Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10117740 | Aquatic Botany | 2018 | 29 Pages |
Abstract
The attenuation of photosynthetically active radiation (PAR) through the filamentous alga Cladophora glomerata was investigated both in situ and in an experimental flow tank under natural and artificial lighting using a fiber-optic sensor. Over 35 separate experiments were completed to characterize downward light attenuation and water velocity effects. Measured extinction coefficients ranged from 4.3 to 150.7âmâ1 for biomass samples ranging from 40 to 253âmgâchlorophyll-a mâ2 (41 to 381âg ash free dry weight mâ2) at shear velocities from 0 to 51.8âcm sâ1. An exponential relationship between light attenuation coefficient (Kalg) and algal biomass thickness (δ) was found (lnKalgâ=ââ1.1831 lnδ + 8.3789; r2â=â0.41, pâ<â0.001). Unexpectedly, chlorophyll-a (Chla) and ash free dry weight (AFDW) areal density were poor predictors of Kalg. No significant correlations (pâ>â0.01) were found amongst any of the other experimental variables (e.g., shear velocity, Reynolds number, etc.). Cladophora mat thickness (δ) and volumetric biomass (Chlaâmâ3) provided the greatest explanation of downward light attenuation in flowing water, reducing irradiance in proportion to how closely the filaments are pressed together. Observed δ generally decreased with increasing shear velocity, albeit not predictably. Results have important implications on aquatic systems where macroalgae generate variable light regimes on understory aquatic species.
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Authors
Kyle F. Flynn, Wayne Chudyk, Vicki Watson, Steven C. Chapra, Michael W. Suplee,