A recent study by researchers at UC Santa Barbara found that long-term ocean warming is decreasing the nutritional value of kelp.
Heili Lowman is the lead study and postdoctoral fellow at the University of Nevada, Reno. She did this research while doing her PhD. Student at UCSB.
Lowman said her team found that the nutritional quality of kelp in the Santa Barbara Channel decreased over time as temperatures rose steadily. In particular, the nitrogen content has decreased by 18 percent over the past 19 years.
Lowman said researchers have known for years that there are seasonal variations in the nitrogen content of giant kelp. But these long-term data show a decade-long steady decline.
Lowman called this a hidden effect of climate change.
“We think about how the nitrogen is present in the surrounding seawater, how the seaweed uses it to grow and multiply and finally how this seaweed feeds other populations such as abalons and sea urchins in the ocean, which form the basis of several productive fisheries” said Lowman.
She said this is cascading as giant kelp is a major food source for the inshore fisheries catch. Industries could see economic repercussions if the seaweed diet continues to decline.
Mammals and shorebirds also depend on giant kelp to survive.
Lowman said there is still a lot of work to be done regarding giant kelp and rising sea temperatures.
“Seaweed is resilient in many ways, so we may not yet know how it adapts to warming seawater,” Lowman said.
Kyle Emery is the study co-author and current Ph.D. Student at UCSB. Much of his research focuses on seaweed washing ashore and its effects on the stability of sandy beach ecosystems.
He said the nutritional decline of seaweed isn’t necessarily permanent. He said he hoped this research can serve as a motivation to reflect on how we will address broader climate issues in the future.
“In our region, despite the warming of the water, the seaweed has not disappeared like in other parts of the world,” said Emery and in those places where seaweed ends up. “
Emery says there isn’t a lot of long-term seaweed nutritional data around the world, so it’s hard to say if coastal environments have similar effects everywhere.
