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2013 Shelfwide Cruise: July 21 - July 28


Daily Log

Jul 21, 2013 - Day 1
Most of the first day of any shelfwide cruise is getting to the Mississippi River from Cocodrie and finding the lowest salinity values with which to conduct mixing diagrams of various constituents. The Mississippi River is above normal flow and was on another upswing as the R/V Pelican departed Cocodrie the night of July 21. We usually have difficulty finding the lower salinities, but not this year. We have excellent low values for the mixing diagrams, but finding something higher than 20 salinity was a lost cause. This yearu2019s low salinity data coupled with previous yearsu2019 data make a valuable data set.

Once away from the mouth of the river, we started as usual on the inshore side of transect A'. And, the first station is always one of the longest while we get things straightened out. Hypoxia was extremely low at the two inshore stations less than 10 m deep, but further offshore to a depth of 50 m values ranged between 2 and 4 mg/L. Donu2019t give up the ship yet.

Night One: An Introduction 
The 29th Shelfwide cruise began yesterday morning sampling up the Mississippi River to survey nutrients across a salinity gradient. When the night shifters awoke last night, sampling was finishing up on the first shelf transect, A'.

For the next 7 days, the R/V Pelican will be home to 13 scientists and 7 crew members as they map the extent of the low oxygen area, a.k.a. the "Dead Zone" along the shelf of the Gulf of Mexico.

Sampling will take place from roughly the Mississippi River delta to Galveston, TX. In order to survey this area, the boat will travel night and day along consecutive north to south transects u2013 similar to how one would mow a lawn.

The size of the Dead Zone varies each year depending on several factors. Dr. Turner from LSU, present on board, has been able to predict the extent of the low oxygen area using a relationship between two factors u2013 Mississippi River nutrient load and river flow.

These factors reflect the dominant mechanisms that cause the Dead Zone. Elevated nutrients increase phytoplankton (one-celled plants) growth in the water column, again think of lawn care and fertilizer application. High riverflow stratifies (layers) the Gulf of Mexico with warm fresh water on the surface and cool salty water on the bottom. When the phytoplankton die and sink to the bottom, the bacteria that consume them breathe in oxygen in the process. Under stratified conditions the bottom water is not re-aerated by surface water and the bacteria decrease the oxygen concentration in the bottom water - think James Bond in a bank vault. The result is low oxygen in the bottom water u2013 concentrations below 2 mg O2/L are considered hypoxic.

Every year presents unique circumstances, however, as tropical storms with their high winds can mix the water column, breaking up stratification and re-aerating the bottom water. These tropical storms also make for a very exciting boat ride for the scientists and crew.

So far we sail with calm seas and a full moon to guide our way; but are ever on the alert for what the dynamic ocean may bring. Stay tuned on the blog for tales of our adventures on board. We are excited for you to join us along the way.

~The Night Shifters.

Jul 22, 2013 - Day 2
The early morning started on the offshore end of transect A with salinities ranging from 20-22, which normally would coincide with strong stratification. However, the halocline was in the upper water column and the expected strong thermocline in the lower water column was not present. The resultu2014oxygen values in the range of 3 to 5 mg/L. At three of the inshore stations of transect A in 11 to 18 m. The shallowest station was fairly well-mixed with dissolved oxygen of 8 mg/L. the remainder of the 7 pm to 7 am shift ended at the inshore end of transect B off Port Fourchon with tangled winch cables, and the remedies for working off one cable engineered by the marine tech and crew. The remainder of this day was spent working our way from nearshore to offshore, depths of 8 to 28 m without a bit of hypoxia. Values were mostly 3 to 6 mg/L. Surface salinities were higher than transect A in the range of 27-28. The temperature profiles indicated a strong mixing event with evidence of temperature turnover. With less salinity stratification and an inverted (at times) temperature structure, it was not surprising that there was no hypoxia. What was surprising is that the extensive stratification and low oxygen values found in early July were no longer present.

