From:	PO2::"QUATERNARY@MORGAN.UCS.MUN.CA" "Research in Quaternary Science" 27-FEB-1996 15:12:59.67
To:	Multiple recipients of list QUATERNARY <QUATERNARY@MORGAN.UCS.MUN.CA>
CC:	
Subj:	late-glacial Pediastrum

Dear all:
     At long last, here is a summary, including refs., of the
responses to my request a couple of months ago re. the significance
of Pediastrum changes in late-glacial sediments:
 
References on the morphology/ecology/taxonomy of Pediastrum:
Nielsen, H., and Sorensen, I. (1992).  Taxonomy and stratigraphy of
the late-glacial Pediastrum taxa from Lysemosen, Denmark -- a
preliminary study.  Rev. of paleobotany and palynology, Amsterdam,
74: 55-75.
Janovska and Komarek (199?).  in Folia Geobotanica and
Phytotaxonomica.
Elster, H.J. and Ohle, W. (1983).  Die Binnengewasser and Parra
Barrientos, O. 1979.  Revision der Gattung Pediastrum Meyen
(Chlorophyta). Published by Cramer.
R.L. Kendall (1969).  Ecological Monographs 39: 121-176.
Fredlund, G.G. (1994).  Paper on Cheyenne Bottoms , Kansas.
Published in Quaternary Research. vol?
Lotter and Holzer (1994).  Dissertationes Botanicae 234: 365-388.
Barrientos, O.O.P. (1979).  Revision der Gattung "Pediastrum" Meyen
(Chlorophyta).  Bibliotheca Phycologia 48
Prescott, G.W. (1962).  Algae of the western Great Lakes area.
Dubuque, W.C. Brown Company.  977pp.
Sulek, J. (1969).  Taxonomische Uberisicht der Gattung "Pediastrum"
Meyen.  Studias in Phycology (Praha) 1969: 197-261.
Whiteside, M.C. (1965).  On the occurrence of "Pediastrum" in lake
sediments.  J. Arizona Acad. Sci. 3: 144-146.
Beardall, J. (1985).  Occurrence and importance of HCO3 utilisation
in microscopic algae.  In Lucas, W.J. and Berry, J.A. (eds)
Inorganic carbon uptake by aquatic photosynthetic  organisms, 83-96.
Am. Soc. Plant Physiologists, Rockville. (Doesn't deal specifically
with Pediastrum).
Birks, H.H. pp. 377-405.  In Haworth and Lund: Lake sediments and
environmental history (1984).  Leicester Univ. Press.
Wolfe, A.P. and Butler, D.L. (1994).  Boreas 23: 53-65.
 
The range of responses I got back shows that the palaeoecological
signif. of Pediastrum is still poorly understood.  I (along with
other people working on the late-glacial of Scotland and Ireland)
find that high Pediastrum levels tend to correlate with high erosion
and high herbs/low trees (i.e. Younger Dryas and minor interstadial
oscillations), while low values correlate with warmer parts of the
interglacial (less erosion, more trees/shrubs) and the early
Holocene.
In late-glacial sites in Newfoundland, peaks tend to occur at the
sedimentological boundaries, e.g. high values at Younger Dryas
boundaries but low elsewhere.  In Norway, Pediastrum peaks occur in
the Allerod and early Holocene, but are absent in the Younger Dryas.
Holocene sites appear to show no clear correlation between pollen and
Pediastrum changes.
Causative factors that have been cited include changes in:
turbidity, water chemistry, nutrient status, erosion, pH.  Modern
studies suggest that pH may be a factor.  The range of responses may
be due to lumping different species together.
 
Clearly, lots of workers have counted Pediastrum, but the environ.
factor that it's responding to appears to be far from clear.
Many thanks for all those on the list who gave me info. and
references and apologies for my delay in replying.
 
Sincerely,
 
Francis Mayle
Department of Geography
University of Leicester,
Leicester LE1 7RH
England
fem1@le.ac.uk
fax 0116 252 3854
phone 0116 252 3831