*3.2. Species Abundance*

In this study, the total rotifer abundance was 522.7 ind L−1. Rotifers represent the most abundant group in the lake; their numerical abundance is considerably higher than that recorded for copepods, including immature stages (7.1 ind L−1). Cladocerans were almost absent from our samples.

Species with the highest abundance at all sites were the rotifers *B. havanaensis*(109 ind L<sup>−</sup>1) and *K. americana* (304 ind L−1), with a considerably lower abundance in the eastern area (9.3 and 121.8 ind L−1, respectively). Species of the family Brachionidae were the most abundant mainly in the western region (sites OC, BPO, and MICH), whereas the lowest abundance of rotifers occurred in the eastern region (site EC) (see Table 2).


**Table 2.** Abundance (ind L<sup>−</sup>1) calculated from zooplankton samples for all the studied points of Lake Amatitlán in 2017.

The local copepod abundance was represented mainly by nauplii and juvenile stages of Calanoida and Cyclopoida (average = 2.6, 2.5 and 1.9 ind L−1, respectively), values resembling those recorded for the Rotifera like *B. plicatilis* (1.1 ind L−1) and *A. sieboldi* (2.3 ind L<sup>−</sup>1) in all the study sites, compared with adult copepods, where the abundance of the adult *M. thermocyclopoides* present only in EC was 0.23 ind L<sup>−</sup>1.
