Dataset: Data set 4: TEP production and aggregation of Chaetoceros sp. as a function of light climate, pCO2, and temperature

All samples were processed at UCSB in the Passow Laboratory. Samples for the carbonate system, DOC, and cell concentration were collected first to forestall changes due to bacterial activity and cell sinking. All carbonate system samples were overfilled by a minimum of 50% volume into acid rinsed borosilicate glass bottles leaving ~1% headspace and fixed with 130µL of saturated mercuric chloride solution (Dickson et al., 2007). All samples were stored at 2 degrees C until analysis. DOC samples were gravity-filtered through precombusted 0.2µm GF/F filters into combusted glass vials and acidified with 60µL of 4N HCl. Samples were collected in duplicate for each replicate tank. All samples were refrigerated until analysis. Approximately 20ml of well-mixed background water was collected and fixed with buffered Formalin (10%) to determine cell concentrations. Background tank water was then sampled for inorganic nutrients, POC, TEP, and biogenic silica (bSi). Inorganic nitrate, nitrite, phosphate, and silicate were collected into 20ml HDPE vials and frozen until analysis. Samples for POC were filtered onto precombusted 0.4 GF/F filters, dried at 60ºC for 24h and stored in a desiccator until analysis. TEP samples were filtered onto 0.4lm polycarbonate filters and stained with Alcian Blue following Passow and Alldredge (1995). The Alcian Blue dye was calibrated using Gum Xanthum equivalents per liter. Samples for bSi were filtered through 0.6lm polycarbonate filters and frozen until analysis.

Once the background water was sampled, aggregates were collected from the bottom of the rolling tanks and transferred with minimal surrounding seawater to acid washed 1L polycarbonate bottles. The aggregate slurry was then mixed gently and measured for cell concentration, POC, TEP, and bSi following the same methods outlined above. Due to the time required to sample each tank, samples for both background water and aggregate slurry were sampled for one replicate before moving on to the next. The entire sampling process took approximately 4h per treatment. Tanks were opened and sampled in a 2 degrees C temperature controlled room to slow bacterial remineralization throughout the sampling process.