DOC-processing capabilities of bacterial assemblages associated to the invasive kelp Undaria pinnatifida in Patagonian coastal waters

LOZADA, MARIANA; ZABALA, MARÍA SOLEDAD; BIGATTI, GREGORIO; DIEGUEZ, M. C.; GARCIA, PATRICIA E.; FERMANI, PAULINA; DIONISI, HEBE M.

Modalida Virtual

Congreso; ASLO 2021 Aquatic Sciences Meeting; 2021

In this work, we analyzed changes in water chemistry and microbial communities associated with the presence of high seasonal biomasses of the kelp Undaria pinnatifida, a worldwide invader that has spread on Patagonian coasts. Epiphytic, algal bed or surficial seawater samples were obtained from a densely colonized coastal environment. Sampling was performed monthly in late spring and summer, during the period of senescence of the algae. Throughout the study period, dissolved organic carbon (DOC) concentration increased while U.pinnatifida dry weight decreased. Several optical indices associated with DOC quality showed a transition towards an increase in fresh organic matter (associated with component 1 in PCA analysis, 43 % of variance). PC2 (28 % variance) correlated positively with aromaticity indices, and PC3 (13 %) with DOC and DIC, which were higher in the algal bed. Microbial communities from all types of samples were capable of degrading alginate, a major component of macroalgal cell walls, as evaluated in overnight incubations. Alginolytic potential (mean &pm 1SD) was much higher in epiphytic microbial communities (3.39 ± 1.09) compared to bed (0.12 ± 0.04) and surficial (0.08 ± 0.02)(pairwise comparisons P < 0.02). These results suggest an active role of bacterial communities, specially epiphytic, in the degradation of macroalgal-derived organic matter in this shallow water environment. These findings will be related with patterns in bacterial abundance and community structure analyzed by flow cytometry and 16S rRNA gene amplicon sequencing, which are currently underway