Moving on to transect C, we expected at least some hypoxia in the 10-20 m range, but no. Values in the range of 3 to 5 mg/L from 30 m offshore to 10 m inshore. There is always transect D'.

Night Two: Neighbors 
When one thinks of going to sea and venturing to the open ocean, words that come to mind are solitude, alone, only ocean as far as the eye can see. Not so with the Gulf of Mexico. When you journey onto the Gulf of Mexico continental shelf you are never really alone. Tonight we got to see two of our neighbors up close u2013 dolphins and oil platforms. [N.B. there are also rigs that do the drilling, but are movable.]The beginning of the night shift was quite the time to be out on deck u2013 The sun setting into the sea with orange and red strokes painted into the sea and sky, dolphins playing alongside the boat, and a huge oil platform looming in the background.

There are many different types of platforms in the Gulf, both manned and unmanned. The one we approached was a manned platform that we affectionately call "C6C," really for no better reason than it comes right after C6B in the C-Transect. The station is particularly important, however, as the Rabalais lab attaches sensors that continuously measure water column parameters to one of the platformu2019s support pilings.

C6C is a massive platform with dorms for workers to live in as well as a helicopter pad. Though we all kept an eye out for Bruce Willis hitting golf balls off of the helicopter pad, he was nowhere to be found. There were some other workers out on the deck though as our boat approached and we waved a hello. Again, no Ben Affleck out there either, sigh.

In addition to C6C our sunset vista included oil rigs dotting the sky line, surrounding the boat. Just a subtle reminder of the delicate balance within which humans and the Gulf live; like that neighbor who always comes over to borrow something, or whose kids are perpetually chasing your cats.

Jul 23, 2013 - Day 3
Third day's a charm, at least for hypoxia lovers. A brief occurrence of hypoxia at shallow (6 m) C1 right off Terrebonne Bay, but continuing offshore with transect D'5 to 32 m and no hypoxia. We moved west to transect D off Isle Denieres in 30 m and began our steam inshore as hypoxia decreased from 3.2 to 2.8 mg/L and then 0.7 mg/L in 17 m. The denitrification scientific crew and those studying microbial genomes in hypoxic waters gleefully began gathering samples. Extremely low oxygen levels to 0.1 mg/L continued into the coastal end of transect D1 in 10 m. Portunid crabs (Callinectes similis) were swimming at the surface where the oxygen was extremely low. The Pelican headed west to the inshore end of transect E off of Fourleague Bay and the denitrification and microbial crews jumped partly into action, really wanting to wait for the traditional transect F, where the sampling protocols called for hypoxia. But then again, so did those for transect C, which was not hypoxic. Expecting some more hypoxia as the night crew takes over for the remainder of transect E before heading west to transect F.
Night Three: There it is! 
The sun set into calm waters as the Nightshifters began their work.

After murmurs through the last few days as to the state of the bottom oxygen, namely that there was so much of it, hypoxia abounded during tonight's shift. Not only was this seen on the real-time output from sensors at depth, but also in the fauna at the surface.

At several stations, bottom dwelling lesser blue crabs (Callinectes similis), and in one case a benthic eel, were seen on the surface. These critters are not normally seen in surface waters, but likely came to the surface searching for oxygen-rich water. Being able to move away from low oxygen areas is a luxury only mobile species have. Some species, however, are not mobile and instead find themselves stuck in the mud (pun intended).

Another new sight for the Nightshifters was clear blue waters. Transects now take us into deeper, offshore waters. With these clear waters, we were able to see the rosette sampler for several meters as it descended down through the water column. Much further than in the murky green-ish, brown waters closer to the river delta and the coast.

We were welcomed into this new realm by flying fish, needlefish, schools of squid, and a pod of dolphins. We have been very hopeful that both the full moon and boat lights would help attract sea fauna and are very excited for what the rest of our blue water encounters will hold.

