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2015 Shelfwide Cruise: July 28 - August 3

Final 2015 map KM

Daily Log

Jul 28, 2015 - Day 1
Departure from Port Cocodrie on the R/V Pelican for the 31st shelfwide hypoxia cruise. The river is in above average long-term flow since 1935 and the nutrients are not diluted. These have been the conditions for the last month. River discharge and nutrient loads will remain high for the duration of the cruise. Arrived at the Mississippi River about 0800 and began the search for the salinity gradient. Freshwater was everywhere along with water hyacinths and other wetland vegetation. Because the river was in flood conditions, it was easy to find the 0-1 psu end member. The freshwater seeped out of the delta in all directions, and the salinity was quite low with water hyacinths throughout the Au2019 transect parallel to the river delta. Hypoxia from very near shore to depths of 30 m. Some very low dissolved oxygen concentrations as evidenced by the portunid crabs swimming at the surface.
1900 -  
The day shift turns the work over to the night shift which works the A transect from offshore to inshore. They also document widespread hypoxia, low salinity waters, and floating wetland vegetation.
Night Shift Blog: Night 2 July 28-29 
The 31st Gulf of Mexico hypoxia cruise began with calm seas. On Monday night, the R/V Pelican left the salt marshes that surround LUMCON and entered open Gulf waters with 1-2 foot seas en route to the Mississippi River. The night shifters stayed awake into the wee hours of the morning setting up laboratory equipment, preparing datasheets, and attempting to ignore their bodiesu2019 desire to sleep after a full day's work in the daylight.

While the night shifters slept, the dayshift tackled the river stations and the Au2019 transect. The night shifters awoke to an amazing dinner of enchiladas and a gorgeous sunset of red and orange sinking behind a horizon dotted with oil rigs.

It was a slow start to the A-transect for the night shift as new team members were trained, old team members remembered details, and the ship received a little TLC.

A note on our new home: the Pelican is gorgeous this year. With new flooring in the laboratory, new cushions in the mess hall, and new mattresses in the bunks, she is a fine vessel and a great place to call "home" this week. Much admiration to our captain, Tad, his crew, and our amazing chef.

Creature of the night -- Remora 
During the night shift when the ocean is dark, a spotlight is used to Illuminate the deck and the adjacent waters so the science team can safely collect their samples. These lights, however, also attract schools of fish, and following those fish are bigger fish and so on, as a food chain drama is played out. Tonight we were visited by a Remora, also referred to as a sucker fish, preying on these schools. Traditionally these fish are observed while they are attached to a shark, whale, or even a boat. Tonight's, however, was flying solo, allowing us full view of the suction cup on the top of its head. The suction cup is actually their first dorsal fins modified into an oval, sucker-like structure with visible slats that open and close to create suction. The fish use this structure to latch onto a host, giving them a free ride and protection.
Jul 29, 2015 - Day 2
Most of this day was spent transiting to the inshore end of transect B, collecting data as deep as 43 m, before heading over to the offshore end of transect C. Again, widespread hypoxia from close to shore to depths of 30 m offshore. Extremely low concentrations, with more portunid crabs swimming at the surface.
1900 -  
The day shift turns the work over to the night shift who begin transect C, the longest-term transect of hypoxia data in the many years of conducting hypoxia research. More and more samples will be taken at these stations to coincide with prior year studies for microbial ecology, nitrogen cycling and respiration.
Night Shift: Night 3 July 29-30 
Another brilliant sunset and delicious dinner (crawfish u00e9touffu00e9e!) greeted the night shift.

A Haiku to start the night

Looming oil platform

Hypoxia awaits us

C6C arrives

Tonight's transect is a historic one. Tonight the night shifters sample the C-transect. In addition to 31 years of annual sampling on the Shelfwide cruise, the C-transect was sampled monthly for almost 20 years. Additionally the C6C station, located on an oil rig, is the site of a continuous monitoring station with sensors deployed at discrete depths through the water column measuring parameters that include oxygen, temperature, and salinity 24/7.

Such a rich dataset of one area consistently sampled is a rarity in the ocean sciences and as such, it is quite a popular transect for the diverse array of researchers represented on the cruise. In addition to oxygen mapping, the transect was also sampled for: archaea, bacteria, denitrification, chlorophyll, nutrients, oil, and metabolism rates.

