CORAL REEFS References: Dr.Tim Flannery – We are the Weather Makers (2007 Australian of the Year and Scientist at Macquarie Uni) Sydney Aquarium Stacey and Lucas – Investigating Geography GBRMPA – web site Paine – Macquarie Revision Guides Professor OveHoeghGuildberg, University of Queensland.
Coral Reefs are found where the following biophysical conditions exist: • Coral reefs occur where: - shallow areas in tropical latitudes, or where warm ocean currents flow in temperate areas - a zone extending from Latitudes 30°N to 30°S of the equator; - water depths from 2 to 30m because they need light to allow the algae (zooxanthellae) to photosynthesise in the coral - warm waters where the water temperature does not fall below 17°C nor exceeds 34˚S with the optimum temperature being 26-27˚ for coral growth. - where waters are clear and free of nutrients otherwise algae and slime will cover the coral and stop it photosynthesising - constant levels of high salinity - high oxygen levels where wave activity continually oxygenates the water - low sediment levels as this will smother the coral and stop photosynthesis
Global locations of large reef-building areas: - the Caribbean Sea, - the western Indian Ocean - the western reaches of the South Pacific. - Non-tropical coral reef zones of : (a) the Red Sea, where heat from the surrounding desert climate warms the ocean and (b) Australia's Great Barrier Reef which is warmed by a tropical Pacific Ocean current.
The Great Barrier Reef – Spatial Pattern (where is it?) • LOCATION: off the coast of Queensland in northeast Australia from Latitude 8˚S to Latitude 24˚S stretching from Papua New Guinea to Fraser Island. The World Heritage area extends from Cape York to just north of Bundaberg • SIZE: is the largest coral reef system in the world but is not one continuous reef but a series of 2,900 individual reefs and 600 islands that stretch for 2,300 kilometres and covers an area of approximately 348,700 km². • SHAPE: it has four distinct regions Northern, Central, Mackay and Southern ranging from the continental shelf to coral cays and islands.
CONTINUITY: the northern section of the reef is older (15 million years) and in the south younger (2million).
Key Words • Zooxanthellae – microscopic algae that live inside the coral polyp • Symbiotic relationship – where two organisms benefit without damaging either organism • Spatial – where it is found? location or distribution.
GLOBAL SPATIAL PATTERNS: • Worldwide coral reefs are estimated to cover 284,000 sq km • the largest area is in the Indo-Pacific region with 92% - of this South East Asia accounts for 33% and Australia 41%; • the Atlantic and Caribbean coral reefs only account for 7.6% of the world total • Coral reefs are either restricted or absent from along the west coast of the Americas, and the west coast of Africa due to cold ocean currents that reduce water temperatures. • Corals are also absent from fromPakistan to Bangladesh and the coast around north-eastern South America and Bangladesh due to the release of vast quantities of freshwater from the Amazon and Ganges Rivers
Coral reefs are one of most biodiverse ecosystems in the world • although located in nutrient-poor tropical waters the process of nutrient cycling between corals, the zooxanthellae, and other reef organisms explains why coral reefs flourish as the recycling ensures that fewer nutrients are needed overall to support the community
The GBR has the richest fauna biodiversity on the planet • Over 2000 fish species • 500 coral species • 300 hard coral species • Over 400 sponge species • 4000 molluscs species • 23 species of marine mammals • 11 species sea snakes • 6 species of turtles • 215 species of birds • Migrating whales
Conditions necessary for Coral Reefs to grow: Corals are animals related to jellyfish. They have microscopic algae called zooanthellae which photosynthesise living inside their tissues in a symbiotic relationship. Therefore, Corals need the following: • Shallow water 2 to 30 metres so photosynthesis can occur • Warm ocean temperatures 20-35˚C (ideally 26 to 27˚C) to build limestone • Clear water low in nutrients. Nutrients such as phosphates and nitrogen increase algae growth and will smother corals. • Constant high salinity • High oxygen levels where wave action oxygenates the water • Low sediment levels as silt will smother the algae and stop photosynthesis occurring.
Natural stresses on the GREAT BARRIER REEF • Cyclones – breaks off coral, changes salinity of the water column, turns over the water column to lessen warm water in upper layer and reduces global warming threat • Marine organisms – burrowing, boring and breaking • Predators - Crown of Thorns Star Fish – native top predator kills the coral– dependant on currents and water temperature for larvae to spread • Sea Level change – 15,000 years ago sea level was lower forcing corals to die and re-colonise new areas • Flooding and runoff from mainland – can affect salinity levels and carry sediment into the reef system • Subsidence and continental drift has affected where corals colonise over the last 15 million years
Value of Coral Reefs: • Coral reefs yield around US$30 billion in income each year mostly to people in developing nations • One in four organisms in the ocean spends part of its life in coral reefs
Threats to Coral Reefs: GLOBALLY • Coral Bleaching episodes due to climate change • Sea level change due to global warming occurring around Pacific Islands will affect depth of coral growth • Over fishing including dynamite fishing and cyanide fishing in poorer countries and illegal fishing of endangered species • Algal Blooms from nutrient runoff • Fisheries – trawling; aquaculture – nutrient waste; • Tourism – anchor damage, litter, touching, souvenirs, sewage from resorts and boats, hand feeding changes feeding habits, development on islands, moorings, • Shipping – oil spills, sewage, litter, anti fouling agents on hulls • Agriculture and logging activities creating increased silt and nutrient runoff particular problems in South East Asia • Introduced species • Acidification of the oceans due to increasing CO2 which when dissolved lowers pH and weakens carbonate ions in coral and shellfish.
GREAT BARRIER REEF THREATS • Crown of Thorn Starfish damage due to food chain disturbance – increased nutrient runoff and warming oceans allowing more larvae to survive • Road building - in 1982 controversy over unsealed road built in Daintree rainforest Qld caused silt runoff onto coral reef/one of only two places in the world where coral reefs live next to rainforest – caused political issue/campaigns and ultimate protection of Daintree as World Heritage Wet Tropical Rainforest Area • Acidification of the water causing brittleness of coral due to warming oceans • Extinctions and threats to endangered species eg. Green turtle protected – once processed into soup; • Tourism • Runoff of silt and nutrients from fertilizers from farms • Global Warming
The Great Barrier Reef and climate change: • Is the most vulnerable reef in the world to climate change • 42% was bleached in 1988 • 18% suffered permanent damage • 2002 90% all inshore corals killed by ocean warming • 2006 coral bleaching avoided due to Cyclone Larry which mixed the warm top layers of the ocean with the cooler water below (water column mixed) however 50,000 homes in Queensland destroyed, crops wiped out and people killed.
Coral Reefs in the future: • Coral reef scientists warn that : • 1°C rise in global temperature will cause 82% of GBR to bleach and die • 2°C rise in temperature will bleach 97% reefs • 3°C rise will cause total devastation
Latest News Cargo ship's oil spill threatens wildlife 12/3/09 A cocktail of 650 tonnes of fuel and fertiliser has been lost from a cargo ship caught in fierce seas from cyclone Hamish off the south-east Queensland coast, potentially threatening wildlife