2012 Shelfwide Cruise: July 22 - July 28
- 1800 -
- Begin loading at the dock in Cocodrie, homeport of the R/V Pelican Xinping with the most complicated set up was a whiz at getting all his bottles and pCO2 instrumentation
- 2200 -
- All onboard in time for safety meeting, and general discussion of what each person on the cruise was doing and why (see Cruise Research Activities).
- 2400 -
- Depart Cocodrie for Southwest Pass of the Mississippi River
- Night Shifters
- Rain beat against my windshield as I headed south along the Bayou towards LUMCON. The downpour relentlessly obscured my vision and flooded the edges of the road causing my grip on the wheel to tighten. When you are only a couple feet above sea level, just inches of rain cause a mess. Every day of my visit so far has rained. And though I appreciate the beauty of a lightning storm over the salt marsh from the safety of a building, I was not enjoying the storm over the salt marsh that my car was currently driving through.
With so much rain, it is hard to remember that we are in a drought. And by we I mean, pretty much the entire United States. As a result, river flow from the Mississippi River this year is low, really low, and a few days of rain in Cocodrie, LA will not to change that. This year, the flow rate from the Mississippi River is well below the roughly 80 year (1938-2011) average flow and is hovering right above the minimum flow for that time period.
River flow from the Mississippi is important, as it is a critical determinant for hypoxia and the size of the Dead Zone. The river flushes nutrients into the Gulf, sparking phytoplankton blooms. These provide the organic matter to fuel oxygen consumption in the bottom water. The fresh water itself is also very important. As fresh water is less dense (i.e., lighter) than salt water, when a large amount of fresh water enters the Gulf it will stay above the saltier water effectively partitioning, or stratifying the water column. Under these conditions, the oxygen rich surface water is not able to mix down to the oxygen depleted bottom water and hypoxia occurs. Without the river input this spring and especially summer, the Gulf may have a bit of a reprieve from hypoxia, and we're all gripping the wheel tight, waiting to see how much.
- 0930 -
- At the outside end of the Mississippi River plume near Southwest Pass to begin finding a range of salinities towards zero for a nutrient dilution curve. Took about 2 hrs to find the lowest salinity at 6 psu units. Back out the river and headed to inshore end of transect A'.
- 1300 -
- Values of 0.3-0.4 mg/L at the two inshore stations 5 and 9 m water depth. As we sampled farther offshore on this transect, the bottom oxygen values rose to 3 to 4.5 mg/L. Depart to the offshore end of transect A. Yeah, no rain on the day shift.
- 1930 -
- Begin work on transect A at A5, in 28 m. DO values near4 mg/L. A4 is hypoxic at 20 m.
- Night Shifters
- For those of us who have spent the night awake on the Gulf of Mexico, you know, you are never quite alone. Tonight, as the night shifters finished up the A transect and began the B transect, we found ourselves close to shore and in a flurry of activity. Though the sky was pitch black, we could see the haze of civilization on the horizon as well as the bright flashing lights of dozens of oil platformss surrounding us like sentries. Laughing gulls circled the boat, utilizing the spotlights on the deck to lure the fish to the surface. A shrimp boat was working a couple of miles off our stern. All this hustle and bustle is a reminder that the Gulf of Mexico serves many needs and many stakeholders. But perhaps most importantly, it serves as a reminder of just how critical it is to keep the Gulf healthy.
Occurrences of hypoxia have so far been sparse, mainly closer to shore, and we will just have to wait and see what the regions to the West have in store for us.
- Creature of the Night: Feeding Frenzy!
- Off the Starboard side, a school of fish congregated, attracted to the light coming off of the boat. As food chains work, the school then attracted a small shark. We enjoyed watching the shark weave in and out of the school, splicing the school into smaller bits only to reform again. Reactions were so quick it looked like it was a choreographed dance, not a battle by each for survival.
- 0700 -
- The morning shift comes on with the evening shift having finished up the remainder of the inshore end of trans A and all of trans B steaming to the offshore end of trans C.
- 1630 -
- End of trans C and time to let Perry Beeman, journalist from the Des Moines Register, off the ship to go back to Cocodrie. The remainder of us headed back offshore. There were several values below 4 mg/L and below 3 mg/L but no hypoxia on transect C. Hordes of small jellyfish at stations C7 and C6C. Tentacles all over the CTD/rosette, Niskin, YSI, and more when retrieved on board. Beautiful, clear water on trans C, a real treat for those of us that seldom see the transect that clear.
