Coral reefs are the most diverse marine communities on the planet.

The anatomy of a coral is basically a classic polyp cniderian within a CaCO₃ skeleton

They occur only in tropical regions, where salinities and water temperatures allow reef building processes to exceed reef erosional processes.

Symbiosis between corals and zooxanthellae allow for the formation of complex reef assemblages.

Coral Bleaching occurs when zooxanthellae are lost from the host coral (usually because of temperature, salinity, UV radiation, or a combination of these).

Although corals can survive without their symbiotic algae, they cannot grow, and coral mortality often accompanies episodes of bleaching.

Although nutrients are generally limiting in tropical waters, the structural complexity of coral reefs provides many niches for coexistence.

Some species of coralline algae also build reefs, and large algal ridge systems produce extensive reef formations (e.g. along the coast of Belize in the Caribbean).

Primary Production comes from zooxanthellae, as well as many other algae.

Primary Consumers include many invertebrates, as well as fish (e.g. parrotfish, damselfish, surgeonfish, chubs).

Secondary Consumers are represented by many different taxa... however, very few feed directly on corals (e.g. butterflyfishes).

Tertiary consumers are common on coral reefs.

As in other communities, competition for space and food probably play important roles in regulating rates of reproduction and growth, however, their role in population dynamics is more controversial.

Competition between corals has produced many different forms: massive, plating, and branching morphs are common.

Processes of settlement and recruitment are generally perceived to be the most important factors regulating populations.

Coral reefs are threatened from a variety of sources. These include:

Natural disturbances such as hurricanes

Many anthropogenic sources (pollution, siltation, collection of coral for building materials, etc).

Coral diseases and episodes of bleaching may be related to natural and man-made disturbance.

Because many corals are slow growing, they are not easily restored to a region following disturbance and some reefs may never recover.

 

Mangrove habitats (mangels)

Mangrove habitats are intertidal regions in tropical and subtropical latitudes

Mangrove trees extend into areas of moderate tide flux by means of prop roots.

These roots reduce water flow and promote sedimentation increasing shoreline building processes.

Because of their quiet, rich, spatially complex waters, mangroves are extremely important "nursery" habitats for many juvenile fishes.

They also support unique assemblages of filter feeding sponges and bivalves

Pneumatophores allow mangrove roots to "breathe" in saturated sediments.

 

Seagrass beds

Seagrass beds are shallow meadows of flowering plants.

Their blades provide important structural heterogeneity for many small invertebrates and a few species of fish.

Although they produce seeds, reproduction is primarily accomplished vegetatively via rhizomal growth.

Seagrasses generally require high levels of light, and they can dominate shallow water habitats (to 10 m)

Seagrass blades are consumed to varying degrees by a variety of herbivores:

High concentrations of silica and some chemical defenses deter herbivory

Other species of algae (mostly green) are found within many seagrass beds.

Seagrass beds may be especially important nursery habitats for some species.