Resumo

RAMIREZ R., John Jairo; ARCILA L., Mónica Cristina  e  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.

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

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