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Seaweed on a beach in B.C.Nikki Bayley/The Globe and Mail

Should the government allow mass harvest of seaweed on the British Columbia coast?

Certainly there seems to be an overabundance of it on most beaches, where it often collects in long, thick mats known as wracks.

A commercial seaweed harvest has been proposed for B.C. – a new "fishery" that would target an untapped resource potentially worth millions of dollars – but a study led by a group of retired fisheries scientists has raised concerns about its environmental impact.

As coastal gardeners know, seaweed is rich in nutrients and mulched into the soil it can help produce bumper crops. The seaweed slowly rotting away on our shores also has potential commercial value, largely because of carrageenans, thickening and gelling substances that can be extracted from red algae.

Worldwide about 13 million tonnes of seaweed is harvested annually and the carrageenan market alone is worth about $1-billion (U.S.).

So why isn't B.C. cashing in on this crop instead of letting it rot away on the beaches?

To help address that question, the provincial government last year approved a pilot project, near Parksville on Vancouver Island, which allowed licensed operators to scour the beaches to harvest up to 5,000 tonnes of Mazzaella japonica – a red algae that carpets the shoreline around Baynes Sound and Deep Bay.

Beach users may not have missed the smelly wracks that were systematically hauled away by the seaweed harvesters. But now a study, led by Ian Birtwell a former research scientist with Fisheries and Oceans Canada, is calling for caution, saying those mounds of rotting seaweed add a lot of environmental value to our beaches.

"Seaweeds are, fundamentally, of high ecological importance and accordingly their removal whether while living, or dead, will have an ecological impact," states the report.

"There is a scientific basis for concern about the implementation of a potential new industry that would harvest seaweed along the east coast of Vancouver Island, and perhaps other areas in British Columbia," it states.

The report's authors say that as the wracks of seaweed decompose and get broken up by wave action, the material provides nourishment to an array of organisms.

"Nutrients and carbon from beach wrack can be transported via various means to sub-tidal zones," states the report. "The diets of commercially important fish, including juvenile salmonids, herring and surf smelt overlap with the invertebrate food items found in beach wrack … This has important implications for fisheries values in the area; both salmonids and 'forage fish,' along with many other species, will consume amphipods, worms, and insects that are dislodged in the inter-tidal zone during the high tide. Many birds also take advantage of the beach wrack communities, and may be affected by the loss of beach wrack to the ecosystem."

The authors note little research has been done on the effects of harvesting Mazzaella japonica, "but given the stated importance of algal species in beach wrack in marine ecosystems, one must conclude that its removal in any significant proportion will have profound effects on adjacent marine and inter-tidal ecosystems."

The report calls on the government to impose a moratorium on seaweed harvesting "until the ecological impacts of the Mazzaella fishery have been identified and assessed."

It also says ecologically valuable sites, such as intertidal pool and lagoon areas and key bird habitats, should be put off limits to all seaweed harvesting.

The study says there hasn't been enough research to fully assess the potential impacts of commercial seaweed harvesting in B.C. and that work needs to be done, "to ensure that if such an industry were to develop it would be based on sound decisions with low socio-economic and ecological risks."

The government of B.C. will be tempted to cash in on a "crop" that is apparently going to waste on our beaches. But Dr. Birtwell and his co-authors have sent a clear warning that all that seaweed is playing an important environmental role – and stripping it from our shorelines could have serious consequences.

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