Kelp forest (Flickr: NOAA)

CSUN biologists test giant kelp’s capacity to settle for climate-changed waters

Species everywhere in the world face rising temperatures as carbon pollution changes the global climate. Some, however, may be able to evolve as climate change continues — if they have genetic variation to fuel that adaptive evolution.

Giant kelp, a “foundation species” of the Pacific coast, may be among the species with that adaptive capacity, according to research by CSUN Biology Master’s graduate Melissa Kurman and her thesis advisor Casey terHorst. Their results, published over the summer in the journal Marine Ecology, suggest that individual populations of kelp may lack variation to cope with climate change, but that variation may be present across the species’ range overall.

Kurman and terHorst experimented with the earliest growth-stages of kelp, mobile zoospores that disperse from a parent kelp to settle and attach in a new location, then produce male or female gametes which unite into zygotes that begin development into mature kelp. As with other long-lived species, full-grown kelp is difficult to work with in a laboratory setting. However, the earliest life stages are more tractable, and they’re a critical part of the long life cycle — if kelp zoospores can’t settle and mature in warmer water, populations will decline as older kelp dies off and no new individuals grow up to replace it.

Kurman and terHorst tested zoospores from three populations along the Southern California coast for their ability to settle, mate, and begin maturation in the lab under varying temperatures: 16°C, 20°C, and 22°C. The lowest of those temperatures is close to the average for the southernmost of the three sites; the higher two are beyond the high temperatures at any of the sites. Zoospores from all three sites were less likely to settle, survive, and mature in the warmer temperatures, but the impact was less for spores from the southernmost, hottest site. This suggests, the authors say, that giant kelp may have some capacity to evolve to survive in warming waters — if zoospores can disperse from warmth-tolerant populations to cooler sites where kelp are less warmth-tolerant.

The full paper is available open access on the journal website.

Featured image: A kelp forest (Flickr: NOAA)