52 harvests a year
If you ask yourself, why algae — why not something else? From a productivity point of view, think about 52 harvests a year.
In the example of Cellana, the crop is seeded (it’s called inoculating the pond) on Day 1, and by Day 7 we have reached harvest. The harvest is done overnight, and the next crop is seeded and ready to go in the morning. Processing proceeds at the same pace. It’s 52 harvests. For other staple crops, one per season, perhaps two in selected instances.
No need to have a field lay fallow to recover — no need for crop rotation. No need for months of ideal weather patterns to bring off a big harvest. No waiting of months or years from first growth to first cash-producing harvest.