Marine Ecology Lecture 12 Coral reefs

What is a reef?

Hazard to navigation (Exxon Validiz)

Wave resistant biogenic structure: Oysters, polychaete worms, vermetid, gastropods, brachipod reef (biostromes, paleozoic) rudists (mesozoic), cyanobacteria (stromatolites), corals, sponges

What is a stromatolite

A stromatolite is produced by cyanobacteria, oldest fossils on earth, dating back to more than 3 billion years ago

What defines a coral reef?

Corals

Structure, Physical, community

Dynamics accretion

Elements of Coral reefs: Sediment producers

Sediment producers: Sand, silt and mud (Calcareous algae, corals, soft corals, foraminiferans, mollusks, echinderms)

Element of coral reefs: Framework and bafflers

Framework: corals

Bafflers: sea grasses, soft corals, and sponges

Element of corals reef: Binders

Algae, coralline algae, sponges, bryozoans, inorganic cementation

How do reefs form? How old are they?

Corals reefs are one the oldest reefs systems on Earth. Following the Permian- Triassic mass extinction, the scleractinian, bialves and crustose coralline algae have dominated the construction of wave resistant organic carbonate structures on the planet

Processes that control Reef Development: Marco-scale

Thousands of kilometers and over longer periods of time

Tectonics

Sea Level: geological time, the formation of the reef is determined by the rise of sea water rise

• The fate of the reef depends on the rate of relative sea level rise compared to the rate of calcium carbonate production on the reef.

What is prograde?

How the reef builds up and how fast, but can’t grow too fast, because the sea level is rising, so instead of going out of the water, they grow to the side.

But what happens when the water level is rising, but they’re not going fast?

• They move to shallow waters

What is backstep?

The process of jumping into a new shallow area

What are different things reefs can do?

Keep up, catch up, and give up

• Holocene reeds built at rates closer to 3-4 mm/year

Processes that control reef development: Meso scale

Physical- oceanographic in nature

Temperature

• wave currents is getting pushed to them

• it determines where coral reefs are located

Salinity

• Not really tolerant to it

Wave energy

• Determines which species is present

• Oceanic water

• reef waste

• benthic zonation

Processes that control reef development: Micro scale

Organisms at the spatial scale of individual reefs

Light

Nutrients

• areas with low nutrient dominated by reefs

• areas with high nutrient will be dominated by algae and sponges

Sediments

• the most important effects of sediment stress include (1) smothering (2) abrasion and (3) shading

What are the three different types of reefs?

Fringing Reef: form around a mountain

Barrier reef: form around when a mountain is eroded away

Atoll: circle

What is the coral reef zonation patterns