NCSU GBR Formation
The Great Barrier Reef : How was it formed?
Tyrone Ridgway
Australia’s marine jurisdiction
Under the United Nations Convention on the Law of the Sea, Australia has rights and responsibilities over some 16 million square kilometers of ocean. This is more than twice the area of the Australian continent.
1 Australia’s large marine ecosystems
North Australian Shelf Northeast Australian Shelf/ Northwest Australian Shelf Great Barrier Reef
West-Central Australian Shelf East-Central Australian Shelf
Southwest Australian Shelf Southeast Australian Shelf
Antarctica
The Great Barrier Reef
2 Established in 1975 Great Barrier Reef Marine Park Act
345 000 km2
> 2 000 km long
2 800 separate reefs
> 900 islands
Importance to the Australian community
The Great Barrier Reef contributes $5.8 billion annually to the Australian economy: $ 5.1 billion from the tourism industry $ 610 million from recreational fishing $ 149 million from commercial fishing
Thus the GBR generates about 63,000 jobs, mostly in the tourism industry, which brings over 1.9 million visitors to the Reef each year.
3 It is not just about the fish and corals!!
There are an estimated 1,500 species of fish and more than 300 species of hard, reef-building corals. More than 4,000 mollusc species and over 400 species of sponges have been identified.
4 Invertebrates
Porifera Cnidaria Annelida Crustacea
Mollusca Echinodermata
Vertebrates
Osteichthyes Chondrichthyes Reptilia Aves Mammalia bony fish cartilaginous fish reptiles birds mammals
5 The Great Barrier Reef
The reef contains nesting grounds of world significance for the endangered green and loggerhead turtles.
It is also a breeding area for humpback whales, which come from the Antarctic to give birth to their young in the warm waters.
The islands and cays support several hundred bird species, many of which have breeding colonies there.
How did it all begin?
6 ERA PERIOD EPOCH MYA
Quaternary Holocene 0.01 Pleistocene 1.8 Pliocene 5 Cainozoic Miocene 25 Tertiary Oligocene 37 Eocene 54 Palaeocene 65 Scleractinian Cretaceous 140 corals are Mesozoic Jurassic 210 thought to Triassic 245 have turned Permian 290 Carboniferous 365 up around the Devonian 413 TRIASSIC. Palaeozoic Silurian 441 Ordivician 504 Cambrian 570 Precambrian
Thought to have originated in the Tethys Sea
Tethys Sea
= 40 millon years ago = present day
7 WhatWhat isis aa coral?coral?
Plant or animal?
8 Phylum CNIDARIA
Class Hydrozoa Class Scyphozoa Class Cubozoa
Class Anthozoa
class Anthozoa sub class Alcyonaria Zoantharia Ceriantipatharia 8 tentacles 6 tentacles
order Alcyonacea Scleractinia Antipatharia
Gorgonacea Actinaria
Pennatulacea Zoanthidea
9 Order Scleractinia (reef-building corals)
ring of tentacles
mouth
stomach
10 Structure of the coral polyp
Tentacle
Oral disc Mouth Pharynx Gonads Mesenteries Gastrovascular cavity Calcifying ectodermis External skeleton
ectodermis
mesoglea
endodermis
11 Structure of the corallite
Costa(e)
Septa(e)
Paliform lobes
Coenosteum
Collumella
Wall
Solitary vs colonial?
solitary / free-living
Fungia sp. Heliofungia sp.
12 Solitary vs colonial?
Majority of scleractinian corals are colonial
Each coral is made up of many genetically identical polyps
Courtesy Krupp 2001
Solitary vs colonial?
colonial
arrangement of corallites within a colony
13 Colony growth forms of corals
Courtesy Veron 2000
How do corals get their food?
Capture and ingestion of plankton and particulates from the seawater.
Absorb nutrients directly from the seawater.
Utilize the photosynthetic products of the zooxanthellae.
14 Hermatypic vs ahermatypic?
Hermatypic corals have symbiotic dinoflagellates (zooxanthellae). Have the ability to build reefs.
Ahermatypic corals do not have zooxanthellae. They are poor builders of calcium carbonate skeletons and therefore are poor reef builders.
What are zooxanthellae?
Single celled dinoflagellates from the genus Symbiodinium that are located in the endodermis of the coral.
