Monitoring Algae

How can one know what algae are in the water? Sometimes the growths are large enough that someone can see enough with the naked eye to make at least a preliminary identification, but for the most part algae identification requires the use of substantial magnification. For many years (literally over 200) we have used lens systems organized into what we call a microscope to magnify algae enough to tell what they are, and there are few substitutes for looking. Even then, considerable training is needed to know what is being observed, leading to bottlenecks in getting algae data to support lake management. Having a trained phycologist (one who studies algae) look at algae under a microscope remains the most preferred option, but some useful substitutes have arisen with digital technology. A digital microscope can magnify an image on a screen for under $1000. That image can be captured as a photo that can be compared with online sources or sent to an expert. The USEPA, Region I, has been pioneering an effort to get lake groups with an interest in harmful algae blooms to use such systems to report algae in their lakes. The accumulation of images can be turned into useful data that allow characterization of bloom frequency, common bloom species, and possibly trends within or among lakes.

The advent of automated systems for detecting and photographing particles makes it possible to process samples quickly, but we are just getting to the point where image libraries can be used by instruments to actually make identifications. The FlowCam, made by Fluid Dynamics in Maine, counts particles and photographs them, allowing the user to catalog and identify them with some expertise. At even a rudimentary level, such systems allow fast assessment of possible threats to lake uses. The Imaging FlowCytobot, developed by Woods Hole MA scientists, has been adapted by PhycoTech of Michigan to actually make identifications, and this technology could meet the need for rapid but taxonomically detailed and accurate data generation. These instruments are expensive, but contracting for identification can be affordable.

While lack of images (visual or digital) limits identification, use of fluorescence systems to determine the amount and types of pigments present can help discern algae blooms. Chlorophyll-a, a photosynthetic pigment common to all algae, can be assessed with fluorescence, which is basically the amount of light at a particular wavelength emitted from a water sample after excitation by light at another wavelength. The amount of chlorophyll-a in different types of algae varies, so this is not a direct measure of biomass, and the quality and amount of natural light and the concentration of non-photosynthetic organic matter in the water can cause variation not related to algal biomass. However, in a general sense, fluorescence can be used to get a rough appraisal of how much algae is in the water. Further, phycobilin sensors that detect pigments specific to cyanobacteria and provide an estimate of how much cyanobacteria are in the sample. There are even more sophisticated systems that excite samples with a range of wavelengths and record fluorescence in a way that allows a relative approximation of multiple algae types in the sample. Calibration and “training” of the instrument for specific waterbodies improves reliability.

Compared to identification and mapping of rooted aquatic plants, algae assessment is more challenging, but effort is needed if one wants to understand all important aspects of a lake.