Chapter 9: The Deep Sea

Question 1

What is the range of the deep sea?

Answer 1

continental shelf to the abyssal plains. 200-5000m

Question 2

what depths can the trenches get to?

Answer 2

10000m

Question 3

does the deep sea have highly variable environments?

Answer 3

nope, rather constant physical environment, low abundance of animals, although can demonstrate gigantism

Question 4

name the 4 deep-sea benthos regions

Answer 4

• shelf break
• continental slope and rise
• abyssal plain
• hadal region (bleow 6000)

Question 5

what is the mid-ocean ridge?

Answer 5

• most expansive mountain chain on earth
• spreads 2-5cm per year
• smooth, volcanic peak
• distributes minerals via hydrothermal vents

Question 6

what is the topography like in the abyss?

Answer 6

• not uniform
• many small topographic features resulting in ‘rolling hills’
• sea mounts

Question 7

how has deep-sea sampling improved?

Answer 7

• use of photography
• development of manned submersibles
• Bathysnap: submerged stationary frame-mounted cameras

Question 8

how do the environmental parameters change below 2000m?

Answer 8

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

Question 9

Break down the light penetration regions

Answer 9

• euphotic (photosynthesis)
• dysphotic (vision) 1000m
• aphotic (no light)

Question 10

with no photosynthesis available, what does the food web depend on?

Answer 10

• energy from detritus
• carrion originating from systems above
• chemosynthesis of hydrothermal vents

Question 11

what are the three types of currents found in the deep sea?

Answer 11

• 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

Question 12

Hydrostatic pressure:

its cause, its gradient, its result

Answer 12

• 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

Question 13

in which way can sediments be divided?

Answer 13

• Clay particles: inorganic sediments found mainly under oligotrophic surface waters
• Biogenic oozes: found below productive surface waters containing >30% biogenic skeletal baterial

Question 14

how can biogenic oozes be divided?

Answer 14

• Siliceous oozes: silicon based from diatoms and radiolarians
• Calcareous oozes: foraminifer and coccolithofores

Question 15

what do organisms of the deep sea rely on for food sources?

what sort of system is this?

Answer 15

• POM
• allochthonous (rely on the input of organic material from outside the system, compared with autochtonous systems that mainly generate their own production)

Question 16

what is the importance of DOM in the deep sea?

Answer 16

• providing carbon to sediment-dwelling organisms

- 10x greater than overlying waters

Question 17

what are the three main groups of plankton waste?

Answer 17

• faecal pellets
• moults
• marine snow (amorphous aggregates)

Question 18

is there seasonal variability for food inputs?

Answer 18

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’

Question 19

hydrothermal vents (general)

Answer 19

• form ‘island communities’
• located in regions with high tectonic activity
• superheated water erupts from vents
• can reach up to 350*C

Question 20

production of hydrothermal vents

Answer 20

• higher biomass than other areas of the deep sea
• chemosynthetic bacteria is primary producers
• hyperthermophiles 80-115*C
• superthermophiles >115*C

Question 21

name some representative species of hydrothermal vents

Answer 21

• Vestimentiferan Tube Worms: found in Pac, polychaetes, 1-2m
• White bivalves: giant clam, vent mussel
• shrimp

Question 22

what are the most dominant organisms in the mid-atl range? how?

Answer 22

shrimp.
- form large groups around vents
- thermal radiation detecting abilities

Question 23

how does depth and size relate?

Answer 23

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.

Question 24

what are some representative species of the deep sea?

Answer 24

Macrofauna: polychaetes, bivalvevs, molluscs
Meiofauna: nematodes, copepods, foraminifera

Question 25

what three groups can megafauna be divided into?

Answer 25

• 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

Question 26

Deep sea: the kingdom of ________.

why? who?

Answer 26

Echinoderms

• Brittle star and sea cucumber
• really diverse, fantastic range of morphological development

Question 27

what is the dominant group of decapod crustaceans? what is another one of interest?

Answer 27

squat lobster.
red crab (fishery)
prawns

Question 28

name some of the fish of the deep ocean

Answer 28

• rays
• hagfish
• flatfish
• anglerfish

Question 29

why do deep fish swim at benthopelagic depth?

Answer 29

• no swim bladder
• lipids instead
• reduce body density by converting tissues to substances lighter than water, such as gelatinous materials or cartilage

Question 30

what are some proposed reasons for gigantism?

Answer 30

• metabolic effects
• DO level
• method of food capture (mobility)

Question 31

what is the average depth of the abyssal plains?

Answer 31

4000-5000m