Microbes can function as both the agent and remedy of water quality problems
The supply of drinking water for human consumption and irrigation water for our food and fuel crops is under pressure due to population demands, changing management practices and climate change.
Algal blooms are occurring with greater frequency, duration, and spatial extent in both fresh water and coastal systems around the world. They are driven by elevated nutrient (nitrogen and phosphorus) loadings in bodies of water with sufficient clarity, warm temperatures, and low mixing. Agricultural intensification is a primary cause of increased nutrient runoff and resulting algal blooms, referred to as eutrophication. These impacts are exacerbated by the shift toward surface application of fertilizer prior to the growing season and increased runoff resulting from more frequent severe rainfall events. Together the confluence of these factors has increased nutrient loading in surface waters that feed inland water bodies such as Lake Erie (Michalak et al, 2013). It is expected that under current land management scenarios that further intensified agriculture due to increased population demand for fuel and food and elevated run-off (agricultural, municipal, urban) due to increased frequency of extreme weather events will lead to further exacerbation of these events globally.
Microbes in soils, sediments, surface water and groundwater are key to water quality, they can regulate the flux of nutrients from terrestrial systems that cause eutrophication, or when nutrient loadings are excessive, other toxin-producing microbes can bloom, resulting in significant health risks. Microbes can immobilize heavy metals and radionuclides preventing the spread of contamination from legacy activities, but in some circumstances microbes may actually stimulate the release of toxic metals such as Arsenic. These examples highlight the need to understand microbes in the context of their biomes, that is the heterogeneous physical, chemical and biological environment in which they reside.
Developing a sustainable solution to water quality issues such as Harmful Algal Blooms requires the multi-physics, multi-scale systems approach that has been pioneered by the Department of Energy, and is particularly relevant to the DOE mission in sustainable bioenergy. Food, feed, and energy crops all rely on phosphorous fertilizer because the majority of soil phosphorous exists in a form plants are unable to access. For example, modeling of watershed conversion from continuous corn to switchgrass by Great Lakes Bioenergy Research Center scientists (Jha et al., 2009) suggests that phosphorus loadings can be reduced by more than 80% however removal of crop residues for bioenergy production will further increase demand for fertilizer. Given the clear interactions between projected climate change, land management practices and water quality, building a path towards responsible and sustainable bioenergy feedstocks will require addressing these issues in a coupled manner to design management scenarios that preserve both environmental and human health while allowing economic production of bioenergy crops.
Michalak, A. M., Anderson, E. J., Beletsky, D., Boland, S., Bosch, N. S., Bridgeman, T. B., Chaf, J. D., Cho, K., Confesor, R., Dalo, I., et al. (2013). Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions. Proc. Natl. Acad. Sci, USA. 110. doi:10.1073/pnas.1216006110.
Jha, M., Babcock, B.A., Gassman, P.W. and Kling, C.L. (2009). Economic and environmental impacts of alternative energy crops. Intl. Agri. Eng. J. 8:15-23.
