Experimental and comparative methods have been referred to as “the two great methods of science” (Mayr, 1982). To reach valid scientific conclusions, the processes of interest should be studied through repeated investigations, preferably over a range of differing conditions. The most direct way to accomplish this is the experimental method, wherein controls are imposed that allow the scientist to systematically vary conditions of interest while holding other factors constant. Marine ecosystems, however, are not amenable to experimental control. One way to address this shortcoming is through the comparative method (Mayr, 1982), which allows the processes of interest to be examined on repeated occasions using naturally occurring temporal and spatial variations in existing conditions and phenomena. In this case, the range of natural variability in conditions and mechanisms substitute for controlled experimental treatments.

Anderson, D.M., G.C. Pitcher, and M. Estrada. 2005. The comparative “systems” approach to HAB research. Oceanography 18(2):148–157, https://doi.org/10.5670/oceanog.2005.50.

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