Culturing of Synechococcus clones:

Monocultures of four Synechococcus clones (1333, 1334, 2515, 2370) were used to examine variation and controls on Si quotas and rates of Si accumulation. Cultures were procured from the National Center for Marine Algae and Microbiota (NCMA) at the Bigelow Laboratory for Ocean Sciences in Boothbay Harbor, Maine. Many of these clones are also available in other culture collections and have various strain names; here we will refer to each by their NCMA strain number (a.k.a. CCMP number).

All clones were maintained in aged surface Sargasso Sea water with f/2 media constituents. The temperature was 21C with low light 65 microeinsteins per second per square meter (uE/m2/s) on a 12 h light:12 h dark photocycle. pH was regulated in all cultures by bubbling with humidified ambient air which was sterilized by passage through a bacterial filter prior to entering each culture vessel. Unless otherwise specified, all experiments were conducted under these temperature and light conditions. pH was monitored daily and remained below 8.5 in all experiments.

Si:P treatments:

Cultures were kept over several generations in media with different Si:P mole ratios. Silicic acid concentration was held constant at 100 uM with three treatments representing Si:P ratios of 1, 5, and 10 created by varying phosphate concentration. Soluble reactive phosphate was measured daily (Strickland and Parsons, 1972). When declines in P concentration were observed cultures were supplemented with additional P to maintain targeted Si:P ratios. Cells were harvested and processed as for total cellular silicon. Cellular quotas of biogenic silica were determined using NaOH–HF digestion in Teflon tubes as described in Krause et al. (2013)

Full details of culturing and experimental methods are described in Brzezinski et al. (in review as of 05 Jan 2017).

Cellular quotas of biogenic silica were determined using NaOH–HF digestion in Teflon tubes as described in Krause et al. (2013).