What do I think about
when I look at Diatoms?
Reflections from a sabbatical
2014 Convocation at Johnson State College
Robert B. Genter, Ph.D.
On behalf of the faculty, I would like to welcome you to Johnson State College.
The tradition for years has been for the faculty speaker to talk about what they did on sabbatical. A
sabbatical is an opportunity for us to focus on our concentrated fields of study for a time.
So, I guess they invite one of the faculty to talk after returning from sabbatical is because they figure
that we should be in a very good mood!
Stream Coliform Assessment Team 2014
The research that I do would not be possible without the
help of students. When I’m not on sabbatical, during the
summers I lead a group of student researchers studying
water quality of streams in the Lamoille River basin. This are
members of the 2014 team. I have been doing this Lamoille
project since 2008, but have had students working with me
on research since starting at JSC in 1986!
Elizabeth Mine & Copperas Brook, 2003
My sabbatical was spent studying the impacts of an abandoned copper mine on the rivers in the area. My
research specialty is on a group of microscopic organisms called diatoms, which are important because they are
very sensitive indicators of environmental stress. For sabbatical I studied the diatoms related to the pollution
caused by the Elizabeth Mine near White River Junction, Vermont.
On the left is a picture of the tailings pile of rock that was dug from underground, the copper was removed,
and the ground-up waste rock was dumped into, and filled up, the valley of a small stream The water that you
can see on the left flowed across and through the pile to a stream that became known as Copperas Brook,
which you can see on the right. The orange color on the right is from toxic metals that flowed out of the
abandoned mine site. I saw no visible forms of life in Copperas Brook itself, and this is where it flows into the
West Branch of the Ompompanoosuc River.
West Branch Ompompanoosuc River
2003
Here you can see where Copperas Brook flowed into the West Branch of the Ompompanoosuc River. There
were basically no living visible organisms in Copperas Brook when this picture was taken. The five students on
the right were in my Environmental Toxicology class in 2003, and we did a study of the pollution caused by the
mine.
Diatoms are a part
of the algae community
That was the background to my
research. Now let me introduce
you to my little friends.
The diatoms are very important to
life on Earth even though many
people have never heard of them.
They belong to a group of
microscopic plants called the algae.
By scraping the algae off of rocks,
and looking at it under the
microscope, we would like to see a
lot of diatom diversity. To see this
diversity we clean a sample with a
very strong acid solution, which
cleans away all of the other
organisms so that we can see the
glass cell walls of the diatoms.
Diatoms are beautiful and have a
diverse assortment of species: big ones,
little ones, all kinds of shapes.
The acid has cleaned out all the other
living things in the sample so only the
glass cell walls of the diatoms and silt
remain.
Epithemia
I’ll use Epithemia to explain the basic shape of diatoms. These are
cells viewed under a microscope.
The cell wall is like a glass Petri dish. Hence, it is not harmed by
the strong acid used to clean them. There is a top and a bottom.
The cells reproduce by separating the two halves to make a new
matching plate for each half.
Top view
Side view
http://weste
rndiatoms.co
lorado.edu/i
mages/page_
images/1_Ep
ithemia.jpg
The left image is a view of the top, and the middle one is from the
side. Imagine a glass box that has been stretched and then bent
into a crescent shape. Petri dishes are designed so that nothing
can get in or out, but living things need to get rid of wastes and
take in nutrients. Hence, the glass cell wall of diatoms has rows of
pores that allow the organism to get rid of wastes and take in
nutrients.
Diatoms are microscopic plants, but instead of being green their
chloroplasts are a yellow-green color. Diatoms also have the same
orange pigment that carrots have. What do you get when you mix
green and orange? Brown! Hence, diatoms are also called the
golden-brown algae.
Diatoms are golden-brown algae
So when you see a rock covered with diatoms it will have a golden brown to copper-like color. This may look
like mud, but it is actually a bunch of different kinds of diatoms.
Diatoms are also important because they are at the base of the food chain, and along with the other kinds
of algae they produce half of the world’s oxygen that we breathe; so every second breath thank the algae!
Diatoms are Small But
Very Important
This picture shows you that the measure that we use for diatom size
is the micrometer. 10 micrometers is smaller than most animal and
plant cells. Diatom species can range from 5 to over 200
micrometers in size, which is shown by the upper three-fourths of
the yellow area in the scale on the right.
[This diatom may be renamed to the genus Handmannia (Spaulding, S., and Edlund, M.
(2008). Puncticulata. In Diatoms of the United States. Retrieved August 23, 2014, from
http://westerndiatoms.colorado.edu/taxa/genus/Puncticulata).]
Cyclotella a
centric
diatom.
The Araphid Diatoms
How many different ways can the
shape of a petri dish be arranged
with different the pores, ribs, and other
structures? I would like to show you some
slides to give a sense of the biological diversity
of my microscopic friends.
These are different species of long-thin diatoms.
Eunotia
Eunotia belongs to an old lineage
of diatoms that can propel
themselves across hard surfaces
such as rocks. This is done with a
slit called a raphe in the glass
wall. and it allows the diatoms to
move probably by spewing out
slime trails. This is like a jet
engine or rocket ship that is
pushed through the air by the
force of its exhaust.
