CyanoFluor U
ser’s Manual
Rev. A
14
4 Measurement Parameters
4.1
Phycocyanin (PC) to Chlorophyll (CHL) Ratio Table
PC to CHL ratios indicate what portion of the total phytoplankton population is comprised of
PC-containing algae (cyanobacteria). PC changes proportionally with the abundance of
cyanobacteria and can be tracked using fluorescence of PC. When cyanobacteria are not
present in water the fluorescence from PC is very low yielding ratios less than 0.1; when
cyanobacteria make up 50% of the total phytoplankton population the PC:CHL ratio will be
0.5 or greater. The table below is a quick guide that displays empirically determined
PC:CHL ratios using lab cultures. The species of cyanobacteria used to generate these
data was
Cyanothece ATCC5201
. Other algae used were
Dunaliella salina
,
Tetraselmis
sp.
, and
Rhodomonas salina.
This table is simply a guide; PC:CHL ratios will vary
depending on algal species, light history, physiology, etc. It is important to note and monitor
the rate of change for the PC:CHL ratio over time to determine relative changes in the
abundance of cyanobacteria group. As the PC:CHL ratio increases so does the chance that
a harmful algal bloom will occur.
4.2 Turbidity Effects
Suspended sediments may decrease accuracy in measurements. Coastal marine
environments typically have sediment loads between 5 and 10 NTU equivalents. High
sediment loads typically around 25 NTU equivalents will have minimal to no impact on the
measurements (estimates). At really high sediment loads (>>25 NTU), consider settling
samples prior to measuring as you will see effects especially at low algal abundances.
Always check PC and CHL RFU values and compare with blank RFU values to determine
whether there is enough response from both channels to give a good estimate. As a
general rule of thumb, response for at least one channel (PC or CHL) should be more than
3x the blank RFU values.
4.3 DOM Effects
Dissolved organic materials will affect the chlorophyll channel. If working in areas where
DOM is high, it is recommended that you turn on your filtrate blank (section 2.4) and use the
filtrate correction method described in the Quick Start Guide or Section 2.5/2.6 of this
manual. This will correct for any interference or error in estimate due to a high background
fluorescence which may be cause by dissolved organic materials.
Cyanobacteria portion
PC:CHL
100% cyanobacteria
> 1.00
75% cyanobacteria
0.75
50% cyanobacteria
0.50
25% cyanobacteria
0.25
< 10% cyanobacteria
< 0.15
