Submitted to: Hydrobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2000
Publication Date: N/A
Interpretive Summary: Traditionally, researchers interested in studying photosynthesis by aquatic algae in a laboratory setting have been hampered by the inadequacies of artificial lighting. Specifically, the lights used to grow algae are generally white and of a constant irradiance: the irradiances that algae see in nature, however, are highly variable in intensity and spectral distribution (or "quantity" and "quality"). The photobioreactor described in this manuscript addresses this problem by introducing a variable thickness of a dye solution (saturated Copper Sulfate in this case) between the white-light source and the algae culture vessel. The amount of dye is precisely determined by a computer- controlled peristaltic pump that is programmed to pump dye in and out of the dye-tank at rates based upon real mixing data. This culturing device should prove beneficial to any researcher interested in mimicking the effects of the variable natural light in order to achieve more realistic, photophysiological responses.
Technical Abstract: An inexpensive and simple, analytical microalgal photobioreactor with a highly controllable, dynamic, spectrally attenuated light source is described. Spectral attenuation is achieved through the introduction of a variable thickness of CuSO4 solution between the photobioreactor and a light source. The level of liquid is precisely determined via a computer-controlled peristaltic pump, which can be programmed to pump at a variety of rates. The resultant light fields consist of a wide range of irradiance intensities with concomitant spectral narrowing, which closely mimics modeled clear water attenuation patterns. Irradiance dynamics associated with virtually any mixing regime can be achieved. The culturing apparatus of the analytical photobioreactor is based on traditional flat-plate, photobioreactor design, but with several modifications: 1) The light path has been reduced to 1 cm to assure a uniform light field is experienced by all phytoplankton at relatively low cell densities; 2) carbon dioxide concentrations are kept constant through a negative feedback mechanism that pulses CO2 into a constant air stream when culture media pH rises above a set point; 3) temperature is controlled in a similar manner, through the addition of cooling water to a water jacket in response to an increase in culture media temperature. This design is intended for use in photophysiological and bio-physical studies of microalgae under highly controlled culture conditions. It should prove easily adaptable to any number of more complex configurations.