Diatom Dissolution Replies
Collated by Kurt Haberyan
Biology Dept, NW Missouri State Univ, Maryville MO 64468 USA
0100730@acad.nwmissouri.edu
Note: Below I post the original inquiry about the dissolution of
diatoms. Each reply has been posted and (in some cases)
edited, with permission of its author, and includes his/her
direct e-mail address. In the case of inadvertent changes in
meaning, I apologize and will correct the error as soon as
I'm notified.
I can also add new messages if that is warranted.
I'm missing 'permission to post' from a few people; if you contri-
bution is not here and you'd like it to be, let me know.
Thanks to all!
Kurt
0100730@acad.nwmissouri.edu
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THE ORIGINAL QUERY
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On Wed, 29 Jan 1997, HABERYAN wrote:
Greetings, fellow diatomists!
I'm still working with these recalcitrant sediments from Costa
Rica and have encountered another 'challenge.' One of the longest
and most interesting cores only has diatoms near the top, but
sponge spicules throughout. There are fragments of diatoms on the
slides, but these too become more common upcore. Dissolution is
clearly a major factor.
What kinds of conditions enhance dissolution? I remember a
'roundtable' discussion at the Diatom Symposium in Philadelphia
(1983?) in which it became clear that there's no one answer. Would
anyone be willing to comment to me (don't reply to the LISTSERV),
or direct me to the important references (and/or send reprints)?
Is there ANYTHING we can conclude from the lack of diatoms?
Thanks for the help!
Kurt Haberyan
0100730@acad.nwmissouri.edu
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THE REPLIES
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From: SMTP%"pasiv@conncoll.edu"
Date: Wed, 29 Jan 1997
From: "Peter A. Siver"
Dear Kurt,
I have found through our examination of 60+ lakes in
Connecticut that dissolution is mostly a problem in our alkaline
lakes. I think this is a real problem for us under these
circumstances.
Also, one other comment. Are you sure its really dissolu-
tion? Or is everything broken into small fragments? I often
check closely with SEM to see if the silica fragments are really
"etched" or not. In a few instances we had all broken fragments,
but the scaled chrysophyte scales were in great shape - thus, no
dissolution problem here.
Peter Siver
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From: SMTP%"slcooper@acpub.duke.edu"
Date: Wed, 29 Jan 1997
From: Sherri Cooper
Kurt,
I am also finding the same thing in some cores from the
Everglades. I think that in our case it has something to do with
organic acids. (See Bennett et al. "Fate of silicate minerals in a
peat bog" Geology, v. 19, pp. 328-331 (1991)). Although with the
sponge spicules present, not sure what is going on... we also have
the same thing in many samples. I know that it is not strictly a
pH problem in our case.
Best wishes,
Sherri Cooper
Duke Wetland Center
Box 90333, Durham, NC 27708
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From: SMTP%"haskell@maroon.tc.umn.edu"
Date: Wed, 29 Jan 1997
From: Brian Haskell
Hello Kurt,
Silica tends to be undersaturated in just about all systems,
so a tendency towards dissolution is a given. Dissolution is also
affected by pH, and very strongly affected by temperature.
I did a quick search on my references database and came up
with the following references that might have bearing on your
question on the listserver.
Thayer, V. L., T. C. Johnson and H. J. Schrader, A preliminary
study of recent diatom assemblages in Lake Superior sedi-
ments, Journal of Great Lakes Research, 9, 508-516, 1983.
Barker, P., J.-C. Fontes, F. Gasse and J.-C. Druart, Experimental
dissolution of diatom silica in concentrated salt solutions
and implications for paleoenvironmental reconstruction,
Limnology and Oceanography, 39, 99-110,1994.
I have done some silica dissolution as part of other studies
and sponges are very resistant to dissolution. I am not sure why
this is, although the low surface area/volume ratio might account
for it. Might there be a difference in the opal structure
(guessing)?
Cheers,
Brian J. Haskell Telephone:
Limnological Research Center (612) 624-7005
University of Minnesota (612) 378-3242
310 Pillsbury Drive. S.E. Fax:
Minneapolis, MN 55455-0219 (612) 625-3819
http://lrc.geo.umn.edu/people/haskell/
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From: SMTP%"bsgeol@u.washington.edu"
Date: Wed, 29 Jan 1997
From: Brian Sherrod
I have read that when conditions are too alkaline, diatom
frustules can dissolve. I wonder if the same is true for high
pH's??? Try looking at Mikkelson, N., 1980. Experimental
dissolution of Pliocene diatoms. Nova Hedwigia, 33(2): 893-911.
