Scientists seek to understand underwater forests

Kelp forests are known to stretch under the sea for several miles with towering vegetation, thick canopies and abundant wildlife

May 10, 1999
Web posted at: 3:00 PM EDT

Off the coast of San Diego, California, scientists are exploring vast forest communities through the lens of a diving mask. The scientists are looking for clues to help them understand the impacts of large-scale oceanographic processes, such as El Niño and La Niña, on kelp forest communities.

Researchers from the Scripps Institution of Oceanography at the University of California San Diego have been investigating the ebb and flow of the Point Loma kelp forests community, one of the largest of these underwater forests, for 30 years.

The goal of their research is to evaluate the roles of large-scale, low-frequency oceanographic processes on the size, density, distribution and other vital statistics of the area's most conspicuous species of kelp. These processes range from seasonal climate variability to episodic nutrient-rich La Niñas and nutrient-poor El Niños.

By repeating experiments over an extended period of time and in different areas, the researchers were able to observe certain changes within the kelp forests that occur from shifts in nutrients and temperature.

For instance, the researchers state that in one of the studies, Macrocystis species were not affected by competitive effects from other species of kelp. On the other hand, Pterygophora californica, an important understory species, exhibited reduced growth and reproduction by the light-limited conditions and competition with Macrocystis during La Niña periods when Macrocystis thrived. When El Niño conditions led to poor Macrocystis growth, the understory kelps did much better.

"By doing small scale experiments over large scales, researchers can gain a much more realistic understanding of oceanic ecosystems," says marine ecologist Paul Dayton from UCSD.

Through their research, Dayton and his colleagues have concluded that the most lasting effects on the kelp communities were the result of very large-scale, low-frequency events, such as the El Niño and especially the La Niña phenomena.

"Statistics analyzing small-scale experiments can give the illusion of power, but our study shows that they might lack generality because very different patterns appear over larger scales," concludes Dayton.

More can be found on the research in the May issue of Ecological Monographs published by the Ecological Society of America.

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