The potential of the mesopelagic zone (200–1000 m depth) to provide natural resources and ecosystem services is of increasing interest to a broad range of societal stakeholders. As this interest grows, divergent ideas about its current and future role in supporting human life are being expressed in scientific and public discourse. We use automated content analysis to identify 13 key topics about the mesopelagic zone from 2226 scientific abstracts and 4066 tweets. Two dominant ideas emerge: (1) the exploitation of fish resources and (2) the role of the mesopelagic zone as a carbon sink. We find that, in the absence of significant mesopelagic zone policy, science plays a de facto governing role by shaping how the ecosystem is known to the public and policymakers alike. These results indicate the need and potential for new knowledge and governance arrangements that can broaden the range of meanings and knowledge needed to anticipate future uses of deeply uncertain ecosystems and resources.