The HPMA method for producing
algal sample slides provides an optically clear background while permanently
infiltrating and preserving the sample for archival purposes (See references).
Mounting distortion is minimal and the method provides the advantage
of being able to go 100x to 1000x on the same specimen. Wet sample is
always maintained in case clarification of identification is necessary.
We strongly encourage our customers to use glutaraldehyde (final concentration
of 0.25-0.50 %) for preservation of samples. It offers minimal distortion
and allows the use of epifluorescence on the sample while counting,
which can dramatically improve the final results.
GENERAL PROTOCOL FOR MAKING
PERMANENT ALGAL MOUNTS USING HPMA
EQUIPMENT:
Bunsen burner
Beaker tongs
Ice bath
Pyrex beakers (150 ML)
2 Dropper bottles
Mixed ester nitrocellulose filters (0.45 µm, 25 mm, plain)
Glass slides (25 mm x 75 mm)
Avery Laser Labels: #2181
Glass coverslips (25 mm x 25 mm, #1 or #1.5)
Full view series support/drying racks (102 pin)
Graduate cylinders
Dumont forceps
Glass filter towers (25 mL)
Rubber stoppers (#2, #10)
Filtration Manifold (6 station)
Vacuum pump (plus appropriate plumbing, 25-50 mm Hg)
Drying oven (60"C, not forced air)
Hood
REAGENTS:
HPMA (2-hydroxypropyl methacrylate)
Catalyst (azo-bis-iso-butyronitrile)
Iodine
Glutaraldehyde (25%, general grade)
Distilled water
CAUTION: Store
HPMA and catalyst in refrigerator. Keep glutaraldehyde under hood.
METHOD:
SAMPLE:
Add enough
glutaraldehyde to bring the final concentration to approximately 0.25%
to 0.5% (for periphyton samples or "bloom tows", increase
the final concentration to approximately 0.5%-1%). Keep the sample
dark and refrigerate if possible.
Remove the sample from the
refrigerator and let it warm to room temperature before mounting.
RESIN:
Prepare ice bath in plastic
tub.
Measure 25 ml of HPMA and
0.025 g of catalyst into a 150 ml beaker.
Deal with HPMA under hood
and use gloves for both HPMA and catalyst.
Under hood, light Bunsen
burner and set to high flame. Heat HPMA
(with catalyst added) until you see density currents starting to
form. Cool mixture by swirling in ice bath, and return to flame.
DO NOT LET MIXTURE BOIL!!!!!. Keep heating and cooling, alternately,
until the mixture is approximately the thickness of Kayro syrup.
Make sure the mixture is cool when it reaches this point or it will
polymerize further. Transfer to a clean, glass jar for storage until
usage. The entire procedure takes 1-2 hours, depending on how brave
you are.
THIS
REACTION IS EXOTHERMIC ONCE IT REACHES A CERTAIN TEMPERATURE AND WILL
TAKE PLACE ALMOST EXPLOSIVELY IF YOU LET IT GET TOO HOT. THE FUMES ARE
TOXIC. KEEP WATER OUT OF THE PRE-POLYMER.
NOTE: Wash beakers in ethanol
by letting them soak for 24 to 48 hours twice; wash with soap and rinse
with distilled water. Be careful to keep dust out of the beakers when
making the resin.
Fill 2 amber dropper bottles
with resin. Add crystalline iodine to one of the bottles until the resin
is nearly opaque. The iodine-resin will be slightly thicker than normal
resin. (Resin is light sensitive -- be sure to cover the extra resin
with foil.)
SLIDES:
MAKE THREE SLIDES FOR EACH
SAMPLE -- SHAKE SAMPLE WELL (100 TIMES-phyt. or 200 TIMES-peri.).
Use Millipore 6-place stainless steel manifold and Millipore Filtration
Towers.
Put membrane filters onto
filtration bases and wet with distilled water. Drain excess water through
filter. If filter has any opaque areas (very white when wet), replace
with another filter.
Assemble filter towers.
Measure out phytoplankton
sample using micropipetor or macropipetor (use graduate cylinder for
very dilute samples, e.g. 30+ ml). For periphyton samples, remove sample
with micropipetor (usually from 0.05-0.5 ml) and dilute to 10 ml in
a graduated cylinder with distilled water. Agitate to mix. Choose sample
volume so that each field at 200x contains approximately 20-30 cells.
Add sample to the tower
and open valve. For periphyton samples or large phytoplankton samples
using cylinders, rinse graduate cylinder into tower. Filter sample until
water just clears the filter surface. Close valve and remove filtration
tower just after the water disappears from the inner edge of the tower.
Place filter, FACE down,
on a cover slip (# 1.5). Be careful to avoid bubbles under the filter.
