The Department of Energy’s (DOE) ARPA-E (Advanced Research Projects Agency – Energy) MARINER (Macroalgae Research Inspiring Novel Energy Resources) program, is developing tools to enable the United States to become a global leader in the production of marine biomass. Primary interest is in the potential for large-scale offshore seaweed cultivation to provide a renewable substrate for biofuel production while decreasing atmospheric carbon and ocean acidification. There is a lack of understanding on how different nutrient sources affect carbon uptake and emissions surrounding the seaweed farm. As part of a MARINER project lead by Ocean Era, Inc. we are attempting to estimate the net carbon impact of three different nutrient sources (ambient surface water, deep sea water upwelling, and artificial fertilization) that could be used to cultivate seaweed commercially. To do this, we will examine the carbon emissions related to the different the nutrient sources and the carbon sequestration potential for different seaweed candidate species that could be cultivated on Ocean Era’s single point mooring system being launched off of the island of Hawaii.