Chuck and the Rad-van

Tweeted this ad because "Chuck and the Rad-Van" sounded like a band
that could be playing in our destination: Seattle!

As a junior grad student under Dr. Cochlan at San Francisco State University, Charles "Chuck" Wingert, 27, is earning his master's degree in marine biology with a rare opportunity to work with the brightest and best from Romberg Tiburon Center for Environmental Studies. Chuck's been tirelessly working onboard, and the major-majority of that time has been spent in a 8 foot by 20 foot container box that has been converted into a mobile science lab. This one in particular is called the "Rad-Van" because Chuck is working with radioactive materials inside. He has the proper certification and dons the appropriate safety gear as he handles the radioactive isotopes needed for his work.

 

Calibrating the light intensity before
departing San Francisco, no protection
needed at this point

All plants gain their energy for production of glucose from carbon dioxide (CO2) and sunlight. Phytoplankton are no different in this respect; they are autophototrophs--converting the sun's energy into food for themselves and for consumers. Carbon dioxide (CO2) is relevant to us because of oceanic acidification (OA). Increased CO2 production is leading to a decreased pH, an increased acidity by the production of carbonic acid. "It's all about the free positive H's" as Chuck and Chris have said to me, both graduate students at RTC-SFSU. Acids have a surplus of positive hydrogen ions, and as the ocean's pH lowers, the more "positive H's" are floating around. But, the question is: Does a lower pH affect the efficiency of the "plants" (phytoplankton) ability to make its own food? Our research team hypothesizes that a lower pH due to OA decreases the photosynthetic ability of phytoplankton, some more than others. This is one of the many questions being answered on this research cruise.

Remember that every group on board has a specific focus for their research, but they all collaborate, sharing data and using differing methods to compare data as well. For example, Brian Bill' s taxonomy of phytoplankton was supported by Julia Matheson's work with the flow cytometer. Andrew Schellenbach's FIRe work determined photosynthetic health, happy versus distressed cells; now, we look at Chuck Wingert's work in the Rad-Van, testing similarly for the cells photosynthetic health but with another method.

Photosynthetron with samples, notice
the brighter intensity light at the
bottom of the picture

Chuck is using an instrument called THE PHOTOSYNTHETRON, a name so futuristic it deserves all caps. Basically, the photosynethetron measures the rate of photosynthesis at each intensity of light, providing a nice standard curve, steadily increasing then flattening out. This machine with Star-Trekish name measures the amount of carbon uptake to make glucose from the varying light intensities. Some species of phytoplankton are low-light adapted while others are high-light adapted. This is the way that we can determine their efficiency to perform photosynthesis at differing light intensity levels.

Photosynthetron without
samples added; each of these
cells are tuned for a specific
light intensity. 

In order for the photosynthetron to measure carbon uptake, Chuck has to add a radioactive isotope of carbon, C-14. Every atom of carbon has 6 protons, and on the periodic table, carbon has an atomic mass of 12.011 amu. That means every atom of carbon has not only 6 protons but 6 neutrons as well, combining to make up the atomic mass. An isotope is when the neutrons differ from the stable atom of the element on the periodic table; therefore, C-14 is an isotope of carbon that has not 6 neutrons but 8.

6 protons plus 8 neutrons equals 14, C-14.

Fume hood takes up all gases from the reaction. 

After Chuck adds the radioactive isotope C-14, he allows the phytoplankton to incubate for 2 hours to take up the radioactive carbon, C-14.  Afterwards, he then moves the samples to the fume hood and adds 10% hydrochloric acid, HCl. The hydrochloric acid, HCl, helps remove any C-14 that is not taken up by the cells. Through a chemical  reaction between the C-14 and HCl, carbon dioxide is produced as a gas and taken up in the fume hood safely to the atmosphere. This degassing takes 12-24 hours. All the C-14 that is left is that which is taken up by the cells; the excess removed.

After degassing, he adds a special solution and places the samples into another machine, called a liquid scintillation counter. This device detects radioactive isotope, C-14 without detecting the stable carbon (C-12). The machine provides a printout of "disintegrations per minute" or DPM. The higher the DPM, the more C-14 present in the sample which means that it has a higher photosynthetic capacity. Chuck then uses this number in a formula to find the carbon uptake or the "rate of photosynthesis."

Liquid Scintillation Counter detects C-14.

Two photosynthetrons with samples for testing

Different species of phytoplankton all have the same general shape of the curve, increasing photosynthetic rates with higher light intensity but leveling off at capacity, but this curve varies with its values. In other words, some species will be better adapted than others for the chemistry of the ocean and the changes of the future. Our work here is particularly interested in which phytoplankton cells are best adapted for the higher acidity and lower available nutrients as well as the effect of higher acidity on photosynthetic health. 

Chuck is playing a huge role in this grand investigation. And, it continues long after this month of science at sea. In order for Chuck to truly see the photosynthetic abilities of each sample, he will need to input data for the formula to work. That data will come later as the group from University of Washington in conjunction with NOAA-PMEL (post upcoming) analyzes samples for DIC, dissolved inorganic carbon. It's all coordinated and connected--a beautiful picture of the ocean which we are studying.

Chuck Wingert and Chris Ikeda are both graduate students
 at RTC-SFSU under Dr. Cochlan.