Jul 24, 2013 - Day 4
Hypoxia loversu2019 delights along the E and F lines today, with oxygen values mostly less than 1 mg/L. More scrambling for low oxygen loving microbes, and denitrification rates. Starting to fit into a routine with everyone knowing whatu2019s going on and the stations and transects coming farther apart. And, again several stations with hypoxia along transect G in the wee night shift. Seems all the fun is on the night shift. ;-(
Night Four: A Night in the Life 
At this point in the cruise, the Nightshifters have settled into a routine. As we sample through calm blue waters, we have decided to share that routine with you.
At the crack of 1600, the Nightshifters awake from their slumber. They get ready for the night ahead and rendezvous in the mess hall around 1630 pm.
Almost immediately after arriving in the mess hall two things happen: 1) We start pestering Dayshifters as to where we are and how the sampling has been going and 2) we begin ingesting caffeine. We then disperse to check e-mail, catch a few glimpses of the sun, and get ready for the night.
After smelling delicious cooking, dinner is finally served! Around this time we also often delightfully chuckle as the Dayshifters have to squeeze in one more station before our shift starts.
The Nightshift begins! Motoring through transects (invisible lines we trace through the Gulf of Mexico, see station map), we stop at regular intervals along the lines to sample our stations, (dots on the station map defined by GPS coordinates). Each Nightshifter has their own set of tasks, working together as a well-oiled machine; collecting data from sensors deployed into the water, and water samples to take back to the laboratory on land. Between stations we catch up on onboard laboratory work and data entry. We sample continuously from 1900 to 0700, sampling one station and immediately moving on to the next.

One of the favorite tasks at each station is to visual survey the surface waters near the boat for flora and fauna, while we wait for the rosette sampler to descend (sometimes over 50-meters!). Not only is this a lot of fun, but it also serves as an important aspect of data collection. By noting what critters are on the surface we can help characterize what is going on in the water column. Tonight we saw squid, needlefish, Sargassum seaweed, flying fish, AND a "chicken dolphin."

A note on "chicken dolphins." Neither a chicken (bird) nor a dolphin (mammal), this beautiful, brightly colored creature is small Mahi Mahi (fish). "Chicken dolphin" is its local nickname. We saw individuals at several stations and they were very active, zipping around the boat and leaping out of the water.

The Nightshifters become increasingly confused about what day it is. We also get hungry and start raiding the pantry.
More coffee is made and the Nightshifters talk (as they do every night) about their preferred caffeine routine.
The night is almost done! Where did the time go?!?
Somehow we manage to arrive at a station minutes before breakfast begins and now the Dayshifters chuckle as we rush out to station smelling the delicious breakfast thatu2019s so close yet so far.
Breakfast starts without the Nightshifters.
Nightshift ends and for some reason the Dayshifters are always pestering us about where we are and how the sampling has been going.
Time for bed.
Jul 25, 2013 - Day 5
Hey! The day shift is a well-oiled and syncopated machine! And, we appreciate the night shift getting to a station just before they are about to get off shift. Gives us more time to wake up. July25 was another bonus day for hypoxia lovers. From 35 m into 14 m on transect H provided low oxygen waters in the range of 0.05 to 0.1 to just below 1 mg/L. Moving west to the inshore end of transect I we continued with the mixed water column until I3 in about 17 m to start into the low oxygen waters as we moved further offshore. Hypoxia went on and on and on south along transect I. We thought we would be going to Mexico. Finally in xx m the bottom oxygen levels rose above 2 mg l-1 and we headed west to transect J.

The seas began to calm early afternoon and we are at 1 to 2 ft now.

Weu2019ve been seeing large rafts of Sargassum weed during the day when we were out of the turbid coastal current.

Box coring was finally a success at stations I3 and I4. This area had been cored between 1989 and 1997 for various projects and station I3 had an accumulation rate of 0.41 cm y-1. Box coring on transects B and C was unsuccessful, and was not attempted along transect A because the area was disturbed by Hurricane Katrina in 2005. The new cores will be split so that material for dating the core and for conducting dinoflagellate cyst analysis could be from the same horizons. Additional measurements representing indicators for increased productivity or worsening hypoxia will also be made. The dinoflagellate work will be done by a Ph.D. student, Andrea Price, from McGill University (a student of former LSU colleague, Dr. Gail Chmura).

