DETERMINATION OF VITAMIN B sub(12), THIAMINE, AND BIOTIN IN LAKE TAHOE WATERS USING MODIFIED MARINE BIOASSAY TECHNIQUES 1

Seawater bioassays for dissolved vitamin B sub(12), thiamine, and biotin have been modified for freshwater samples. The assay algae are: Cyclotella nana; thiamine, Monochrysis lutheri; and biotin, Amphidinium carterae. The lowest detectable levels of dissolved vitamins are: B sub(12), 0.1 ng/liter; thiamine, 4 ng /liter; and biotin, 0.4 ng/liter. Summer and winter samples in a water column near the center of Lake Tahoe were assayed using this method, and, with one exception, vitamins were found only in the euphotic zone.