Coral Reefs

 Calcium carbonate (CaCO 3 ) makes up coral reefs.  Limestone is left over when animals grow and die.  This carbon containing molecule is the basis for coral formation.  As we will see, coral production exhibits huge impacts on ecosystem diversity and success. Introduction

Requirements for Reef Formation High Light Levels High Water Transparency Water Temperatures > 20°C (68°F) Low Nutrient Waters Hard Substrate for Attachment Good water circulation

 Hard (Stony, scleractinian, “true”) corals build the reef by extracting calcium carbonate from the ocean water.  They create a home in which primary producers can live.  They create a diverse 3-D space in which many other organisms can find homes. Coral Types:

What is Coral?? Animal, Vegetable, Mineral? Reminder: Coral are actually a special group of cnidarians, the same family as jellyfish!!

 Hermatypic Corals (a):  Ahermatypic Corals (b): Corals that are solitary or form small colonies (often lack zooxanthellae and do not help build reefs). Hermatypic vs. Non-Hermatypic Corals a. brain coral (Diploria) b. Mushroom coral (Fungia)

founder colony Coral larva are called planula, since they don’t like soft sea floors, they often metamorphose into a polyp which establishes a founder colony in a new location. Boulder coral Montastrea cavernosa Medusa’s are a mobile polyp.

 Coral Polyp  Provides a home for the zooxanthellae.  Provides nitrates and phosphates.  Gives off CO 2. Mutualism Between Corals and Zooxanthellae

Here is a good example of a live coral.

The one on the left is in trouble

Coral take on many shapes!!

Once this Halimeda(calcareous green algae) dies, 95% of what remains will be sediment and real estate for new coral colonies. Coral benefits from the death of other organisms.

Coral exhibit limited range in growth patterns.

From this…

To this…. Temperature increases and competition from red algae have killed much of this coral reef.

 Coral Reef primary production ranges from 1500 to 3700 g of C/m2/yr.  This makes Coral Reefs one of the most productive communities on earth!  Rapid nutrient cycling between zooxanthellae and corals may be partially responsible for this. Coral Reefs Have High Primary Productivity

Fringe Reefs

Growth on reefs are often limited by tidal action.

Disease is another major factor limiting growth. Here is an example of elkhorn coral (Acropora palmata) infested by “white band disease.”

Barrier Reefs

An excellent example of a Pacific barrier reef.

Barrier reef structure can be influenced by spur and groove formations such as these.

The Great Barrier Reef

Atoll Reefs: Volcanic Left-overs!

Atoll Reef Fulanga

Atoll Formation: Step by step

Reef Ecology: Edge effect again…

Food Webs: Same concept, more complexity

Again, we see that real estate is at a premium with these soft corals. Soft corals are fast growers, making them excellent competitors.

Harmony? Not really, most animals on reefs compete daily for everything, from food to mating opportunities.