A historical paper on the Importance of Diatoms.

1. The Economic Importance Of The
Diatoms
(1917),
Albert Mann
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FROM THE SMITHSONIAN REPORT FOR 1916, PAGES 877-886
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1917

2. THE ECONOMIC IMPORTANCE OF THE DIATOMS.
By Albert Mann
Scientific study is constantly giving emphasis to the fact that in nature there is little, if
any, relationship between size and importance. Charles Darwin long ago made it plain that
among the myriad of living creatures the earthworm plays a very important role in the
economy of nature, especially as applied to mankind, and is in fact a greater animal than the
elephant. The lowly grass outweighs in importance the loftiest tree of the forest. A brilliant
series of discoveries led by Pasteur has revealed to us that the most gigantic power, in some
cases beneficent, in others baleful, is exercised by the minutest of all living things, the
bacteria. It is, therefore, not to be wondered at that the plants here under consideration,
although as a class quite invisible to the naked eye, and many of them so minute that a
hundred can be laid upon the head of a common pin, are at the same time of great economic
importance,
But for a long time the attention of mankind was diverted from the more practical values
that we are here to consider by that most striking characteristic of these plants, their
surprising beauty and the unequaled complexity of their ornamentation. Coupled with their
minuteness there is a daintiness of structure and an artistic diversity of design among the six
thousand and odd species which has doubtless been the cause why until recent times they
have been objects of merely esthetic interest. They have never been neglected, for from the
time of the invention of the microscope they have been the darlings of the microscopists; but
only to-day are they beginning to be recognized as an important factor in the welfare of the
human race.
Each diatom plant secretes for itself an incasing box or investment of pure silica,
somewhat as a clam or oyster secretes its shell; and these crystalline walls, within which the
tiny living plant is housed, are sculptured and carved with such bewildering complexity of
design and yet with such perfection of finish that their attractiveness has absorbed the
attention of students to the detriment of their many less spectacular qualities.
Only one practical use has been developed from this esthetic study of the diatoms; they
have been long recognized as the most accurate and satisfactory test objects for determining
the perfection of microscopic lenses and accessories, the ability of any microscope to render
visible the fine lace ornamentation which overspreads some of the species being the best
index of its optical excellence. As a consequence of this, all microscopes are to-day tested
with one or both of two species of diatoms, Pkurosigma angulatum, or Amphipkura
pellucida.

3. One of the oldest of the economic uses of diatoms has been that of employing fossil
diatom earth as a polishing powder, especially in metal work. These organisms appeared
geologically about the middle of the Cretaceous period, and although, therefore, among the
later of the now existing forms of plant life, their prolific multiplication has resulted, during
former periods of time, in the formation of enormous fossil beds composed of the silica
remains of these minute aquatic plants. Such beds are found all over the world, famous
deposits being located at Luneburg, Germany; Bilin, Bohemia; Sendai, Japan; Ananino,
Russia; Oamaru, New Zealand; Moron, Spain; Keene, N. n.; Nottingham, Md.; the coast of
California, and many other places of minor importance. The first considerable fossil deposit
of diatomaceous earth used was .confused with a polishing material called " rottenstone,"
mined at Tripoli, in Africa, and it was therefore referred to in commerce by the same name,
"Tripoli powder," and is in fact so sold in drug stores at the present time. Its high abrasive
value comes from the fact that the material, silica, has a high degree of hardness and the
grain of the diatom powder is so fine as to produce as' a polish the highest luster. Its extreme
fineness of texture is shown by a computation made by Ehrenberg, that in 1 cubic inch of
the Bilin diatom earth there are 40,000,000 individuals.
This abrasive quality of the diatoms has led to their use for other purposes than metal
polishing, as for example, for tooth powder. One of the widely advertised tooth powder
preparations upon the market is composed entirely of diatomaceous earth. It cannot be said
that this is a good material for the purpose, as the cutting quality of this siliceous substance
is too great to be used constantly upon the thin layer of enamel of the teeth. It is, however,
interesting to think that many of the users of this diatom dentifrice would be amazed if they
could see the thousands of exquisite gem-like organisms lying upon their tooth brush and
used as a toilet preparation.
As a curious instance of perverted use, it might be well here to mention the fact that
diatomaceous earth was at one time extensively eaten by the impoverished and half-starved
tribes inhabiting the remoter portions of eastern Europe and Asia. Generally the diatom
earth was mixed with flour, and although the nutritive value of this added substance is
practically nothing, the advantage of its use was an actual one; because, when the normal
requirement of the human stomach for a "square meal" is a quart, and the available flour for
that meal is a half pint, the unfortunate consumer gets at least the semblance of a full dinner
by adding to his food supply three times its volume of harmless and inert matter. This is
probably the explanation of the custom of those tribes known as the "earth eaters.”
A number of years ago and shortly after the invention of nitroglycerine, the diatoms came
into an economic use of great importance, namely, the manufacture of dynamite. This
substance, so great a blessing and a curse to mankind, is essentially nothing but nitroglycerine absorbed into the cavities of dried diatom earth. As each diatom plant is a

