Like most aquatic vegetation, kelp is being negatively impacted by climate change and warming ocean temperatures have led to shorter growing and harvesting seasons, including for sugar kelp – one of the most commonly farmed kelp species.

Already we have seen how the loss of kelp populations can negatively impact ecosystems, throwing biodiversity into crisis. But its loss could also have a potential impact on the economy, too – particularly within the nascent sustainability sector where kelp has become an innovative new source for farming food, feed, fertiliser, and even medicine and cosmetics.

To give kelp a chance against climate change then, scientists from the Woods Hole Oceanographic Institution (WHOI) have identified kelp species with natural adaptations to cope with this heat. It’s all laid bare in a new study – published in the Journal of Applied Phycology – in which WHOI experts single out the new kelp strain that could just prove to be more resilient in warmer waters.

“There is genetic diversity among sugar kelp populations, so it’s likely that some kelp may already have useful adaptations to cope with warmer temperatures,” said Sara Gonzalez, a guest investigator in WHOI’s Applied Physics and Ocean Engineering Department, and lead author of the study.

To identify this kelp strain, Gonzalez and her team first assessed the heat tolerance of kelp gametophytes, the microscopic male and female stages (of the sexual phase) in the life cycle of plants and algae, that fertilise and produce kelp blades.

These gametophytes were isolated from 14 different populations collected from nearshore waters between New York and Maine. These were grown in a lab environment for four and a half years before they were tested for their tolerance to temperatures as high as 24°C.

In the second round of research, gametophytes that were more heat tolerant were crossbred with other, more heat tolerant strains. At the same time, strains with lower heat tolerance were also crossbred. Researchers then tested the heat resistance of their offspring (those aforementioned kelp blades) in a controlled environment.

“We found that when we crossed gametophytes that we identified as heat-tolerant, they produced kelp blades that grew better under heat stress compared to the offspring of gametophytes that were not heat tolerant,” said Gonzalez. 

“This is an important step towards understanding how to breed heat-tolerant kelp and helping kelp farmers increase reliability in their yields in warming ocean waters.”

This study area focused on strains found in the Northeastern US, where kelp beds are declining and, in some cases, are no longer growing. This is particularly important to note in the Gulf of Maine, which is the fastest-warming body of water in the world.

It’s here that productive kelp farms play a role in the fight against global warming by acting as a carbon sink through sucking up carbon dioxide from the ocean. Kelp has also been found to elevate pH levels in their immediate surroundings and supply oxygen to help mitigate the local effects of ocean acidification.

“Kelp is incredibly versatile. It can also be converted into new fuel sources and can potentially reduce greenhouse gases and our dependence on fossil fuels,” said WHOI’s Scott Lindell, a research specialist in aquaculture technology and co-author of the study.

“In a hotter and drier world of the future, it will be hard to find a better resource for biofuels than farmed seaweed. This study allows us to accelerate the breeding of heat-tolerant kelp strains, thus helping sustain the industry.”

It’s Lindell’s belief that future research in this area could address whether one kelp parent transfers more heat tolerance to their offspring than the other. 

“A larger sample size and further work could also show which part of the kelp gene is related to heat tolerance,” he concluded. 

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