2023 Shelfwide Cruise: July 22 - July 28

2 Mettler Toledo G20S Compact Titrators (one in use and a backup) used to measure dissolved oxygen in the water and make a regression against the YSI and Seabird measurements.

From now on, I, the cruise fairy, have decided (with the imaginary power I have) that Wednesdays are for Wet Labs!

Well, at least this Wednesday is anyway. So join me, your cruise fairy, on a wonderful walk through the wet lab we get to use here on the Pelican.

Upon entering, we have a space for the life jackets and hard hats we needed when we were on the back deck collecting samples. (You had yours on out there, too, right?!)

There is also a sink if needed for research like combining through mud samples, but we are currently using it for work gloves and rain gear to be easily accessible when needed.

Crossing over the threshold (where there use to be a door), we enter the part of the lab where all of our samples are processed, stored, or prepped for future processing.

The first contraption we see on the right is a method of processing sediments.

This process requires a vacuum that pulls a volume of water through a pre-weighed filter that collects the sediment on top. Then the filter tower and filter are rinsed with DI water. That filter, now covered in sediment, is frozen and then taken back to the land lab to be weighed and further processed to measure turbidity.

Moving on to the next (similar looking) set of equipment, we have the first part of our chlorophyll processing station.

This station uses the same vacuum-style set up as the sediment (and the same vacuum). However, the individual pieces of equipment differ. Where the sediment is run through a plastic filter tower (the thing that looks like a cup on top), the chlorophyll sample is poured into glass filter towers. The chlorophyll filter is then rolled up like a burrito with forceps (tweezers) and put into a small vial with DMSO (dimethyl sulfoxide) acetone solution and must be placed in the dark. We use some tried and true wooden boxes that have journeyed on this cruise many times before!

Brock, one of the science crew members on the trip said it looked like you would find treasure when you opened the box.

Perhaps, I might suggest, we do! But once the treasure (the chlorophyll sample) is placed into the box, it has to wait(extract) 2 hours before it can be retrieved again. Two hours later- and no more than 24- the filtered chlorophyll samples are ready to go through the second part of the process!

Each chlorophyll tube is vortexed (mixed, intensely) for 30 seconds, the filter is carefully discarded, and then placed into a centrifuge, where it is spun around at 2000 RPMs for 5 minutes to make sure that the remaining filter particles do not impact fluorometer readings.

In between each step, the vials are placed back into the treasure box, as Brock called them! This ensures that the samples become dark acclimated so the fluorometer can properly measure chlorophyll. We want to be sure that the measurements are accurate to that of the location and time that we took the sample initially.

After placed in the centrifuge, the vials go back in their box and await their turn in the fluorometer.

This instrument measures the absorption of light in a fluid. Essentially, the more chlorophyll in the solution, the more light absorbed, the higher the number on the fluorometer. The vial is measured right when it is taken out of the box. Then, hydrochloric acid (HCl) is added to the sample, which converts the chlorophyll to phaeopigments. The same sample is measured a few minutes later, after the HCl has acidified the sample. Both of these recorded measurements are plugged into an equation that helps us determine the amount of chlorophyll that each vial sample had.

The last instrument set up on the starboard side of the wet lab is known as a titrator. *When looking towards the bow/front of the ship, starboard is to your right. When looking towards the stern/back, it’s on your left.*

We use the titrator to measure samples collected in the CTD- specifically, we are measuring the amount of dissolved oxygen in the water. This procedure done on the titrator is compared to the YSI and CTD measurements of Dissolved Oxygen that are taken when the respective instruments are cast into the water themselves. When talking about water being hypoxic, low oxygen, that is determined by measuring the dissolved oxygen in the water.

The last stop on our wonderful journey of the wet lab is the sink where we collect and prep nutrient samples for processing.

We take both bottom and surface samples of nutrients, just like we take bottom and surface samples of chlorophyll. However, nutrient samples and their replicates (always have spare!) are poured into vials that are then put in the freezer, where they will be taken back to a land lab for processing and analyzing.

Well. The clocks about to strike breakfast time here and we have completed our tour! Time for me to bibbidi bobbidi bounce on over to the galley for a magical meal from Chef Lawrence! I hope you enjoyed the tour. And remember! WEDNESDAYS ARE FOR WET LABS!!!