Samples:
Samples preserved
in glutaraldehyde:
3 slides: Add 1-2 drops of clear resin to the back of the filter,
and rotate the cover slip until the resin covers the back of the
filter.
Samples preserved
in lugols:
3 slides: Add 1-2 drops of the iodine-resin to the back of the
filter, and rotate the cover slip until the resin covers the back
of the filter.
Place cover slips on the
drying rack and place in drying oven for 12 to 24 hours.
Remove cover slips from
oven. Add 1 drop of resin to the filter side of the cover slip and attach
to a labeled slide. Add as little resin as possible to cover the filter
surface!!!! The less resin, the faster it will polymerize and the better
the prep.
Put slides in the oven and
let polymerize for approximately 24 hours. If the resin is not completely
polymerized, replace and heat for as long as 2-3 days. Make sure that
the slides are completely polymerized before you store them or they
will run and/or evaporate!!!! And believe me, its a mess!!!!
Quality Assurance Plan
Taxonomic Accuracy
Dr. Ann St. Amand, a senior
level phycologist and taxonomic expert, will perform all phytoplankton
and periphyton identifications and biovolume measurements. Dr. St. Amand
has published extensively in the area of algal ecology and has processed
over 23,000 algal and bacterial samples and is qualified to analyze
zooplankton and macroinvertebrates. Outside taxonomists will be utilized
for taxonomic verifications when necessary.
All samples are initially test
mounted for counting density before final mounting. Any major questionable
IDs are noted in the database during counting, and indicated on the report
as uncertain for taxonomic clarity. If enough sample is present, samples
are sent out to other taxonomists for taxonomic confirmation. Distribution
is checked on approximately every tenth sample, during the counting process.
All biovolume calculations have been verified by comparing with current
literature, and by comparing calculations using outside mathematical consultations.
Sample Custody
The chain-of-custody requirements
for all laboratory operations for each sample (broadly interpreted to
include procedures for the preparation of reagents or supplies which become
an integral part of the sample, record keeping associated with sample
acquisition, documentation of sample preservation, sample labeling, sample
tracking to establish chain-of-custody, and shipping and packing) and
laboratory analysis (i.e., laboratory coding, storage, check-out, and
documentation of sample movement) will be fully documented in our data
management software. Each sample received will be assigned an individual
tracking number. The sample bottle, chain-of-custody, and sample log sheet
which accompanies each sample sent are then used in conjunction with one
another, to enter the samples individual tracking number and all available
sample information, into our sample database, ASA System. The database
allows for quick and accurate tracking of each sample received by PhycoTech.
Dated and initialed entries by appropriate personnel on all worksheets
and in the log database are required for data validation. All information
entered into ASA System is fully QA/QC'd for content and accuracy. Sample
receipt is confirmed with each customer.
COUNTING:
Microscope:
There are two microscopes used to process algal samples: an Olympus BHT,
research-grade compound microscope equipped with Nomarski optics (100x,
200x, 400x, and 1000x), Phase Optics (400x), epifluorescence (blue, green
and UV Excitation), and a trinocular head for photography, with a Ricoh
Camera Back attached using traditional slide and print film and 2) an
Olympus BX60, research-grade compound microscope equipped with Nomarski
optics (40x, 100x, 200x, 400x, and 1000x), Phase Optics (400x, 1000x),
a 1.25-2X multiplier, epifluorescence (blue, green and UV Excitation),
and a trinocular head for photography, with a Microfire digital camera
attached. For larger material PhycoTech also has a dissecting microscope.
The BX60 is the primary microscope used for algal and zooplankton identification.
Data Entry:
Samples are enumerated within ASA System directly. ASA System is a database
driven program with an integrated virtual TallyMeter module. Up to 400
taxa can be enumerated within any one sample, and the entire database
currently contains almost 33,000 taxa. All calculations are completed
within ASA System, including concentrations, biovolumes and diversity
indices. Data files are also generated by ASA System and saved in Excel
format, while reports are formatted and saved to pdf format utilizing
Microsoft Access, including summary graphics on a per sample basis. PhycoTech
can then format data files in any format required by the customer. QA/QC
on counting is a recount done on approximately every 10th sample. ASA
System produces a QA/QC report comparing the original sample and the recount
sample (quantitatively and qualitatively), including the distribution
check. Samples pass that are within 10% of the QA/QC recount, quantitatively.
Percent similarity may vary up to 20% on exceptionally diverse or sparse
samples.
Phytoplankton:
The magnification used will
depend on the size of the dominant taxa and the size and number of particulates.