Eunotia is usually found in water
that is slightly acidic with low
dissolved minerals
Raphe
Side view
The Monoraphid Diatoms
Here are diatoms that have that slit-like raphe on one valve but
not on the other. Hence, they are called monoraphid. The
monoraphids tend to be bent, or “boat shaped.” The one in
the lower left has the sides bent up two ways, like the rim of a
cowboy hat.
When we look at diatom communities in healthy
rivers we expect to see a lot of diversity -- many
different kinds of diatoms. One thing that we see in
places like the Elizabeth Mine, is that in metalpolluted streams, this diatom called Achnanthidium
minutissima , shown below, can be pretty much the
only one found.
Achnanthidium minutissima
Achnanthidium minutissima
Toxic levels of copper, zinc, and nickel on the rocks (October, 2000)
This sample [on the left] was collected in the rust colored region where Copperas Brook flows into the West
Branch of the Ompompanoosuc River. You can see that Achnanthidium minutissima is basically the only
species there. Other extremely metal-polluted sites have no diatoms at all.
[Above USEPA PEC (probable effects concentration). “The probable effect concentration (PEC) is the concentration above which
adverse effects are likely to occur more often than not” (http://www.epa.gov/R5Super/ecology/casestudies/ihsitecug.htm).]
The Gomphonemoid Diatoms
Here are diatoms that are club
shaped like the genus
Gomphonema.
Didymosphenia
People who fish know this diatom as “rock snot.”
It has become a real problem in some parts of
the world because it’s thick growths have
harmed other aquatic life, which earned it the
name “rock snot.” The Vermont legislature has
actually passed a law that bans felt-soles on the
boots of waders so that this diatom doesn’t get
transported from one river to another.
However, Didymo occurs naturally and is usually
rare in many places in the United States, and was
very rare in my samples from the Elizabeth Mine
area.
“Rock snot”
Crescent-shaped Diatoms
These diatoms are shaped like crescent moons
or are asymmetrical on different sides of the
raphe.
Naviculoid Diatoms
These diatoms tend to be symmetrical longitudinally (down the long axis)
and have a raphe. They are called naviculoids.
Keeled Diatoms
These diatoms have a ridge, called a keel,
that is lifted above their surface like the
sail of Dimetredon. It is most easily seen on
this diatom (Nitzschia sinutata tabellaria).
The keel holds the raphe, like a Roman
aqueduct carries water. These diatoms
are experts at moving through mud.
Nothing is too small to be harmed by
pollution. Diatoms can be indicators of
pollution, and they help us understand
whether cleaning up pollution
has a positive effect.
2014
Where
Copperas Brook
flows into
the West
Branch of the
Ompompanoosuc River
today
The good news is that things can bounce back. The Elizabeth mine has since been remediated (cleaned up) and is now
covered in grass like a field. This is where the Copperas Brook now flows into the West Branch of the
Ompompanoosuc River. As you can see, there is still some evidence of its history, but the river has been largely
protected. When I look at diatoms, I think about the mistakes of the past and our hopes for the future. Even though
diatoms are microscopic and studied by a small group of scientists, they are very important to life on earth. When I
think of diatoms I think about their diversity in shape and because of their importance as environmental indicators.
Other people think of their importance at the base of the food chain and that they with other algae produce half of
the oxygen that we breathe.
North American Diatom Symposium 2013
I may seem a little obsessed
with diatoms, but this is proof
that I’m not alone!
Who would have thought that
there would be a job available
for people who studied
diatoms? These people work
as college professors and
their students as well as
environmental scientists in
state and federal agencies.
Some of them just study
diatoms as a hobby. Many
others have gone on to a
variety of other fields.
One thing is that I hope that
you are able to experience in
College is being part of the
academic community. This is
a picture of my community of
people who study diatoms.
They are good friends, work
very hard, and have a lot of
fun together.
Our future generations
While I am counting
diatoms, I think about
our future generations
as represented by my
son, who recently
learned a new word:
diatom.
Healthy =
Diversity
So what do I think about when I look at
diatoms? There are all kinds of diatoms in
the world. Probably at least 40,000 species.
Each species has individuals that are different
from each other.
•
•
•
•
•
•
Beauty
Diversity
Interactions between species
Protecting the environment
Being part of an academic community
Our future generations
It doesn’t matter if it is a big diatom, a little
diatom, whether it is abundant or rare. It
doesn’t matter what nutrients they specialize
in to stay alive or whether it can tolerate high
concentrations of metals. After 3.8 billion
years of biological evolution, we are all here.
We made it this far. Make the most of this
opportunity.
Diversity
When I look at diatoms I think about my students as the hope of the future.
Who would have thought that there would be a job available for people who studied diatoms? Even if you do not
know what your passion is yet, keep turning over the rocks and you will find it.
The Earth needs your help. In Congress, the mega-corporations of the world have all the money they need to buy
lobbyists to have their voice heard. The Earth and the living things on it have less of a voice in Congress. I anticipate
that, working together, we will leave a more natural planet for our grandchildren and their grandchildren.
More Information About Diatoms:
http://westerndiatoms.colorado.edu/about/what_are_diatoms