First steps toward standardizing dynamic light regimes for the quantitative study of light-controlled growth in shade-limiting water columns

• Published in: Journal of applied phycology 2016-12, Vol.28 (6), p.3225-3234
• Main Authors: Hewes, Christopher D., Hewes, Sebastian O.
• Format: Article
• Language: English
• Subjects: Algae; Algae harvesting; Biomedical and Life Sciences; Deep water; Ecology; Freshwater & Marine Ecology; Growth conditions; Life Sciences; Natural environment; Plant Physiology; Plant Sciences; Quantitative research; Thalassiosira pseudonana; Water column
• ISSN: 0921-8971; 1573-5176
• DOI: 10.1007/s10811-016-0901-9

The diurnal solar cycle is the single most common influential variable for algae growing in a natural environment. In spite of its importance, relatively few laboratory studies have been directed towards photophysiological responses to dynamic irradiance regimes. Further, most of these studies have utilized optically thin cultures. However, phycological technologies utilize optically dense cultures grown in depths measured by centimeters. In this case, algae are harvested under self-shading conditions (all usable incident irradiance being absorbed), and the response of the entire water column to the dynamic irradiance regime is of interest. Thus, the area integrated under some modeled curve for a dynamic irradiance regime becomes the independent variable for the photobiological response being measured of a water column in laboratory studies, and this is important. But what curve should be used to model a dynamic irradiance regime? We suggest that a Gaussian (normal) distribution be used to model this dynamic irradiance because of its well-known statistical attributes. In this study, Thalassiosira pseudonana (marine diatom) was grown under shade-limited growth conditions in a 20-cm deep water column with a dynamic irradiance regime using our SolarStat™. A Gaussian distribution modeled this regime having an 11-h day length (standard deviation ±1.85 h) with an irradiance maximum of 1900 μmol photons m −2  s −1 . The daily productivity of batch culture in the linear phase of the light-controlled growth dynamic is compared with those of semi-continuous cultures maintained at 1.0, 0.5, and 0.25 doublings day −1 .