4. microscopically small silica box, the walls of which are perforated with intensely minute
openings, the diatom earth serves to isolate tiny particles of nitroglycerine in such a way as
to render the liquid practically a solid and at the same time to obviate the dangerous quality
of free nitroglycerine of exploding by means of shock and at low temperatures. To-day,
although diatomaceous earth is used to a considerable extent as an element in nitroglycerine
explosives, it has been somewhat replaced by other substances, as for example, wood meal.
If the meaning of the word economic is not too rigidly taken and may include our increased
facility in certain lines of research, it is proper to mention among the economic uses of these
plants their value in the determination of certain problems of oceanography, especially in
the determination of the direction and the extent of the great ocean currents. Those familiar
with this phase of research are aware of the great difficulties attendant upon the accurate
measurement of the extent and speed of an ocean current, due to the fact that the vessel from
which such observations have to be made is itself a drifting object, acted upon by the current
in question, as well as by the wind and other forces difficult to compute. Could the ship be
anchored, this disadvantage would vanish; but inasmuch as this phase of oceanographic
research is carried on in the deep seas, anchoring is not practicable. These organisms, on
account of their peculiar structure, composition, and size, lend themselves perfectly to
studies of this kind. It is perhaps safe to say that they are the only organisms which meet
fully the requirements. Being composed in part of an indestructible substance, they do not
suffer the rapid decay of many of the microscopic organisms of the sea. This is equally true
of other marine organisms incased in silica; but none of these have a second characteristic of
the diatoms which is of equal importance, namely, a minuteness of size sufficient to enable
them to be carried hundreds or thousands of miles by ocean currents. Such animal denizens
of the sea as the Radiolaria are as immortal as to their silica. encasements as are the diatoms;
but their larger bulk and more massive construction precipitates them to the bottom, while
the diatoms are held in suspension like the finest dust for an indefinite distance. When we
add to these two qualities a third one, the large number Oof well-defined species, differing
in kind according to the parts of the world in which they are found, we see that the presence
of these organisms in an ocean current, even thousands of miles from land, will often
indicate the direction, the extent, and to some degree the speed of the current by which they
are borne along. It should be here stated as a factor in this problem that the diatom flora of
any part of the world is always peculiar to that locality, just as the land flora varies at
different latitudes and on the different continents. Thus we have a north and south arctic, a
north and south temperate, and a torrid diatom flora, which are in strong contrast to each
other and which, wherever met with, indicate the place of their origin. In the same way the
fresh-water forms, which are poured in large quantities into the sea by the rivers, are still
more distinctive, and each section of the coast of our continent has at least some of these
plants to be found nowhere else upon the earth.

5. The student of these minute plants is constantly made aware of this sharp distinction of the
diatom flora of one part of the world from that of the rest. Let us take some examples: A
recent study of some living material from the Hawaiian Islands yielded a large and
elaborately ornamented diatom, Biddulphia imperialis, and search through diatom
literature revealed this in an obscure monograph, where it was recorded that it also had
been found" at the Sandwich Islands." Doubtless, the locality of the original specimen was
practically that of the one later found. Another species was named by a Philadelphia
diatomist as having been found in a gathering at Magdelena Bay, Lower California, and
marked as "very rare," The writer subsequently found it to be very plentiful in a dredging
of the U. S. S. Albatross, and, by comparison with the record of the original discovery, it
was shown that the two localities were within a mile of each other. The writer named a
new species discovered in the Arctic Sea., and subsequently, in a study of the dust
collected in pockets on the ice floes of the Arctic, this diatom was rediscovered; and on
comparison it was found that the latitude and longitude of the two were practically
identical. Material secured by the Smithsonian Institution adjacent to the openings of the
Panama Canal and previous to its completion has yielded a great many remarkable forms.
A. rare species known as Pleurosigma spectabile occurs abundantly in one of the
gatherings. This was previously reported by Prof. Grunow, of Vienna, as occurring along
the coast of Brazi1; that is to say, it is a coastal, middle Atlantic diatom. An even more rare
form known as Campylostylus stiatus was recently rediscovered in an irrigation ditch
leading from the Everglades, in Florida. It was first found by Mr. Shadbolt, of England, on
some mahogany logs shipped to London: from the shores of Honduras; in other words, it
is a Gulf of Mexico diatom.
An argument, and doubtless a valid one, to support the theory of Prof. Nansen that a
current passes northward from the Bering Strait across the north polar region and southward
along the western shores of Norway is based upon the fact that the diatom flora of Bering
Sea was found by Prof. Nansen to be singularly similar to that of Greenland and the
Norwegian coast, thereby indicating a connection between these apparently remote
localities. From such examples as the foregoing it is reasonable to believe that when the normal diatom floras of the different seas have been investigated and the local diatom floras of
the shallower waters, and especially of the rivers of the land, shall be known, we can tell by
samples taken at remote points of the ocean the parts of the earth traversed by the current in
which are found the specimens in question. In this same way a problem of no little
importance to ocean travel becomes one of easy and certain solution, namely, the area of
contact between the cold Arctic water of the north and the warm. waters of the Gulf Stream
of the coast of Newfoundland, this contact being the cause of the dangerous fogs prevalent
in that locality; for a sample of sea water taken anywhere in that neighborhood must reveal
at one to a diatom expert whether the water came southward from the Arctic, or northward

