Sediment-water incubation experiment data under a controlled temperature gradient and low dissolved oxygen concentrations in sediments from Macleay River

Incubation experiment: The experiment involved temperature-controlled batch incubations, conducted over 21 days, with sediment (15 g), algae (2 g, dry weight) and water (400 mL; MilliQ) placed in a 500 mL Pyrex glass bottle that was open to the atmosphere. Five temperatures (8, 14, 20, 26, 32oC) were selected, to bracket the environmental range of water temperatures in the Macleay River. Sediment was collected from the Macleay River (30°39'46.98"S; 151°54'36.05"E). Temperature was controlled via a water bath and water chiller in combination (+0.2oC; Grant, OLS200; Ratek, TH8000). Aqueous samples were collected at 24 h, 72 h, 7 d, 14 d and 21 d. During incubation, the Pyrex vessel was stationary, thereby allowing sediment and algae to settle at the bottom of the vessel and O2 to naturally diffuse from the atmosphere into the water column. At 1 hr prior to each sampling interval, the Pyrex vessel was sealed with a screwcap lid and inverted several times to thoroughly mix settled sediment / algae with the water column, followed by the screwcap lid being removed for the remainder of the hour. This approach of being open to the atmosphere combined with static conditions and occasional mixing (rather than a closed system with sediment-water homogenisation via constant stirring) was employed to mimic both diffusive and occasional re-suspension-induced interactions that may occur between hyporheic zone benthic sediments and the water column. Such interactions are expected in a low-flow, oxic yet eutrophic, river system comprised of pools and riffles.