Luc's research explored the impact of the invasive dense-flowered cordgrass (<em>Spartina densiflora</em>) on the primary productivity of a Humboldt Bay (California) salt marsh using above and belowground biomass measurements coupled with paired closed-chamber carbon dioxide flux measurements. Although samples dominated by <em>S. densiflora</em> displayed higher aboveground net primary productivity compared to samples dominated by native vegetation, samples dominated by <em>S. densiflora</em> also displayed lower belowground net primary productivity, net primary productivity, and net ecosystem exchange measurements compared to samples dominated by native vegetation; therefore, <em>S. densiflora</em> colonization reduced primary productivity. In plots dominated by <em>S. densiflora</em>, less benthic macroalgae was present and less photosynthetically active radiation reached the substratum. Therefore, increased shading of the sediment surface in plots dominated by <em>S. densiflora</em> contributed to lower net ecosystem exchange measurements. Luc's research contributed to understanding the impact of <em>S. densiflora</em> on the primary productivity of Humboldt Bay salt marsh ecosystems.