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Teeming with life and covering approximately 30% of the world's coastlines, kelp forests are some of the most productive and biodiverse marine ecosystems in the world. With cool temperatures, high nutrient levels, constant wave motion, and a rocky seafloor, California coasts are perfectly suited to host these unique forests.
All kinds of organisms benefit from California kelp forests, living amongst the kelp for protection against predators, camouflage, and food. Sea otters, for example, hunt for purple urchins, clams, and other shellfish feeding along the forest floor. Additionally, when mother otters go hunting, they will 'anchor' their pups using kelp fronds at the ocean surface to prevent their children from floating away - a unique example of a service that the forest provides for one of its inhabitants. Many types of fish also call the kelp forests home: sardines, bass, rockfish and sculpin, to name a few. Naturally, with so much prey, there are also hungry predators: namely, harbor seals, elephant seals, and sea lions. To defend themselves from these numerous predators, these fish have many unique adaptations and behaviors. Some fish find safety in numbers, others seek shelter amongst tangled kelp holdfasts, while yet others practically 'disappear,' camouflaging themselves near perfectly with the swaying kelp blades that surround them.
Not only do the organisms that make up these beautiful ecosystems benefit from kelp forests, humans do too! Some of the most well known and highly protected kelp forest ecosystems flourish in California's Monterey Bay National Marine Sanctuary, where visitors can dive and forage (with a fishing license) in the forests, watch sea otters and sea lions play on the water's surface, and visit the iconic Monterey Bay Aquarium.
Species Highlights
Our Dying Forests
Sea Star Wasting Syndrome (SSWS)
Ochre Sea Star with SSWS - Duxbury Reef SMCA, Marin County, CA (June 2023)
Starting around 2013, sea stars along the eastern Pacific coast started rapidly dying off due to a widely spreading disease called sea star wasting syndrome (Konar et. al. 2019). Sea stars with this disease appear anywhere from deformed to disintegrated, seemingly melting into nothing but an organic mass. It seems that this disease is highly contagious, with its impact on sea star populations being exacerbated by warming waters due to climate change. While much remains unknown about SSWS, its impact on sea star populations and their individuals is beyond obvious.
Because of the SSWS epidemic, populations of sunflower sea stars (Pycnopodia helianthoides), a keystone species of kelp forest ecosystems, have plummeted, causing this species to become critically endangered along the western North American coast. In fact, in California, the species was thought to be locally extinct since the epidemic took hold until one individual was miraculously discovered in November 2021 (MARINe 2023). Since then, local sunflower star populations have improved slowly, but are still significantly lower than before the SSWS outbreak.
Urchin Barrens
Sunflower stars provide an important service in preserving kelp forest ecosystems: they are one of the top predators of purple sea urchins, a key player in keeping urchin populations at bay. However, with so few sunflower stars remaining due to SSWS, urchin populations have skyrocketed. These voracious herbivores have become so abundant that they're literally overrunning entire kelp forests. The severe urchin overpopulation means not only are the urchins eating and killing the kelps themselves, but because of the disappearing shelter and camouflage that kelp forests typically provide, all the organisms that live amongst and within these kelps are either dying off or seeking shelter elsewhere.
Now, flourishing and expansive kelp forest landscapes are effectively being replaced by urchin barrens: a desolate underwater desert of spikey purple urchins carpeting otherwise deep blue emptiness as far as the eye can see.
Beyond Biodiversity: Why Conservation Matters
(Christensen et. al. 2023)
1) Economic Significance
Besides food, kelp, which has indeed become increasingly popular for its numerous health benefits, is also being commercially farmed and harvested for aquaculture feed, bioplastics, and biofuel. With the growing climate crisis, kelps and other microalgae are at the frontlines of research for renewable and more sustainable (both environmentally and economically) alternatives to the destructive plastics and fossil fuel emissions that our economy currently runs on.
2) Coastal Protection
Not only do kelp forests directly support many diverse marine life, but they also have direct impact on the stability of our coasts, including beaches and coastal towns. These forests act as natural protection for shorelines - a physical barrier of sorts - by significantly decreasing the size and impact of tidal waves when they crash on shores. This helps prevent excessive coastal erosion and preserve our coastlines.
3) Curbing Ocean Acidification
Ocean acidification is the result of excess carbon dioxide in the ocean reacting with the surrounding water. This has many negative impacts on organisms in the ocean, including disintegrating the calcified shells and exoskeletons of marine invertebrates, and killing off many soft-bodied organisms that are sensitive to pH changes in the water. Through the process of photosynthesis, kelp can help curb the effects of ocean acidification by absorbing some of the excess carbon and storing it as biomass.
4) Carbon Cycle
Like many other photosynthesizers, kelps are crucial in moving carbon from the short-term carbon cycle into the long-term carbon cycle. More specifically, this means that through photosynthesis, kelp can take inorganic carbons, including carbon dioxide, out of the ocean and atmosphere (short-term sinks) and convert it into organic carbon as biomass. When the kelp dies, organic carbon from the kelp sinks to the ocean floor, and over thousands of years, turns into fossil fuels embedded deep in the Earth (a long-term sink).
Sources
Multi-Agency Rocky Intertidal Network (MARINe). (2023). "SSWS Updates". Regents of the University of California, https://marine.ucsc.edu/data-products/sea-star-wasting/updates.html. Accessed 02 August 2023.
Christensen, S., Potouroglou, M., and Pedder, K. (2023). "What Is Kelp and Why Is it Vital to People and the Planet?". World Resources Institute, https://www.wri.org/insights/what-kelp-forests-protect.
Konar, B., Mitchell, T.J., Iken, K., Coletti, H., Dean, T., Esler, D., Lindeberg, M., Pister, B., and Weitzman, B. (2019). "Wasting disease and static environmental variables drive sea star assemblages in the Northern Gulf of Alaska". Journal of Experimental Marine Biology and Ecology, 520, pp. 151-209. https://doi.org/10.1016/j.jembe.2019.151209.
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