This past winter, Jose Ayala and I extracted the key pigments for photosynthesis–fucoxanthin, chlorophyll a, and chlorophyll c–faithfully, every day, within 24 hours of measuring each kelp sample in the flume respirometer. We used the method of Seely et al 1972, which employs methanol, acetone, and dimethyl sulfoxide to extract the two pigment types. We started noticing inconsistencies in the final color of the extracted sample–it should have looked like a white translucent disc, drained of all life force (think Bunnicula); but instead, it was often pale or mottled green. We extended the extraction time, we increased the stirring frequency, we eventually, in a rage, macerated a batch to see if that would help the solvents penetrate the tissue; nothing worked. So, at the end of our herculean test tube efforts, we graphed it all up–and sure enough, the grams of pigment extracted declined as the thickness of the tissue sample increased.
There are two possible situations going on here.
- We are somehow incompetent and have not figured out how to completely extract 100% of the pigment mass out of the kelp tissue, and that this gets worse when the sample is thicker and the tissue is more complex.
- We are not incompetent, and thicker blades actually contain less pigment per square centimeter than thin blades; this is possible, since thicker blades usually have larger medullas, which are completely unpigmented.
If it is #2, we can trust our data and publish it. Why can’t you behave, pigment?