The Influence of Water Quality Upon Recovered Diatoms

The focus of my research is the recovery and identification of diatoms from the sediments of three reservoirs located in the northwestern section of South Carolina. The quantity and types of diatoms recovered are used to assess differing water qualities. I am being assisted by Dr. John Hains at Clemson University.

Two of the reservoirs, the North Saluda and Table Rock Reservoirs are pristine impoundments entirely owned and operated by the Greenville Water System. They are totally off limits for any access or use by the public and serve as two of three water sources for the Greenville Water System.

The third reservoir, Lake Hartwell, is a federal impoundment managed by the Savannah District of the U.S. Army Corps of Engineers. Built between 1955 and 1963 and covering an area of 56,000 acres with a shoreline of 902 miles, the lake was initially constructed for the purpose of flood control. It is now used for the generation of hydro power, recreation (used by millions throughout the year), fish and wildlife management, as well as contributing to the local water supply. It is subject to both urban and rural intrusion.

Diatoms (a class of algae known as the Bacillariophyceae) are found in both freshwater and marine habitats. The diatom shells, known as frustules, are composed of two halves of highly silicified cell walls which overlap. The frustules can be found in an almost endless array of dots called punta, ribs called costae and fissures. These and other patterns of external ornamentation are used to separate diatoms into genus and specie. The basic configurations are the Centrales, which have a circular, pillbox‐structure and the Pennales which are ovate to elongate in their structures.

As diatoms die off, they sink and accumulate in the sediment. The accumulation of frustules is, in essence, a record of diatom activity in the life of the lake, over time. From the cleaned sediments recovered from the three different water sources, one can correlate the mix of diatom genus and species to water quality over time, including such factors as nutrient loading of nitrates and phosphates from rural and urban sources.

Lately, I have had the task of identifying the diatoms to name and specie. This involves a lot of textbook review and time, but is rewarding and enjoyable. The structures one sees at 1250 powers of magnification are phenomenally beautiful! With enough data, I should be able to draw conclusions about the effect of water quality on diatom populations.

Marion Freeman, RM(NRCM), Spartanburg, SC, was certified by the NRCM in 1979.

Copyright© National Registry of Certified Microbiologists. Reprinted from The Loop, 2010, Issue 3.