What are Diatoms?
• Diatoms are unicellular,
photosynthetic organisms
that have unique cell walls
made of hydrated silica,
which gives them
protection and strength to
withstand large amounts of
pressure
• Some species are
widespread and others are
restricted to only establish
themselves in one area
Figure 1: Multiple Diatoms
McMurdo Dry Valleys
Figure 2: McMurdo Dry Valley
Figure 3: Location
• Located 3,500 km due
south of New Zealand
• Multiple ice covered lakes
fed by meltwater streams
that flow during the austral
summer
• Air temperature averages
between -16‫ﹾ‬C and -21‫ﹾ‬C
and only receives 10 cm of
rainfall
Antarctic Diatoms
• Live in hostile conditions because they only
have 6-10 weeks of stream flow
• Diatoms are able to assimilate the nutrients
that are needed to survive until next summer
Figure 4: Austral summer 2013
Antarctic Diatoms
• During the winter, the streams stop flowing
and everything is dark.
• Diatoms are capable of surviving desiccation
and low temperatures and algal mats become
reactivated when flow resumes in the summer
Figure 5: Antarctic Winter
Why do they survive?
• By desiccation biofilms
or Mucilage
• Mucilage is a
biocomposite containing
four additional adhesive
components, including
single modular proteins
that are likely to be the
structural units
Figure 6: Mucilage with diatoms
Diatoms used in research
• Hantzschia amphioxys f.
Muelleri
• Psammothidium papilio
– Length: 5-18µm
– Length: 33-44 µm
Figure 7: Hant Muell
Figure 8: Psamm
Importance
•
•
•
•
Better understanding of environment
Past climate conditions
Water quality
In fields:
– Paleoclimatology
– ecology
– Anthropology
– paleontology.
Figure 9: Studying Water
Objective
• How certain diatoms react or persist in
freezing and drying events.
• Hypothesis:
– If the two different taxa of diatoms are put in
extreme desiccation and low temperatures for an
extended period time then their morphological
structures are going to change measurably until
they become accustomed to the new environment
Experiment
• Conducted in a 24
well plate
• 3 treatments with
250 cells
• Each well will have
1.5 ml of DY-V
Figure 10: Psam
beaker
Figure 11: Hant
muell beaker
Freezing
• Manually decrease the temperature
on the freezer until it reaches -20‫ﹾ‬C.
• Subject the diatoms to -20‫ﹾ‬C for 4
hours.
• Test how diatoms react to different
amounts of water before they
freeze
– 1.5 ml of DY-V
– 1.0 ml of DY-V
– 0.5 ml of DY-V
Figure 13: Freezing plates
Results of Freezing Experiment
300
250
200
Average cells
150
Live cells
Death Cells
100
50
0
Psam 1.5 ml
Hant Muell 1.5 ml
Psam 1.0 ml
Hant Muell 1.0 ml
Psam 0.5 ml
Hant Muell 0.5 ml
Desiccation
• The desiccation process consists of
sucking up with the pipette all the
medium without taking the cells.
• Monitor the wells until the
remainder of the medium has
evaporated.
• After the medium has fully
evaporated, the diatoms will
desiccate for an additional
Figure 14: Desiccation plates
– 10 minutes
– 1 hour
– 2 hours.
Results of Desiccation Experiment
300
250
200
Average cells
150
Live cells
Death Cells
100
50
0
Psam 2 hours
Hant Muell 2 hours
Psam 1 hour
Hant Muell 1 hour
Psam 10 min.
Hant Muell 10 min
Microscope pictures of diatoms
Psammothidium papilio
Hantzschia amphioxys f.
Muelleri
Conclusion
• The finding of the experiments was that all
diatoms act and react different to desiccation
or freezing scenarios.
• The Psam because it is smaller is able to
survive the longest in both of the scenarios.
• The Hant Muell is bigger, but my theory on
why they are not able to survive is because
the frustules are bigger therefore they break
easier making the diatom lyses.
Acknowledgements
• Prof. Dr. McKnight who was an incredible
source of information.
• Special thanks to Deena Garland without
whose knowledge and assistance in this study
would not have been successful.
• Thanks to Aneliya Sakaeve for taking over and
being my mentor
• Thanks to the Kiowa Lab for providing
laboratory facilities.
• Thanks INSTAAR.