When biologist Dr Cayne Layton first scuba-dived in a giant kelp forest, he says the overwhelming impression was one of feeling very small, dwarfed by kelp that grew to 30 metres above him. “It was a sobering kind of reality check,” he says. “And there was something about the way the light shone through that makes it such a special environment. It makes you slow down.’
That was in Fortescue Bay on the Tasman Peninsula, where he was on holiday from the mainland. The year was 2010. Less than three years later he returned to take up a PhD in marine science and, on revisiting the same site for his studies, found the dense forests of giant kelp gone. There were some stragglers, but within 18 months of field work, even these had vanished. The marine forests that had so moved him five years before were no more.
Fortescue Bay is not an isolated case. Since the 1960s, it is estimated that 95 per cent of giant kelp along Tasmania’s east coast has died, largely due to warming seas. Giant kelp has also been lost off California.
It is little wonder a research project to restore giant kelp to sites where it once reigned supreme has become a more recent passion for Layton. The project aims to locate warm-tolerant families of wild giant kelp among the remnant populations, grow them in the laboratory and replant them on reefs where the species once thrived.
The kelp restoration project is a collaboration between the Institute for Marine and Antarctic Studies (IMAS), the Climate Foundation, the National Environmental Science Program (NESP) Marine Biodiversity Hub and salmon farmer, Huon Aquaculture. Senior leader of the project, Professor Craig Johnson, of IMAS, says early results are promising.
In an exciting spin-off, crosses that include the warm-tolerant kelp identified in the study have been “planted” adjacent to salmon pens in trials that will potentially provide both environmental and commercial benefits in the form of giant kelp mariculture (marine culture).
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For many Tasmanians, seeing vast ribbons of giant kelp (Macrocystis pyrifera) washed up on beaches, or bobbing in the waters off rock platforms to be avoided by passing boats, is still a recent memory. So recent, the sudden demise of the iconic species has come as something of a shock.
The dramatic decline has seen giant kelp become the first marine community to be listed as endangered in Australia under the federal government’s Environment Protection and Biodiversity Conservation (EPBC) Act. So what went wrong?
Kelp is key to cool water marine ecosystems globally, with giant kelp supporting biodiversity from the seabed to the canopy, like forests on land. In Tasmania, kelp forests support endemic species, such as the leafy seadragon, as well as commercial fisheries, including rock lobster and abalone, together worth $180 million statewide annually.
“Kelp forests are not only the foundation of the food chain in these ecosystems, but physically they create the habitat, they create that complexity,” Cayne Layton says.
“The losses of giant kelp are primarily associated with changing oceanography, predominantly the increasing influx of the East Australian Current water in eastern Tasmania. The East Australian Current is a warm, nutrient-poor current. As water from that current moves further south due to climate change, it displaces the cooler, nutrient-rich water more characteristic of southern Tasmania.”
The consequences have been large and far-reaching. According to Craig Johnson, “This warmer, nutrient-poor water has proven devastating to giant kelp, with the vast majority of the forests gone from the east coast where it was once abundant, with impacts on habitat and ecotourism operations.”
The 2012 decision to list the giant kelp marine community as endangered under the EPBC Act acknowledged that the key driver of the decline is climate change, with other threats including grazing by invasive sea urchins from New South Wales.
“The sea urchins have extended their range south, transported with the warmer northern waters,” Johnson says.
Addressing climate change and the related expanding urchin population remains key to protecting giant kelp, but replanting giant kelp that is more tolerant of warmer waters is urgent and part of the solution if we are to conserve these important ecosystems, he says.
Layton agrees that the kelp restoration research is “a buying time exercise”.
“Twenty-four degrees Celsius is about the maximum temperature giant kelp can survive at globally. That is, there is an upper limit, so we definitely have to slow climate change and ocean warming.”
And in the meantime? “We’re trying to identify ‘super kelp’ – kelp that naturally exist in the population, that through natural selection and variability are better able to tolerate warmer waters,” Layton says. “These are the ones we will outplant onto reefs where it used to be abundant.”
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Giant kelp – which is not a plant but an algae – has a remarkable reproductive cycle that involves two phases: microscopic and macroscopic.
