Combined effect of an increase in temperature and an input of terrigenous dissolved organic matter (tDOM) in a small freshwater reservoir ecosystem.

A mesocosm experiment was carried out to study the combined effect of two disturbances - input of tDOM and temperature rise - on pelagic communities from a small freshwater reservoirs. The experiments were conducted within the National Experimental Platform for Aquatic Ecology (PLANAQUA) at CEREEP-Ecotron Ile-de-France located in Saint Pierre les Nemours, France. The experiment was carried out in twelve 1m3 mesocosms placed outside over a period of 6 weeks, from June 8 to July 19, 2021. Three replicates of two crossed treatments were carried out in these mesocosms. These treatments included a temperature differential of 6°C (18°C and 24°C) maintained throughout the experiment and the addition or not of tDOM (addition of 65 µM dissolved organic carbon, representing a total enrichment in organic carbon of +25%). Changes in microbial community structure under different treatment conditions were analyzed using shallow shotgun metagenomic sequencing.