Unit 3 Topic 1 The Reef and beyond Flashcards
Abiotic factors which impact coral growth
Factors include
- Dissolved oxygen
- Light availability
- Salinity
- Substrate
- Temperature
- Aragonite
- Low levels of nitrates and phosphates
Reefs first appeared
Globally - 250 million years ago
Australia - 500 000 thousand years ago
Describe The Great Barrier Reef formation
Was shaped by changes in sea level that began around 20 000 years ago before the present time and only stabilised around 6 500 years before present time.
Different types of reef formations (5)
-Fringing Reef
Form around coastlines and islands on the appropriate substrate and are separated by the shoreline by small lagoons
-Platform Reef
A reef that forms on an optimal substrate that is close enough the adequate light availability
-Barrier Reef
Reefs that form and can reach the surface of the water creating a barrier for waves and are separated by wider and deeper lagoons
-Atolls
A ring of coral forms around a volcanic island. When the volcano sinks a circular shaped lagoon remains
-Coral Cays
Are an island formed from sediments derived from the reef and swept by waves into a focal point on the reef flat where they are deposited
Reef zonation
Parts of reef zonation
- Reef Slope
- Reef Crest/Rim
- Lagoon/Back reef
Groups of coral
Alcyonacea - Soft coral
Scleractinia - Hard coral
Two types of Scleractinia include
- Reef Forming (Hermatypic)
- Non-Reef Forming (Ahermatypic)
Anatomy of a typical reef-forming hard coral (8)
- Skeleton
- Corallite
- Nematocyst
- Coelenteron
- Coral Polyp
- Tentacles
- Mouth
- Zooxanthellae
The limestone skeleton of coral is built
When calcium ions (Ca^2+) combine with carbonate ions (CO3^2)
Coral Feeding patterns
Corals feed at night when phytoplankton sink firing the nematocyst to spear the plankton.
Symbiotic relationships in coral community
Mutualism:
Zooxanthellae and coral
Clownfish and Annanome
Parasitism:
Fish lice and small fish
Isopods and fish
Commensalism
Whale and Barnacle
Shark and Sucker Fish
Life Cycle of reef-forming coral
- Mature coral produce gametes through meiosis
- When the time is suitable, eggs and sperm are released into the ocean fertilization takes place
- The fertilized egg is called a zygote and drifts in the current
- Zygote conducts cell division known as mitosis
- The zygote continues to divide over and over creating an embryo
- The larva forms a planula, a type of zooplankton, and can move using its cilia
- The larva searches for the suitable substrate to settle on
Coral larva dispersal
Coral larva dispersal
-Occurs when planktonic larva stages of coral are distributed throughout the reef and spread between reefs
Site Selection
-Coral planula begins to search for the appropriate substrate. The planula can distinguish certain chemosensory cues from algae in appropriate locations
Settlement
-Occurs when the larva has metamorphised into a primary coral polyp
Recruitment
-Coral begins to grow and is subjected to competition and predation from other organisms
Growth of reefs
Reefs can grow when the rate of accretion is faster than the rate of reef erosion
Types of erosion:
-Chemical erosion involves increasing ocean acidity which slows the rate of coral accretion
Biological erosion
-Includes organisms that consume coral such as sea urchins or parrotfish
Ecosystem engineers
Ecosystem engineers are organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials.
Types of ecosystem engineers
Autogenic engineers
-Change the environment via their own physical structures (coral)
Allogenic engineers
-Change the environment by transforming living or non-living material from one physical state to another (bump head parrotfish)
