I would like to read the story to see what is being proposed.
Anyone with half an interest in gardening will know of the properties of sea weed (Kelp), and it's been commercially harvested for many years elsewhere.
However, my understanding is that commercial Kelp harvesting is done by hanging "seeded" ropes in a suitable flow, and leaving them to grow. Once mature, the ropes and kelp are hauled aboard, and the process starts again (on rotation of course).
If this is the case, and its done on rotation, the additional kelp forests will be a benefit to wildlife. Where one set of ropes and fronds are removed, the fish etc will still have others in the area to move to.
Cass did her dissertation on the bio-accumulation of Arsenic in marine plants, particularly those fed to sheep on the Western Isles. One of the issues she came across is that it is illegal to remove living marine plants from rocks and the shore. She could only use washed up material...hence us getting up early on stormy days and trekking down to the beach to collect "sea weed" before it was too far gone. The smell of gently rotting kelp in the bath tub is not one I wish to repeat
So, although the crofters etc have an age old "permission" to harvest, I would like to think commercial harvesting of wild kelp would still be illegal, too difficult and too costly and that the artificial kelp forests as used elsewhere is what they are proposing.