Karina Arzuyan
BIOL354 – Section #, Group #
Ecological challenge: Invasive Species
The presence of the invasive alga Sargassum horneri on the southern California coast
Introduction/Background
● Native habitat in Japan, first discovery on eastern Pacific coast in 2007 (Miller et al.
2007)
● Physiological features of S. horneri (Choi et al. 2007)
Subtopic 1: S. horneri distribution
● Habitat distribution from central CA coast to Baja California (Cruz-Trejo et al. 2015)
● Presence in kelp forest and intertidal zones (Marks et al. 2017)
Subtopic 2: Potential for S. horneri removal via herbivory/grazing
● S. horneri palatability for herbivores (Kaplanis et al. 2020)
● Potential for S. horneri control via grazing pressure (Marks et al. 2020)
Subtopic 3: Effects S. horneri has on kelp forest organisms.
● Neutral effects on organisms (Ginther & Steele 2020)
● Potential negative effects on organisms (Sullaway 2017)
Discussion/Conclusion/Future Directions
Sargassum horneri has taken over a massive habitat space in several of California’s most
productive ecosystems fairly recently, and it is important to track the progression of its
ecological capabilities pertaining to control via herbivory and methods to outcompete native
seaweeds for vital nutrients and space. Although menacing at first, it can be concluded that S.
horneri is not a voracious competitor, but more so an organism that can successfully occupy
empty niches and take advantage of abundant resources.
References
Marks, L. M., D. C. Reed, & A.K. Obaza (2017). Assessment of control methods for the invasive
seaweed Sargassum horneri in California, USA.
Ginther, S. C., & M. A. Steele (2020). Limited effects of Sargassum horneri, an invasive alga, on
temperate reef fish assemblages. Marine Ecology Progress Series, 643, 115-131.
Sullaway, G. H. (2017). Assessing the Impact of the Invasive Species, Sargassum horneri, on
Kelp Forest Net Community Production (Doctoral dissertation, San Diego State University).
Cruz-Trejo, G. I., S. E. Ibarra-Obando, L. E. Aguilar-Rosas, M. Poumian-Tapia, & E.
Solana-Arellano (2015). Presence of Sargassum horneri at Todos Santos Bay, Baja California,
Mexico: its effects on the local macroalgae community. American Journal of Plant Sciences,
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Kaplanis, N. J., J. L. Harris, & J. E. Smith (2020). A cross-genus comparison of grazing pressure
by two native marine herbivores on native, non-native naturalized, and non-native invasive
Sargassum macroalgae. Helgoland Marine Research, 74(1), 1-8.
Miller, K. A., J. M. Engle, S. Uwai, & H. Kawai. (2007). First report of the Asian seaweed
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Choi, H. G., K. H. Lee, H. I. Yoo, P. J. Kang, Y. S. Kim, & K. W. Nam. (2007). Physiological
differences in the growth of Sargassum horneri between the germling and adult stages. In
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