In the shallow waters of Monterey Bay, giant kelp sway gently in the ocean currents. Pristine water conditions allow it to thrive as the base of the kelp forest ecosystem, an iconic and critically important feature of the California coast. The newest research and climate models show these forests shrinking rapidly as the ocean warms and ideal chemical conditions are disrupted. 

These impacts of climate change were addressed in the most recent Kraw Lecture Series event “Forecasting the Future of a Changing Ocean.” The lectures are a selection of virtual discussions with UC Santa Cruz professors and other members of the scientific community that cover topics such as climate change, medicine, and chemistry.

In the lecture, UCSC professors Raphael Kudela and Kristy Kroeker elaborated on the impacts of climate change on California’s kelp forests and pinto abalone in Alaska. Ecosystems such as the kelp forests are critical to preserving biodiversity and mitigating global warming through carbon dioxide absorption. Pinto abalone is culturally significant to several Indigenous nations and its population decrease has changed the ways in which traditional knowledge is used and practiced. 

Climate change and algae blooms 

Ocean studies professor Raphael Kudela is a phytoplankton ecologist. He researches the causes of toxic algae blooms, massive swells of harmful plankton that poison marine life. 

“As algae blooms increase, we’ve lost all of that biodiversity and all the wonderful things that kelp does for us, including pulling down carbon dioxide and helping to mitigate climate change.”

Kudela’s most recent research concerns marine heat waves, which have increased in frequency since 2014. He has been working in collaboration with several agencies including the National Oceans and Atmospheric Agency and the Central and Northern California Ocean Observation System to catalogue changing ocean conditions and the places where algae blooms occur. 

Kudela explained toxic algae require specific conditions to grow, and temperature is a major factor. The chemical domoic acid is produced by a prolific strain of toxic algae called alexandrium monilatum; when produced in high enough concentrations, the acid damages kelp forests. Recent warmer temperatures along California’s coast are ideal for this species.

“Humboldt Bay is a new toxin hotspot. It appeared after the marine heat waves, and it’s still persistent. We can attribute this to climate change,” Kudela said. “Temperature combined with biology is keeping our iconic kelp forests from recovering.”

Acid Levels in the Ocean

Ecology and evolutionary biology professor Kristy Kroeker studies the impacts of ocean acidity and works to mitigate these impacts as a UC climate action champion and as part of the UCSC Coastal Sustainability office. 

Ocean acidity levels determine the health of the global ocean ecosystem. In her lecture, Kroeker explained how high acid levels resulting from increased carbon in the atmosphere prevent animals from developing strong shells and limit kelp photosynthesis. Kelp forests can help mitigate the amount of carbon absorbed by the coastal waters, and the disappearance of giant kelp has worsened the problem.

One organism affected by ocean acidity is the pinto abalone, a culturally significant shellfish found from northern California to southeast Alaska. Several Indigenous nations along the California coast historically included abalone in all aspects of their lives, but the drastic decrease in the abalone population has heavily impacted the ways in which abalone can be used. 

Kroeker’s research seeks to understand why pinto abalone are disappearing so rapidly. She conducted an experiment to determine how much energy the shellfish need to grow and develop their shells during the summer and the winter. Kroeker found that high acidity levels increased the energy abalone needed to survive in the winter, when there is less food. 

“When we limited their diet to what was ecologically realistic in the winter, we found that they were losing mass,”Kroeker said. “Their populations are very vulnerable to what might be happening in the future.”