The Collection and Mounting of Foraminifera.
Images by Jan Parmentier (NL)
Text By Brian Darnton (GB)
The Foraminifera have been known to microscopists since the
time of van Leeuwenhoek, but very few people actually seem to
collect them. In the study of geology and within the petroleum
industry in particular, fossil deposits have become familiar
markers of time periods and allied climate in the earth's crust.
Living creatures are to be found in marine conditions from the
ooze of the deepest ocean to the seaweed's of the littoral zone.
They can also exist in hyposaline estuarine situations. There is
even one non marine environment where they can be encountered in
brackish pools of the eastern shore Neusiedlersee which divides
Austria from Hungary. Some claim that this is a residue from the
Miocene period sea which existed here 10 Million years before the
If the "greenhouse effect" does become more than a
theory, then it would be important to record the content of the
seas around us before the sea conditions begin to change.
Although the Mediterranean Sea and the North Sea share one or two
species each has a very distinctive "assemblage" of
Foraminifera and the Shelly remains of other calcareous
marine creatures would be an ideal component of the School
Curriculum: The empty "Shells" have considerable
aesthetic appeal. Material from shore gatherings does not require
to be killed or fixed, nor would their collection affect the
environment in any significant manner. Investigation would be
quite suitable for low magnification, low cost microscopes.
Soundings or dredgings from the sea bed are beyond the means
of the amateur, but beach gatherings are very useful indicators
of foram associations. They are to be found amongst the debris of
the upper tide marks of sheltered bays. Open storm beaches are
not fruitful sites for investigation.
The bays of the Irish and
Scottish Atlantic coast like Dogs
Bay (Ireland) and Calgary Bay (Isle of Mull) are excellent
sites where the forams are blown into dunes. Pure cultures can
discovered growing on seaweed in the early summer. The common
Foram Elphidium crispum enjoys the Sargassum muticum
fronds along the Southern English coast. In the Netherlands there
can be some confusion. In tidal lagoons like at Het Zwin, and
broad estuaries like the WesterSchelde, fossil Forams may be
found alongside recent ones as much of the Zeeland landscape
consists of covered or exposed tertiary beds. The United Kingdom
also has a few similar sites: Bracklesham Bay is a good example
of an area where Tertiary beds have an input into the marine
||In the bay situation the spread of Foraminifera is
confined to a very limited deposition zone which is to be
found towards the headland from which the tidal flow
originates. Local newspapers usually indicate which local
harbours have the earlier high tide times. Frequently the
sample is marred by particles of discarded coal or
natural lignite but the black and white banding is a
useful indicator at the deposition zones. In the
Mediterranean Sea the Foraminifera are numerous but
because of the lack of strong tides, the deposition zone
extends to most of the sandy coastline with large numbers
to be found to the lee of headlands. In the open sea,
depressions in the sand near submerged rocks can reveal
pockets of "Shells" In gathering from the shore
a good X10 hand lens is a useful tool and material is
best scraped from the sand with a flat children's spade.
Do not forget to label samples in a plastic bag.
Its a good idea to tip the sample into a bucket of water for
the salt must be removed. A certain amount of separation from the
sand can be achieved by stirring vigorously with a wooden spoon.
If the suspension is observed in bright light, after almost one
second most of the heavier sand will have sunk to the bottom but
the white calcareous remains will still have some buoyancy.
This suspension may be
decanted off into a 50 micron sieve or a fine sieve may be used
to fish for forams in the suspension. If the bucket is carefully
emptied and filled with a tap water at pressure some of the
forams will fill with air and float on the surface for a while
and may be captured. The Mediterranean types float well. The
physical separation from sand can become the most challenging
part of the business. When a fairly pure mixture of Forams has
been cleaned then sieves can be used to separate species. Each
seems to have a well defined size.
less than 100 microns may be strewn in water and when dry mounted
in Numount or a similar mountant. Its always a good idea to smear
the slide first with a trace of gum tragacanth paste in order to
prevent the "Shells "moving after mounting. Bubbles
emerge after mounting in Numount for about five days and can
spoil the mount. It is best not to use any heat for a week. The
larger faction will probably have to be dry mounted. A fine oooo
art brush is a good tool for manual selection. Here again Gum
tragacanth is a suitable adhesive because it tends to leave no
unsightly smear. At first, a simple 1 mm deep cell with a black
background is very suitable but when one becomes familiar with
species then some form of numbered grid is a good idea. NBS do
produce some plastic cell slides which are very useful for this
This is a traditional substance for dry mounting but it
should be prepared at least 2 days before use. The key to its use
is to dilute it as thinly as possible so that there is little or
no trace on the slide surface when dry. NBS now produce a dry
mount adhesive which works very well.
Mounted Foraminifera from home or distant oceans were a
familiar attraction of the Victorian microscope cabinet. World
travel is now open to a much larger portion of the community,
therefore there is no reason why an interest in these fascinating
creatures should not be rejuvenated. Our own European seaside
will provide a very good introduction to the subject.
Comments to the author Comments to the author sent via our contacts page quoting page url plus : ('bdarnton','')">Brian
J.W.Murray. "An Atlas of Recent Foraminifera" 1971,
ISBN 0 435 62430 X, Heinemann Press with 96 ESM plates
R.W.Jones "The Challenger Foraminifera" 1994, ISBN
19 854096 5, Oxford University Scientific Press
J.A.Cushman " Foraminifera" 1980 fifth printing, SBN
674 30802 8, Harvard University Press.
Tregouboff G an Rose M. 1957 "Manuel de Planctonologie de
Mediterraneenne" (2 volumes).
Faber Dr.F.J "Geologie van Nederland" Deel 3
Editor's note: to read other
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Published in November 1998
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