LEWIS SMITH LAKE - Auburn University

In August 1986, iron and manganese concentrations in Clear Creek embayment were 700 l!g!L
and 400 l!g!L, respectively (Bayne et al. 1987). In fact these metals were frequently found at
concentrations exceeding detection limits (100 l!g!L for iron and 50 l!g!L for manganese) used in 1986
when sampling was done monthly for 9 months. During that study iron, manganese, copper, chromium
and zinc concentrations did exceed, on at least one occasion, levels considered acceptable by the
Environmental Protection Agency (1986). Even though metal ion concentrations appear lower in 1995
than in 1986 based on limited 1995 sampling, the pH and alkalinity ofSmith Lake remain low (Tables
10-17, 10-18, 10-19 and 10-20). Heavy metals toxic to aquatic life are more soluble in acid waters and
therefore any acidic substances (e.g. acid precipitation or acid mine waste) entering this poorly buffered
(low alkalinity) lake may threaten the aquatic biota.
10.2.2 Phytoplankton
The photic zone composite water sample collected at each sampling station (Table 10-2) was the
source of water used for analysis ofphytoplankton related variables. Aliquots ofthe composite sample
were separated for total organic carbon (TOC) analyses, phytoplankton identification and enumeration,
cWorophyll!! analyses and Algal Growth Potential Tests (AGPT) (Table 10-34). Phytoplankton
enumeration, chlorophyll!! analysis and TOC analysis were conducted in January and monthly April
through October 1995 (Table 10-1). Phytoplankton primary productivity was measured May through
September of 1995 at mainstem stations 1,5 and 7 (Table 10-2 and Figure 10-1). The carbon-14 method
ofestimating net productivity was used (Table 10-34). Duplicate light and dark bottles were incubated
for 3 h at midday at each of three depths within the photic zone: the lower limit of the photic zone,
midway between the lower limit and the surface and about 0.3 m below the surface. The lower limit of
the photic zone was determined by multiplying the Secchi disk visibility by a factor offour (Taylor
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