How Does Kelp Pick Its Home?
Meet the algae that help settle the spore.
Kelp starts life as a free-swimming cell called a zoospore. At some point, that zoospore will settle, and there it will spend the rest of its life. Rocky, hard ground will give it the best chance at survival, while softer muddy bottoms could prevent it from growing. No pressure.
It turns out that decision could be aided by another variety of algae, known as coralline (coral-like) red algae. These organisms tend to live in rocky habitats, and therefore settling near them could be a good way for a kelp spore to find a good home.
“If we lose the corallines, the scent of home may go away,” explains Dr. Patrick Martone, a phycologist at UBC. “We know that the oceans are changing, we know that the climate is getting warmer and that the oceans are getting more acidic. So how marine communities are going to respond is a big question.”
Some kelp species are actually expected to benefit from ocean acidification, growing faster with more CO2 in the water. But as with many other marine plants and animals with calcium carbonate in their structures, coralline red algae are facing a gloomier picture, struggling to deposit calcium carbonate and even degrading faster in the acidic water.
“The question is, what happens if we lose the corallines?” says Martone.
Ocean acidification could present an interesting balance, where some kelp species will be growing faster but their spores may not be able to find the best places to settle and grow. Kelp forests could start to shrink even as the plants themselves thrive.
It’s not just kelp spores that like the corallines, either. Many invertebrate species also use some kind of cue from coralline algae to home in on a good place to live.
“Corallines play a central role in the ecology of marine communities,” says Martone. The Hakai Institute’s Calvert Island research station, for example, is home to 53 species of coralline algae among its 280 different algae, including the recently named Bossiella hakaiensis.
Sea urchins, worms, and important commercial species like abalone have all been shown to depend on the corallines to tell their juvenile life stages where to set up shop. The mechanism of how the creatures find the corallines is still up for debate. One experiment found that the signal could be lost by treating the corallines with antibiotics, suggesting that the cue is coming not from the algae themselves but from bacteria living on them.
This problem could be a future research direction for Martone and his lab.
“We have some ideas of field experiments that could test this,” he says. To figure out what the future of kelp forests will look like, he’ll have to understand the tiny plants that live on the rocks below. To understand them, he’ll have to distinguish between 53 nearly identical species by eye.
“In some cases it’s really difficult, and in some cases it’s nearly impossible,” he says.