Tracking A Lake's Single-Celled Life

Marco Simona, Science Institute of the Earth

No Hands Researcher Francesco Pomati prepares a probe for real-time monitoring of microorganisms in Lake Lugano, Switzerland.

Life in a freshwater lake changes from day to day, with swings in temperature and water chemistry. To track those changes and the ways phytoplankton and other single-celled organisms respond, ecologists must conduct tedious microscope work and rely on sporadic field sampling. Now a new method automates the task, with an eye toward forecasting drinking water quality (Environ. Sci. Technol., DOI: 10.1021/es201934n).

Led by Francesco Pomati of the Swiss Federal Institute of Aquatic Science and Technology, researchers paired and automated the monitoring of two commercially available devices: a vertical depth monitor and a buoy containing a flow cytometer. The cytometer, a biological tool that counts and characterizes single cells, can describe cell size and shape, allowing identification of organisms, as well as monitoring characteristics like chlorophyll content, which can signal biological activity. The vertical monitor tracks physical and chemical conditions in the water column.

The researchers tested their floating setup over 34 days in Lake Lugano, at the border of Switzerland and Italy. As often as six times a day, the monitoring platform collected data about changes in populations of different species, distinguishing between organisms such as free-floating cyanobacteria and phytoplankton that swim using cilia. Along with monitoring daily shifts, the researchers were able to track population changes caused by a three-day storm that mixed shallow and deeper water in the lake.

The monitoring data could feed into models that forecast water quality, particularly for drinking water reservoirs, comments Justin Brookes, of the University of Adelaide, in Australia: Lake-living organisms can affect water taste and odor, as well as create toxic algal blooms.

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