Verification of Suitability of Fly-Ash-Shell Blocks for Algal Growth: Understanding Growth Characteristics of Periphytic Diatoms by Using Non-Distractive Measurement Method

We evaluate the suitability of a fly-ash-shell blocks (FSBs) for periphytic diatom growth. FSBs and concrete and granite blocks (length 4 cm, width 16 cm, and height 4 cm) were immersed in an aquarium filled with sea water for two weeks. The upper surfaces of the blocks were photographed by digital cameras every weekday. The increase of the periphytic diatom biomass (Chl-a) on the blocks with time was understood from image analysis using a color channel having a high correlation with Chl-a. Factors defining the growth characteristics, such as specific growth rate in the exponential phase and initial recruitment rate, were obtained from the temporal change in the biomass, and were compared among each type of material of the blocks. The results, show that while the diatom recruitment rate was fastest on concrete, the specific growth rate in the exponential phase showed no difference among the materials.