subtidal

The subtidal zone is the portion of the coastline and continental margin that remains underwater during all tidal phases. It lies seaward of the mean low-water line and extends downward to the outer edge of the continental shelf, or to depths where light and habitat conditions support marine life, typically from a few meters to several hundred meters depending on water clarity.

Because it is never exposed to air, the subtidal supports communities adapted to continuous immersion. Wave exposure, light, temperature, salinity, and sediment type shape habitats. Common subtidal habitats include kelp forests and other macroalgal beds, seagrass meadows, coral and sponge reefs in shallow subtidal zones, and soft-bottom communities with burrowing invertebrates and demersal fish.

Subtidal ecosystems often function as nursery habitats, feeding grounds, and biodiversity reservoirs, supporting fisheries and influencing coastal processes. They are productive, yet sensitive to disturbances such as bottom trawling, dredging, sedimentation, pollution, warming, and ocean acidification.

Research and management: Subtidal zones are studied using scuba, remotely operated vehicles, submersibles, and acoustic mapping. Protected areas, sustainable fishing practices, and restoration efforts aim to conserve subtidal habitats and their ecological and economic benefits.