The ocean’s health may depend on a tiny microbe inside fish

A surprising new discovery suggests that tiny microbes living inside fish may be helping shape the chemistry of the world’s oceans. Scientists found evidence that bacteria in the guts of marine fish work alongside their hosts to produce calcium carbonate, a mineral that plays an important role in ocean health and carbon storage. For years, researchers believed fish handled this process on their own, but the new findings point to a hidden partnership between fish and microbes.