"This study quantified chlorophyll-a (as a proxy for biomass of microbial photoautotrophs) on rock surfaces (µg/cm2) and in surface waters (µg/L) collected from non-perennial stream sites (descriptions below).These samples were collected in support of the Talladega flow manipulation experiment, part of Approach 4 of the Aquatic Intermittency effects on Microbiomes in Streams (AIMS) Project. Briefly, a before-after-control-impact (BACI) experimental design was followed to assess the impacts of flow reduction and flow recovery on microbial communities and ecosystem processes. A small plywood dam and plastic drainage pipes were used to divert flow from an 85-m section of the stream. This resulted in two study reaches: 1, an impacted reach downstream of the dam, where flow is reduced when the dam is activated but recovers when the pipes are detached dam, and 2, an un-impacted reference reach upstream of the dam where flow is not impacted by the damming. Within each reach, five transects (spaced ~15-m apart) were sampled at six time points, including before flow reduction (t1), during a 1-month-long flow reduction (t2, t3), and after flow recovery (t4-t6).
For rocks, rock surfaces were scraped with a sterile wire brush over a known area, and the loosened epilithic biofilms were rinsed into a sterile container with a known volume of sterile deionized water. Then 10 mL of the resulting biofilm slurry was filtered through a 0.7 µm GFF filter. For water samples, a known volume of stream water was filtered through a 0.7 µm GFF filter. These Chl-a samples (GFF flters) were stored at -20ºC.
For quantification, chlorophyll-a was extracted from collected GFF filters in 90% ethanol at 80ºC for 5 minutes, steeped overnight (4ºC in darkness) and immediately quantified using high performance liquid chromatography (HPLC) via fluorescence detection (Halvorson et al., 2019; Meyns, Illi, & Ribi, 1994) with a Shimadzu 10ADvp series equipped with a Shimadzu RF10Axl fluorescence detector (excitation 430nm, emission 670 nm). Chlorophyll-a content was calculated as µg per cm2 of rock surface area sampled, and µg per L of surface water sampled.

Talladega Site Description:
Talladega (stream code=TAL) research watershed (outlet location: 33.76219799, -85.59550775) in the Talladega National Forest (Cleburne County, AL, USA). The watershed drains a non-perennial unnamed tributary of Pendergrass Creek, and contains 0.92 km^2 of mixed coniferous and deciduous forest in the Piedmont Upland physiographic section. Located near Anniston, AL, the watershed spans an elevation range from 345 to 456 m above sea level and is a tributary to the Coosa River (within the larger Mobile-Tombigbee basin). The region has a humid subtropical climate, with mean daily January and July air temperatures of 5.3°C and 25.3°C respectively, and mean annual precipitation of 1,400 mm/yr.

Entries are listed as NA's a sample was not collected (all flags described in Data Types tab).