We should not have to prove that a marine species is useful to humans before we care about it. That is a narrow way to value the living world. But sometimes usefulness is what makes people look twice.
The ocean is full of organisms that produce powerful chemical compounds. Some use them to defend themselves. Some use them to deter grazers. Some use them to compete for space. Many of these compounds are being investigated for human uses, including pharmaceuticals, antimicrobials, anticancer drugs, cosmetics, agriculture and biotechnology. You can check out a couple of posts that I’ve written that touch on this:
Often, this chemistry comes from species most people would swim straight past without noticing: seaweeds, sponges, soft corals, molluscs, microbes and other small, strange, easily overlooked creatures. One of those species is a red alga called Asparagopsis taxiformis.
We were watching ABC’s Landline programme earlier this week, and there was a segment on Asparagopsis spp., an alga that is being used to reduce methane emissions in cattle. It reminded me of a conversation I’d had with Anna Wilson, a researcher of this alga, two years ago, but more on that later.
Like many red algae, Asparagopsis taxiformis does not have a simple one-body life cycle. It has different stages, and those stages can look so unlike one another that, historically, they were thought to be separate species.
The stage most people are likely to notice is the gametophyte, which is the stage shown in the photograph at the top of this post. This is the more obvious seaweed-looking form – the soft red, feather-duster stage, with plume-like branches. Anna kindly sent me a Field Identification Kit, which can be viewed here.
The other main stage is the sporophyte. It is much less obvious. Instead of looking like a little red seaweed plant, it is made up of fine filaments and can look like reddish-brown cotton wool, turf, or a small pom-pom. When it is attached to the reef, it may be mixed in among other algae and easy to overlook (see the photo, below). When it is dislodged by waves or turbulence, it can float around as a little fluffy ball. This makes it a beautiful little reef oddity.
But back to Asparagopsis and cattle methane.
The popular version is that it can make cows ‘fart-free’, which sounds catchy, but isn’t quite right. Most methane from cattle comes out through burping, not farting, because it is produced during fermentation in the rumen. Whatever the exit point, it has been found that small amounts of Asparagopsis in feed can substantially reduce the methane released by ruminant livestock.
The key compound is bromoform, a naturally occurring chemical produced by the alga. In the rumen, methane-producing microbes use hydrogen and carbon dioxide to form methane. Bromoform interferes with that process, reducing how much methane is produced before it leaves the animal.
Trials with beef cattle have shown large reductions in methane when Asparagopsis taxiformis is included in feed. ABC’s Landline has followed the Australian asparagopsis story for several years, from early commercial promise to the recent sale of lower-methane beef in South Australia.
So here we have a red seaweed, growing in the ocean, now being used to change the emissions profile of cattle on land, which I find quite extraordinary.
But it also needs to be kept in proportion. This is not magic seaweed powder. The active compound has to be present at the right level. The seaweed has to be grown, harvested, processed, stored and delivered properly. The dose has to work for the animal and the farming system. There are also valid questions about scale, residues, regulation, animal health, occupational safety and long-term monitoring.
Here is how Norfolk Island entered the story, albeit in a very minor way. I was contacted by Anna Wilson, a researcher working on this species, about an image of mine that she’d seen on Instagram. (see also my blog post Free Weed!) She was wanting more information about where I’d seen it and when. She was trying to piece together where it occurred, when different life stages appeared, and whether local populations might differ genetically.
So while we know it occurs here, Norfolk Island was not ultimately included in her sampling because of the familiar realities of cost, access and permits. But the exchange stayed with me.
Asparagopsis taxiformis hidden among other algae in its natural habitat, Norfolk Island
The Asparagopsis taxiformis specimen is circled in black (top right)
That is one of the strengths of repeated local observation. A single image may not answer a research question on its own. Dated photographs, taken over months and years, can show presence, seasonality, life stage and habitat.
Which brings me to a bigger point. Every species on the reef has its own place, whether or not we understand it. Most will not become a cattle supplement, a medicine or a commercial product. But then they don’t, or shouldn’t, need to earn their place by being economically useful to us.
But as a feathery red seaweed has shown, sometimes the smallest things on the reef are carrying stories much bigger than we realise.