The goal is to count at multiple magnifications in order to correctly
enumerate and identify taxa present that may vary by several orders of
magnitude in size. If the sample is dominated by cells below 10-20 µm
or the cells are fragile and difficult to identify, the majority of counting
will be completed at 400x-1000x. Measuring for biovolume includes measuring
GALD and additional measurements including length, width and depth of
different aspects of the colony or cell. ASA System allows up to 28 separate
measurements per taxa. Cell and colony shapes are approximated to a geometric
figure and or figures and the appropriate calculations made. Currently,
ASA System has over 44 different shapes defined. From 10 up to a total
of 30 natural units (sometimes higher on exceptionally variable taxa)
are measured for each taxa depending on variability and number encountered.
Use ONE of the following
methods depending on sample composition:
DOMINATED BY SOFT
ALGAE: If the
sample is dominated by soft algae greater than 10-20 µm in
GALD, count a minimum of 300 natural units and 15 fields at 200x
(when possible, maximum of 100 fields). In addition, count taxa
below 10 µm or fragile, difficult to identify taxa at 400x
(minimum of 100 natural units and 10 fields). Spread the number
of fields counted evenly over the three slides provided for each
sample (i.e. 30 total fields, 10 fields per slide). Counting is
completed when the standard error of the mean of the total number
of natural units per field is less than 10%. For large taxa (200+
µm): scan at least one whole slide at 100x. This tiered counting
method should yield a minimum of 400 natural units per sample (well
over 400 cells per sample). Extremely sparse samples or samples
with high particulates will yield less than 400 natural units.
DOMINATED BY SOFT
ALGAE: If the
sample is dominated by soft algae less than 10-20 µm in GALD
or is dominated by fragile, difficult to identify taxa, count a
minimum of 400 natural units and 15 fields at 400x (when possible,
maximum of 100 fields). In addition, count taxa above 20-30 µm
in GALD at 200x (minimum of 15 fields). Spread the number of fields
counted evenly over the three slides provided for each sample (i.e.
30 total fields, 10 fields per slide). Counting is completed when
the standard error of the mean of the total number of natural units
per field is less than 10%. For large taxa (200+ µm): scan
at least one whole slide at 100x. This tiered counting method should
yield a minimum of 400 natural units per sample (well over 400 cells
per sample). Extremely sparse samples or samples with high particulates
will yield less than 400 natural units.
DOMINATED BY DIATOMS:
If the sample is dominated by diatoms other than large, easily identified
taxa (e.g. Asterionella), count a minimum of 15 fields at 1000x,
and a minimum of 400 natural units total (when possible, maximum
of 100 fields). In addition, count soft algae according to size
distribution (see A or B above) for a minimum of 15 fields at either
200x or 400x. Spread the number of fields counted evenly over the
three slides provided for each sample (i.e. 30 total fields, 10
fields per slide). Counting is completed when the standard error
of the mean of the total number of natural units per field is less
than 10%. For large taxa (200+ µm): scan at least one whole
slide at 100x. This tiered counting method should yield a minimum
of 400 natural units per sample (well over 400 cells per sample).
Extremely sparse samples or samples with high particulates will
yield less than 400 natural units.
*** NOTE: The
goal, regardless of magnification, is to enumerate and identify a minimum
of 400 natural units per sample exclusive of misc. microflagellates.***
Periphyton:
The magnification used will
depend on the dominant taxa. If the sample is dominated by diatoms, the
majority of counting will be completed at 1000x. If the sample is dominated
by soft algae, the majority of counting will be completed at 200-400x,
whichever is appropriate considering cell size and particulates. The goal
is to count at multiple magnifications in order to correctly enumerate
and identify taxa present that may vary by several orders of magnitude
in size.
The general counting method
is as follows:
Use ONE of the following
methods depending on sample composition:
DOMINATED BY SOFT
ALGAE: If the sample is dominated by soft algae greater than
10-20 µm in GALD, count a minimum of 300 natural units and
15 fields at 200x (when possible, maximum of 100 fields). In addition,
count taxa below 10 µm or fragile, difficult to identify taxa
at 400x (minimum of 100 natural units and 10 fields). Spread the
number of fields counted evenly over the three slides provided for
each sample (i.e. 30 total fields, 10 fields per slide). Counting
is completed when the standard error of the mean of the total number
of natural units per field is less than 10%. For large taxa (200+
µm): scan at least one whole slide at 100x. This tiered counting
method should yield a minimum of 400 natural units per sample (well
over 400 cells per sample). Extremely sparse samples or samples
with high particulates will yield less than 400 natural units.
