Plankton
The analysis of similarities anoism gave an R of 0.598 for the sampling times, indicating that differences existed among the treatments at a significance level of 0.001. The MDS (multivariate analysis of multidimensional stepping) revealed a greater dispersion in the samples at times D5 and D11 in the initial stage of the flooding, while both times presented a low total density of organisms. As the flooding progressed, the total density increased; with the replicates becoming progressively more homogeneous, as evidenced by the greater similarity in the composition of the species (Fig. 9, panels a and b). The contribution to the similarity on D5 was mainly by some testaceous amoebae, bdelloid rotifers, and nematodes; whereas on D11 was no grouping of species occurred since the composition of the replicates became very heterogeneous. In the intermediate stage, from D18 through D25, the taxa with the greatest contribution to similarity were the ciliates Frontonia sp. and Euplotes sp. at both times and the rotifers Lecane clara on D18 and Cephalodella sp1 on D25. In the final stage of the flooding, from D32 through D47, the contributions to the similarity were made by the same taxa as at the previous times along with the contributions of the ciliates Cinetochillum sp. and Dileptus sp. on D47 (Fig. 9, Panel b). Many of these species were the ones that provided the most contributions with respect to the total density at each stage of the flooding (Fig. 9, Panel a).
The dissimilarity (SIMPER) among the different flooding times, especially during the first days (D5 to D11), was caused by the nematode Dorylaimus sp., two species of Euglypha (on only D5), certain ciliates such as Litonotus sp., and a taxon of the family Oxytrichidae recorded on D11 but absent on D5. Between D11 and D18, ciliates such Cyclidium sp., Euplotes sp., and Frontonia sp.—the latter registered on only D18—contributed to the dissimilarity. In addition, between D18 and D25, Cyclidium sp. and Chilodonella sp., both taxa present on D18 made a contribution; while Frontonia sp. and Cephalodella sp1 evidenced a higher abundance on D25. From D25 through D32, contributions from ciliates of the family Oxytrichidae and Litonotus sp.—the latter present on only D25—gave rise to the dissimilarity detected. The rotifer Cephalodella sp1 was detected at both times, though in greater abundance on D32. Euplotes sp. and Chilodonella sp.—the latter more abundant on D32—and two species of rotifers, Cephalodella sp1 and Lecane pyriformis, contributed to the dissimilarity between D32 and D39. Between D39 and D47, the dissimilarity contributions were made by the ciliates Dileptus sp. and Cinetochillum sp. and by a heliozoan, all being present on only D39. Moreover, Cyclidium sp. and Cephalodella sp1 were recorded on only D47.
Artificial substrates
The ANOSIM analysis revealed an R of 0.798 between the sampling times for both zones of artificial substrates (zones I and II), pointing to significant differences between the sampling times. In contrast, the R between the zones of artificial substrates was 0.056, indicating that the differences between the two sites were almost insignificant. The MDS, for both zones, evidenced a distribution of the samples during the three stages of the flooding time, with increases in the total density mainly occurring in the intermediate stage (Fig. 10, Panel a). Chilodonella sp. was the sole taxon in the initial stage. The intermediate stage, D18 through D25, contained Chilodonella sp., Litonotus sp., and Philodina sp1 along with Frontonia sp., Euplotes sp. and the rotifer Lecane clara in Zone II. The final stage of the flooding comprised Chilodonella sp.; Frontonia sp.; Euplotes sp.; and two rotifers, Cephalodella sp. and Lecane clara plus Lecane pyriformis in that same zone. By D47, Chilodonella sp. was absent from both zones, whereas Cephalodella sp1 and Philodina sp2 became dominant. Many of those species were the ones that contributed the most greatly to the total density for each stage of the flooding (Fig. 10, Panel a, S2). Litonotus sp. and Euplotes sp. were the ciliates that most greatly contributed to the dissimilarity (Fig. 10, Panel b) in the initial stage (D11 through D18), with those being present on only D18 along with the alga Euglypha laevis detected on only D11. From D18 through D25, Euplotes sp., Litonotus sp., and Lecane clara—it, though, present on only D18—were more abundant on D25. The taxa that contributed the most greatly to the dissimilarity at times D25 and D32 were Cephalodella sp1, Dorylaimus sp., and Frontonia sp. During the last days of the flooding, D32 through D39, the dissimilarity was due to Frontonia sp., with it being more abundant on D39, along with Dorylaimus sp. and Chilodonella sp., both exhibiting a greater abundance on D32. The rotifers Lecane clara and Cephalodella sp1 and the ciliate Euplotes sp contributed principally to the dissimilarity between D39 and D47. These taxa were recorded at both sampling times, but with higher abundances in D39. Euglypha laevis was responsible for the dissimilarities between the two zones of artificial substrates, with that species being recorded in only Zone I. Euplotes sp., Frontonia sp., Lecane clara, and L. pyriformis were found in both zones, but in all instances at a greater abundance in Zone II.