Ocean Acidification buoy validation measurements

An example of NOAA’s synergistic efforts to monitor coastal ocean acidification using a variety of platforms

Author: Leticia Barbero 

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OA buoy with the Ron Brown in the background. Image credit: Jay Hooper

We have just finished the third set of stations in our cruise, the Louisiana Line. This line is interesting for many reasons. The outflow of the Mississippi river into the Gulf changes the characteristics of the water we are sampling, sometimes dramatically. In the stations closest to the coast, which are more influenced by the riverine outflow, surface salinities are so low that they test the limits of the method we use for measuring pH with high precision and accuracy.  High nutrients from the outflow promote high primary production in the surface waters, which in turn ends up causing hypoxia (low oxygen concentrations) in the bottom waters. While regular oxygen values might be in the range of 120-250 umol/kg,  a sample from one of these bottom waters had an oxygen concentration of less than 20 umol/kg. Imagine having ten times less breathing oxygen than you are used to!

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One of many oil rigs we sailed close to during the sampling of the Louisiana Line. Image credit: Leticia Barbero

Besides the very interesting data we get from these stations, the Louisiana Line also affords us the chance to sail close to the dozens of oil rigs peppered along our route, which makes for good pictures for our personal albums.

And unexpectedly, two days ago the opportunity arose for an unplanned collaboration. We were notified that a buoy partially funded by NOAA’s Ocean Acidification Program, which also sponsors our GOMECC-3 cruise, has just been moved to a location close to our route. This buoy has pH, pCO2 and oxygen sensors. Our measurements on board can be used to validate the data from the buoy, so we decided to bring the ship as close to the buoy’s position as we could and take samples on site over a period of three hours. The scientists maintaining the buoy back on land will be able to use our data to calibrate their sensor data.

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Chief Bosun Mike Lastinger drives the Ron Brown’s small boat from the ship to the buoy. Image credit: Jay Hooper

Additionally, the ship was willing to accommodate a very last-minute request to use the ship’s small boat to get a water sample from right next to the buoy, for best quality comparisons. I am very grateful for our science team’s willingness to add extra samples to their already loaded stack of backed-up samples after a succession of stations that were very close together,  for Jay Hooper’s hard work handling the buoy sampling logistics on short notice and I am especially appreciative of  the efforts of the ship’s officers and deck crew to get us to the buoy in time to sync our sample with the buoy’s hourly measurements. We really have amazing science and ship teams working together on this cruise to collect the data we need to monitor ocean acidification conditions in the Gulf of Mexico.



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