample collection for me. While it was raining in Baton Rouge, we had a beautiful warm day in the Gulf. Water temps were ~69˚F, max bottom depth was 46 ft. There were some Portuguese man of war on the surface, but they were drifting away from the platform and posed a minimal danger. On our third dive of the day, I shot this GoPro footage (Hero 3). It’s a little shaky, sometimes pointed in the wrong direction, and I need to move my head more slowly. But it’s useful and you can see a massive school of catfish that were hanging out in the middle of the rig, along with some other interesting creatures.

-jct

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.

-jct

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.

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A beautiful day for diving. Our whaler ready to go.
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Closeup of our whaler with dive tanks visible.
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Busy day at C6C with supply boats and helicopters buzzing around.
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The section of the platform where our gear is mounted. The closest pylon has the moored SONDEs
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Station C6C, with supply boat visible.
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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.
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DSO Lora Pride
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A thoroughly encrusted SONDE
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Lora cleaning a SONDE mount
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Blurry photo of a new SONDE going in
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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.
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More of the sea life on the platform leg
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Coming home
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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.

-jct