Ectodermis Mesoglea
Zooxanthella
Endodermis
Gastrovascular cavity
15 Reef building corals live in an obligatory symbiosis.
waste products from metabolism
coral zooxanthellae
products from photosynthesis
coral zooxanthellae
N and P Light energy (visible and UV)
H2O Photosynthesis Organic
energy O2 ZOOXANTHELLAE
Respiration CO2 excess
H2O Nitrogen poor food Respiration CO2
Ca + CO Zooplankton Nitrogen CORAL 3 or DON rich food Waste CaCO3 products
Skeleton formation
16 WhereWhere dodo wewe findfind corals?corals?
17 Areas of major coral reef development
Caribbean realm: Indo-Pacific realm: Up to 20 genera Up to 70 genera
Areas of major coral reef development
18 Areas of major coral reef development
Yellow and Red = 18oC isotherm of average winter sea temperature
Factors important in formation of coral reefs
Temperature - 18°C (64°F) rule of thumb
19 Reef building corals live in an obligatory symbiosis.
waste products from metabolism
coral zooxanthellae
products from photosynthesis
Factors important in formation of coral reefs
Temperature - 18°C (64°F) rule of thumb
Light - functioning of symbiosis
20 Nutrients
high
temperate
25°N sub-tropical
0° tropical low
25°S sub-tropical
temperate high
Nutrients
Competition with macroalgae.
Algae have faster growth rates than corals.
21 Factors important in formation of coral reefs
Temperature - 18°C (64°F) rule of thumb
Light - functioning of symbiosis
Nutrients - low importance of zooxanthellae - competition with macroalgae
Factors important in formation of coral reefs
Temperature - 18°C (64°F) rule of thumb
Light - functioning of symbiosis
Nutrients - low - competition with macroalgae
Sedimentation/turbidity - rivers - reduces light levels - smothers benthic organisms
22 northern (coral)
24 major central rivers entering (no coral) the ocean
southern (coral)
Temperature Nutrients Light
cold high lower temperate sub-tropical
low tropical warm higher sub-tropical temperate cold high lower
23 Temperature Nutrients Light
Great Barrier Reef
Coral species attenuation with latitude
350 300 250 200 150 100 No. of species 50 0 18 20 22 24 26 28 30 32 Latitude
WAUS EAUS JAPAN
500
400
300 species
of 200
No. 100
0 18 20 22 24 26 28 30 32 34 Latitude º
24 CURRENTS
Global patterns of water movement are key to the explanation for the distribution of marine animals.
Why are currents important?
Differences between land and sea
Animals in the sea tend to have external fertilization and blastulas that develop in the sea. land – internal fertilization.
The larvae of marine animals tend to be highly dispersive. - currents play a major role
25 land sea
restricted dispersal great potential (10-1000 kms)
Pocillopora damicornis: Larval life can be as long as 40-60 days. Very broad distribution.
Australomussa rowleyensis: Larval life may be only as long as a day. Highly restricted distribution.
26 Why are currents important?
Currents help link reefs (connectivity) and hence offer larvae the ability to travel (often large distances) between reefs.
SOURCE
= sink reef CURRENT
Factors important in formation of coral reefs
Temperature
Light
Nutrients
Sedimentation/turbidity
Sea surface currents
27 Principle types of coral reef development
Mainland Coastal Island Continental Barrier fringing fringing island Cay reef reef reef Lagoon Platform reef
Continental Continental shelf slope
Fringing reefs
Well-developed reefs (with platform reefs) attached to mainland or continental islands.
Lizard Island
28 Submerged reefs
A large number of reefs occur in which there is no intertidal component.
GBRMPA
Patch reefs
Young patches of coral growing up off bottom (common in lagoons). Often reach surface and spread outwards with a pool forming in the centre.
GBRMPA
29 Platform or lagoonal reefs
Akin to a large patch reef, these reefs begin by growing toward the surface of the ocean, eventually spreading out laterally. In many cases, wave action hollows the interior and a lagoon forms.
One Tree Island
Ribbon reefs This type of reef is that which makes up the reefs that line the continental shelf (the so-called “outer barrier”) It is riddled with narrow passages that drain the lagoon during tidal flux.
Outer GBR
30 Atolls This is the classic type of coral reef structure. It was the type of reef development that Darwin focused on in his studies of the origin of coral reefs.
Note: Atoll reefs are not typically found in Australia but are common in the central and western Pacific
31