Microbial assemblages associated with the invasive kelp Undaria pinnatifida in patagonian coastal waters: Structure and alginolytic potential

LOZADA, MARIANA; ZABALA, MARÍA SOLEDAD; GARCÍA, PATRICIA E.; DIÉGUEZ, MARÍA C.; BIGATTI, GREGORIO; FERMANI, PAULINA; UNREIN, FERNANDO; DIONISI, HEBE M.

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2022

0048-9697

Undaria pinnatifida is a brown algae native to Asia that has settled in various regions worldwide,periodically contributing with large quantities of C and nutrients during its annual cycle. In thiswork, we analyzed a coastal site in Patagonia (Argentina) that has been colonized for three decadesby U. pinnatifida, focusing on associated microbial communities in three different compartments.An important influence of algae was observed in seawater, especially in the bottom of the algalforest during the austral summer (January) at the moment of greater biomass release. This wasevidenced by changes in DOC concentration and its quality indicators (higher freshness and lower humification index) and higher DIC. Although maximum values of NH 4 and PO 4 were observedin January, bottom water samples had lower concentrations than surface water, suggesting nutrientconsumption by bacteria during algal DOM release. Concomitantly, bacterial abundance peaked,reaching 4.68 ± 1.33 x 10^5 cells mL -1 (January), showing also higher capability of degradingalginate, a major component of brown algae cell walls. Microbial community structure wasinfluenced by sampling date, season, sampling zone (surface or bottom), and environmental factors(temperature, salinity, pH, dissolved oxygen, nutrients). Samples of epiphytic biofilms showed adistinct community structure compared to seawater, lower diversity, and remarkably highalginolytic capability, suggesting adaptation to degrade algal biomass. A high microdiversity ofpopulations of the genus Leucothrix (Gammaproteobacteria, Thiotrichales) that accounted for alarge fraction of epiphytic communities was observed, and changed over time. Epiphyticassemblages shared more taxa with bottom than with surface seawater assemblages, indicating acertain level of exchange between communities in the forest surroundings. This work providesinsight into the impact of U. pinnatifida decay on seawater quality, and the role of microbialcommunities on adapting to massive biomass inputs through rapid DOM turnover.