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References for addressing quality and calibration of visual
phytoplankton cell counts
#
# This file is derived from a thread of discussions from the ALGAE-L listserv (whose archive
is searchable at
http://www.seaweed.ie/algae-l/)
# If you have anything to add, please send it to me at jcz@wzrd.com.
# Posted: 2001-12-23, by John Zastrow
###################################################################################
From:
Michael Agbeti [magbeti@BIO-LIMNO.COM]
Sent: Wednesday, December 05, 2001 1:47 AM
To: ALGAE-L@LISTSERV.HEANET.IE
Subject: Criteria for QA/QC
Dear Colleagues:
Following is the list of responses I've had to my request. Apparently, not much
work has has been done on this topic.
REQUEST:
I am wondering if there is any standard criteria (published or report) for QA/QC
acceptability i.e. if algal identifications and counts from two taxonomists are
compared for QA/QC, at what level of differences between the two counts are the
results acceptable. I believe Bray-Curtis dissimilarity index may be used. What
value can be acceptable.
I would be glad to hear from those who have any information that I will find
useful. Also, any publication on this would be highly appreciated.
RESPONSES
1) Although we have been tracking QA/QC for our algal identifications for about
2 years now, we really don�t have a good idea of what might be deemed
�acceptable�. We know that a portion of the variability in counts and taxa found
is due to the patchiness of the distribution of the algae within the sample. We
have been using our QC results to give users of our data an idea of the
variability in that data so that they can take that into account when doing data
analysis. If you get any helpful replies to your inquiry, could you forward them
to me? We are in the process right now of looking at ways to increase things
like number of taxa in common and decrease things like percent difference in
cell counts.
Elizabeth B. Miller
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2) I have addressed this question from the point of view of benthic diatoms
rather than phytoplankton, but the principles should be fairly similar. I posted
a similar request on ALGAE-L when I started this work and got the impression
that there was a lot of interest in what I was doing, but not a lot of
experience to tap.
For benthic diatoms, we use the Bray-Curtis similarity measure, but be aware of
the following:
a) you need an agreed taxon list, so that differences do not reflect taxonomic
conventions or "splitters versus lumpers" debates
b) diversity is a big issue: hard to get good agreement with very diverse
samples
Bray-Curtis is fine for proportion / percent data. For simply comparing
presence/absence, we have tried Jaccard's coefficient and also a method based on
"gains" and "losses" that is used in invertebrate QC in the UK. However, because
we tend to be looking at replicate sub-sub-sub samples whilst our invertebrate
colleagues perform repeat analyses on the same sample, we also use a de minimus
value, so that "rare" taxa are excluded from the analysis.
We have tried using these techniques on phytoplankton and I think that they
should work as a means of comparing the contents of replicate counting chambers.
The final difference in numbers will depend upon inherent errors in the chamber,
scaled by errors associated in concentration, sample collection etc.
I've attached the proof of a paper that I've just had published in Water
Research outlining the basis of the diatom QC method. I hope that this is
helpful.
Martyn Kelly
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3) I also wonder about this. Together with this taxonomist difference, there may
be also method difference, there are several methods for phytoplankton counts
and identifications. We use sedimentation method for preparing the samples for
identification and we count the phytoplankton within a Sedgewick Rafter cell.
Some other people centrifuge the samples, some other ones use settling chambers.
I will also be glad if anybody have any information related with this and share
it with us.
Thanks, Elif
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4) You may already have it, but otherwise, this could be of use:
Kelly, M. G., Use of similarity measures for quality control of benthic
diatom samples. Water Research, 35(11): 2784-2788.
Best wishes,
John.
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5) I did a pretty thorough search of phytoplankton QC criteria, and at present
there's little information out there. One exception is some work that's being
done in England. Martyn Kelly has recently (I think this past year) published
some work on using Bray-Curtis for comparing replicate diatom samples. I assume
that is the study you referred to. As far as I can tell, that's about it. Martyn
and I had been in touch while he was preparing that report, in response to an
enquiry that I sent to the algae list a few year back when I was looking for QC
criteria. It happened that we were both developing ideas along similar lines. If
you want, I can try to dig up that paper. I'll be out of town the next week,
though - among other things, I'm going up to Duluth to meet with Mary Balcer,
specifically about QC procedures for the EPA project. I assume that's what
prompted your post.
I hope things are going well with you up there. We'll probably be seeing you in
the next few months.
Best wishes,
--->Rick
Thanks for all those who have responded.
