Year Established: 2012 Start Date: 2012-03-01 End Date: 2013-02-28
Total Federal Funds: $20,800 Total Non-Federal Funds: $41,619
Principal Investigators: Xiaozhen Mou
Abstract: Microcystin contamination has become an increasing issue that causes water quality degradation in many Ohio lakes, especially the Grand Lake St Marys (GLSM) and Lake Erie Western Basin (LEWB). The toxicity level of microcystin in lake water is determined by both production and degradation processes of microcystin. However, in contrast to extensive studies on microcystin production, knowledge on microcystin degradation in natural environments is limited. This knowledge gap prevents a comprehensive understanding on microcystin turnover, which is critical for wise management decisions on water quality issues. GLSM and LEWB both suffer from frequent microcystin-producing cyanobacterial blooms during summer seasons. In GLSM, microcystin concentration frequently builds up to over tens of g/L and the high concentration often lasts for weeks or even months. In contrast, microcystin concentration is lower in LEWB. Occasionally, microcystin concentration in LEWB peaks over 10 g/L, but typically drops back to low levels within days. We hypothesize that this difference in microcystin degradation dynamics is largely due to the variation in the taxonomic structure and activity of in situ microcystin-degrading bacteria in these two lakes. We will test the hypothesis via addressing three specific objectives: (1) to estimate the microcystin microbial degradation potentials (2) to determine the taxonomic structure of microcystin-degrading bacteria and it dynamics, and (3) to identify environmental factors that affect the activity and distribution of microcystin-degrading bacteria. Water samples will be taken at least monthly from GLSM and LEWB in Summer 2012. Dissolved organic substrate and inorganic nitrogen and phosphors as well as other water chemistry parameters will be measured. Water samples will also be used to set up microcosm incubations to examine microcystin consumption, bacterial growth activities and bacterial community structures in microcosms including 1) with and without microcystin addition, 2) with and without bacterial community and 3) with and without light irradiation. As one of the pilot studies to investigate the role of heterotrophic bacteria in microcystin degradation in Ohio lakes, this project will provide a better understanding of the turnover of microcystin and factors that regulate this process. The new insights into microcystin degradation will lead to better predictions on the harmfulness of cyanobacterial bloom and promote timely decisions on the management of Ohio lake water resources.