Nonreef

Nonreef is a term used in marine ecology to describe coastal and continental-shelf environments that do not host coral reef structures. It is used to contrast reef-dominated systems, where hard corals build frameworks, with other habitats that either lack reef-building corals or prevent reef formation due to environmental or historical reasons.

Definition and scope

The term is not universally standardized and is applied variably in the literature. In broad usage, nonreef encompasses open-ocean and nearshore habitats such as sandy or muddy substrates, seagrass meadows, mangrove forests, kelp or other macroalgal forests, and rocky shores where corals are absent or rare.

Ecology and services

Nonreef habitats can support diverse communities and provide essential services including carbon storage, nursery grounds for fish and invertebrates, shoreline protection, and nutrient cycling. They often display different trophic structures and production regimes compared with coral reefs, and may be more resilient to certain disturbances but vulnerable to others.

Formation and drivers

The absence of reef development can result from historical contingencies (absence of coral larvae) or from environmental conditions that are unsuitable for corals, such as temperature, light limitation, high turbidity or sedimentation, inappropriate salinity, or strong wave energy. Human impacts like pollution, overfishing, and coastal modification can degrade nonreef habitats, sometimes allowing reef species to invade or shift community composition.

Geographic distribution

Nonreef environments occur worldwide, especially where conditions are not favorable for reef formation or where reefs have been degraded by stressors. They are common along temperate coasts, soft-sediment shelves, and estuarine systems.

See also: Coral reef, Seagrass meadow, Mangrove forest, Kelp forest, Coastal ecology.