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'Habitat' describes the place where a particular community of species lives. Attributes of 'habitat' important to species include, among others, type of  substratum (e.g. rock, coral, mud, sand), exposure to waves, water depth, pressure, salinity and temperature. Pelagic waters have no substratum, but variation in physical factors such as light, temperature and pressure define habitats such as epipelagic, midwater and deep water, each with its own biological communities.

Habitat forming species, such as mangroves, seagrass, kelp, Sargassum, warm and cold water corals, and mussels modify habitats in ways that support the existence of rich biological communities.  

The huge and deep ocean, with its varied submarine topography, dynamic system of currents, upwellings and downwellings, numerous islands, extensive coastline and abundant estuaries provides many different kinds of habitats. Some, such as deep water trenches, hydrothermal vent systems and seamounts have only begun to be studied in any detail.

The Ocean Health Index assesses six important habitats for which global data exist. They are: Mangroves, Seagrass, Salt Marsh, Soft Bottom Subtidal, Coral Reefs and Sea Ice.  

How Was It Measured?

Habitat health affects the delivery of many ocean benefits, so habitat condition and extent are important components for Ocean Health Index goals. 

Habitat 'condition' would normally be assessed with measures such as presence or absence of disease(s) or percentage of the habitat occupied by a key species (e.g., live coral cover). 'Extent' describes the amount of area that the habitat covers.  Since global information on condition is not available for most of the habitats evaluated in the Ocean Health Index, data on change of extent is used to represent habitat condition. 

Habitat information is used in the following ways:

  • For the Carbon Storage goal, Mangroves, Seagrass and Salt Marsh are components of Status. 
  • For the Coastal Protection goal, Mangroves, Seagrass, Salt Marsh and Coral Reefs are components of Status.
  • For the Biodiversity goal, all six habitats are evaluated as components of Status.
Damage or destruction to these habitats, as well as Intertidal habitats, is used as a Pressure component for all goals, with harm to different habitats weighted differently for different goals. 

Web pages for each goal and Habitat provide further information about these habitats and how they are measured.