Brian Sherrod
Department of Geological Sciences/USGS
University of Washington, Box 351310
Seattle, Washington 98195
bsgeol@u.washington.edu
(206)685-1960
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From: SMTP%"msvd@opal.geology.utoronto.ca"
Date: Wed, 29 Jan 1997
From: "M.S.V. Douglas" 9 (Andrejko and Cohen 1984). Dissolution also occurs in
environments such as peats which have no minerogenic input
other than atmospheric inputs. In those cases, silica is in
such demand that it is used up by living organisms. ie., the
material is undersaturated with respect to silica.
2. Dissolution of diatom valves was evident and sponge spicules
showed evidence of dissolution and borings. Andrejko et al
(1982) have shown these borings and pitting to be present in
sponge spicules and attribute this to bioerosional features
originating from organisms such as fungi and possibly
diatoms (!).
3. Andrejko, M.J., R. Raymond Jr, A.D. Cohen. 1982. Scanning
electron microscopy observation features on freshwater
sponge spicules. Scanning Electron Microscopy. II:629-638.
4. Andrejko, M.J and A.D. Cohen. 1984. Scanning electron
microscopy of silicophytoliths from the Okefenoke
swamp-marsh complex. pp 466-491. In Cohen, Casagrande,
Andrejko and Best (Eds). The Okefenokee Swamp: Its natural
history, geology and geochemistry. Wetland Surveys. Los
Alamos.
Marianne Douglas
Department of Geology
University of Toronto
22 Russell St 416 978 3709 (voice)
Toronto, ON 416 978 3938 (fax)
M5S 3B1, Canada
msvd@opal.geology.utoronto.ca
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Date: Thu, 30 Jan 1997
From: Hedy Kling
Hi Kurt,
Both high pH and increasing temperature, plus low Si in the
interstitial water near the sediment-water interface, enhance
dissolution. See the following papers:
Lawson, D.S. D.C Hurd and H.S. Pankratz. 1978. Silica dissolution
rates of decomposing phytoplankton assemblages at various
temperatures. Amer. Jour. Sci. 278:1373-1393.
Hecky, R.E. H.J. Kling and G.J. Brunskill. 1986. Seasonality of
phytoplankton in relation to silicon cycling and
interstitial water circulation in large shallow lakes of
central Canada. Hydrobiologia 138:117-126.
Another place you may find dissolved diatoms is a deep lake
that is very oligotrophic, with low soluble reactive Si concen-
tration and low biomass of diatoms. Much of the diatom is
dissolved before it reaches the bottom. With low productivity, the
diatom may not be buried for quite a while, so dissolution will
tend to be more pronounced, so all you find are the thickest
parts. Also, once the external organic membrane is off of the
diatom, it can start dissolving (even if still living). This
happens in Si limited conditions under increased P.
Kling H.J. 1992. Valve development in Stephanodiscus hantzchii
Grunow (Bacillariophyceae) and its implications on species
identification. Diat. Res 7(2) 241-257 p 248.
There's a bit more in my paper and Gensemer's papers on
Asterionella:
Kling H.J. 1993. Asterionella formsa Rahlfs: the process of rapid
size reduction and its possible ecological significance.
Diatom Res. 8(2) 475-479.
Bob Gensemer confirms my hypothesis in his paper in the last
proceeding of the international Diatom Meeting:
Gensemer, R.W., R.E.H. Smith, and H.C. Duthie. 1994. Interactions
of pH and aluminum on cell length reduction in Asterionella
ralfsii var. americanum Kormer. Proc. 13th International
Diatom Symposium, D. Marino & M. Montresor (eds), pp. 39-46.
Hope this helps a bit.
Cheers,
Hedy
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Date: Thu, 30 Jan 97
From: David Ryves
Dear Kurt,
I looked at diatom dissolution for my PhD (from which
nothing as yet has been published). I was working on the Northern
Great Plains of America, in the same lakes and on the same flora
as Sheri Fritz, Steve Juggins and Rick Battarbee. My angle was
trying to quantify dissolution and modify the salinity transfer
function to take into account susceptibility to dissolution; now
I'm working on a small project to recount those surface sediment
samples and modify the transfer function "at source" in the
calibration dataset.
To answer your questions, the single most important factor
affecting diatom dissolution is pH - above about pH 9 and silica
dissolves extremely rapidly and often completely. Other factors
can be important though: if diatom valves are dissolving slowly
over an extended time dissolution can be equally extensive. For
example, diatoms in sediments are often preserved as pore water
silica concentrations become saturated; but if there is pore water
movement (due to geohydrological conditions or bioturbation
perhaps) then pore waters may remain undersaturated with respect
to SiO2 and dissolution contines until such time as that
equilibrium is established. Breakage also speeds up dissolution
rate; there is some interconnection as dissolved valves break more
easily, which then dissolve more rapidly...
