59: Coral Bleaching Flashcards
(26 cards)
What are corals?
belong to Phylum Cnidaria (like hydras and jellyfish)
- sessile (don’t move) and live in colonies
- about 900 different species
What is a coral polyp?
a little bag/sac
What do coral larvae do?
not sessile, it moves/swims and then affixes at some point
What is the process of corals?
- corals take calcium dissolved in sea water and use it to build a skeleton of calcium carbonate
- as coral die, the new generation build a skeleton on top of the dead coral skeleton
- polyps and their skeletons build a permanent structure that is called a coral reef
What is a coral reef?
places of enormous biodiversity that is home to many different species
- rain forest of the seas
What is the relationship between corals and zooxanthella?
corals live in a symbiotic, mutualistic relation with a type of algae called zooxanthella
- algae perform photosynthesis and provide the corals with food and help them build their skeletons
- corals give algae a place to live inside their body
What are two types of coral reefs?
1: warm-water coral reefs
2: cold-water coral reefs
What are warm water coral reefs?
on shallow, sunlit, warm and alkaline (basic) waters
- ex: coral reef from the Great Barrier Reef, Australia
What are cold water coral reefs?
found in deeper waters and receive less light
- ex: community from the Mississippi Canyon at 450m depth
What is coral bleaching?
when corals are under heat stress, they expel the symbiotic algae
What did symbiotic algae do?
give the corals their color, when they are expelled, the corals look bleached
- corals receive less food without the algae
What is a bleached coral?
a weakened coral
Is coral bleaching a new phenomenon?
no, this has occurred in the past however, events are occurring more often and with more intensity
What human activities that act at the LOCAL level threaten coral reefs?
- pollution
- coral harvesting
- overfishing
What are cold-water reefs also being affected by?
- fossil fuel exploitation
- sea mining
- pipelines
- cables
- trawling
What human activities that act at the GLOBAL level threaten coral reefs?
climate change and ocean acidification
What is climate change causing?
- warmer waters (primary cause of bleaching)
- rising sea levels (changes the amount of sunlight)
- more intense storms (more wave action)
How does ocean acidification affect coral reefs?
higher CO2 in atmosphere results in lower pH levels in seawater, which in turn reduces calcification rates
What can the corals do?
- adaptation
- acclimatization
- range-shift
What is adaptation?
natural selection may act and in the long run, more tolerant species and more tolerant individuals within a population may replace the less tolerant
What is acclimatization?
corals may shift to more heat resistant zooxanthella
What is range-shift?
migration to higher latitudes or deeper waters
What can humans do?
stop adding CO2 to the atmosphere and reduce local stress
What does reducing local stress involve?
- ban fishing and trawling and mineral extraction to protect cold-water corals
- reduce pollution, overexploitation, and damage to coastal areas
- prevent the establishment of invasive species
