Limnological characteristics
Limnological characteristics varied among the sampled reservoirs (see
Appendix S1 in supporting information). Principal component analysis
(PCA) identified three major axes of limnological variation (axes that
explain more than 10 % of the variation). PCA reduced the data set to
three components that explained 64.27% of the variance in the original
variables. The first and second axis of the PCA explained 51.07% of the
total variation observed. PC1 explained 28.69% of the variation and can
be interpreted as a measure of altitude, surface area, total nitrogen
(TN) and total phosphorus (TP) (Fig. 2). PC2 explained 22.38% of the
limnological variation and was loaded heavily by electrical
conductivity, pH and depth. PC3, which explained 13.2% of the
variation, was loaded mostly by Temperature and transparency. As can be
seen in Fig. 2 three major clusters of reservoirs is created based on
the PCA components. Cluster 1 is composed of 6 lowland reservoirs and
cluster 2 is composed of 12 highland reservoirs while cluster three is
composed on 17 reservoirs of mixed elevation but mostly with high
nutrient concentration (Fig. 2; see Appendix S2 in supporting
information).