PH08 Metals in the Environment: Aquatic Biological Perspectives
Exhibit Hall
8:00 AM - Thursday
(PH106) Photosynthetically mediated Zn uptake in biofilm in High Ore Creek, Montana.
Morris, J.1, Morris, B.1, Farag, A.2, Nimick, D.3, Meyer, J.1, 1 University of Wyoming, Laramie, Wyoming, USA2 U.S. Geological Survey, Jackson, Wyoming, USA3 U.S. Geological Survey, Helena, Montana, USA
ABSTRACT- Cadmium, manganese and zinc (Zn) concentrations cycle daily in some mining-impacted streams in the Rocky Mountains. Our research on upper High Ore Creek, Montana, USA, during the past three years has demonstrated that the diel cycle for Zn is strongly associated with photoperiod; Zn concentrations decrease during the day and return to a constant, higher concentration at night. Additionally, laboratory and streamside experiments using lab-cultured biofilm (free of abiotic particles) indicate that photosynthetic biofilm accumulates Zn during the day and releases Zn at night. The objective of this streamside experiment was to determine if Zn uptake in biofilm in High Ore Creek was caused by processes occurring in the biofilm layer. These processes might include (1) photosynthesis increasing the pH in the biofilm, which could cause precipitation/sorption of Zn, and (2) photoreactions with abiotic particles embedded in the biofilm. We collected cobbles covered in biofilm from the creek, placed them in 12 transparent PVC plastic chambers, and exposed the chambers to four treatments (three replicates each): sunlight, sunlight occluded, photosynthesis inhibited, and formalin. Aqueous Zn concentrations in the sunlight chambers decreased during the 4-h experiment and were significantly lower (P≤0.05) than the other three treatments in which the aqueous Zn concentrations did not decrease. Therefore, we believe that photosynthesis in the biofilm played a role in causing aqueous Zn concentrations in the sunlight chambers to decrease.
Key words: diel cycling, biofilm, photosynthesis, zinc