- Night Shifters
Along the Shelfwide Mapping Cruise, we examine several different gradients: East to West, offshore to inshore, surface to bottom. East to West, allows us to examine the reach of the Mississippi River outflow as it enters the Gulf of Mexico and moves west hugging the coast. Similarly, inshore to offshore provides the perspective of deeper, offshore stations, closer to slope waters and shallower inshore stations more impacted by the Mississippi River and other tributaries. Surface to bottom tracks from the fresher, warmer, more oxygenated surface waters down to the saltier, cooler, and more oxygen poor waters.
Tonight the night shifters sampled the length of the D-transect marveling at the differences between the sites on this transect and previous transects. Starting offshore we saw deep, deep blue waters so clear we could watch the rosette of Niskin bottles as it descended several meters below the surface. We were greeted by schools of fish, jellyfish, needlefish, a shark, and a very small flying fish in these offshore waters. Closer to shore, the water took on a greenish hue from high chlorophyll levels; laughing gulls and oilrigs surrounded us. The brilliant green of these inshore waters are a stark contrast to the brown murky waters to the east in previous transects, closer to the river outflow, full of suspended solids. In such a way, even without looking at the data we can see the differences between regions in the Gulf.
- Creature of the Night: It's a squid, it's a shrimp, nou2026.it's a thousand tiny jellyfish!!!
- Thousands of tiny (one-inch or less in length) pink sea nettles were seen off the starboard side of the Pelican as we pulled up to D4, blanketing the surface. Fish darted in and out of the school of jellies hunting for zooplankton and avoiding being stung. We got a closer look at one of these jellies after pulling up the rosette and finding some clinging to the cage. Check out the photo gallery for pictures!
- 0200 -
- Moving west along transects D' and D as dissolved oxygen dips towards 3 mg/L, but no hypoxia.
- 0700 -
- Continuing west along trans E with DO values approaching 3 mg/L.
- 1400 -
- Begin the offshore end of trans F, off the Atchafalaya River and one of the transects that is visited on a monthly or biomonthly basis since 2001. A similar pattern to the June trans F data with lower oxygen in the middle of the transect and hypoxia on F2 and F2A in 7 to 15 m water depth.
- Night Shifters
- Tonight the Night Shifters completed the G-transit (unfortunately we stopped just short of station G6). As we move West, hypoxia remains scarce, focused in the stations closer to shore. This lack of hypoxia, throws a wrench in some sample plans as folks were specifically looking for characteristics of anoxic (no oxygen) environments, such as the presence of hydrogen sulfide or lead species.
For others, monitoring the system in both hypoxic and oxic environments adds variability that teaches us more about what drives the system such as with the sampling of water column chlorophyll and nutrients, carbon dioxide exchange between the air and the sea, light attenuation through the water column, and carbon cycling from inorganic to particulate forms.
One study in particular on the cruise actually benefits from the almost universal presence of oxygen u2013 the study of aerobic respiration. u201cRespirationu201d referring to the process of metabolizing organic matter, and u201cAerobicu201d referring to the use of oxygen in this process. This is what we, humans (as well as kittens and ponies, etc.), do u2013 we break down organic matter (i.e., our food) using oxygen in the process (why else would we breathe it in?)
The Roberts laboratory from LUMCON is examining how aerobic respiration varies across the gradients of the cruise u2013 East to West, inshore to offshore, and surface to bottom. In addition to examining how respiration changes, his lab is also examining potential drivers of respiration including different forms of organic matter (dissolved and particulate) as well as nutrients in the water column. Respiration is an important part of the hypoxia puzzle, as it is the process that ultimately draws down oxygen in the bottom water under conditions of stratification.
- Creature of the Night: Hitching a Ride anda Hiding Place
- Over a dozen juvenile Blue Crabs of all sizes were seen on station taking refuge in chunks of floating Sargassum u2013 a type of macro-algae. Some were smaller than my pinky nail, while others were as large as my thumb. The crabs were likely taking shelter in the Sargassum for several reasons - hitching a ride to be able to float along without any effort or to hide from predators using the macro-algae as refuge.
- 0100 -
- Late in the evening and through the evening, more hypoxia was recorded on trans G hypoxia in 10 m water depth.
- 0700 -
- Day crew takes over at the offshore end of trans H in 30 m. We continue to occupy stations in 10, 20 and 30 m depth for water column respiration experiments.
- 1100 -
- Hypoxia again in a narrow band on trans H in 15 m.
