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Marine Ecology Progress Series

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MEPS 429:1-17 (2011)  -  DOI:

Environmental controls of giant-kelp biomass in the Santa Barbara Channel, California

Kyle C. Cavanaugh1,*, David A. Siegel1,2, Daniel C. Reed3, Philip E. Dennison4

1Earth Research Institute, 2Department of Geography, and 3Marine Science Institute, University of California, Santa Barbara, California 93106, USA
4Department of Geography, University of Utah, Salt Lake City, Utah 84112, USA

ABSTRACT: Synthesizing long-term observations at multiple scales is vital for understanding the environmental drivers of ecosystem dynamics. We assessed the role of several environmental drivers in explaining temporal and spatial patterns in the abundance of giant kelp Macrocystis pyrifera in the Santa Barbara Channel between 1984 and 2009. We developed a novel method for estimating the canopy biomass of giant kelp from Landsat 5 Thematic Mapper satellite imagery, which allowed us to examine the dynamics of giant-kelp biomass on spatial scales ranging from 100s of m2 to 100s of km2 and temporal scales ranging from several weeks to 25 yr. Comparisons of changes in canopy biomass with oceanographic and climatic data revealed that winter losses of regional kelp canopy biomass were positively correlated with significant wave height (r2 = 0.50), while spring recoveries were negatively correlated with sea surface temperature (r2 = 0.30; used as a proxy for nutrient availability). On interannual timescales, regional kelp-canopy biomass lagged the variations in wave heights, sea surface temperatures, and the North Pacific Gyre Oscillation index by 3 yr, indicating that these factors affect cycles of kelp recruitment and mortality. Results from cluster analysis showed that the response of kelp biomass to environmental conditions varied among different subregions of the Santa Barbara Channel. The dynamics of kelp biomass in exposed regions were related to wave disturbance, while kelp dynamics in sheltered regions tracked sea surface temperatures more closely. These results depict a high level of regional heterogeneity in the biomass dynamics of this important foundation species.

KEY WORDS: Ecological succession · Marine phytoplankton · Competition · Nutrient perturbation · Domain shift · Ocean turbulence · Climate change

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Cite this article as: Cavanaugh KC, Siegel DA, Reed DC, Dennison PE (2011) Environmental controls of giant-kelp biomass in the Santa Barbara Channel, California. Mar Ecol Prog Ser 429:1-17.

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