Effects of terrigenous dissolved organic matter (tDOM) and temperature increase in coastal waters.

A microcosm experiment was conducted in May 2021. Water from the coastal Thau lagoon (France) was collected at the subsurface, gravity filtered over 20 µm sieve and then used to filled 12 bottles (2-L clear polycarbonate bottles). Four treatments were studied in triplicates: control ; warmed treatment ; tDOM input ; warmed + tDOM. The control and tDOM treatment bottles were placed in an incubator with the temperature set at 16°C to mimic Thau lagoon in situ temperature at that time of the year. The warmed and warmed + tDOM treatment bottles were placed in another incubator with a temperature set at 19°C. Both incubators were equipped with a light that was set to mimic natural daylight. The microcosm experiment lasted 9 days. Changes in microbial community structure under different treatment conditions were analyzed using shallow shotgun metagenomic sequencing.