Report: Marine heat waves threaten Greater Farallones preserve

While human activities such as shipping and fishing affect the ocean's health, climate change is the root cause of the most concerning problems, according to a new study.

Marine heat waves, which are increasing in frequency and intensity along the northern California coast, have caused disruptions among prey and predators and the habitats they rely on, according to a new report.

The Greater Farallones National Marine Sanctuary condition report released Monday says that while human activities on land and sea, including shipping and fishing, do impact the ocean health, climate change is the root cause of the most concerning of problems.

“The marine heat waves affected food in the ocean — where forage fish are, where sea birds eat, where whales eat,” said Maria Brown, superintendent of the Greater Farallones and Cordell Bank National Marine Sanctuaries. “It brought in a concentration of whales closer inshore into the shipping lanes of the San Francisco Bay … putting them in closer contact with human activities.”

That puts the giant marine mammals at greater risk of being struck by vessels or being entangled in fishing gear, Brown said.

“In the changing ocean condition, climate is the biggest impact to our national marine sanctuary, and what is impacting the sanctuary the most is marine heat waves,” Brown said.

The 3,300-square-mile sanctuary expands from southern Mendocino County to San Mateo County. The core of the habitat area is off the coast of Marin and Sonoma counties.

The condition report is a followup to a 2009 assessment. The update explores findings from 2010 through 2022. Overall, the condition of the marine sanctuary ranges between fair, poor and good.

“Overall most of the offshore resources and species were in fairly good condition but the impacts of El Niño and the heat wave were very clear there,” said Jaime Jahncke, director of the California Current Group at Point Blue Conservation Science. The organization is a nonprofit research group that monitors the Farallones and provided data for the report.

“I think a lot of discussions will focus on how to prepare for what the future may bring to make sure that the species that we care for and the prey they rely on are resilient to this area,” he said.

Marine heat waves have become more frequent as the global average sea surface temperatures continues to climb, the report says.

A multi-year heatwave in the north Pacific led to dramatic changes in the sanctuary ecosystem, including a noticeable decline in krill that many predators feed on. That decline led creatures such as humpback whales to seek out forage fish instead, the report says.

Meredith Elliot, principal scientist at Point Blue Conservation Science, was on the research team that provided data for the report. On research cruises, scientists were finding fewer adult krill, and the ones they did find appeared smaller than before.

“That’s alarming,” Elliot said. “With climate change, the marine heat waves are expected to be more severe and more frequent, and, yeah, what is that going to mean for the species that depend on krill?”

The report also highlights the decline of bull kelp forests on the coasts from Marin to Mendocino County by more than 90% since 2014.

The significant decline has been attributed to a combination of factors in the 2010s. A marine heat wave coupled with El Niño weather patterns resulted in unusually warm water, preventing the growth and nutrient availability for the kelp. At the same time, a wasting disease decimated sea stars, allowing sea urchin populations to explode unchecked and devour kelp forests, converting them into urchin barrens.

The loss of kelp in turn depleted the native endangered red abalone population, forcing the closure of the red abalone sport fishery. The fishery is a recreational tourist attraction that brings up to $44 million per year to the local economy, according to the report.

Heat waves have also contributed to harmful algal blooms that poisoned shellfish and fish, disrupting commercial fishing. When phytoplankton bloom, shellfish and fish consume it. Saxitoxin and domoic acid are the biotoxins of concern. While they don’t make fish sick, they can make a person sick if they eat the fish.

The Dungeness crab fishery experienced temporary closures due to domoic acid from 2015 through 2018, the report says.

Richard Ogg, a commercial fisherman and member of the Greater Farallones and Cordell Bank National Marine Sanctuary Advisory Councils, said the impact on the local fishing industry is great.

“Imagine your boss came to you and said, you’re not going to have an income for six months, and maybe in six months you’ll have a job, maybe not,” Ogg said. “That’s what’s happening to us. How do you prepare?”

Ogg said members of the local fishing industry are conservationists who have an interest in a healthy ecosystem.

“What we do is provide sustainable resources to people,” Ogg said. “We’re on the water every opportunity we get because that’s where we make our living and we want to make sure our environment is maintained as pristinely as we can.”

Brown said the findings of the report are expected to be presented to the the Sanctuary Advisory Council next month. Staffers also plan to host community forums this winter to solicit community input.

Jahncke, who also serves on the council, said the condition report is a precursor to a discussion on what to include in a sanctuary management plan update.

“Most of the actions that are being considered are ways to mitigate additional stressors in the face of climate change,” Jahncke said. “There is very little we can do to control temperature; there is very little we can do to reduce overall ocean acidification and change the chemistry in the ocean. But we can mitigate other activities and other direct threats to give time for species to adapt and change.”

The condition report is available at bit.ly/4bWZeMp.