Michael
Providing services in algal and zooplankton analyses
*********************************************
Michael D. Agbeti, Ph.D., CLM
Bio-Limno Research & Consulting
8210-109 Street, PO Box 52197
Edmonton, Alberta
T6G 2T5 CANADA
Telephone/Fax: (780) 439-1558
E-mail: magbeti@bio-limno.com
Website: www.bio-limno.com
*******************************************
From: Forum for marine,
freshwater and terrestrial algae.
[ALGAE-L@LISTSERV.HEANET.IE] on behalf of Janice Moore [JMOORE@CRD.BC.CA]
Subject: Criteria for QA/QC
Hi Michael,
I have located a couple of papers that discuss the intercalibration errors in
using Uterm�hl's technique:
(1) Hobro, R. and E. Will�n. 1977. Phytoplankton countings: intercalibration
results and recommendations for routine work. Int. Revue ges. Hydrobiol.
62(6):805-811.
(2) Rott, E. 1981. Some results from phytoplankton counting intercalibrations.
Internationaler Phytoplankton-Workshop. Schweiz. Z. Hydrol. 43(1):34-62
Munawar (see below) also touches on QA/QC considerations with long term (100 yr)
data sets.
With respect to your query, "at what level of differences between the two counts
are the results acceptable", should the answer be that no level is acceptable?
What if the specie(/taxa?) misidentified is a keystone or indicator specie? How
can one use long term data sets if the data is riddled with identification
errors due to different individuals collecting the data over time?
What I have done is develop a phycological catalogue containing images, line
drawings, authorities, etc. Each summer I have a different technician that I
have to train. The only way that I can standardize the IDs and hence the data is
to have the technician constantly refer back to my standardized phycological
catalogue.
Following is a list of other papers I routinely refer to when I am using
Uterm�hl's technique. I would be interested in receiving from others any
additional references that I may have missed.
Lucey, W.P. 1993. Periphyton functional and structural response, within
semi-natural surrogate streams, to artificially induced water quality
perturbations. Masters of Science Thesis. University of Victoria: Victoria, B.C.
Lund, J.W.G., C. Kipling and E.D. Le Cren. 1958. The inverted microscope method
of estimating algal numbers and the statistical basis of estimations by
counting. Hydrobiologia. 11(2):143-170.
Munawar, M., I.F. Munawar and L.H. McCarthy. 1989. Phytoplankton ecology of
large eutrophic and oligotrophic lakes of North America: Lakes Ontario and
Superior. Arch. Hydrobiol. Beth. Ergen. Limnol. 25:51-96.
Paerl, H.W. 1978. Effectiveness of various counting methods in detecting viable
phytoplankton. New Zealand Journal of Marine and Freshwater Research.
12(1):67-72.
Paxinos, R. and J.G. Mitchell. 2000. A rapid Uterm�hl method for estimating
algal numbers. Journal of Planktonic Research. 22(12): 2255-2262.
Reid, M.H. 1983. Biomass estimation of components of the marine nanoplankton and
picoplankton by the Uterm�hl settling technique. Journal of Planktonic Research.
5(2): 235-251.
Sandgren, C.D. and J.V. Robinson. 1984. A stratified sampling approach to
compensating for non-random sedimentation of phytoplankton cells in inverted
microscope settling chambers. Br. Phycol. J. 19: 67-72.
Sournia, A. (Editor). 1978. Phytoplankton Manual. Unesco: Paris
Tangen, K. 1976. A device for safe sedimentation using the Uterm�hl technique.
J. Cons. int. Explor. Mer. 36(3):282-284.
Throndsen, J. 1978. Chapter 4. Preservation and storage. In Phytoplankton
Manual. Edited by A. Sournia. UNESCO.
Uterm�hl, H. Neue Wege in der quantitativen Erfassung des Planktons. (Mit
besonderer Ber�cksichtigun des Ultraplanktons. Verhandlungen der Internationalen
Vereinigung f�r Limnologie. Budapest, 1930. 567-596. In German.
Venrick, E.L. 1978. How many cells to count? Pages 167-180. In A. Sournia
(Editor). Phytoplankton manual. Unesco, New York. 337 pg.
Will�n, E. 1976. A simplified method of phytoplankton counting. British
Phycology Journal. 11:265-278.
Cheers,
Janice Moore, Aquatic Ecology
Water Quality Division
Water Department
Capital Regional District
Mailing Address: 2995 Sooke Lake Rd, Victoria, BC, CAN, V9B 4P9
Lab/Office Location: 3034 Humpback Rd, Victoria
Lab/Office: (250) 474-9644
Fax: (250) 474-9167
Email: jmoore@crd.bc.ca
Web http://www.crd.bc.ca
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