The Scottish Parliament has voted to curb mechanical kelp harvesting if it prevents the seaweed regrowing.
Holyrood backed the change, which applies to commercial licensed activity on Scottish Crown Estate seabed, as part of the Scottish Crown Estate Bill, which was passed unanimously.
Prohibiting the practice was proposed by the Scottish Greens after more than 10,000 people signed a petition calling for a ban.
Environment secretary Roseanna Cunningham told MSPs during the final parliamentary debate on the legislation to reform the governance and management of the Scottish Crown Estate that she had listened to all the views before supporting extra controls on harvesting.
She said her support was on the basis it would not prevent kelp-based scientific research, including for public health purposes, and would not prevent power stations or ports from removing kelp or prohibit hand harvesting of wild kelp.
Green MSP Mark Ruskell's amendment to the Scottish Government's amendment, which ruled out unsustainable commercial harvesting, passed by 89 votes for, none against and 28 abstentions.
Ms Cunningham also announced a review of the regulations surrounding all kelp harvesting activity, including that which does not require a licence.
She said: "I would plan to keep the situation under review, and not wish unreasonably to block the future development of forms of harvesting which might in time be established, through a proper assembling of the evidence, as sustainable."
Mr Ruskell said: "Kelp forests are hugely important to our marine environment. They dampen waves, protect coastal communities from flooding and erosion, act as a habitat for hundreds of species including commercial fish and store more carbon than the rainforest.
"Greens have been working extremely hard to ensure unsustainable dredging practices are prohibited in legislation and I am delighted that this has now been realised."
Sandy Dobbie, chairman of Ayr-based Marine Biopolymers, behind a plan to collect 30,000 tonnes of kelp off the Scottish coast, said it was "disappointed" by the parliamentary debate but welcomed the review.