Diatom of the Month: December 2016 - Tabellaria fenestrata

           by Kristen Dominguez*
          
          As an undergraduate student in Evelyn Gaiser’s Lab at Florida International University (FIU), I was
          provided the opportunity to visit and study the algae of the pristine and gorgeous Lake Annie.
          Located at the Archbold Biological Station (halfway from Miami to Orlando), this sinkhole lake fed
          by rainfall and groundwater is home to a wide variety of organisms, including many planktonic
          algae. In 2006, this tiny lake became part of the Global Lakes Ecological Observatory Network that
          examines global trends in lake ecosystems.












Fig. 1. Kristen taking Secchi depth measurements of water transparency at Lake Annie.


Fig. 2. Kristen Dominguez (left), Dr. Evelyn Gaiser (middle) and Dr. Emily Nodine (right) collecting samples at Lake Annie.

          In monomictic lakes such as Lake Annie, little mixing takes place between the warmer surface
          waters and the deeper colder waters during the hotter months; but, as fall and winter come, the
          water on top gets cooler and thus mixes with the cold water below. These temperature fluctuations
          occur each year with some variations between different lakes. Our key research questions are:
          what species would be affected by these changes in thermal structure, and how would water
          column stability affect phytoplankton diversity?  For several months, I worked on a microscope to
          identify and count the algae found in 72 samples from a period covering the transition from
          winter mixing to summer stratification in Lake Annie.      
         The same work is being done by students at GLEON lakes all over the world! Now that I am
         analyzing the data, I realize the significance of our work. We observed a strong positive
         relationship between water column stability and the number of dominant species (comprising 95% of
         the total biovolume). Among these was Tabellaria fenestrata, our new diatom of the month. This
         diatom is adapted to oligotrophy in Florida (Whitmore 1989), neutral pH of 7, and lives either in the
         plankton (Krammer and Lange-Bertalot 1991) or attached to vegetation or other hard substrates
         (Koppen 1975). It can form long straight chains1Other key features of the frustule of T.
         fenestrata are illustrated in Fig. 3.


Fig. 3. Tabellaria fenestrata: 1. Central inflation wide; 2. Central striae reach axial line; 3.
Girdle bands open; 4. Septa present (scalebar = 10 µm; source: DeColibus, 2013).
     

          In Lake Annie, various diatoms, including T. fenestrata was more dominant in later dates after the
          lake mixing events, and so they seem to prefer more stratified conditions. Here climatic oscillations
          have led to marked changes in transparency and thus stratification via heat budget variations; and
          even small rainfall changes may lead to significant consequences on the biota (Gaiser et al. 2009).
          Diatom communities changed due to acidification caused by atmospheric pollution during
          industrialization, and consequent recovery from around 1970, as well as hydrological, phosphorus
          loading and alkalization (Quillen 2009). We are fine-tuning our hypotheses in order to enhance our
          understanding of the relationships between water column stability and diatom abundance,
          dominance, and diversity patterns in this subtropical ecosystem.


*        *Undergraduate student in the Gaiser Lab at the FIU Southeast Environmental Research Center.
           This post was written in collaboration with Dr. Evelyn Gaiser and Dr. Luca Marazzi.


          References

1.                DeColibus, D. (2013). Tabellaria fenestrata. In Diatoms of the United States. Retrieved December
     
2.               Gaiser E.E., N.D. Deyrup, R.W. Bachmann, L.E. Battoe, H.M. Swain. (2009). Effects of climate variability on
           transparency and thermal structure in subtropical, monomictic Lake Annie, Florida. Fundamental and Applied
           Limnology 175: 217–230.

3.               Koppen, J.D. (1975). A morphological and taxonomic consideration of Tabellaria (Bacillariophyceae)
          from the northcentral United States.Journal of Phycology 11: 236-244.

4.              Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae,
          Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von
          Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.

5.              Quillen A.K. (2009) Diatom-based Paleolimnological Reconstruction of Quaternary Environments in a
          Florida Sinkhole Lake, PhD- Dissertation. Florida International University, Miami, 131 pp.
     
6.               Whitmore, Thomas J. (1989). Florida diatom assemblage as indicators of trophic assemblage and pH. 
          Limnology and Oceanography 34(5): 882-895. American Society of Limnology and Oceanography, Inc.

 




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