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Appendix D
5/20/2009
11
11.1.7 Shake tubes, and then centrifuge at ~2300 rpm for 5-10 minutes. If
a refrigerated centrifuge is used, a longer spin time may be used,
but not necessary. Again, allow the samples to come to room
temperature. Pipette liquid into a 13 mm round cuvette for reading
on the TD700 fluorometer or into a 2 ml vial for the Trilogy.
Avoid pipetting the fines within the sample tube.
11.1.8 If phaeopigments are to be measured, add 2 drops of 5%
Hydrochloric Acid and read on the fluorometer again. If using the
Welschmeyer (non-acid) technique,
do not
acidify the sample.
11.2
Chlorophyll α in Sediments and Epiphytes
Along with filtered water samples, sediments and epiphyte Mylar
strips are also analyzed for chlorophyll α and phaeophytin. The
method is modified in the volume of extract used, and the samples
are not ground.
11.2.1 Procedure - Sediments:
11.2.1.1 A known volume of sediment, usually the top 1 cm
section of a core, or a known wet weight is placed in a
polypropylene 50 ml centrifuge tube and frozen. The
sample may be kept frozen for up to 4 weeks before
analysis.
11.2.1.2 Forty milliliters of 90% acetone are delivered into the
centrifuge tube. The tube is shaken and placed in a dark
box and put in the refrigerator to extract for 2-24 hours.
Overnight is recommended.
11.2.1.3 After extraction, weigh the tubes to balance the centrifuge.
Spin for 5-10 minutes @ ~2300 rpm. Note: If using a
refrigerated centrifuge, spin time may be longer.
11.2.1.4 Allow the samples to come to room temperature before
analyzing.
11.2.1.5 Pipette liquid into a cuvette for analysis on the
fluorometer, being careful not to aspirate any particles.
Dilute the sample as needed. Take initial reading. Add 2
drops of 5% HCl to the cuvette and read again to
determine phaeopigments and corrected chl
α
.
11.2.2
Epiphyte Mylar strips – Mylar strips are deployed in the water
column for a set length of time to allow epiphytic algae to attach
and grow.
11.2.2.1Cut Mylar strips short enough to stay below the 40-ml
mark on a plastic 50-ml centrifuge tube. Freeze until ready
to analyze, up to 4 weeks.