A Lesson from Darwin

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When British naturalist Charles Darwin traveled to the Galapagos Islands in 1835, he took notice of the giant kelp forests ringing the islands. He believed that if those forests were destroyed, a significant number of species would be lost. These underwater ecosystems, Darwin believed, could be even more important than forests on land.Since then, much scientific research has focused on the presence of giant kelp and the range of biodiversity it supports. Many marine biologists think of the world’s biggest alga as the keystone species of its ecosystem, not only in terms of its structure — a huge forestlike environment under the sea — but also in terms of its tremendous productivity in supplying food for the near-shore ecosystem. 
New analysis by UC Santa Barbara researchers has found that the kelp’s structure may be more important than the food it provides. Using over a decade’s worth of data from the Santa Barbara Coastal Long Term Ecological Research project, supported by the National Science Foundation, the investigators examined the effects of kelp on groups of organisms in the kelp forest ecosystem. Their results appear in the journal Proceedings of the Royal Society B.
“We posited that giant kelp fed herbivores in the system and provided structure and habitat for predators, and that it was fed upon by sea urchins and affected the understory communities of algae and sessile invertebrates in the kelp forest,” said lead author Robert Miller, a research biologist in UCSB’s Marine Science Institute (MSI). “We found that the giant kelp affected some of these groups more than others. Predator diversity was increased by it, but understory algae decreased as expected because the giant seaweed shades the bottom and prevents other algal species from doing well. In turn, giant kelp positively affected the sessile invertebrates — sponges and sea squirts — that live on the bottom but can often …

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