Deep-sea fish just changed what we know about Earth’s carbon cycle

Mesopelagic fish, long overlooked in ocean chemistry, are now proven to excrete carbonate minerals much like their shallow-water counterparts—despite living in dark, high-pressure depths. Using the deep-dwelling blackbelly rosefish, researchers have demonstrated that carbonate production is consistent across ocean layers, bolstering global carbon cycle models. These findings reveal that these abundant fish play a hidden but crucial role in regulating Earth’s ocean chemistry and could reshape how we understand deep-sea contributions to climate processes.