Over-fishing is already a concerning problem, but new research indicates that not only could it mean losing fish species, it could also contribute to global warming more than we’d previously thought.

That’s because researchers from the Marine Institute and the University of Southampton have found that fish that feed on our ocean floor and do not come to the surface actually act as carbon sinks. Other examples of naturally occurring carbon sinks include forests and, indeed, the oceans themselves. What’s more, the UK-based researchers have found that deep-sea fish might be capturing more than a million tons of carbon dioxide from UK and Irish waters.