Artwork featuring a marine ecosystem and the words Florida Keys National Marine Sanctuary
This poster image, created for Florida Keys National Marine Sanctuary in celebration of the 50th anniversary of the sanctuary system, depicts the complex range of habitats located here, and how closely connected they are to one another. Illustration: Matt McIntosh/NOAA

The habitats we see today in Florida Keys National Marine Sanctuary are shaped by the area's unique hydrogeologic past. The chain of islands comprising the Florida Keys is made of limestone, remnants of ancient coral reefs (Upper Keys), and sand bars (Lower Keys) that flourished during a period of higher sea levels approximately 125,000 years ago (Pleistocene Epoch).

During the last ice age (100,000 years ago) sea level dropped, exposing the ancient coral reefs and sandbars which became fossilized over time to form the rock that makes up the island chain today. The two dominant rock formations in the Keys are Key Largo Limestone and Miami Oolite.

During this time of lower sea levels, the Florida land mass was much larger than it is today and the area now referred to as Florida Bay was forested. As glaciers and polar ice caps started melting 15,000 years ago, flooding of land combined with tidal influence changed the geography of the Keys and their surrounding areas. All of this activity has produced an extraordinary range of habitats that are all interconnected and dependent upon one another.

Traveling by boat, you can within minutes venture from the mangrove and seagrass flats of Florida Bay, to iconic coral reefs and deep-water fishing on the oceanside. This diversity of habitats is what makes Florida Keys National Marine Sanctuary one of the most special places on Earth — and one of the most challenging to protect.

Divers swimming above a stand of elkhorn coral

Coral Reefs

Coral reefs are the lifeblood of the Florida Keys. Learn about the invertebrate animals that build our reefs and the different types of coral reef formations.

seagrass growing underwater

Seagrass Meadow

Learn how a seagrass meadow grows and why seagrasses are essential to mangrove and coral reef health.

A small boat in a channel with mangrove trees all around

Mangrove Forest

Red, black, and white mangroves are specially adapted for life here in Florida Keys National Marine Sanctuary. Learn why these trees are vital to coral reefs and people living in the Keys.