Lec 14: Case Study - Biotic/abiotic interactions in marine reefs Flashcards
what are coral reefs?
big underwater structures of the skeletons of corals, largest living structure on the planet, rainforest of the sea
what are corals?
- animals
- colonial marine invertebrates
name the 2 types of corals
hard corals
- produce calcium carbonate
- have rock-like skeleton
soft corals
- produce less calcium carbonate
- don’t produce reefs but live on them
which type of corals produce reefs?
hard corals
why are reefs important?
- biodiversity
- provide habitats
- protect coastlines from waves and storms
- support marine food chains (source of nutrients)
what are the individual coral animals called?
polyps
where do coral reefs grow
in shallow tropical and subtropical waters, in waters at 23-29 C and 32-40% salinity
where do branching, plate-like corals grow?
in quieter waters
why type of coral is photosynthetic?
hard corals are photosynthetic through a symbiotic dinoflagellates living within them
what are the two ways corals can feed?
1) dinoflagellates through photosynthesis
2) catching small marine life
what is exchanged in the polyps-dinoflagellate symbotic exchange?
algae give: energy and color
polyps give: CO2 and home
what is the maximum depth of coral growth? why is it so shallow?
25m because they need sunlight
are dinoflagellates hetero or auto trophic?
can be either one (50/50)
how long have corals existed?
500 million years
what have been the causes of coral extinction?
- warming due to rising CO2 and CH4
- ocean acidification
what is the name of the extinction event that took place as Pangea formed? What happened to corals and why?
- ordovician-silurian extinction event
- ocean circulation affected
- sea levels and temp drop
- corals dissapear
describe the presence of corals throughout the devonian
devonian reefs were present almost everywhere and were ecosystems, but were wiped out by the late-devonian mass extinction 360 Ma.
what are ancient coral reefs now?
tight oil and gas reservoirs
what are threats to coral reefs?
- natural phenomena
- local human-imposed threats
- climate change
How does coral bleaching occur?
when corals overheat, they respond by expelling their algae. their energy needs are then not met, and they begin to starve.
What led to the 2015-16 Bleaching event?
- ocean warming due to climate change
- combined with El Nino
How does plastic in the ocean affect corals?
- increases chance of disease in corals
- block sunlight
what is formed when co2 dissolves in seawater?
carbonic acid
what do corals build their skeletons with?
calcium carbonate
what does increased carbonic acid content in seawater do to corals?
- carrying capacity of water for calcium carbonate is lower
- corals cannot build skeleton
