Reef Growth and Erosion

Which species of coral is a dominant reef builder?

Acropora

What does reef construction-reef destruction equal?

reef growth

What other non-stony coral species contribute to reef framework?

fire coral, coralline algae, and giant clams

What three things contribute to reef construction

1) skeletal growth framework

2) sediment incorporation

3) submarine lithification

What other species are space occupiers that help hold framework together and sediments in place?

Sponges, algae, and soft corals

What is sediment infilling?

when wave action slams rubble and sediments into existing calcium carbonate skeletal framework and rock

What is submarine lithification?

coral reef structures and associated sediments are turned into rock underwater by chemical cementation processes

What are the four different grain origins in submarine lithification?

Coral skeleton, coralline algae, foraminifera, and sponge spicules

What three processes break apart coral framework, create sediments and/or dissolve calcium carbonate?

Mechanical erosion, bioerosion, and biodissolution

What are examples of mechanical erosion?

Storms, hurricanes, waves, sediment scouring, and rubbing of diadema spines

What is bioerosion?

organisms break down calcium carbonate

What is biodissolution?

organisms dissolve calcium carbonate

What happens if construction is greater than destruction?

reef growth

What happens if destruction is greater than construction?

reef loss

What is accretionary stasis?

when net reef growth is equal to net reef loss

What is a bioeroder?

any organism that erodes or weakens the calcareous skeleton of a reef-building species

What do internal borers do?

generally reduce reef framework to smaller particle sizes (silt and fine sand) than do external grazers (fine and coarse sand)

What are examples of external grazers?

Hermit crabs (crustacea), chitons and snails (mollusca), sea urchins (echinodermata), and fish (osteichthyes)

What can Coralliophila predation be easily confused with?

coral disease

What are some species of fish that are external grazers on a reef?

Triggerfish (balistidae), filefish (moncanthisdae), pufferfish (tetraodontidae, canthigasteridae), and parrotfish (scaridae)

What is the role of damselfish on the reef?

Damselfish are not direct mechanical or chemical bioeroders, but their aggressive territorial behavior and algae farming can indirectly increase internal and external bioerosion on the reef

What are examples of internal borers?

cyanobacteria, endolithic algae, sponges (porifera), worms (polychaeta), peanut worms (sipuncula), barnacles and shrimp (crustacea), and clams (mollusca)

What two conditions is bioerosion favored by?

1) conditions causing coral tissue death

2) conditions that provide a growth advantage to bioeroders compared with calcifying species

What is meant by bioeroders being endolithic species?

they live within coral skeletons