In order to assess the relationship between sea otter population and the abundance of kelp forests, researchers conducted surveys in Alaska, comparing the densities of kelp forests in areas with a large sea otter population and areas with a small sea otter population. At several different sites lining the Alaskan coast, the density of kelp forests were measured by a scuba diver counting the amounts of kelp in specific sectioned off areas, with varying sea otter populations that were calculated in previous experiments.
The experiment concluded with results that showed that the decrease in kelp forests coincided with the decrease in sea otter population. Kelp density varied strikingly between areas with an abundance of sea otters in comparison to areas with a lower abundance, suggesting that the presence of sea otters protected the surrounding kelp forests and encouraged their propagation.
Estes, J., & Duggins, D. (1995). Sea Otters and Kelp Forests in Alaska: Generality and Variation in a Community Ecological Paradigm. Ecological Monographs, 65(1), 75-100. doi:10.2307/2937159
