It’s all a matter of perspective.
Before I go into the details of what I’ve been looking at I wanted to give you some perspective. If the human race were my micro algae experiment, stick with me for a second, the entire world would fit in about 4.5 liters of filtered sea water.
With some serious help from K we were able to complete a calibration curve for the second species of microalgae for my experiment. This was accomplished by finding the number of algae (cell count), mass (dry weight), and transmittance (using a spectrophotometer) of the algae sample at predetermined concentrations. (ie 100%, 80%, 60%, 40%, 20%) Here are some details that will help you wrap your mind around the calibration curve.
Transmittance: In an undiluted sample the transmittance is 40.50%, but in a 40% diluted culture the average transmittance is 67.29% (These numbers were arrived at by using a spectrophotometer, and averaging three trials at each dilution, triplicate of each trial so 9 transmittance readings in total for each dilution. So the first piece of the puzzle is in place, the more algae you have in a culture the less light can pass through the culture.
Dry weight: When we calculated dry weight we took a standard volume, centrifuged it, and placed the algae in a 25ml beaker in a drying oven for two days and weighed it. From my culture that has been growing for about a month we calculated the density to be 0.9g/L. So to put that in perspective 1 liter of culture is about 1/3 the mass of a US penny (post 1982 2.5 g)
Cell Count: This is the part that everyone in the lab detests, but is the missing piece of the puzzle that puts size into perspective. When I say microalgae how small are these little photosynthetic guys? Well we count # of cells in 100 ul. 1 ul is 10^-6 liters. Or 100 ul is 1/10 of a ml. After counting the number of cells in 3 replicates of 3 samples we determined that there are 1,612,222,222 cells per liter in an undiluted culture. 1.6 billion micro algae (single celled algae) and that would weight less than a gram. Pretty small huh!
What do you think? These little guys are constantly photosynthesizing, and making potentially beneficial products such as pigments (link to pervious post), and lipids which make them useful for biofuels(link to previous post), and potentially the most important oxygen. Some sources estimate as high as 70-80% of atmospheric oxygen is produced by marine plants. Had you thought of that perspective?