coral reef Flashcards
location
tropical and sub-tropical
shallow, warm and clear seawater
great barrier reef - australia’s east coast (2600 km)
deep sea corals found throughout world’s oceans, from tropical to polar regions
characteristics of corals
Some have a calcium carbonate skeleton (hard corals)
Some have symbiotic algae (zooxanthellae)
Some build reefs (hermatypic) and some don’t (ahermatypic)
All corals are polyps with tentacles surrounding a mouth
what are the limiting factors for corals?
temperature depth light sedimentation salinity air exposure energy nutrients
what’s the optimal temperature?
between 23&25 (hermatypic)
cannot drop below 18
light
Mutualistic association with endosymbiotic algae (zooxanthellae) which photosynthesize and provide nutrition for coral
what impact can sedimentation have on coral reefs?
often correlated with freshwater input
Leads to increased turbidity (decreased water clarity) which reduces photosynthesis
Clogs coral feeding structures
Corals can remove small amounts of sediment using mucus and cilia but cannot handle heavy sedimentation
what’s the range of salinity corals can tolerate?
corals can only tolerate a narrow range of salinity (32-35 ppt)
A large influx of freshwater will kill corals
air exposure
corals can only survive short, infrequent periods of air exposure
Mucus can prevent desiccation for an hour or two
Coral reefs are therefore limited by the level of the lowest tide
Some species can withstand exposure
energy
moderate amounts of energy are best
Too much energy can damage corals while too little energy results in sediment build up
Hurricanes affect coral reefs
Wave action provides oxygenated, nutrient rich seawater for corals
nutrients
coral reefs are in low nutrient areas but are very productive ecosystems
substrate
Three distinct habitats/substrates
1.Reef (living corals)
- Rubble (dead and broken corals)
- Sand (dead, digested corals & algae)
anatomy of a reef
Reef flat
Reef crest
Outer reef
formation of a coral reef
Fringing reef
- Anchored to land, typically quite young, in the shallows of a mountainous island
Barrier reef
- Reef growing parallel to the coast, separated by a lagoon
Atoll
- Circular, continuous reef without a central island and a central lagoon
biodiversity
Most diverse marine ecosystem
Comparable to tropical rainforest biodiversity
More than 25% of marine fish species live in coral reefs
current state of the coral reefs
25% of reefs have already been lost
Mass bleaching event in 97/98 alone killed ~16% of the worlds reefs
66% are under serious threat
33% are at elevated risk of extinction
All corals may be threatened by extinction by mid-century
human impacts
Aquarium & souvenir trade
Overfishing and destructive fishing
Tourism
Pollution
Climate change & coral bleaching
Coral diseases
Plagues of predators/invasive species
coral bleaching
Gradual loss of color as corals lose symbiotic zooxanthellae
Zooxanthellae provide ~90% of coral nutrition
Corals starve when they bleach
Bleached corals can recover but will die if stresses persist
mangroves locatio
Distributed across tropical and subtropical intertidal forests
Most mangroves found in South East Asia
mangroves requirements
Substrate: prefer fine grained substrate (mud) but can grow on sand, rock, or coral
Temperature: greater than 20c but no less than 16c, not cold resistant
Salinity: mangroves are salt tolerant
Energy: low, shores must be free of strong wave action and tidal current
Sediment: anoxic and waterlogged, but mangroves have aerial and shallow roots to obtain oxygen
Biomass, productivity, biodiversity: high
mangroves significance
Act as nurseries for many species
Protected ecosystem for adults of many species
Buffer coasts from hurricanes and storms
Reduce erosion of coast and siltation of water
Plants can absorb nitrates and phosphates, cleaning up and restoring water near the shore
mangrove human impact
Oil spills
Charcoal and timber industries
Input of pesticides and fertilizers
Clearing of thousands of hectares of forest to create man-made shrimp ponds for shrimp aquaculture industry
Coastal development
Climate change
Warming
Sea level rise
mangrove restoration
Locals using their own natural resources
Planting new mangroves
Education and awareness
invertebrates: giant clam adaptations
microstructures called ocelli that help get sunlight to the algae
produces metabolic waste products, which serve as a second nutritional source
invertebrates: christmas tree worms
feathery tentacles - radioles- part of respiratory system=> external gills covered with hairlike cilia that help the filter-feeding worm trap plankton and pass the food down to its mouth.
vertebrates: sea snake
- flattened and oar-like tail=> allows sea snakes to propel themselves through the water more effectively.
- salt glands and nostrils located at the top of their snouts to breathe more efficiently.
vertebrates: lionfish
- red and white stripped color- camouflage
- ability to remain practically motionless in the water
- venom glands
what are the stresses that impact coral reefs?
changes in water temperature, increased UV radiation, ocean acidification, variation in salinity, sedimentation, disease, toxins
