However, when nutrients were added, macroalgal biomass was not significantly different across all herbivore treatments, which suggests reduced top-down control of herbivores (hence a greater standing algal biomass) in open areas. During the cool season, macroalgal biomass was significantly higher in herbivore exclusions than in open areas under ambient nutrient conditions. However, we found different interactive effects of nutrients and macro-herbivores between the two seasons. Excluding macro-herbivores had a clear effect on standing macroalgal biomass, independent of season or nutrient availability. We manipulated nutrient availability and herbivory in field experiments performed in two seasons: the first during a cool, upwelling season, and the second during a warm, non-upwelling season. We assessed the effects of nutrient availability, temperature, and herbivory on macroalgal biomass on a subtidal nearshore rocky reef in the Galápagos Islands. For example, herbivory and temperature, via their effects on primary producers and the metabolic demands of consumers, can also influence macroalgal biomass and productivity, respectively. However, other factors can strongly impact macroalgal communities. Increased standing macroalgal biomass in upwelling zones is generally assumed to be the result of higher nutrient flux due to upwelled waters. 4The Department of Biology, Boston University, Boston, MA, United States.3The Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.2Galapagos Science Center GSC, Universidad San Francisco de Quito USFQ & University of North Carolina at Chapel Hill UNC, Puerto Baquerizo Moreno, Galápagos, Ecuador.
1Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador.Margarita Brandt 1,2*, Isabel Silva-Romero 2,3, David Fernández-Garnica 2, Esteban Agudo-Adriani 2,3, Colleen B.
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