Night Five: The wind beneath our wings 
Tonight the Nightshifters sampled many blue water stations and at each were greeted by schools of flyingfish. Until tonight we had only seen very small flyingfish, about an inch long, but tonight we saw numerous individuals ~6 inches long. We got quite the show at one station where the flying fish leapt out of the water and took flight for several feet.

In honor of our flying friends we dedicate this blog post to flyingfish. Check out the photo gallery for a flying fish photo!

There are over 50 species of flyingfish, living mainly in the tropics and subtropics. Eight of these species live in the Gulf of Mexico. Some flyingfish species are monoplanes with just one set of "wings" u2013 only their pectoral fins (just behind their head) are enlarged. Other species are biplanes with two set of "wings" u2013 both the pelvic and pectoral fins are enlarged. We have seen primarily monoplanes at our stations, with a few biplanes.

Please note here that the use of the term "wings" is more for a mental image of the fish rather than a functional description. Flyingfish do not flap their wings like birds, but instead glide through the air. To take flight, the fish accelerates to top speeds using its tailfin and as its body leaves the water, it spreads its large pectoral fins. It then gains lift using winds, or updrafts from waves. This take off process is similar to an airplane taking off as it speeds down the runway.

Flying is an important predator avoidance mechanism for the flyingfish. Flyingfish are an important food for several speedy predators including dolphin, tuna, and billfish, as well as slower predators like humans. Flyingfish are actually a delicacy in Barbados where they are the official national fish u2013 the author has dined on flyingfish in Barbados.

Flyingfish are predators themselves, feeding on small fish and crustaceans in the surface waters. They are further connected to the surface ecosystem as they lay their eggs in mats of Sargassum u2013 a type of seaweed named for its prevalence in the Sargasso Sea. We also saw lots of Sargassum at the blue water stations this evening where we saw the flyingfish.

I know an entry discussing lush life in the surface waters seems a bit odd for a blog about a cruise mapping the "Dead Zone" on the bottom. But it serves as a reminder of the delicate Gulf ecosystem and the importance of its protection. On our cruise, we seek to not only describe the extent of the Dead Zone, but also to gain a better understanding of the mechanisms behind its formation. I doing so we can learn how to better protect the Gulf as an amazing natural resource.

Jul 26, 2013 - Day 6
What a let down! Jazzed by the expanded depth coverage with hypoxia on transects H and I, the depths at which bottom-water hypoxia was found on transect J became more restricted. Then only one station was just below 2 mg l-1 on transect K. But, well, well, well. Just in: station K7 was 2.1 mg l-1, so we continue south. Sometime we will finish up the southern stations on transect K, then move to the offshore stations on transect S to map to inshore. This is just to make sure that we donu2019t miss something. We will then find our way back to station J5 for re-sampling in support of the microbial work. With time, we should be able to re-sample some of transects Du2019 and C. Our real-time bottom-water data from station C6C indicate that the oxygen levels have fallen below 2 mg l-1, stratification is re-establishing and oxygen consumption is continuing, since we sampled this station on July 23rd.
Night Six: Entering the Lone Star State 
Tonight, the nightshifters were living on the edgeu2026the edge of the Dead Zone that is. After working hard for six days and nights, the scientific crew finished mapped the 2013 extent of the Dead Zone just as the sun rose this morning and our shift came to a close.

Our journey to map the extent of the Dead Zone has taken the R/V Pelican across Louisiana, the sportsmanu2019s paradise, into Texas, the lone star state. We could tell when we crossed the border into Texas as everything seemed a bit bigger, particularly the waves. The entire way across Louisiana we had 1 to 2 foot seas (liar, liar pants on fire; day shift had seas up to 5 ft), and once we entered Texas waters, the seas increased to 3 to 4 feet.