6. on the current of the Gulf Stream, or is a blending of the two.
A consideration of the economic value of the diatoms requires mention of some minor
uses. The large diatom. beds of the western part of the United States, and especially those
along the Pacific coast, where there are cliffs several hundred feet in height almost wholly
made of this material, are coming to be of commercial value because of tile use of this
substance as a substitute for asbestos or in combination with asbestos as a nonconducting
coating for steam pipes, as a filler for refrigerators, and for many other uses where a.
noncombustible material is needed. Fossil diatom deposits are also of value to the art of
pottery making, being combined with various other ingredients in the composition of certain
grades of porcelains and glass.
There has recently come into notice another use for diatomaceous earth which bids fair to
become of considerable value to medical science. The material is compressed into filters in
the shape of hollow cylinders or plates to be used for the filtration of serums, toxins, and
other sterile liquids of service in the modern treatment of diseases. The porosity and extreme
fineness of this material, coupled with its resistance to the action of acids and most
solvents, renders it peculiarly well suited for this purpose.
A. rather baleful use, at one time more extensive than at present, thanks to our purefood laws, and reminding us of the «earth eaters" previously mentioned, was the
employment of diatom earth as an adulterant of candies. A large diatomaceous earth
deposit in the eastern United States which formerly did a thriving business along this
line has been practically abandoned at the present time, because certain candy
manufacturers who used this substance have been compelled to resort to other means
for cheapening their product. It is only to be hoped that the substitute, whatever it is, is
as little harmful to the consumer as was the diatom material.
It seems right to revert to the artistic beauty of these minute organisms, mentioned at
the opening of this article, because their economic importance should not exclude their
practical value to the a.rts in the matter of designs. Those who are familiar with these
organisms find their great beauty consists not only in the delicate and complex tracery
of their surfaces, surpassing in this respect the most ingenious arabesques of the Moor,
but in the symmetry and great diversity of form and outline displayed by the members
of this group. Nearly every symmetrical figure possible to curves and straight lines is
represented in the diatoms. Elongated forms of graceful sigmoid structures, like
Hogarth's line of beauty; thin crescents, like the face of the new moon; triangles, rigidly
exact or varied by all graduations in the curvature or undulations of their sides and by
the blunted or keenly sharpened character of their angles; spindles and ellipses of every
variety of breadth and convexity; squares; double squares; stars, from five to twenty
pointed; circles, so accurate in their periphery as to correct the errors of the most perfect

