Module 4 Stream Ecology Laboratory. Measuring Periphyton Biomass. Periphyton Biomass Measurements. Ash-Free Dry Weight Pigment Analysis Biovolume Measurement. Periphyton Biomass Measurements.
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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.