Saturday, April 9, 2016

Laser Scanning for Life


While everyone onboard has a love for the ocean, our specific interests are pretty diverse.  Many of our scientists are focusing on the different chemical compounds in seawater to explore biogeochemical processes, trace water masses, and examine inorganic chemical processes occurring in these waters.  Some scientists are in charge of deploying instruments that collect data of the relative motion and heat exchanged between local water parcels.  There are also a number of scientists onboard who are interested in studying seawater from a biological perspective, from examining the DNA to investigating the community structure of marine microorganisms. 

Steven Baer, a postdoctoral researcher at the Bigelow Laboratory for Ocean Science, is studying phytoplankton ecology and biogeochemistry onboard.  He’s part of a team of four (more on the Bigelow/UCI Lab Group to come!) who collect seawater from the surface ocean down to a depth of around 200 meters – the layer of the ocean where they expect to have the greatest signs of productivity in the ocean.  They filter the seawater to collect microscopic evidence of life.  


[On the aft deck, Steve prepares his samples for analysis.]

From Steven Baer:

I’m broadly interested in how phytoplankton make a living, and their impacts on nutrient cycling in the ocean.  This means I do a number of different types of experiments to determine how microscopic organisms compete for nutrition, and under what conditions different types of phytoplankton succeed.  
While phytoplankton are small, they have an outsized impact on the biology and chemistry of our planet...  Because the oceans are so vast, marine phytoplankton account for at least half of all the oxygen in the atmosphere!  They have a major impact on the fluxes of the primary elemental building blocks of life: carbon, nitrogen, and phosphorus.

However, because phytoplankton are so small, they can be hard to find.  Traditionally, oceanographers would spend a lot of time looking at water samples under a microscope.  With recent advances in optics and processing power, we are now able to automate cell counting procedures, specifically using something called a FlowCAM.  This instrument is akin to something called a flow cytometer, which allows us to enumerate small cells quickly.   Basically, we pass a narrow volume of water past a laser.  When the laser hits a cell with chlorophyll in it, it is picked up by a detector and a picture is taken.  It can do this for large volumes of water, and very accurately.  

[Laser light of the FlowCam system]
This method is an improvement over the microscope, which would require a lot of time and expertise to get an accurate count of microorganisms.  In this case, we can detect cells in the range of approximately 5-300 microns.  For comparison, the width of human hair is about 6 microns, and 1 micron (micrometer) = 1x10-6 = 0.000001 meters!  For phytoplankton (and bacteria) that are smaller (which is most of them here in the surface of the Indian Ocean), we take samples back to the lab on shore and analyze them with an even more powerful laser and instrument setup.

Below, Steve works in the BioLab onboard and preps his FlowCam to capture images of marine microorganisms.

[Images of plankton cells recorded by the FlowCam on 4/2/16] 
These scientists will continue to sample the ocean for signs of marine life throughout this cruise.  Stay tuned for more!

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