Growth rate was measured in batch culture by pooling all plant thalli and summing them to attain the datum for the culture pot. Hence, the culture pot is the unit of replication. Growth rate was measured by recording the fresh weight of living material approximately every 6 days. Plant tissue was lightly stacked and gently pressed between layers of Kimwipes. This method reduced handling time and removed superficial water prior to weighing. The stack was then weighed together to attain the fresh weight for the pot. Relative growth rate was then calculated following Lüning (1990):  RGR(% . day-1 = (100*Ln(W2/W1))/(t2-t1), where W1, W2, t1, t2 correspond to fresh weights at times 1 (t1) and 2 (t2), respectively. The weekly relative growth rates track the dynamics of growth and its variation during the experiment. In addition to growth rates estimated approximately weekly, estimates of overall net and absolute growth rates integrated across the 3-week experiment were also made using the initial and final starting masses. The difference between the overall net and absolute growth rate estimates is that the latter estimate includes small tissue fragments derived from whole thalli that occasionally appeared at the end of a weekly growth interval, but were thought to not be healthy viable fragments that would generate new growth in the subsequent interval so were discarded at the beginning of the next growth interval.

Note: Trial 1 was a pilot test of culture system and methodological procedures so was not used for data collection