For the algae incubations on August 18, 2020, transparent gas impermeable plastic vacuum bags (Packing24, PA/PE 20/70, 90my) with a single F. vesiculosus thallus, were closed with rubber bands around PVC end cap fitting of 12 cm diameter and attached to a bottom-anchored line at ~1 m depth. Thalli of ~50 cm length were detached close to the base by cutting the few millimeters thick, old stipe. Half of the incubations were covered with black bags to simulate dark conditions. Immediately prior to starting the incubations, water was sampled from the ambient water to determine initial conditions. At the end of the incubation, all algal tissue was collected. Water from within chambers was collected for analyses and the total volume measured. In the laboratory, the algal thallus was spread out across a cutting mat with a grid for surface area estimation. Epiphytes and epifauna were scraped off thalli using a razor blade, and collected separately from the algal biomass. All biomass was frozen and subsequently freeze-dried for 24 hours, and weighed to determine dry weight.