Gromia is a genus of protists, closely related to foraminifera, which inhabit marine and freshwater environments.

However, research from the 1990s and early 2000s identified gromiids inhabiting depths up to 4,392 m, leading to several new deep-sea Gromia species being described and recognized.

[5] Gromia became better characterized throughout the 1960s, when electron microscopy revealed more details on their morphology, including their honeycomb membranes.

It inhabits intertidal zones and other regions of shallow waters; it is often found attached to rocks, kelp, weeds, Cladophora algae, or within sediments.

Deep-sea gromiids have been found in the Arabian sea,[11] off the coast of Antarctica and in the water of the Northwest Atlantic Ocean.

Gromia are thought to acquire nutrients from the organic matter in sediments on the sea floor, as they are often found in areas with abundant phytodetritus.

[2] Waste pellets (“stercomata”) and mineral grains accumulate inside the cell – another characteristic feature of Gromia.

Gromiids are hypothesized to be important for carbon cycling, as they are often found in carbon-rich sediments and feed on detritus.

The ability of the giant, deep-sea species G. sphaerica to produce tracks on the sea floor has been used to propose a re-evaluation of the use of fossils with similar traces as evidence for dating the origins of animals with bilateral symmetry.