1.Coral Reefs
What is a coral reef?
Habitat forming scleractinians
Different types of reef
Symbiosis
Biogeography
Controls on Biogeography
The value of reefs
29 April 2008OCN 621 – Biological Oceanography
2.What is a coral reef?
“Reef”
Feature lying beneath the surface of the water with which a boat could get stuck on
Typically diverse assemblage of habitat forming scleractinians
Mainly Shallow
But……not always……
Important engineers
Biodiversity
“Rain forests of the ocean”
Cover less than 1/10% of ocean floor
Habitat for 25% of all marine species
3.Scleractinians (primarily)
Other organisms also produce calcium carbonate structures
Forminifera, cocolithophores, pteropods, halimeda, red algae, soft coral spicules, sponge spicules
Reef structure is cemented together by calcareous red algae or by lithification
Organisms creating non-carbonate skeletons
Chitin, silica, gorgonin
Octocorals, sponges
What is a coral reef?
4.Coral Reefs of the World
Great Barrier Reef, Australia
Largest coral reef in the world, 2600km
Belize Barrier Reef
Second largest in the world
New Caledonia Barrier Reef
Second longest double barrier reef – 1500km
Andros Barrier Reef
3rd largest barrier reef, 167km long and 64km wide
Red Sea Coral Reef
Egypt & Saudi Arabia
Pulley Ridge
Florida, Deepest photosynthetic coral reef, 60m deep
5.Scleractinian morphology
Branching
Often fast growing
Plate-like
Often found in deeper environments
Massive/lobed
Generally slower growing, k-selected
Encrusting
Sometimes parasitic
6.Branching
7.Plate Like
8.Massive, Lobed
9.Encrusting
10.Types of Reef
4 Main types of reef
Fringing, Barrier, Patch and Atoll
Also – Apron, Bank, Ribbon & Table
Fringing reef
a reef that is directly attached to a shore or borders it with an intervening shallow channel or lagoon
Bora Bora, French Polynesia
11.Bora Bora
12.Types of Reef
Barrier Reef
a reef separated from a mainland or island shore by a deep lagoon
Great Barrier Reef - Australia
13.Great Barrier Reef, Australia
14.Types of Reef
Patch Reef
an isolated, often circular reef, usually within a lagoon or embayment
Outer edge of each patch reef is surrounded by a halo of sand that extends out to adjacent seagrass beds.
The width of this ring of sand is determined by the distance that herbivorous fish feel is within safe foraging range from the reef.
Florida
15.
16.Types of Reef
Atoll Reef
a more or less circular or continuous barrier reef extending all the way around a lagoon without a central island
Midway, Hawaiian Islands
17.Midway
Maldives
18.Island erosion
Island sinking
Reef accretion
Atoll Formation
19.Spur and groove formation
Reef Zones
20.Symbiosis
Photosynthetic algal endosymbionts
Dinoflagellates
Algae located in gastrodermis
Carbohydrates and lipids excreted by the algae
Protection and nitrogenous waste provided by host
Other marine taxa also engage in similar symbiosis
Sea anemones, jellyfish, sponges, clams, forams
Can provide up to 90% of corals energy
21.Symbiosis
22.Symbiosis
Genus Symbiodinium
Different species live in different corals
Controversial
Ingested by corals
But not digested
Reproduce by budding
3 Life Stages
Vegatative
Cyst
Motile
23.Shallow water coral biogeography
Warm tropical climates
Low latitudes (30ºN to 30ºS)
High solar insolation
Warm water currents
Clear shallow waters
good light penetration
~30m
low sedimentation and turbidity
Oligotrophic waters
nutrient poor but not exclusively
Hard substrata
24.
25.
26.Annual Pattern of Daily Solar Insolation
27.Biogeography
28.Biogeography
What limits shallow coral reefs?
High latitude and depth
Temperature, chronic low temperature stress
Light irradiance, insufficient solar insolation
Aragonite (CaCO3) saturation state
Competition with temperate fauna
Kleypas, 1999, Grigg, 2006
29.Biogeography
Distinct fauna between Atlantic and Indo-Pacific
Lower diversity in the Atlantic
Younger, smaller ocean basin with less thermal capacity
North-south mountain ranges did not impede glacial advances during ice ages
More extinction events
But older coral genera ~60 mya ?
30.Modified from Spalding, M. et al. 2001
Biogeography
31.Biogeography
Higher diversity in the Indo-Pacific
Older ocean basin with more stability through geological time
Larger body of water with more thermal capacity
East-west mountain ranges limited glacial advances during ice ages
But younger coral genera ~30 mya ?
Center of diversity in the Indo-Australian Archipelago (IAA)
Diversity gradient as radial distance from center increases
32.Veron, 1995
Biogeography
33.Reef $$ Value
Found in over 100 countries
Over 500 million people worldwide rely on coral reefs
Major source of food
Poorer countries
Fish and invertebrates
Conch, bivalves, octopus, squid….
Food for pelagic fish species
Limestone
Building materials, breakwaters, cement
Jewelry
Aquarium trade
Tourists
$6-10billion US tourist industry
Beach protection
Wave breaks
34.Conclusions
Majority of coral reefs are shallow, warm tropical, made from carbonate accreting species
Majority have photosynthetic algae
A reef can be in many different forms
Limited in latitude and depth
Higher diversity in the Indo Pacific
Reefs are worth $$s