Effect of aquatic macrophytes on the survival of Escherichia coli in a laboratory microcosm

Abstract

Kleinheinz, G., A. Coenan, T. Zehms, J. Preedit, M.C. Leewis, D. Becker and C. McDermott. 2009. Effect of aquatic macrophytes on the survival of Escherichia coli in a laboratory microcosm. Recreational beaches are very important as engines for tourism revenue in many areas of Wisconsin, United States, and microbial contamination of beach water can be very costly. Escherichia coli (E. coli) is the indicator organisms used in the Great Lakes region of the United States for recreational water monitoring. The overall objective of this study was to determine if aquatic macrophytes (Sagittaria sp., Myriophyllum sp.) allow for prolonged E. coli survival in the environment by using a laboratory microcosm as a test system. This study tested whether E. coli survival was greater in lake water alone or in lake water containing a high density of macrophytes (HDM), a low density of macrophytes (LDM), or plastic plant material. Water and plant substrate samples were analyzed for E. coli concentrations. ANOVA analysis indicated a significant difference between all treatments (p < 0.001). The Scheffe test revealed a significant difference between E. coli concentrations in water in the HDM treatment and the plastic plants (p = 0.003) and the controls (lake water only; p < 0.001), as well as differences between the LDM treatments and the plastic plants (p < 0.001) and the controls (p < 0.001). Attachment of E. coli to the macrophytes was rapid and may contribute to the rapid decline of E. coli found in the microcosm water samples. The presence of aquatic macrophytes did not appear to provide growth factors or other substances that could prolong the survival of E. coli in water, but the plants may contribute to bacterial survival by providing a medium for bacterial attachment. To our knowledge this is the first study reporting on the effects of aquatic macrophytes on E coli concentrations in water.