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UCSB scientists from the Earth Research Institute and Marine Science Institute recently discovered a new method to analyze fluctuations in giant kelp biomass in the Santa Barbara Channel that enables them to track changes in the kelp populations spatially and temporally.
According to David Siegel, co-author of the kelp report study, giant kelp are crucial to marine ecosystems because of their role in marine systems.
“Giant kelp are the ecosystem engineers of the kelp forest ecosystems,” Siegel said. “These canopy-forming macro algae create habitats for a wide diversity of organisms.”
Giant kelp, also known as Macrocystis pyrifera, can be critically damaged by changes in the climate, especially those resulting in increased storm activity or a reduced supply of nutrients. In an attempt to better understand the effects of the environmental factors on the variations in kelp density and biomass, UCSB researchers have been using underwater divers to gather data from specific kelp plots for over 10 years.
“These plots are roughly 40 meters on a side and this work is very intense. So how can we assess changes in giant kelp populations throughout our region?” Siegel said. “That’s where satellite data comes in.”
The satellite images originally came from the Landsat 5 satellite, which has been in operation since 1984. Until recently, the cost of the images produced by the satellite was prohibitive at $500 per piece. However, in 2009 the satellite images became free to the general public, giving first-time author and UCSB graduate student Kyle Cavanaugh the opportunity to use the images to piece together hundreds of pictures of the giant kelp from the 25-year period between 1984 and 2009.
While previous studies have shown that satellite imaging can accurately depict kelp biomass, this UCSB study is the first to describe kelp density on such a large temporal scale. The numerous pictures from Landsat 5 significantly enhanced the diver data and allowed the scientists to precisely describe alterations in kelp population size.
The scientists found that kelp biomass varied greatly over time, with kelp density both declining and recovering in rapid succession. In light of the results, Siegel emphasized the role of satellite images in helping unearth new information about the changes in giant kelp biomass.
“This [variation] demonstrates how ephemeral these forests are,” Siegel said. “This gives us a much greater understanding of the underlying processes driving giant kelp population variations.”
The satellite data also contributed to the understanding of wave removal and nutrient concentrations as driving factors for the rapid decline and recovery of giant kelp. According to Siegel, satellite images were absolutely necessary to draw these deductions.
The results and the analysis of the study were published in the May 16 issue of Marine Ecology Progress Series. In sum, the continued use of satellite imaging technology in giant kelp research may pave the way for future studies, including colonization analysis of potential habitat patches as well as the role of neighboring patches. Further analysis of offshore kelp forests may aid in the study of metapopulations and reveal the environmental factors that affect population densities, as well as provide information to prevent further ecosystem degradation.