Creature of the night -- school of larval fish 
When we arrived at C8 we were surprised to hear the pitter patter sound of rain...particularly because it was not raining. Looking over the side we saw the source of the noise: the water was thick with larval fish in a feeding frenzy. As they frantically swam along the surface bumping into one another and jumping out of the water they agitated the surface of the water emulating the sound of rain. Quite the fascinating show to watch as it stretched the length of the boat. A few Remorau2019s and a handful of blue crabs showed up to join in the fun. One larval fish made its way into a BOD bottle!
Jul 30, 2015 - Day 3
Another day of low salinity water, 22-26 psu over most of the Du2019 and D transects off Cat Island Pass and Isle Derniers. Hypoxia quest fooled us for a while today. We worked our way offshore on transect Du2019 and seemed to run out of hypoxia. We headed west to a similar depth station on transect D, but it WAS hypoxic, so we sampled it, and then headed south to close off the line and contours. Back north towards Ship Shoal with most stations hypoxic, mingled in with a few hovering above 2 mg/L.
1900 -  
We turned over to the night shift just in time. A large squall associated with a front descended on them at their first station. Winds up to 38 knots, lots of rain, and soaked scientists and log sheets. Day shifters got photos and stayed dry.
Night 4 July 30-31 
As the boat weaves its way to the west along consecutive north-south transects, stations grow farther apart, the water becomes clearer, and the fauna resembles an open water ecosystem. The nightshifters have gotten into their groove and are functioning as an efficient team. After the frantic pace of the first few days it feels glorious to have time to breathe between stations and catch up on data tasks.

Speaking of fun, today was one of the scientists birthdays so we celebrated with a freshly made blueberry pie a la mode from our wonderful cook.

As we traveled along the E-transect, we were visited by yet another remora, as well as jellyfish, baby flying fish, and a school of needlefish. The needlefish tried their best to be awesome enough to be our creature of the night tonight -- they came in large numbers, were very large in size, made great leaps out of the water, and even went so far as to swim into the boat! But alas, they were no match for our creature of the night...the squall. A note on the remora....as we have seen one at nearly every station it begs the question, is it attaching itself to the Pelican??

Creature of the night: the squall 
The galley clock read 6:50pm as the ship pulled into station D1. Technically, the night shift would not begin for another 10 minutes, but given our excessive gumption and do-good-dery we immediately stepped up and volunteered to take the station. We emerged from the boat blinking into the bright sunlight looking out to a calm sea. As the boat drifted into position we took the time to wander around the deck and take in the scenery, and then we saw it...to the north, a squall was coming. The sky went black as the wind and chop picked up and then the rain began. Heavy droplets hit us from above and the side, while the ocean waves lapped against our boots.

The deck crew was soaked to the bone as we paid out cable and collected water samples. There just hadn't been time to dig out our foul weather gear and the station must be sampled! As rain beat against my face from the direction of the sea I turned my head toward the ship to blink rain from my eyes. As my vision cleared I noticed our crew chief standing dry, in a rain coat, and inside a doorway looking out at us. "I have to keep this data logger dry" was her reply to my gawking expression followed by a "well didn't you pack a rain coat?"

The storm left as quickly as it came, timing itself perfectly with the completion of the station. We quickly got ourselves dry and warm again thanks to hot cocoa and crawfish u00e9touffu00e9e -- have I mentioned how awesome our cook is? -- and unpacked our raincoats leaving them next to the door.

Jul 31, 2015 - Day 4
Night shift found, and then did not find hypoxia on transect E. Quite a variable set of concentrations. But, even when not less than 2 mg/L, they were less than 3 mg/L. We began on the offshore end of transect F. This is also a long-term transect for the hypoxia group. Starting in 30 m we expected to be offshore of the hypoxia boundary, but no.... So we headed out to 40 m to close it off, then back to station F5 to pick up the remainder to shore near the boundary of Atchafalaya Bay. This transect was set up years ago because our research group needed observations from there to compare to transect to C, the former with more influence from the Atchafalaya River and the latter from the Mississippi River. At times, however, especially in the summer, winds from the west blow a lot of fresh water from the Atchafalaya to transect C. Transect F was sampled bimonthly from 2001 through 2012.

