### formation | ridge:

Reef
* Many reefs are visibly regenerating.
* Most reefs are in warm, clear, tropical seas with a lot of sunlight
  - attract fish
  - form protective barriers
* Most reefs grow best in warm, shallow, clear, sunny and agitated waters
  - in considerably warmer areas
* Most reefs have a solid front which receives much of the force of the ocean swell
  - biodiversity
  - corals
  - fish diversity
  - high biodiversity
  - occur in poor countries
* Most reefs provide habitats
  - shelter
* Reeves is self-fertile, producing bright red berries with no pollinator needed.
* Some reefs also exist in cold, deep waters
  - are even older than our old-growth redwood forests
* Some reefs have numbers
  - resources
* also contribute to the world's marine biodiversity
  - create sheltered lagoons and protect coastlines and mangroves against wave damage
  - grow unaided on marine structures such as oil rigs
  - protect the shoreline by acting as natural barriers between the open sea and coastlines
* also provide protection against wave action
  - from currents and many predators
  - serve as important buffer against coastal erosion and damage from tropical storms
* also tend to develop in areas of strong wave action
  - thrive in clear water because it allows more sunlight to reach the corals
* are among the most complex and diverse biological communities in theworld
  - biological keystones
  - build-ups of carbonate away from the shoreline
  - carbonates
  - chronically at risk of algal encroachment
  - especially vulnerable because they take so long to regenerate
  - healthy and colorful, many bright-colored sponges and soft corals
  - in fact host to the ocean's most spectacular galaxies of fish
  - like inner-city apartment blocks, where each one room flat is occupied to two organisms
  - part of sails
  - primarily a habitat for a wide variety of plants and animals
  - resilient and they bounce back quickly when protected
  - self-sufficient in terms of nutrients
  - some of the world's most diverse ecosystems
  - strips
* are the big cities of the sea
  - most productive ecosystems of the world
  - useful to the environment and to people in a number of ways
* are very sensitive systems and can only survive in a narrow salinity range
  - stable, and provide a protective barrier around many islands and coasts
* become homes.
* begin when a polyp sticks to a rock on the sea bed, then buds, into thousands of clones.
* can act as sources or sinks of larvae over various spatial scales
  - be huge
  - provide a number of medicinal compounds
* commonly reside in shallow marine water and are found only in tropical environments.
* consist of calcium carbonate, produced by tiny creatures called coral polyps.
* exist as a congre- gation of coexisting species, many of which eat each other.
* flourish everywhere.
* form barriers.
* form in shallow tropical and subtropical waters, and host huge numbers of plants and animals
  - the open bay, as well as along the edges of saltmarshes
* grow as generation after generation of individual coral polyps add to the matrix
  - best in sunny, shallow, clear water
  - in a special environment and form coasts that can evolve into atolls
  - only near sea level, and they grow away from shore into the waves
  - very slowly over time
* have biodiversity
* live in nutrient poor waters.
* maintain a network of intimate ecological relationships and delicate food webs
  - or develop a structure of positive relief during deposition
* occur in mainly tropical seas, but can be killed if the ocean temp gets too high.
* play major roles
* predominate in tropical areas and are often unsurveyed.
* preserve biodiversity.
* protect mangroves from wave action and mangroves, in turn, protect corals from siltation
  - many islands from the ocean and are rich in fish
  - our shorelines
* provide habitat for over one million species of plants and animals
  - protection from erosion to coastlines and sand for beaches
  - resources for fisheries
* save lives.
* serve as a buffer, protecting inshore areas from the pounding of ocean waves
  - atmospheric carbon dioxide sinks
* thrive in low-nutrient situations.
* yield a host of benefits for humans, including food, medicines and tourism income.