7. mathematical instruments; and combinations of these fundamental figures are to be seen
in great abundance. It comes about from these qualities that the diatoms have a
suggestiveness in the matter of design that should render them of great value to certain
kinds of the mechanical arts. Jewelers, though they might well despair of copying the
elaborate perfection of some of these forms, could doubtless obtain useful suggestions
for new figures in ornamentation. Manufacturers of articles of artistic quality, such as
laces, wall papers, printed fabrics, oilcloths, etc., have readymade in this gallery of art,
the diatom flora, new and better ideas in designing; and, although the difficulty of
obtaining and preparing diatom material for examination will limit their use in this field
to some extent, the expense and toil of studying these objects would in many cases be
well repaid.
At the risk of stretching a little the legitimate meaning of the title of this article, I wish
to mention an element of importance connected with these organisms, namely the value
they have in throwing light upon a study of the differences between objects which are the
product of mere mechanical construction and those the construction of which is coordinated
with life. There are two things to be said in regard to the ornamentation of these plants.
First, there is a perfection attained that is essentially absolute, and yet not so servilely exact
to the type as to preclude the marks of individuality in each separate plant. Take a diatom,
upon the surface of which are found some hundreds of glittering hemispherical beads, and a
careful examination with the finest optical apparatus will discover no trace of crudity or
irregularity in these hemispheres, each one being polished with a perfection and curved with
an accuracy that is absolute; and yet it would be hard to find two individuals with the same
number of beads. Among the thousands of these organisms that can be found in a spoonful
of ooze dredged from the bottom of the sea and extending for thousands of miles beneath its
waters, each separate form will show the same adherence to its type, the same perfection in
its workmanship, but the same unmistakable individuality. This is not mere mechanical
accuracy, but an accuracy associated in some unknown way with the qualities of that master
builder within each cell, cytoplasm. The distinction here insisted on is precisely that
between the flight of a bullet and the flight of a bird. It is well illustrated by the contrast to
be seen in two of the accompanying illustrations; the sculpture of the living organism being
shown in the figure of Surirella baldjikii copied from a photograph of that diatom, while the
sculpture represented in the figure of a very similar diatom, Surirella gracilis, is a
mechanically drawn counterfeit. How this living, almost formless jelly, plays the role of a
peerless artificer it still remains for science to discover.
The other point in a study of the structure of these organisms is that the principles of
design are sui generis and not at all associated with the substance of which they are
composed. Silica, like all other mineral matter, has its definite lines and angles of
crystallization; so that a particle from one part of the world fits with infinite nicety into a

8. particle from any other part of the world. But this silica is woven on the looms of the
diatoms into fabrics the mesh of which may be one of many thousand patterns, and no
principle of curves and no combination of lines known to geometry correspond in the
slightest degree to those found in the ornamentation of these plants. For example, a line may
begin straight, bend gently into a curve, gradually or instantaneously be changed again and
thus make up, with the thousands of other lines of the pattern, a-variety of arrangement that
has no relationship to the principles of mathematics. And yet there is a law within this
apparent lawlessness so rigid that the individual species hold their characteristics through
thousands of years, and a Navicula lyra newly born in the Delaware River is a sister plant of
a Navicula lyra born millions of years ago in the island of New Zealand. When,
furthermore, it is borne in mind that we are here dealing with a unicellular organism the
wonder becomes accentuated. Great complexity is also found in the flowers; but a flower
consists of millions of cells and the complex of the whole is the sum total of the different
parts. But here is one cell, with a. single nucleus and microscopic droplet of cytoplasm,
which builds for itself its own palace and is to itself its own architect. It is certainly not too
much to say that here is a problem in the constructive resourcefulness of animate nature
which must long woo and puzzle the observer.
There is at present a growing interest in the theory that the diatoms have contributed
largely to the world's stock of petroleum. The author does not consider the evidence for
this at all conclusive; as, among other things, there is a significant lack of contiguity between the world's great oil, fields and the chief diatom deposits. But the subject is here
mentioned because certain curious facts do lend a strong plausibility, if not a probability,
to this theory. That these oils are of organic origin is generally recognized; and a physiological peculiarity of the diatoms, their enormous secretion of oil, explains why these
tiny organisms suggest themselves to an explanation of the origin of petroleum. Most
plants, during a part of their existence, manufacture more food-material, that is, building
material, than is at the time required for growth; and this is temporarily stored up as a
reserve supply. The chief reserve plant-food material is starch, with sugars, cellulose,
insulin, asparagin, etc., as minor substances. But, outside of seeds and nuts, only a few
plants store up their reserve supply in the form of oil. The diatom is perhaps the most
remarkable in this respect. Living diatom plants will always be found to contain from
two to ten shining oil globules, deep orange-yellow in color, and with a high refractive
index. The bulk of this oil, in proportion to the size of the diatom, rarely falls below 5
per cent; and the author has samples of diatom material in which a careful measurement
of the contained oil shows a proportion of 50 per cent. If we consider, therefore, the
large extent of many of the known diatom deposits and their frequency in most parts of
the world, it becomes evident that the potential volume of organic oil from this one
source is very large. But, as above intimated, the application of cause and effect to the

