Module 4 Stream Ecology Laboratory. Measuring Periphyton Biomass. Periphyton Biomass Measurements. Ash-Free Dry Weight Pigment Analysis Biovolume Measurement. Periphyton Biomass Measurements.
Measuring Periphyton Biomass
Nearly all the stuff scrubbed off this one was organic matter –most of it living algae
S.Loeb and J.Reuter imagesPeriphyton (attached algae) sampling
Resulting material from a rock scrub contains macroinvertebrates, detritus, fungi, bacteria, as well as algae.
Here’s a portion of the previous sample after being pulled on to a GF/C filter is preparation for chlorophyll extraction or AFDW determination.
The filter is then placed in 90% acetone to extract the chlorophyll.
The filter is dried to a constant weight then ashed at 555 ºC to burn off all of the organic matter.
The difference in weight is called ‘loss upon ignition” and is a measure of the % organic content of the material
Once you have a measure of chlorophyll or AFDW you’ll need to calculate per unit area.
Some formulas to estimate biovolume from cell dimensions (also see Wetzel & Likens 2000)
Determining size is basically like using a ruler. The standard ruler for a microscope is called an "ocular micrometer", which is fitted into the eyepiece of your microscope.
If you don’t have a micrometer, you can use the diameter of the field. Each of these methods requires that you first standardize your microscope against a ruler of known length; at low magnification, this standard could be a transparent office ruler, but at higher magnifications a stage micrometer is needed.
Be aware that different microscopes are not exactly the same and the size goes down with increased magnification.