Kaplan, L.A., and T.L. Bott. 1989. Limnology and Oceanography 34:718–733.
Diel fluctuations in stream water temperature and chemistry, microbial biomass, and bacterial activity were measured in White Clay Creek, Pennsylvania, during vernal algal blooms in three different years. DOC concentrations increased 24–37% over early morning minima and temperature increased nearly 10°C over a 7–10-h period. Total carbohydrates and monosaccharides exhibited irregular fluctuations with total carbohydrates showing concentration peaks in the morning and afternoon. Acetate concentrations were highest in midafternoon, while the concentration pattern for primary amines differed from the DOC pattern with highest values at midnight. No distinct diel patterns were found for streambed ATP, : ATP, Chl a, and total or active bacteria, although significant year-to-year and between-habitat differences were observed. Bacterial activity, measured by phospholipid biosynthesis, total lipid biosynthesis, respiration, and incorporation of [3H]thymidine into DNA increased 1.4-fold to 3.0-fold from morning to afternoon. Microcosm experiments indicated that the activity of bacteria attached to sediments was more sensitive to increases in water temperature than to changes in water chemistry, whereas bacteria attached to porcelain disks responded to the influences of both temperature and water chemistry.