Giant Kelp Stabilizes Coastal Communities Through Biodiversity

Researchers studied 18 years of data from California kelp forests to understand how the stability of giant kelp affects the stability of the diverse community living beneath it. They found that when giant kelp populations are stable, the understory communities are also more stable, primarily because stable kelp supports higher species diversity. Researchers analyzed 18 years of biomass data from 32 plots across 9 rocky reef sites in the Santa Barbara Channel, measuring giant kelp and 114 species of understory algae and sessile invertebrates. They calculated stability as the inverse of variability over time and used mathematical frameworks to understand how species richness, individual species stability, and species asynchrony contribute to overall community stability. The stability of understory communities was positively and indirectly related to giant kelp stability, primarily through kelp's direct positive association with species richness. Community stability was positively related to species richness via increased species stability and species asynchrony. The stabilizing effects of richness were three to four times stronger when algae and invertebrates were considered separately rather than in combination. Competition for shared resources played a more important role in stabilizing the community than differential responses to environmental conditions. The research provides important evidence for how foundation species like giant kelp stabilize entire ecosystems through biodiversity. With increasing threats to structure-forming foundation species worldwide due to climate change and human impacts, understanding these relationships is essential for predicting ecosystem responses and developing conservation strategies for kelp forests.

Citation

Lamy, Thomas; Koenigs, Craig; Holbrook, Sally J.; Miller, Robert J.; Stier, Adrian C.; Reed, Daniel C. (2020). Foundation species promote community stability by increasing diversity in a giant kelp forest. Ecology.

"Competition for shared resources played a more important role in stabilizing the community than differential responses to environmental conditions."

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