Jordan Hollarsmith and Michael Doane collecting reproductive fronds from a San Diego kelp forest. (Photo: Jordan Hollarsmith)

Climate change may impact kelp’s ability to reproduce

November 21, 2019

Marine heat waves may be impacting one of the ocean’s major sources of food and shelter for sea life—kelp.

A recent study by SFU post-doctoral student Jordan Hollarsmith published in the Journal of Experimental Marine Biology and Ecology examined how giant kelp respond to increasingly warm and acidic oceans. Researchers found that in lab settings, high-latitude kelp completely failed to reproduce when stressed by heat.

Hollarsmith, who undertook the research as a graduate student at UC Davis, is now applying her expertise at Simon Fraser University, where she is working with biology chair and professor Isabelle Coté on strategies for managing stressors on kelp in the Salish Sea off B.C.’s southern coast. The researchers are bringing together various experts on local kelp, from scientists to First Nations groups, and will also work to determine what management actions might mitigate similar impacts on Salish Sea kelp.

A microscopic kelp forest composed of early life stages. (Photo: Jordan Hollarsmith)

“Ecologically speaking, kelp habitats up and down the Pacific coast are important as they form habitats for many different species,” says Hollarsmith. “These species are critical not only as food sources for other species, but for various industries including fisheries and even tourism.”

Hollarsmith’s initial research grew from her interest in how giant kelp responded to a 2014 marine heat wave that brought higher ocean temperatures to much of the northeast Pacific Ocean. Though anomalously high for higher latitudes, these temperatures were fairly normal for the Southern California Bight. Her investigation focused on why much of the northern kelp died while the southern kelp survived.

Her team examined giant kelp populations in both regions, as well as further south around Chile, by exposing the kelp to various temperatures and pH levels in a lab setting. They carried out their research at the UC Davis Bodega Marine Lab and at the Universidad de Los Lagos Instituto Marino (Puerto Montt, Chile). 

A diver ready to enter the dense Chilean kelp bed to collect reproductive fronds. (Photo: Jordan Hollarsmith)

“We found more resistance to elevated temperatures, with developmental failure in the early stages among high-latitude and Chilean populations, suggesting a greater vulnerability to climate-warming events,” she says.

She hopes the results will help to enhance our ability to predict how projected declines in ocean pH and increases in ocean temperature might trigger population extinctions and ecosystem range shifts.

Fishing boats on a beach in southern Chile. (Photo: Jordan Hollarsmith)