The creature of the day is the manta ray. Sheina saw one break the surface of the water and come up into the air. Quick but verified by a crew member. Besides, she knows what they look like. I missed it.

1900 -  
Turning over to the night shift to finish transect F and head west.
Night 5, July 31-August 1 
Today, the day shifters took on the F-transect. Like the C-transect,
the F-transect was sampled monthly for several years. The F-transect
also marks the mouth of the Atchafalaya River (don't worry it took my
northern tongue a whole cruise to learn how to pronounce that!). The
Atchafalaya can be thought of as a second arm of the Mississippi.
After passing from Minnesota to Mississippi a portion of the flow of
the Mississippi (approx. 30%) is diverted at the Old River Control
structure to the Atchafalaya River. Just as hypoxia forms near the
mouth of the Mississippi, so it does at the mouth of the Atchafalaya.
In some years the area of hypoxia from the two River mouths are
distinct and in others, like this year, the two areas merge together
into one large area.

The night shifters ate their amazingly delicious fish tacos complete
with guac, chipotle mayo, beans, and fresh cilantro -- seriously, our
cook is amazing! Still blows my mind the tastiness she creates in our
little galley -- and took in a gorgeous sunset. We finished off the
rest of the F-transect and motored over to G taking advantage of the
downtime to process samples in the laboratory. Our night chugged along
as the infamous blue moon rose in the sky. A bit of wind and chop has
developed, but no need for rain gear.

Creature of the Night: the Blue Moon 
"Blue Moon, you saw me standing alone, without a dream in my heart,
without a love of my own..." Richard Rogers & Lorenz Hart 1934

Tonight's cruise was during a blue moon. Much to the chagrin of myself
and others on the boat, the blue moon is not actually blue. A blue
moon is simply the term applied to the phenomena of a second full moon
occurring in one month. I guess "second moon" just didn't have the
same ring to it.

In recognition of the blue moon, we kept our eyes out for things that
might only happen once...say during a blue moon. And we were not
disappointed - we caught a fish on the rosette as it was coming out of
the water. The rosette is a large metal cage that houses the Niskin
bottles for water sample collection as well as sensors to measure
parameters through the water column. So it is a large structure but
has lots of gaps for a fish to pass through. Having spent a lot of
time staring down at the rosette preparing to guide it from the water
to the deck,I have often thought how cool it would be to catch a fish
with it, but the thought to myself...nah what are the odds of
that?...Well apparently only once in a blue moon !! Tonight as the
rosette was lifted put of the water a small fish (6") was caught on
top of a niskin bottle and carried out of the water. With some frantic
flopping it managed to escape prior to landing on the boat.

Aug 01, 2015 - Day 5
Night shifters always turn the ship over to us when it is rough (3-4 foot swells and windy. Aaaargh. But, by noon it was relatively calm with a nice breeze. Pesky flies still find a way to locate us on the ship as we near the inshore ends of the transects. Transect F had lots of hypoxia, along with the majority of transects G and H. Moving further west now to transect I, the first inshore station was hypoxic near the bottom. Shows the advantage of having a separate Niskin bottle to collect "bottom" water, and the separate YSI 6820 to measure water parameters nearer the bottom than the sensors and bottles of the SeaBird/rosette can go. The YSI read 0.4 mg/L at the "bottom," and at 1.5 m above the bottom the SeaBird read approx. 5.5 mg/L. By the end of the day shift, we should have completed most of transect I (that is, indigo 6 to the mate) with an increasingly large area of hypoxia.
Night 6 - August 1 - 2 
As Hypoxia continues and the ship weaves westward into blue waters, oil rigs have become less and less prevalent and without them to light our horizon, it is difficult to see in the darkness where the water ends and the sky begins.

The waters are so clear here that when the rosette is in the water you can look at it from the side and see its whole profile under water. Additionally, when the Niskin bottle was 7 meters under the sea surface, we could see all of its details very clearly.

So many creatures visited us tonight that in lieu of choosing one creature of the night, we decided to dedicate the blog to a creature feature...