9. diatom-petroleum theory is at present very far from satisfactory.
In the diversified uses of the diatoms, if there be one that is of supreme importance, it
is the value of these organisms as the great fundamental food supply of the marine
world. In the sea as on the land, animal life is dependent upon plant life for the
transformation of the inorganic substances of the earth into organic materials that
shall serve as food. The elements necessary to sustain life must be brought into
certain chemical relationships, known as a class as organic substances, before the
animal can draw upon these to supply its life processes. In other words, carbon,
oxygen, hydrogen, nitrogen, phosphorus, potash, etc., will not juggle themselves
into edible compounds. It is only by the alchemy of the green, chlorophyll - bearing
plants that these combinations are brought about. The diatom is the smallest of all
the green, chlorophyll-bearing plants; but despite its insignificant size, these
lilliputian workers are so numerous that the sum total of their activity is almost
beyond calculation. Prof. Kofoid has estimated that the average number of diatoms
in 1 cubic meter of water in the Illinois River is 35,558,462. Thriving abundantly in
all the waters of the earth, fresh and salt, from the north pole to the south, the
countless myriads of these plants are turning the substances held in solution in the
waters of the streams, lakes, and seas into living material and are doing this in that
.strange alembic where it always takes place, namely, the green, chlorophylgrain.
By harnessing in some way a sunbeam to its machinery it turns out from the crude
material of mineral matter the vital material of plant tissue, and on this plant tissue
there feeds directly or indirectly most of the animal life of the sea. Some of the
minuter forms of economic value to mankind, like the smaller fishes (for example,
the sardine) and the shellfish (clams and oysters) make these plants their principal if
not their exclusive food. The teeming swarms of tiny animal creatures, of which the
copepods may be cited as an example, are the links between the diatoms and those
other organisms which in turn prey upon them.
And thus, as upon the land the carnivore feeds upon the herbivore and the herbivore
feeds upon the plant, so in the sea its animal denizens may be referred back in their food
supply to the final source, the diatoms. It may therefore be said, without stretching the
truth, that these plants are the grass of the sea, because they occupy the same important
relationship toward the life of the sea that grass does toward the life of the land. It is not
meant by this that other marine plants do not contribute to the store of animal food.
Many of the brown and red seaweeds form the pastures of animal sea life; and one plant
especially, the so-called eel grass, Zostera marina, is of great importance to those forms
of life inhabiting the shallower waters along the shore and especia.lly of the bays and
estuaries indenting the coast. Although Zostera does not appear to be extensively preyed
upon while it is growing, it becomes a highly nutritious feast for myriads of forms of

10. animal life at the time of its decay. But its usefulness in this respect is greatly
circumscribed because it is not available during the greater portion of the year and is
available only in those shallower waters in which it is fitted to flourish. Out upon the
wide ocean, comprising roughly three-fourths of the surface of the globe, it is the
diatom which is the plant par excellence as the supplier of animal food. It also shares
this service with the other plants above mentioned in the shallower waters of the coast.
The full value of the diatoms in this particular is only recently being appreciated. It
seems strange that the study of this important point has been so long deferred; as
strange as if the stock raiser should have persistently neglected the study of those
forage crops upon which the welfare of his stock depends. The enormous value of the
fisheries to the world, to the inhabitants of all lands, is the measure of the importance
of the study of these minute organisms, because of their intimate relationship to the
problem of fish food. When the diatom flora of our coasts and of the high seas is sufficiently investigated we shall be in a position to understand better such problems as the
migration of fishes and the prevalence of certain kinds in certain waters; and it is not
improbable that means will be devised for augmenting the fish food supply through the
diatoms, just as the science of agrostology works toward the betterment of the cattle
raising industry.
As a single illustration of this point, let us take the teeming animal life of the
Antarctic. Those who have seen illustrations of recent explorations near the South Pole
were certainly impressed with the enormous fecundity of animal life in that region. It
is strange therefore to note that this life is confined almost entirely to its waters; to
learn that there are no land birds, no land animals, nor insects. This is because there is
no plant life upon the shore. .All bird life, all animal life is marine, penguins, gulls,
petrels, and a long list of strictly aquatic animals. Now, in these waters of the Antarctic
the plant life that is most prominent is the diatom. This plant, more than all others, is
the explanation of the teeming life that inhabits those remote seas. The writer in
investigating the diatoms of the Shackleton Expedition to the South Pole, found in
most of the samples collected a larger percentage of diatoms than in any other samples
known. Some dredgings made at McMurdo Bay were found to be at least 50 per cent
edible diatomaceous material No wonder therefore that the lower animal forms swarm
in these waters and that the carnivorous animal forms of larger bulk are so prolific; for
between them and extinction there stands the abundant and ever-present supply of
plant food represented by the diatom flora.