- 1600 -
- Hypoxia begins on trans I at the shallowest station in 11 m and continues through much of the transect through 18 m. The continental shelf is wider in this region of the Louisiana coast so that the distance from 11 m to 18 m water depth is much greater than on the eastern part of the Louisiana shelf.
- 2000 -
- Continue through the night with trans J from offshore to inshore. Hypoxia along trans J from station J5 in 20 m to J3 in 13 m.
- Night Shifters
- Hypoxia! You wouldn't think that on a cruise to map the hypoxic area of the Gulf that it would be such a big deal to see it; but hypoxia has been sparse for the whole voyage and then in the last day we've had several hypoxic stations on both I and J transects.
Though we previously had thought that we would sample only out to the K-transect, if we find hypoxia in the K-transect, we will continue to sample until we reach the edge of the Dead Zone. So tonight the Night Shifters go to sleep as if it were Christmas Eve, anxious for what we will find when we wake up the next morning(evening?) u2013 either the ship heading home, or more sampling to be done.
Other highlights from the night include a school of about a hundred Blue Runners that came into our spot light, attracted by the accumulating plankton, drawn to the light. Numerous acrobatic fish - Needlefish and Flying Fish - were seen jumping out of the water tonight. Overall, however, the number of fauna tonight was much less than we had seen previously in the trip.
- Creature of the Night: Hypoxia
- Yes, finding hypoxia is so exciting that I am using it as the blog entry and the creature of the night.
- 0300 -
- Finish up the inshore of trans J, which is well mixed with no hypoxia.
- 0800 -
- Heading over to K1 to begin on its inshore station.
- 0930 -
- Begin the inshore end of trans K and head offshore, thinking there would be no hypoxia on this transect.
- 1430 -
- Surprise, surprise. Station K5 in 18 m is hypoxic. Onward to K6, which was just below 3 mg/L.
- 1500 -
- Some quick realignment and entering of prior stations from the grid, and we head to trans S, which we have occupied before.
- 1945 -
- Station S7 to inshore so that we can try to close off the contours.
- 2300 -
- Surprise, surprise once again. Hypoxia at station S5 in 15 m
- Night Shifters
- The night shifters awoke to find that hypoxia was recorded during the day shift on the K transect and we were on our way to the S-transect. Just one more, we thought, one more transect. With those thoughts jinxing us, there was, of course, hypoxia on the S-transect. We then journeyed to the T transect feeling certain that we had reached the edge of the Dead Zoneu2026and you guessed it, more hypoxia! As the Night Shifters wrap up their shift, the boat heads to the next transect looking for the edge. We'll just have to wait and see where we are when we wake up.
Either way, this was the last shift for the Night Shifters. As if the Gulf knew, she bade us a fond farewell by washing a wave over the side of the boat on our last station, flooding all of our boots.
Though we are looking forward to getting back on land and seeing loved ones, we can all agree on things that we will miss from the cruise. A big one is watching the water for fish under the lights at night while we wait for the CTD to descend to the bottom and back up. Tonight we saw a couple Mahi Mahi, several very long needlefish in groups of up to 10, moon jellies, and menhaden. It goes without saying that we will miss the delicious food cooked every night. Less delicious, more intrinsic, we will miss being a part of something so big. These surveys have been going on for 28 years and we wish them a happy 28 more.
- Creature of the Night: Carnival Triumph cruise ship
- Tonight around sunset, the Night Shifters caught a rare sighting of the elusive sub-species Homo sapien carnivalis u2013 i.e., the subset of the human population currently enjoying themselves on a Carnival cruise ship. As we stood mouths open on the deck gaping at the large ship, we couldn't help but note several physical differences between ourselves, and the cruise goers - for one, we were wearing dirty clothes, goulashes, hard hats, and life vest; and for two, we didn't have alcohol in our hands. It was amazing to observe these elusive creatures in their natural habitat as they played basketball 10 stories above the sea surface, went down a green water slide, and watched a TV that was at least 20 feet tall.
As amazing as this rare sighting was, it came with its own dangers. Researchers stipulate that this subspecies was not formed through evolution, rather through a mutating virus (you knowu2026like vampires). Though we were far away from the ship, we were not outside the airborne range of the virus. It took 2 crew members to hold down one of the scientists on board as she came under the influence of the virus. The whole time she screamed, u201cThey have a casino on board! Where are my singles! If I jump over, they have to save me, its Maritime law!u201d Fortunately, she was not exposed long enough for the virus to have a lasting impact.
[N.B., the editor of the daily log gave carte blanche to the Night Shifters and cannot be held responsible for their actions.]
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.