Resumo

VILLABONA-GONZALEZ, Silvia Lucía et al. Main physicochemical and biological variables in the trophic state of five Colombian Andean reservoirs. Rev. acad. colomb. cienc. exact. fis. nat. [online]. 2020, vol.44, n.171, pp.344-359.  Epub 08-Jun-2021. ISSN 0370-3908.  https://doi.org/10.18257/raccefyn.1051.

The models that measure the trophic state in reservoirs differ from those designed for natural ecosystems due mainly to the effect of basin contributions and the reservoir operation. Our study aimed at establishing models based on physical, chemical, and biological variables to explain and predict the trophic state of Colombian Andean reservoirs. The data were collected between February 2010 and December 2015 and we determined the trophic status in five Colombian Andean reservoirs using the index of total phosphorus concentration designed for tropical warm lakes. The relations between variables were established through the Spearman correlation and canonical analyses and the differences among groups through the Kruskal-Wallis and the Dunn post hoc tests. We generated a multinomial logistical model to estimate the probability of assignment of the trophic state category and classification and a regression tree to determine the most relevant explanatory variables. Seven categories ranging from ultra-oligotrophic to hypereutrophic status were found while the discriminating analysis resulted in three groups of reservoirs: hypereutrophic (Porce II), meso-eutrophics (Porce III), and oligotrophic (Amain, Punchina, and San Lorenzo), a classification that responds mainly to the electrical conductivity and the total phosphorus and chlorophyll a contents. Planktonic densities showed no significant relationship with the trophic state, although zooplankton density tended to increase with it. We concluded that the statistical models we generated allowed us to predict the trophic status of the reservoirs under study.

Palavras-chave : Abiotic variables; Plankton; Chlorophyll a; Eutrophication predictors; Tropical environments.

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