Dinoflagellates are a large diverse group of single-celled algae that are of immense importance to marine ecosystems worldwide, forming the base of the food chain upon which all aquatic life depends. Photosynthetic Dinoflagellates, like these three Ceratium, are major primary producers of oxygen. The process is driven by sunlight-absorbing chloroplasts that act as the engines of photosynthesis.

This image is part of Keith’s Space to Sea project, which combines photography and microscopy to make visible the full range of life in Stellwagen Bank National Marine Sanctuary, 25 nautical miles off the coast of Massachusetts.