Diatoms as bioindicators

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&Client=EPA&Index=Prior+to+1976&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5Czyfiles%5CIndex%20Data%5C70thru75%5CTxt%5C00000001%5C2000JIHM.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1&SeekPage=x&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?

4 Comments Add yours

  1. laksiyer says:

    Brilliant idea. @Janice it would be great if we could report either qualitatively or quantitatively essential environmental parameters. What parameters do you think we should report?

  2. Janice says:

    Hi Laks,

    Many parameters can be identified qualitatively. Noting the season in which the taxon was collected is important. Habitat is important as well–is the diatom: found in surface or deeper waters? attached to a plant? attached to an animal? attached to or in the mud? Specifying the substrate is useful information. Is the diatom found in standing water? running water? freshwater? brackish water? high salt content water? Is the diatom found in polluted or non-polluted waters? Is there an odor of nitrogenous compounds? sulphur compounds? Other odors to characterize the pollution content of the waters is important. Is the diatom found in murky or clear waters? Another parameter worth noting.

    Parameters that could be measured would include temperature with a thermometer and pH using pH test strips. There are kits for measuring water quality (https://www.amazon.com/Earth-Force-Low-Cost-Quality-Monitoring/dp/B0080GR71G). Specific kinds of nutrients (nitrate and phosphate) as well as coliform bacteria are among the parameters that one could measure using such kits.

    There’s lots we can do!

  3. laksiyer says:

    Thanks Janice. These are really important for a user. I am trying to see how I can organize all data I collect in a way that is retrievable and useful. Perhaps one could codify some of these parameters for ease of recall and analysis.

  4. Janice says:

    Hi Laks,

    Have a look at the publication, “Environmental Requirements and Pollution Tolerance of Freshwater Diatoms.” On pages 4-9, various environmental categories are given as ranges. Perhaps set up a table of environmental parameter (rows) by categorical range (columns). The ranges may be numerical or descriptive going from, for example, “not very polluted” to “very polluted,” or as another example, “very still water” to “very turbulent water.” In each range, a rank could be assigned from least to most. Eventually, the data could be transformed into fuzzy set(s) for analysis. This is but one way to compile the data. Other possibilities?


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