Dolphins!! Four Dolphins were seen playing at the bow of the boat. Of the four, one was much smaller than the others and looked like a baby/juvenile. It is always so neat to watch the Dolphins surf the boats wake, particularly watching how they interact with each other. These intelligent creatures are constantly communicating with each other, looking at each other, bumping into each other, and I'm sure if we had a microphone underwater we would hear them talking. Occasionally one of them would even turn to look up at us watching them. Probably just as curious of us as we were of them.

Baby Billfish - What at first appeared to be a 4" long needlefish unfurled its dorsal fin to reveal what looked like a sail!! So instead of a needlefish, we had a billfish -- sailfish or marlin -- on our hands. Jury is not out yet as to the exact fish, but one things for sure, it was awesome! Billfish are a large, predatory, and highly migratory group of fish that include Marlin, Sailfish, and Swordfish. Of these, the Sailfish is most known for its large dorsal fin. Though its sail is usually kept folded while swimming, it is raised when the fish is excited or scared in order to make itself seem larger, much like a kitten puffing up its tail. Considering there was a boat, bright lights, and squealing scientists, no wonder the little fish felt the need to raise its sail.

Hurricane of Fish

A cyclonic (yes, it really was counterclockwise!) swirl of a fish school stayed next to the ship for almost an entire station. The fish were small and silver. As they fed they would slightly switch the angel of their bodies, catching the light from our boat, reflecting back a flash of light. This "flashing" behavior is commonly observed in schools of fish. The overall effect of it at night looked like little lightning bolts in our fish hurricane.

Editorial correction: it has been brought to my attention that it was incorrect to say that one could only catch a fish in the rosette once in a blue moon, as we caught another one today. This time the fish was sufficiently trapped at it made it all the way on board. Looks like we landed a 1" long menhaden.

Aug 02, 2015 - Day 6
Well. We were greeted with calm seas, and they just kept getting calmer through the day until it was flat calm with nary a ripple.

Transect J remained hypoxic for much of its depth between 10 to 25 meters, but transect K, so far, has shown no interest in hypoxia. We will continue into Texas waters to make sure we have closed it off and not missed anything. The water is pretty well-mixed with no indication of stratification, and limited fluorescence.

We have conquered the Winkler titrations and know what corrections (minimal) to make on the oxygen data. We (Leslie and Wendy) also figured out the overlap in different depth measurements of the SeaBird CTD and the YSI 6820.

Our daily creatures have been mostly jellyfish, the Crysaora quinquecirrha or stinging nettle, and Aurelia, the moon jelly. High concentrations of Crysaora were seen at some stations. Seemed to be mostly over hypoxic bottom waters, but now there are plenty in well-mixed waters.

Heading home - Night of August 3 
Our last shift was a breeze. We all know our jobs at this point and execute them efficiently; the stations went by quickly. Another baby billfish -- our bet is on it being a sailfish -- came to visit, further proving our theory of the "twice in a blue moon" phenomena. We watched a school of squid feeding on a school of tiny fish. And we watched a blood red moon rise in the night sky.

For dinner we had a Puerto Rican feast with crab cakes, chicken, yucca, plantains, and beans and rice. It was A-mazing!

With no hypoxia to be found on the K or S transects the boat turned east and started to back to LUMCON last night at 3am. This night shifter immediately went to bed in the hope of beginning her conversion to a more regular diurnal cycle. The other night shifters decided to rebel against the sun for another day until we return to port in he wee hours tomorrow morning.

As another year draws to a close, I can't help but reflect on just how awesome this dataset is, and how neat it is to be a part of a 31 year project. Thank you to Nancy, Gene, and our sponsors (NOAA and EPA) for making this cruise possible.

Until next year,

The Nightshift


  • The final dissolved oxygen data will be corrected, as necessary, from linear regression with the Winkler titrations over a range of 0.22 to 8.43 mg/L. Initial observations indicate correction, but the f-factor for the Winkler standard remains to be verified. Any corrected data will be reflected in other derived measurements.
  • Salinity data not yet verified with PortaSal samples.
  • CTD data remain to be post-processed with ALIGN CTD to be applied.
  • Instrumentation was calibrated pre- and post-cruise according to manufacturer's specifications and standard method procedures were applied for several variables, not yet calculated, according to several LUMCON EPA-approved Quality Assurance Project Plans.
  • Data collected as part of process studies remain to be analyzed and synthesized.
  • Final QA/QC'd data will be submitted to NOAA NODC within two years of collection.