In 2014, National Science Foundation graduate research fellow Jordan Hollarsmith, was living on the California coast when a marine heat wave hit. While Southern California experiences high ocean temperatures, those high temperatures are unusual for Northern California. Beside the massive marine heat wave itself, something curious happened: much of the giant kelp in the north died, while the kelp in the south survived.
Giant kelp (as well as other kelp species) are an important part of the marine environment as they provide food and shelter to other organisms and marine life. Hollarsmith was curious as to why the same species of kelp responded differently during the marine heat wave and what this could mean for the future of giant kelp.
Hollarsmith and co-authors decided to examine the reproductive success of different giant kelp populations in Southern and Northern California as well as Chile by exposing them to varying temperature and pH levels in a laboratory environment.
The researchers exposed kelp from each of the three regions to temperatures between 50 to 68 F. Results indicated that the kelp populations of northern California and Chile (which have similar climates) suffered in the heat and completely failed to reproduce. The southern California kelp, however, thrived and were able to complete their reproductive lifecycles.
The researchers also studied the effect of differing pH levels on the kelp populations. They found that their hypothesis on low pH negatively affecting the kelp population was incorrect. In fact, pH levels seem to have no effect on any of the kelp populations, which was good news to the researchers
"This study gave me hope,” Hollarsmith said. “The fact that ocean acidification was not negatively affecting them, and that some populations still completed their life cycles in warm, 68-degree temperatures shows that at least some populations are quite resistant. That knowledge can help move us forward."
While the researchers aren’t sure why low pH didn’t affect the kelp, they have a few ideas involving carbon dioxide and plant flowering that may hold the answer. Further studies are on the horizon.
Photo: Jose Luis Kappes prepares to enter a dense Chilean kelp bed to collect reproductive fronds. Courtesy of Jordan Hollarsmith/UC Davis