Award Date


Degree Type


Degree Name

Master of Science (MS)



First Committee Member

Vernon F. Hodge

Number of Pages



Twenty-four elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Ni, Pb, Rb, Se, Sr, Ti, U, V, Zn, and Zr) were determined in freshwater biofilms from Lake Mead by inductively coupled plasma mass spectrometry and flame atomic absorption spectrophotometry. The uptake of polysaccharides (as glucose) was determined by ultraviolet/visible spectrophotometry. Taxonomic identification of the biofilm was determined using a stereo and compound microscopes. Major components included the diatoms Cyclotella, Fragilaria, Cymbella, and Amphora. Results for both major cations and trace elements presented for filtered lake water and for particulates filtered from the water suggest that the accumulation of the inorganic fraction of the biofilm is 'masked'; possibly by significant accumulation of the organic fraction. This is evidenced by lower bioaccumulation factors determined during later stages of biofilm development. This masking seems to be less of a factor during the winter and spring seasons. The influence of suspended particulates on the bioaccumulation factor of the metals could be much greater than the influence of dissolved species. This is evidenced by comparing the bioaccumulation factors calculated from data obtained by measuring the elements in particulate matter and filtered lake water from five 1-L field samples. Calcification of the biofilm appears to be microbially influenced and was prevalent during the warmer sampling periods. Accumulations of iron and manganese in the biofilm can be attributed to the presence of photo-reducing bacteria and to low concentrations of these elements in the surrounding water. Such elemental enrichments hint at possible photo-reducing reactions taking place within the biofilm involving iron (Fe (III) {dollar}\to{dollar} Fe (II)) and manganese (manganese oxides {dollar}\to{dollar} Mn (II)).


Biofilm; Element; Lacustrine; Polysaccharide; Sorption; Trace

Controlled Subject

Chemistry, Analytic; Environmental sciences; Limnology

File Format


File Size

2508.8 KB

Degree Grantor

University of Nevada, Las Vegas




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