This table contains measurements conducted during the bioassay incubation initiated after the flocculation experiment. Filtrates of gypsum and control treatments were amended with a 10% volume of original river water to reintroduce heterotrophic bacteria and incubated in the dark in 10 C for 15 days. Bacterial growth and properties of colored dissolved organic matter were recorded 3-6 times during the incubation, and respiration was calculated using dissolved oxygen measurements at day 0 and 15. The bioassay was conducted using the replicates 2-6 of the flocculation experiment.