New Research Reveals Deep-Sea Fish's Role in Earth's Carbon Cycle

A groundbreaking study conducted by researchers at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science has unveiled significant insights into the carbon cycle, highlighting the crucial role mesopelagic fish, specifically the blackbelly rosefish (Helicolenus dactylopterus), play in ocean chemistry. Published on July 15, 2025, in the Journal of Experimental Biology, this research indicates that these deep-sea fish, which dwell at depths of 350 to 430 meters (1,148 to 1,410 feet), excrete carbonate minerals at rates comparable to their shallow-water counterparts, thereby contributing to biogenic carbonate production and enhancing our understanding of the global carbon cycle.

The study's lead author, Dr. Martin Grosell, Chair of the Department of Marine Biology and Ecology at the University of Miami, explained the significance of these findings: "Mesopelagic fish live in deep, cold, high-pressure environments, and until now, it was unclear if they produced carbonate like shallow water fish do -- or at what rate. This study is the first to confirm that they do and that the mechanisms and characteristics of ichthyocarbonate formation are remarkably consistent across depths."

Traditionally, the contribution of mesopelagic fish to the ocean's carbonate budget had been overlooked, as most research focused on shallow-water species. The new findings validate existing global models that suggest marine fish are substantial contributors to carbonate production. The research team maintained blackbelly rosefish specimens in controlled laboratory conditions, simulating their natural habitat at 6 degrees Celsius, and observed that these fish excreted approximately 5 milligrams of ichthyocarbonate per kilogram per hour, thus confirming predictions from thermal and metabolic scaling models.

Co-author Dr. Amanda Oehlert, an Assistant Professor in the Department of Marine Geosciences, emphasized the implications of this research: "With mesopelagic fish playing such a significant role, their contribution to carbonate flux -- and how it might change with warming oceans -- deserves greater attention." The findings suggest that ichthyocarbonate composition is consistent regardless of depth, influencing how and where it is stored or dissolved in the ocean, further elucidating the dynamics of the marine carbon cycle.

This research not only strengthens global estimates of fish-derived carbonate production but also opens new avenues for exploring deep-sea carbon dynamics and enhancing Earth system models, which incorporate complex interactions between physical, chemical, and biological processes.

The implications of this research extend beyond academic interest; understanding the role of mesopelagic fish in the carbon cycle could inform climate change mitigation strategies and marine conservation efforts. As the oceans continue to warm, the interactions between these fish species and their environment will likely shift, potentially altering their contributions to the carbon cycle. The study received funding from the National Science Foundation's Chemical Oceanography Program and the University of Miami's Departments of Marine Biology and Ecology and Marine Geosciences.

In conclusion, the study of the blackbelly rosefish reveals a previously unrecognized dimension of marine biology and its intersection with climate science, highlighting the need for ongoing research into the contributions of deep-sea ecosystems to global carbon cycling and climate processes.