Chapter 9: The Deep Sea Flashcards
What is the range of the deep sea?
continental shelf to the abyssal plains. 200-5000m
what depths can the trenches get to?
10000m
does the deep sea have highly variable environments?
nope, rather constant physical environment, low abundance of animals, although can demonstrate gigantism
name the 4 deep-sea benthos regions
- shelf break
- continental slope and rise
- abyssal plain
- hadal region (bleow 6000)
what is the mid-ocean ridge?
- most expansive mountain chain on earth
- spreads 2-5cm per year
- smooth, volcanic peak
- distributes minerals via hydrothermal vents
what is the topography like in the abyss?
- not uniform
- many small topographic features resulting in ‘rolling hills’
- sea mounts
how has deep-sea sampling improved?
- use of photography
- development of manned submersibles
- Bathysnap: submerged stationary frame-mounted cameras
how do the environmental parameters change below 2000m?
they don’t really..
salinity is relatively constant
ph is fairly constant
temp -1 to 4C belo 2000m with average of 2C at the abyssal plains
Break down the light penetration regions
- euphotic (photosynthesis)
- dysphotic (vision) 1000m
- aphotic (no light)
with no photosynthesis available, what does the food web depend on?
- energy from detritus
- carrion originating from systems above
- chemosynthesis of hydrothermal vents
what are the three types of currents found in the deep sea?
- Tidal currents: reach the base of the continental slope and leave ripples on the sea floor
- Oceanic conveyor: constant, unidirectional
- Coriolis: small layer of water moves with the earth, while water in the column moves slower
Hydrostatic pressure:
its cause, its gradient, its result
- caused by weight of the overlying water mass
- pressure increases by 1 atm every 10m. therefore 500atm on abyssal plains!
- compresses gases, slows down enzyme catalysis
in which way can sediments be divided?
- Clay particles: inorganic sediments found mainly under oligotrophic surface waters
- Biogenic oozes: found below productive surface waters containing >30% biogenic skeletal baterial
how can biogenic oozes be divided?
- Siliceous oozes: silicon based from diatoms and radiolarians
- Calcareous oozes: foraminifer and coccolithofores
what do organisms of the deep sea rely on for food sources?
what sort of system is this?
- POM
- allochthonous (rely on the input of organic material from outside the system, compared with autochtonous systems that mainly generate their own production)
what is the importance of DOM in the deep sea?
- providing carbon to sediment-dwelling organisms
- 10x greater than overlying waters
what are the three main groups of plankton waste?
- faecal pellets
- moults
- marine snow (amorphous aggregates)
is there seasonal variability for food inputs?
yes. it is 1-2 months behind the primary production, as this is how long it takes to reach the ocean floor.
- late June the floor is covered in ‘fluff’
hydrothermal vents (general)
- form ‘island communities’
- located in regions with high tectonic activity
- superheated water erupts from vents
- can reach up to 350*C
production of hydrothermal vents
- higher biomass than other areas of the deep sea
- chemosynthetic bacteria is primary producers
- hyperthermophiles 80-115*C
- superthermophiles >115*C
name some representative species of hydrothermal vents
- Vestimentiferan Tube Worms: found in Pac, polychaetes, 1-2m
- White bivalves: giant clam, vent mussel
- shrimp
what are the most dominant organisms in the mid-atl range? how?
shrimp.
- form large groups around vents
- thermal radiation detecting abilities
how does depth and size relate?
that species get larger the deeper you go, but this and gigantism may be more related to temperature than depth, such as with the polar regions.
what are some representative species of the deep sea?
Macrofauna: polychaetes, bivalvevs, molluscs
Meiofauna: nematodes, copepods, foraminifera
what three groups can megafauna be divided into?
- Sessile megafauna: 2 cnidarian spp more successful in deep sea than coastal. Also sea pens
- Sedentary megafauna (mysterious, only traces lef on floor, worms and proboscis)
- Mobile Megafauna: echinoderms, crustaceans, fish
Deep sea: the kingdom of ________.
why? who?
Echinoderms
- Brittle star and sea cucumber
- really diverse, fantastic range of morphological development
what is the dominant group of decapod crustaceans? what is another one of interest?
squat lobster.
red crab (fishery)
prawns
name some of the fish of the deep ocean
- rays
- hagfish
- flatfish
- anglerfish
why do deep fish swim at benthopelagic depth?
- no swim bladder
- lipids instead
- reduce body density by converting tissues to substances lighter than water, such as gelatinous materials or cartilage
what are some proposed reasons for gigantism?
- metabolic effects
- DO level
- method of food capture (mobility)
what is the average depth of the abyssal plains?
4000-5000m
