Abstract

RAMIREZ R., John Jairo; ARCILA L., Mónica Cristina  and  SEPULVEDA A., Sandra Catalina. Quantification of components affecting the vertical attenuation coefficient for downward irradiance in Ríogrande II reservoir (Colombia). Rev. acad. colomb. cienc. exact. fis. nat. [online]. 2015, vol.39, n.151, pp.228-238. ISSN 0370-3908.  https://doi.org/10.18257/raccefyn.150.

In order to determine which component contributes most to the vertical attenuation coefficient for downward Irradiance -{K_d(PAR)}- in Ríogrande II reservoir, a multiple linear regression model was used to obtain -{K_d(PAR)}- considering the sum of partial K_d contributed by water K_w chlorophyll a (K_{chl a}), particulated inanimate material (tripton, K_tripton), and phytoplankton-like particles (K_p-phyto). Samples of water were taken with a Schindler bottle. The photosyntetic active radiation (PAR) was measured with a Li-cor quantameter at five sampling stations every 10 days from July 2002 to July 2003. Total suspended solids, inorganic suspended solids, volatile suspended solids, and chlorophyll a were quantified. Given that the K_tripton (1,14 m^-1) value was the highest, the prediction that the influence of K_{chl a}, K_p-phyto and K_tripton would be high and similar at the upstream Chico River station was partially accepted. The equation to estimate K_d(PAR) for the reservoir was K_d(PAR) = 1,32D_sd^-0,93, with D_sd explaining 62,4 % of the variation in K_d Optically, the reservoir was classified as T-type and case 2, which correspond to a turbid system where despite its eutrophic condition and high productivity, tripton and not phytoplankton was the fraction that harvested more photosynthetic quanta.

Keywords : Ríogrande II; photosynthetic active radiation; vertical attenuation coefficient for downwelling irradiance; Secchi depth; optical classification.

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