Digital SAT Reading and Writing Practice Question #601

In the 1980s, oceanographer John Martin proposed the 'Iron Hypothesis,' suggesting that artificially seeding the ocean with iron would stimulate massive phytoplankton blooms. Because phytoplankton consume carbon dioxide during photosynthesis, Martin argued this process could draw immense quantities of CO2 out of the atmosphere and safely sequester it in the deep ocean (the bathypelagic zone) when the organisms died and sank. However, many contemporary marine biogeochemists remain highly skeptical of iron fertilization as a viable climate change mitigation strategy. They argue that the vast majority of the carbon absorbed by these artificial blooms is ultimately remineralized long before it reaches the deep ocean. Which finding, if true, would most directly support the biogeochemists' skepticism regarding Martin's hypothesis?