Spores grow on “leaf” blades at the base of mature kelp. These spores produce male and female microscopic stages, each containing half the reproductive material necessary to make another individual kelp. After fertilisation, a tiny kelp grows inside the female microscopic stage, attached to the seafloor, eventually forming the large or macro phase we know as giant kelp.
Research to date has successfully taken samples of spores from surviving kelp families from Tasmanian east coast sites and produced the microscopic stages in the laboratory at IMAS in Hobart.
These microscopic stages are kept in a type of ‘hibernation’ in low light and at low temperature, until the time is right to allow fertilisation to occur. After fertilisation, the young kelp are tested for temperature tolerance and then grown in the laboratory to 1–2mm in length before being planted in the field.
One of the most exciting discoveries so far is that some of these remnant families are indeed tolerant of warmer water, with a few even surviving at 24°C, higher than expected for Tasmania, and the known global maximum.
“They are not happy at 24 degrees, but we’ve got survivors, which is pretty exciting,” Layton says. Others that were tested survive up to 20 degrees, which was thought to be the likely upper limit for survival in Tasmania.
While culturing kelp in the laboratory uses existing techniques, the selective breeding for restoration is an Australian first. In Layton’s words, “No one else is selecting for and outplanting kelp, or any other seaweed, to be better adapted to their environment.”
“Super kelp” has been planted out at three sites along Tasmania’s east coast: Fortescue Bay, Trumpeter Bay (Bruny Island), and Dover. The Trumpeter Bay site was decided with the assistance of the weetapoona Aboriginal Corporation from Bruny Island.
Cayne Layton summarises the research goals, “We’re hoping to lay a foundation of knowledge to answer the question – is restoration of giant kelp in Tasmania possible, given we’re dealing with the wicked problems of ocean temperatures and changing climate. Can we restore these patches at these three sites?”
Answers to these questions will flow on to potential restoration efforts. It is not yet known whether the planted kelp will successfully reproduce in such a way that the seeded forests become self-sustaining and spread from a patch to a bay or a region, but that is one of the research goals.
And, meanwhile, the microscopic stages of warm-tolerant kelp currently in suspended animation at IMAS are acting as a precious “seed” bank, conserving these strains of kelp should they disappear from the wild.
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A potential offshoot of the research to locate and culture warm-tolerant giant kelp varieties is the possibility of developing a giant kelp mariculture industry in Tasmania. Kelp farming already occurs in Europe and parts of Asia, where harvested kelp is used in products ranging from nutraceuticals and pharmaceuticals, to animal feed and cosmetics. Internationally, the Food and Agriculture Organization estimates the seaweed industry to be worth more than $8.6 billion annually.
With support from the Climate Foundation and Huon Aquaculture, IMAS researchers have planted giant kelp, grown in the laboratory from spores collected in the field, on ropes adjacent to Huon Aquaculture’s salmon pens in Storm Bay in southern Tasmania. In late June 2020, remote cameras revealed that kelp planted seven months before, when it measured just 1mm, had reached several metres in length, much longer than kelp experimentally planted away from the salmon.
Adam Smark, of Huon Aquaculture says, “These results are really encouraging. We hope to see continued strong growth for the trial, and would love to one day see the kelp break the surface again in Storm Bay.”
Fast growth rates are one of the features in giant kelp’s favour. At up to 30–40cm a day, giant kelp is one of the fastest growing organisms on the planet. According to the Climate Foundation’s Sam Harrington, “Marine permaculture and other kelp mariculture have the potential to be a win-win-win for the environment, as the kelp take up carbon during photosynthesis, regenerate ecosystems and absorb nutrients from the salmon pens, cleaning the water while they grow.”
Craig Johnson has another idea in mind, too. Given that rafts of mariculture kelp can be mobile, there is potential to tow them to areas where giant kelp has been lost, so that the adult kelp on the rafts release their spores over depleted reefs, seeding new kelp forests and further boosting the conservation effort.
Dr Katherine Johnson is a science writer and novelist based in Tasmania. She has published in The Conversation, Good Weekend (Sydney Morning Herald) and CSIRO’s ECOS magazine. Her fourth novel, Paris Savages, was released in the UK in July. Visit www.katherineJohnsonauthor.com and connect on social media via @KJohnsonauthor.
