Lecture 11 - The Deep Sea Flashcards
What is the biggest ecosystem on the Earth?
The deep sea
What percentage of the deep sea is beyond shallow margins?
90%
When does deep sea begin?
At the shelf break, approximately 200m
Give the zonation of the ocean floor.
1) Continental shelf
2) Continental slope
3) Continental rise
4) Abyssal plain
5) Mid-ocean ridge
6) Deep ocean trenches
What is the deepest part of the ocean?
The Mariana trench
What is ALVIN?
A deep-sea submersible operated by WHOI, built in 1964.
How many large submarines operate in the deepest parts of the ocean?
Three
What does most of our knowledge of the deep sea come from?
Videos.
What light is found in the abyssal plane?
- No light from the surface
- Background light that comes from decay of certain compounds
- Bioluminescence
What percentage of mesopelagic organisms have a form of bioluminescence?
90%
Why do deep sea species often have large eyes?
To maximise their ability to see each other’s signals
How do organisms produce bioluminescence?
Using the chemical luciferin, which is oxidised by lucifers to form blue-green light
What is the temperature range of the abyssal plane?
-1 to 4 degrees
Mostly constant around 2 degrees
True or false:
There is a fast current across the abyssal plane.
FALSE.
There is a slow and steady current; cold water from poles sinks and moves gently across the ocean bed in one single direction.
What is the most important group of fish in deep sea environments?
Lanternfish
How many different species of lanternfish are there?
246
How do male and female lanternfish vary?
In the combination of photophores
Explain how lanternfish avoid predation.
Have light organs on the bottom.
Breaks up silhouette from something looking up from underneath.
What percentage of deep sea fish biomass is composed of lanternfish?
65%
How much does pressure increase every 10m into the ocean?
By 1 atmosphere
At the abyssal plane, what is the pressure?
Over 500atm
How do deep sea fish control their buoyancy?
Do not have a swim bladder due to pressure.
Change the density of their lipids to control their buoyancy.
Describe deep sea sediment.
- Fine mud
- Up to 1000m thick
- Hard substrate is rare.
What is biogenic ooze?
Sediment in deep waters, found beneath areas of high productivity, left over from phytoplankton blooms and decaying bodies forming layers.
Describe the composition of biogenic ooze formed by
a) Diatoms
b) Foraminifera and coccolithophores
a) Diatoms = silicon-based ooze
b) Foraminifera and coccolithophores = calcium carbonate based ooze
Describe a hard substrate on the deep sea floor.
Whale falls (whale carcasses), acting as stepping stones for deep sea species.
What often dominates whale fall communities?
Polychaetes
What is Osedax?
A genus of bone-eating worms, relying on symbiotic bacteria that aid in the digestion of whale proteins and oils.
Feed on calcium carbonate of the whale.
Secrete strong acid using protein pumps to dissolve the skeleton and take up nutrients by osmosis
