Causality

Kelps thrive in cool, clear, and nutrient-rich water. They face an array of environmental stressors that challenge their resilience and survival.

Temperature fluctuations, exacerbated by climate change disrupt their delicate balance, as warmer waters can induce bleaching and hinder growth.

Grazers, from sea urchins to certain fish species, feed on kelp and can hinder kelp recovery after substantial losses.

Light availability, essential for photosynthesis, can be compromised by sedimentation, competition with phytoplankton, or shading from anthropogenic structures, diminishing kelp productivity.

Pollution, ranging from nutrient runoff to oil spills, contaminates their habitat, impeding growth and threatening their health. These stressors manifest differentially along the West Coast. Climate change amplifies these stressors, intensifying storms and altering ocean chemistry, further jeopardizing the stability of kelp ecosystems. In the face of such challenges, understanding and mitigating these stressors are crucial for safeguarding the future of these vital marine organisms and the ecosystems they support.

For the entire West Coast, kelp’s worst year on record coincided with a strong El Niño event. During El Niño, warmer waters prevail in the eastern Pacific Ocean, altering the distribution of nutrients and affecting primary productivity. Kelp, which relies on nutrient-rich waters for growth, may suffer as nutrient concentrations decrease due to altered ocean currents and upwelling patterns.

Additionally, the warmer temperatures associated with El Niño can stress kelp populations, potentially leading to reduced growth rates or even mortality in extreme cases. Furthermore, El Niño can influence weather patterns, leading to altered precipitation and storm intensity, which may indirectly impact kelp habitats through increased sedimentation or physical damage from storm events.

In 2023, kelp forests along the U.S. West Coast faced a mix of challenges and signs of recovery. The greatest recent losses have been observed along northern California, where more than 95% of bull kelp canopy was lost from 2014-2019 due to a “perfect storm” of a marine heat wave combined with the decimation of sea stars due to Sea Star Wasting Syndrome and an explosion in kelp-eating purple sea urchin populations. Kelp recovery in northern California remains low. Overall, while challenges persist, there are ongoing efforts to understand and address the complex dynamics affecting kelp ecosystems along the U.S. West Coast. These efforts include, for example, sea urchin removal programs and marine protected areas, which have shown some success in promoting kelp recovery in certain regions.

Photo Credits: Tristin McHugh and Pike Spector