In actuality, what we encountered was a cold front coming down from the Midwest, moving east across the western upper Gulf Coast to Louisiana. By Sunday the weather, and waves, should calm down.

With the ship rockinu2019 and rollinu2019 the Nightshifters frantically scurried around securing equipment. Additionally with the increased seas, ordinary things have become very exciting, like getting a glass of water, or walking to the bathroom. Our greatest sympathies are for the cook, trying to make us breakfast under these conditions.

Jul 27, 2013 - Day 7
Weu2019re running out of steam and hypoxia. One station barely below 2 mg/L on transect K. Closed it off a few further stations south, then picked up one more transect (S) further to the west between Lake Sabine and Galveston Bay. The hypoxic area was definitively closed off in the early hours. The ship headed east back to station J5 for work by the microbiologists. We are a long way from port in Cocodrie. The run to J5 took at least 5 hours. A full station was completed and water of the appropriate dissolved oxygen values was obtained by the microbiology team.

The remainder of the day was spent heading east to the vicinity of transect D' for re-occupation of some stations there and likely to transect C for some resampling. The time to steam from J5 to D'3 is about 14 hours, but closer to port. We know that the dissolved oxygen at station C6C has fallen from 4.8 mg/L on 22 July to less than 2 mg/L on 27 July, and we may re-occupy the transect.

Our not so peaceful summer seas were further disturbed with a cold front moving in early this morning. It is chase us as we headed east. Prediction is for increased sloppiness today.

Great news on oxygen probes. The Winkler titrations (full range from near zero to over 8 mg/L) were a perfect match for the SeaBird primary DO sensor. The YSI 6820 readings were over by 0.1 mg/L, which is within range. However, a correction to the YSI DO data was made for developing the bottom-water hypoxia map, which basically remained unchanged.

Iu2019VE GOT THE NUMBER. Shhhhhh.....

Night Seven: One last hurrah before heading home 
For most of the night, the ship steamed to the east, toward the D' and C transects, and conveniently in the direction of LUMCON. Seems we have left our cold front in the west and intercepted a rainstorm to the east.

Amidst large swells and driving horizontal sheets of rain, the Nightshifters battled their way through their last shift. The sea was angry last night, my friends, but science does not wait for sunny days or fair weather. It was as if we had trained all week for this shift, gaining our sea legs, and perfecting our sampling techniques. What a great way to say goodbye to the Gulf.

As we finish our shift, the Nightshifters cannot help but start to feel like scientific summer camp is almost over. On this last nightshift we take a moment to reflect on the wonderful adventures we had on this cruise. From the delicious meals served by the cook, to the interesting fish observed, and the great research that was conducted, this was a great cruise.

Though the cruise ends tonight, it will leave lasting impressions on all of us over the next several years as we process samples, and sort through data to tell the story of the Gulf in 2013; part of the greater story of the science of the Gulf shelf, 29 years in the making.

Thank you to all of the blog followers. It was a pleasure to once again take you along with us to map the Dead Zone.

Sincerely yours,

The Nighshifters

Jul 28, 2013 - Day 8
Must admit, the worst weather of the cruise occurred in the wee hours of the day during the night shift. But, you can read above how intrepid they are. They were to pick up some stations that Nancyu2019s intuition spoke might be hypoxic, and then head to the end of transect C to work our way in to port. Butu2026.

D'3 and D'2 were not hypoxic, but similar to the values earlier in the cruise. So much for intuition. But Nancyu2019s intuition was correct as we worked transect C from C9 to shore. C8 and C9 were lower than earlier in the week and C7 was hypoxic at 1.8 mg/L. Hypoxia continued into the shallower waters for the remainder of transect C. This will change the map and the overall bottom area estimate of hypoxia some but not by much.

Dock at 2 pm. End of the 2013 shelfwide cruise. 29 years.


Data Quality Control and Quality Assurance

  • 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.