• Illustration: Marissa Webber

Seaweed isn’t just for slipping on and clogging boat motors. In fact, many cultures have been using a particular type of the aquatic plant, rockweed, for centuries. Growing in the rich intertidal zone (the area underwater at high tide and exposed at low tide), rockweed is high in nutrients and used for everything from food to fertilizer. Harvesting the plant is a growing business in Canada, but the ubiquitous brown algae also plays a central role in the health of the intertidal ecosystem, and as the industry develops, so too does the debate over how to harvest this useful resource sustainably. This graphic explains the ecological value of rockweed, what it’s used for, how it’s harvested and much more.

The seaweed harvest debate

Scientists love to disagree. In fact, it’s in the very fabric of the scientific method that experts must occasionally hold opposing views in order to improve our understanding of the world. So it’s no surprise that two eminent phycologists (algae experts), Dr. David Garbary and Dr. Louis Druehl, would disagree when it comes to the harvest of their beloved sea plants. While both phycologists agree that the harvest itself is sustainable, Druehl is more enthusiastic about the practice than Garbary – with Druehl even going so far as to start his own harvesting business.

Louis Druehl is a marine botanist and a small seaweed business owner on the west coast. The alga named after him – Druehlia fistulosa – is among the longest kelp species in the world, and grows all around the north Pacific.

 

David Garbary is a marine botanist and a professor at St. Francis Xavier University in Nova Scotia. The alga named after him – Colaconema garbaryi – is a microscopic red alga common in the Pacific.

Canadian Geographic   How does your work involve algae?

Louis Druehl: I’ve done just about everything you can do with kelp. Most recently, we’ve been working on evolutionary relationships between the various species of kelp, all of this work with DNA. Out of this we’ve come up with a new ordering of various kelp genera and species, which is quite different from what we had before.

Beyond that, I have a company called Canadian Kelp Resources. It’s run by my wife and I. We have two lines: one is we harvest sea vegetables and some kelp chemicals, and the other thing we do is produce what we call kelp seed – a baby kelp plant which a farmer can plant out.

We also provide seed for NGOs who are interested in another kelp on this coast called bull kelp. The issue here is that bull kelp, on the east side of Vancouver Island is disappearing. We provide them with seed, which they can plant out in their environment.

David Garbary: For the last few years I’ve been collaborating with a small family-run business in Nova Scotia. That business is the harvesting and processing of dulse (edible red alga). We did a nice ecological study, and I collaborated with a mathematician who was a resource modeler. We concluded that the way in which they’re harvesting dulse is absolutely sustainable.

I’ve been working on (rockweed) for 25 years, from purely theoretical aspects, and I’ve been gradually pulled into more applied questions.

CG: What do you think of the level of regulation of algae harvesting in Canada?

Louis Druehl: With us, the provincial government directs how we harvest. The government provides a permit on a year-to-year basis. To get these permits, we have to get permission from the local First Nation groups. The license tells us where we can harvest, what we can harvest, how we can harvest, even what we use to harvest. With us it’s always a sharp instrument, hand-operated, i.e. a knife. I mentioned we have to get these each year, which makes it very hard to run a company because you can’t convince a bank that they should loan us money to build a factory, simply because they don’t know whether we’ll be in operation the next year. This is quite a handicap. We’re just a ma and pa operation. We’re totally regulated in every way you can imagine.

When we harvest the plant, we leave quite a bit behind. We cut it off, and leave the attachment part and some of the growing part. If anything, it comes back denser than when we first harvested it. We leave a year (between harvests). We’ve been doing this for about ten years, on the same stretch of beach, going over and over and over it.

David Garbary: I’m not impressed with it, in the sense that the federal government has put very few resources into the actual management and oversight of the industry. Government has virtually no oversight in Nova Scotia.

In Nova Scotia, they have mandated a minimum cutting height of 12.7 cm. But the question is, if you cut a plant at 12.7 cm, how much of the plant are you actually removing?

These plants are roughly a metre and a half in size, so in theory, if the biomass is equally distributed along the length of the plant, you might be harvesting ten per cent or so. But in actual fact, if you cut a plant at 12.7 cm, you are removing 95 per cent of the biomass.
If you cut it at 25 cm, which is the minimum height mandated in New Brunswick, you are removing 90 per cent of the biomass. So the debate about cutting height is essentially moot, because if you are cutting it at those heights, you are destroying the whole system of the plant.

CG: Would you like to see harvesting expanded or minimized?

Louis Druehl: I think I’d like to see it expanded. We haven’t really gotten into the concept of farming kelp. It’s a well-developed technology; they do it in Japan and in China, we do it here. It allows a person access to a valuable resource without any consideration for the natural environment, because you’re in a totally artificial situation. You’re enhancing the amount of material in an area where it doesn’t grow naturally, because it’s over a soft bottom. There’s a lot of opportunity there. There’s a group at the University of Victoria looking into farming kelp as a resource material for bio-energy. They’re trying to call it “kelpanol.”

David Garbary: I have tremendous respect for Acadian Seaplants (a large, Nova Scotia-based, seaweed harvesting company) and what they do. In fact, I collaborate with them.

I don’t have a problem with the harvesting being extended to other areas, but for me the key issue is that Acadian Seaplants doesn’t know the real impact of the seaweed removal.

Acadian Seaplants tells us they’re harvesting 17 tonnes per hectare. But we’re not really being told how much biomass is being prevented from being released into the environment and degraded naturally.

Most of the seaweed harvesting occurs in the summer. In the summer, the plant’s reproductive structures are only just starting to develop. But over the late fall and into the spring, those reproductive structures increase dramatically in mass. They mature in the spring, and all those reproductive structures are released into the environment. The biomass that’s represented in those reproductive structures is at least the same as 50 to 100 per cent of the vegetative biomass.

So if you’re harvesting 17 tonnes from site A per hectare, there’s probably another ten tonnes per hectare that you are preventing from being released into the environment in the fall and the spring. I don’t know of any natural system where you can remove on the order of 25 to 30 tonnes of stuff per hectare and not have there be an impact. I don’t know what that impact is, but to me, neither the company nor the government has asked that question and investigated it.

Click here for an interactive illustration