Janice Pappas

There’s an interest in diatoms in the Foldscope community. Did you know that diatoms can be found not only in pond water, but also in salt water, in the soil, on rocks, in the Arctic and Antarctic, in hydrothermal vents, and in any moist environment no matter how small? Did you know that diatoms are used in forensic science, are found in ancient clays used in making vessels, diatomaceous earth, toothpaste, and cleansers? See if you can collect diatoms from different places and view them with your Foldscope.


 I am a researcher that studies diatoms, and I would be glad to share what I know. What have you found using your Foldscope?

Diatoms are Everywhere

Do you have a freshwater fish tank? Do you notice brown scum coating the glass or other items in the tank? You probably have diatoms growing in your tank! Diatoms exude a polysaccharide gelatinous-like coating in which they reside and can form long end-to-end chains. This chain is what looks like brown slime in the tank. If you are careful, you might be able to sample a “tube” of diatoms to mount on a slide and view with your Foldscope. Can you see the diatoms in the tube?
 
 In the laboratory, many species of diatoms, especially the centrics, can be difficult to grow. However, there are “weed” species that are easily grown, and these taxa are considered to be nuisance or invasive species, depending on where you find them and in what quantity. One case in point is the freshwater diatom Didymosphenia geminata which has become an invasive in the Pacific Northwest. Some species of Nitzschia, a freshwater diatom genus, reproduce at a fast rate and may be a cause of some algal blooms. A fast growing marine diatom genus containing species that are toxic is Pseudonitzschia. These diatoms are capable of producing domoic acid that, if ingested, can affect the neurological system.
 
 Diatoms are sensitive to particular environmental conditions and will grow optimally with the right amount of light, temperature and nutrients. Diatoms feed on phosphorus and nitrogen compounds and incorporate silica into their intricate shells. There are many micronutrients that are important in diatom growth as well. The particular amounts of nutrients and micronutrients are tailored to particular diatom species. There are products that are supposed to enhance the growth of diatoms in marine tanks—do these products work? If you have a marine tank, you could give them a try (for example,
 <a href="https://nualgiaquarium.com/nano-silica-diatoms/">
 https://nualgiaquarium.com/nano-silica-diatoms/
 </a>
 ). There are also kits available for sale for growing different kinds of algae, including diatoms, but growth is dependent on specific growth media and light and temperature conditions (for example, http://www.algaetoday.com/algae_biofuels/algae_nutrients). Growing diatoms can be challenging and require some experimentation on your part. Your best bet for growing freshwater diatoms is a not very clean fish tank. Otherwise, collect diatoms and other algae at your nearest pond, river, or puddle, or scrape some algae and diatoms off of rocks and other wet materials near a pond or river. There are plenty of places to find diatoms in nature!

Growing diatoms

Toothpaste and diatoms

I came across this paper on diatoms found in lichens for the first time in 2004 (http://onlinelibrary.wiley.com/doi/10.1111/j.0022-3646.2004.02-205.x/pdf).  Those of you who are interested in viewing lichens with your Foldscope, you might be able to find diatoms as well.  Try taking a small piece of the lichen thallus and soaking it with distilled or spring water in a very small bowl or cup.  (Don’t use too much water or you will have to make many, many slides to view).  Allow the water to stand undisturbed for about an hour.  Use an eye dropper or pipette and withdraw water from the very bottom of the bowl or cup. You will probably see some debris, but that’s OK–hopefully there will be some diatoms attached.  You can make a number of slides with this single water sample.  Once the water is disturbed in the bowl or cup, though, let it settle again before withdrawing another sample.  I don’t know that you will find diatoms, but if you do, this would be a great find!


 <a href="https://thewinnower.com/papers/5372-diatoms-and-lichens" target="_blank">
 This post is open to read and review on The Winnower.
 </a>

Diatoms and lichens

Diatoms comprise 40-60% of the world’s primary production and provide the basis of aquatic food chains.  They are the basis of our organic carbon an silica cycles and because of their deposits worldwide, diatoms are the source of the fossil fuel deposits that we use.  Diatoms are also used widely as bioindicators of the environment because they occur in conditions specific to particular physical and chemical conditions and are found in particular habitats or on particular substrates.  The Environmental Protection Agency published a report in 1974 by Rex Lowe entitled, “Environmental Requirements and Pollution Tolerance of Freshwater Diatoms” (https://nepis.epa.gov/Exe/ZyNET.exe/2000JIHM.TXT?ZyActionD=ZyDocument&amp;Client=EPA&amp;Index=Prior+to+1976&amp;Docs=&amp;Query=&amp;Time=&amp;EndTime=&amp;SearchMethod=1&amp;TocRestrict=n&amp;Toc=&amp;TocEntry=&amp;QField=&amp;QFieldYear=&amp;QFieldMonth=&amp;QFieldDay=&amp;IntQFieldOp=0&amp;ExtQFieldOp=0&amp;XmlQuery=&amp;File=D%3A%5Czyfiles%5CIndex%20Data%5C70thru75%5CTxt%5C00000001%5C2000JIHM.txt&amp;User=ANONYMOUS&amp;Password=anonymous&amp;SortMethod=h%7C-&amp;MaximumDocuments=1&amp;FuzzyDegree=0&amp;ImageQuality=r75g8/r75g8/x150y150g16/i425&amp;Display=hpfr&amp;DefSeekPage=x&amp;SearchBack=ZyActionL&amp;Back=ZyActionS&amp;BackDesc=Results%20page&amp;MaximumPages=1&amp;ZyEntry=1&amp;SeekPage=x&amp;ZyPURL).  It is used widely, and since then, others have published data on diatom species and their tolerances to particular environmental conditions, but these findings are scattered in disparate sources.  Having all of the data in one publication would be a tremendous accomplishment and be of the utmost utility to scientists, policy makers, and the public.  Having up to date information is also of the greatest importance especially regarding the  study of the connection between environmental conditions and climate change.




 This is where Foldscope users might be able to provide an important contribution to bioindicator studies.  We as a community could develop a database of diatoms documenting the particular environments where they are found.  I am always eager to see diatoms and would do my best to aid in identifications.  Various slide mounting techniques would need to be used (see:  https://microcosmos.foldscope.com/wp-content/uploads/JLP-10K-Foldscope-Project-Oct-2015.pdf, pages 29-30) to enable the clearest possible view of the diatoms.  What do you think?  Is this something Foldscope users would like to do?

Janice Pappas

Earth

Posts

Growing diatoms

Toothpaste and diatoms

Diatoms and lichens

Diatoms as bioindicators

Diatoms are Everywhere

Growing diatoms

Toothpaste and diatoms

Diatoms and lichens

Diatoms as bioindicators

Diatoms are Everywhere

Growing diatoms

Toothpaste and diatoms

Diatoms and lichens

Diatoms as bioindicators

Locations

Statistics

Type of Sample

Foldscope Lens Magnification