Micro-Algae Observations

Quantify those observations!!!

Qualitative observations are great, but they can not be used on an x-y plot!   Below is a list of observations that are QUANTIFIABLE.

  • Cell Shape: Ok, this is qualitative but here are the general classes: coccoid- ball shaped, bacillus- tube shaped, filamentous- like string, spirillia like a spring
  • Color (wavelength, nM). This is best done using light wavelength. Different algae pigments absorb different wavelengths of light.
  • Counting Zooplankton (#individuals/mL). A photograph works best, as most are pretty fast swimmers.
  • Depth (Meters). Use the metric system mm,cm,m to describe things in the algae world. Everyone around the world knows the metric system. Only your lost uncle Fred still uses fathoms.
  • Light (uE/m2s- MicroEinsteins per meter squared second) PAR or Photosynthetically Active Radiation is measured in the SI system using uE/m2s. You can pick up a light meter online for $1-200. You can also use your smartphone for a pretty good analogy for $1. Know that your smartphone will be looking at all light, not just the light between 400-700nM that can be used for photosynthesis.
  • Mixing (RPM- revolutions per minute of an impeller, or volume gas bubbled per time) Mixing is a tough thing to quantify, do a google search on fluid dynamics of mixing- then have an aspirin. For algae studies, they want to know how they can replicate. Describe your impeller, the volume and shape of your system, and the RPM. If you are using gas to mix, describe the gas, the volume of gas per minute into the system (use a timer and a graduated cylinder inverted to see how long it takes to discharge the water in the cylinder). If you think this is exciting lookup Reynolds numbers and the boundary layers around cells.
  • Nitrate (mg/L). Nitrogen is an essential macronutrient for algae growth. Sodium nitrate is an easy nutrient to use for culturing as it is not toxic (up to ~80mg/L for many strains) and is detectable with test-strips that are available for aquarium testing.
  • Oxygen (mgO2/L). Measuring oxygen production is a super powerful and fun way to observe photosynthesis. The easiest way is to use a Clark-type oxygen probe (link) which , an optode (measures the O2 optically, but can be interfered with by the biomass in the water), or with a wet-test that colorimetrically determines the concentration of the gas dissolved in water. Be careful with these experiments as diffusion and equilibrium with the atmosphere are going to play against getting good readings.
  • pH (pH units). This 1-14 scale is the negative-log of the hydrogen ion concentration. Moreover, is the water acidic (low pH) or basic (high pH). FYI- Ocean water pH is 8.2 (and climbing).
  • Phosphate (mg/L). Phosphorus another essential macronutrient for algae growth. It can be quantified using test-strips or with a simple colorimetric wet-test.
  • Salinity (g/L, ppm (parts per million), ppt (parts per thousand) Salinity is the measure of all the salts dissolved in water. Salinity is often measured in parts per thousand (ppt), in the algae world, we like to use grams per liter (g/L) as it is a mass per volume unit that makes logical sense, but is identical to the ppt. The average ocean salinity is 35g/L and the average river water salinity is around 0.5g/L.
  • Secch Disk Depth (mm). This is a tool that determines the optical density of the water and is a method for estimating the amount of algae biomass in the culture.
  • Temperature (degrees Celcius). This is a measure of the heat of the system.
  • Turbidity (NTUs-Nephelometric Turbidity Units). Turbidity is the cloudiness or haziness of water when ‘stuff’ is suspended or dissolved in the liquid that absorbs light. Instruments that are used to measure turbidity can be used to track algae growth in water. But you should consider making a plot of NTU to the dry weight of the algae you are studying (example: NTU as a function of mass of algae per liter).
  • Volume (L). You should always describe the volume of the containers you are growing your algae in. Metric is best.


Give us a ring if you think there are more that we should add!   Service@AlgaeResearchSupply.com