Diatom sampling
Samples of benthic biofilms were collected in the shoreline of 22 ponds
in June 2018. Epiphytic diatom samples were collected from submerged
stems of Schoenoplectus lacustris following the methodology
proposed by Blanco, Ector, & Bécares, (2004). A scheme of the diatom
sampling procedure and the subsequent processes is provided onFigure 2. A total of 10-12 stems were cut 10 cm below the water
surface. Stems were placed in a plastic bottle with 500 ml of distilled
water and shaken for 2 minutes to dislodge attached diatoms following
previous studies (Zimba and Hopson, 1997; Riato, Leira, Della Bella, &
Oberholster, 2018; Borrego-Ramos, Olenici, & Blanco, 2019). The
suspension was split in two samples. One of them was fixed with 4% v/v
formaldehyde and used for morphological identification, and the other
one fixed with 70% v/v ethanol and used for molecular identification.
All samples were transferred to the laboratory in a cool box. Samples
for molecular identification were kept at -20 °C until DNA extraction.