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RESEARCH PRODUCT

Rotifer vertical distribution in a strongly stratified lake: a multivariate analysis

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The main source of variation of rotifer species distributions in lake Arcas-2, a small karstic lake near Cuenca (Spain), was explored by means of principal components factor (PCA) and canonical correlation (CCA) analyses. PCA was performed using rotifer densities and CCA using rotifer densities plus physical and chemical parameters. Factor 1 of PCA separated summer species from winter-spring species and Factor 2 accounted for the variation in the vertical profile. Three summer species with different food habits (Polyarthra dolichoptera, Hexarthra mira and Asplanchna girodi) were grouped together at the positive end of Factor 1, while Factor 2 separated the two hypolimnetic species (Filinia hofmanni and Anuraeopsis fissa) from the rest. The relative position of rotifer species in the space determined by the CCA was roughly the same. The most significant environmental factors that became paired with rotifer distribution in the CCA were temperature and oxygen, and parameters related to water inflow. Segregation of filter-feeding species in the spatio-temporal subenvironments is clearly shown by the multivariate analysis.