Preservation of the light field in turbid lake and river water in laboratory-scale enclosure
Rijkeboer, M.; Gons, H.J.; Kromkamp, J. (1993). Preservation of the light field in turbid lake and river water in laboratory-scale enclosure. J. Plankton Res. 15(5): 517-530. http://dx.doi.org/10.1093/plankt/15.5.517
The laboratory-scale enclosure (LSE), as a physical model of the water column, has been introduced for studies of seston dynamics in shallow, mixed lakes. Preserving the ‘natural’ underwater light climate was among the design criteria. However, lateral exchange of light between the LSE cylinder and its water bath caused deviations from conditions in the water column in situ. Two modifications of the original design are introduced by providing the LSE cylinder with (i) a masking plate and (ii) a reflective coating. The light fields in the original and modified designs are compared for Osciiiatoria limnetica culture and Western Scheldt Estuary water. These test suspensions had dry weight concentrations of ~50 mg l-1 and differed widely in scattering to absorption ratios, i.e. 4 and 12 for the culture and natural water, respectively. Using the reflective coating, the LSE provided an underwater light field conforming to general theory for diffuse attenuation and reflectance. Using the masking plate may suffice for cultures of cyanobacteria, but the reflective coating is needed for studies of phytoplankton growth in relation to the optical conditions in turbid lake and river water.
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