In Lake Baikal, most of the (considerable) dissolution
appears to happen at the oxic sediment-water interface; while in a
marine context, something like 90% of the silica is lost during
sedimentation to the sediment surface, and something in the order
of 1% (I think?) actually gets incorporated into sediments.
There are also factors associated with the age of diatom
silica (it slowly recrystallizes into more insoluble forms; over
hundreds of thousands or millions of years though); salinity
(dissolution rate is reduced as salinity increases); temperature
(again, kinetic dissolution rates increase with temperature). Add
to that the differential susceptibility of differently shaped
diatom valves to dissolution and the complexity of diatom
dissolution becomes apparent.
Another (!) consideration is the treatment diatoms get in
the laboratory - there can be considerable breakage & dissolution
from standard preparation techniques (such as the usual hot
hydrogen peroxide treatment we give valves here!); which can be a
really exacerbating problem if valves are already partly dissolved
and/or fragile to start with. For Baikal material, for example, we
now just add water to wet sediment and make slides up directly;
but then there is far less organic matter in these sediments than
most. Another option would be to use cold peroxide over a day or
two. Acid cleaning also makes valves more susceptible to
dissolution by removing the metal ions from the silica surface,
which retard dissolution (as shown by Joyce Lewin and others since
e.g. Phil Barker).
I hope some of this is of interest and use for your core
material.
All the best,
David Ryves
Environmental Change Research Centre
Department of Geography, UCL, UK
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Date: Fri, 7 Feb 1997
From: Philip Barker
Kurt,
As you note there is nothing simple about diatom
dissolution. Most of the factors you mention (pH, pore water
silica etc) are the usual culprits but the answer will be
site-specific. You don't mention anything about the water
chemistry or the nature of the sediments in which the diatoms are
absent. If your lake is of the Na2-HCO3-CO3 type then high
alkalinity is the most likely explanation. If you have a
situation where Ca(Mg)CO3 is precipitating, the resulting
chemistry can be very hostile to SiO2. If it is very deep, e.g.
Tanganyika, pressure could be a catalyst.
The sponge spicule issue is a bit more puzzling. It could
be due to spicules having (a) higher density silica (b) a lower
surface area/volume ratio than diatoms (c) the spicules are more
easily identifiable than diatoms when partially dissolved (d)
metals are taken into the sponge silica. A longer shot might be
that ambient silica concentrations are higher in the benthos than
in open waters, but this would also preferentially protect benthic
diatoms. If you want to take this further send me some data and
we could put something together.
My publications to date on dissolution are as follows:
Barker, P.A., Fontes, J.-Ch., Gasse, F., and Druart, J.-Cl. 1994.
Experimental dissolution of diatom silica in concentrated
salt solutions and implications for palaeoenvironmental
reconstruction. Limnology and Oceanography 39: 99-110.
Gell, P, Barker, P, DeDeckker, P, Last, W and Jelicic, L. 1994.
The Holocene history of West Basin Lake, Victoria,
Australia; chemical changes based on fossil biota and
sediment mineralogy. Journal of Palaeolimnology 12:
235-258.
Barker, P.A. 1992. Differential diatom dissolution in Late
Quaternary sediments from Lake Manyara, Tanzania: an
experimental approach. Journal of Paleolimnology 7 (3):
235-251.
Cheers,
Phil
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From: SMTP%"aritko@utu.fi"
Date: Thu, 30 Jan 1997
Kurt,
You are probably aware of the information in the following texts:
Jones, B.F. & C.J. Bowser, 1978. The mineralogy and related
chemistry of lake sediments. In A. Lerman (ed.), Lakes -
chemistry, geology and physics. Springer-Verlag, N.Y.:
179-235.
Engstrom, D.R. & H.E. Wright Jr., 1984. Chemical stratigraphy of
lake sediments as a record of environmental change. In E.Y.
Haworth & J.W.G. Lund (eds), Lake sediments and
environmental history. Univ. Minnesota Press, Minneapolis:
11-67.
This one is even older, but I think its is the most complete of
these three:
Merilinen J. 1973. The dissolution of diatom frustules and its
palaeolimnological interpretation. Univ. of Lund, Dept. of
Quat. Geol. Report 3: 91-95.
Cheers,
Arto
Arto Itkonen
Department of Geology
University of Turku
IN-20014 University of Turku
Finland
tel. +358-2-3336389
fax. +358-2-3336580
e-mail aritko@utu.fi