DOMINATED BY SOFT
ALGAE: If the
sample is dominated by soft algae less than 10-20 µm in GALD
or is dominated by fragile, difficult to identify taxa, count a
minimum of 400 natural units and 15 fields at 400x (when possible,
maximum of 100 fields). In addition, count taxa above 10-20 µm
GALD at 200x (minimum of 15 fields). Spread the number of fields
counted evenly over the three slides provided for each sample (i.e.
30 total fields, 10 fields per slide). Counting is completed when
the standard error of the mean of the total number of natural units
per field is less than 10%. For large taxa (200+ µm): scan
at least one whole slide at 100x. This tiered counting method should
yield a minimum of 400 natural units per sample (well over 400 cells
per sample). Extremely sparse samples or samples with high particulates
will yield less than 400 natural units.
DOMINATED
BY DIATOMS:
If the sample is dominated by diatoms, count a minimum of 15 fields
at 1000x, and a minimum of 400 natural units total (when possible,
maximum of 100 fields). In addition, count soft algae according
to size distribution (see A or B above) for a minimum of 15 fields
at either 200x or 400x. Spread the number of fields counted evenly
over the three slides provided for each sample (i.e. 30 total
fields, 10 fields per slide). Counting is completed when the standard
error of the mean of the total number of natural units per field
is less than 10%. For large taxa (200+ µm): scan at least
one whole slide at 100x. This tiered counting method should yield
a minimum of 400 natural units per sample (well over 400 cells
per sample). Extremely sparse samples or samples with high particulates
will yield less than 400 natural units.
*** NOTE: The
goal, regardless of magnification, is to enumerate and identify a minimum
of 400 natural units per sample exclusive of misc. microflagellates.***
ACID CLEANING
Phytoplankton/Periphyton:
If species identifications
for diatoms are required or unknown diatom taxa are present, acid cleaned
mounts in Naphrax are prepared according to the following procedure:
Take 5-20 mL of sample and
transfer to a clean, 250 mL Pyrex beaker in the hood. Add room-temperature
nitric acid to a total volume of 40-60 mL.
Cover with a watchglass.
After at least 24 hours
has elapsed, carefully siphon off acid using glass siphon. Dilute acid
and discard down drain with lots of extra water (Let water run for a
minimum of 30 minutes after discarding acid).
Transfer remaining sample
to a centrifuge tube and bring volume up to 14 mL with distilled water.
Cap tube, mix well, and centrifuge at 3000 RPM for 5 minutes. Remove
tube and carefully remove supernatant to the 2 mL volume marker with
a micropipetor. Bring volume back up to 14 mL with distilled water,
mix well, and repeat process. Complete a minimum of 6 centrifuge cycles.
Check pH. If pH is lower than 7, repeat centrifuging process until the
pH reaches 7.
On the final cycle, remove
supernatant to the 1 mL volume marker and bring volume back to 5 mL.
Mix well to suspend pellet and decant into the storage bottle. Rinse
the centrifuge tube 2 more times with 5 mL of distilled water and decant
into the storage bottle. The total volume of the cleaned sample should
be 15 mL. If the sample is very sparse, lower final volume.
Using a pasture pipette,
transfer enough sample to a cover slip (#1, 22mm square) to cover the
entire area and place in a vibration-free area until dry.
Add 1 small drop of Naphrax
to the cover slip and invert onto a slide. Compress the coverslip with
a clean object and place in an oven (60oC) for 1-3 hours, or finish
on a hot plate.
Ring cover slip with fingernail
polish and store.
Identify taxa at 1000x under
oil immersion. Reference taxa are identified using a diamond scribing
objective and permanent ink labels.
REFERENCES:
Bergquist, A.M. 1985. Effects
of herbivory on phytoplankton community composition, size structure and
primary production. Ph. D. Dissertation. University of Notre Dame, Notre
Dame, Indiana, USA.
Crumpton, W.G. 1987. A simple
and reliable method for making permanent mounts of phytoplankton for light
and fluorescence microscopy. Limnol. Oceanogr. 32: 1154-1159.
St. Amand, A. 1990. Mechanisms
controlling metalimnetic communities and the importance of metalimnetic
phytoplankton to whole lake primary productivity. Ph.D. Dissertation.
University of Notre Dame, Notre Dame, Indiana, USA.
Olrik, K., et. al. 1998. Methods
for Quantitative Assessment of Phytoplankton in Freshwaters, part I. Naturvårdsverket,
Stockholm.
Hillebrand,H., et. al. 1999.
Biovolume Calculation for Pelagic and Benthic Microalgae. Journal of Phycology.
35: 403-424.
PhycoTech, Inc.
620 Broad Street, Suite 100
St. Joseph, MI 49085, USA
Tel: 1-269-983-3654
Fax: 1-866-728-5579 / 1-269-983-3653
E-mail: info@phycotech.com