Deep Sea

Question 1

Many environments

Answer 1

Mid-water dysphotic and aphotic
Continental slopes
Soft sediment benthos
Has-substratum benthos
Ephemera, food falls
Chemosynthetic environments

Question 2

Dysphotic Zone

Answer 2

200m to 1000m
Some down welling sunlight still present but insufficient for net photosynthesis
90% of animals are bioluminescent
Daily vertical zooplankton migrations
Some of the largest invertebrate species

Question 3

Aphotic Zone

Answer 3

No more downwelling sunlight
Bioluminescence
Prey can be increasingly scarce

Question 4

Continental slope

Answer 4

Areas of steeper slope provide rocky seafloor for colonisation by filter-feeders.
Submarine canyons, conduits for OM, from productive continental shelves to the deep.
Deep sea coral provides important habitat for other taxa.
Deep water corals are stony corals.
Growth rates are comparatively slow as a result.
Slow growth makes them vulnerable to damage by trawling of deep-water fisheries.

Question 5

Abyssal plains

Answer 5

Flat soft-sediment seabed, ~25% global ocean floor.
Underlying ocean crust covered sediment up to 1km thick.
Also, areas of sediment abyssal hills covering ~33% of global ocean floor.
High species richness of macrofauna living in sediment
High richness of meiofauna

Question 6

Seamounts

Answer 6

Rise more than 1000m.
>43000 worldwide
bare rock surface for filter feeders.
Enhanced flow around them, increases food.

Question 7

MORs

Answer 7

> 60000km long undersea rift
Rocky habitat
Non-chemosynthetic fauna

Question 8

Ocean trenches

Answer 8

ROVs and HOVs.
Funnel organic input.
Seismic activity leads to smothering events

Question 9

Adaptations to high P

Answer 9

P can trap water on surfaces of unfolded proteins, can’t fold correctly.
Chaperone molecules remove water.
FIsh and decapods use TMAO, concs increase with depth. Too much causes fish to be hypertonic <9000m, elasmobranch have high concs at surface <4000m.
Exoskeletons of amphipods coated in Aliminium hydroxide to protect calcite from dissolving

Question 10

Predation

Answer 10

Prevalent in aphotic and dysphotic zones.
Ambush predation, less E
Deep-sea predators can get bigger prey, flexible jaws and stomach.
Ambush species of usual filter feeders

Question 11

Scavenging

Answer 11

Benthic scavengers have olfactory and other sensory adaptations to find larger food falls.
Arrive quickly and remove flesh rapidly.

Question 12

Exploiting food falls

Answer 12

Skeletons and wood.
Osedax spp. Bone eating polychaetes, symbiotic bacteria digest lipids and bone.
Xylophagidae wood eating bivalves, symbiotic bacteria.

Question 13

Finding a mate

Answer 13

Opportunistic, stick sperm packet to female.
Pairing behaviour.
Accessory dwarf male

Question 14

Sensory and camouflage adaptations

Answer 14

Faint downwelling sunlight present in the dysphotic zone
biolumiscence
Eyes

Question 15

Bioluminescence

Answer 15

Oxidation of a luciferin substrate via enzyme
Substrate compunds involved vary
Substrates from food and some host bacteria in photophore organs
Blue light propagates furthest
Uses:
- Catching prey.
- Attracting mates.
- Evading/deterring predators.
- Counter illumination camouflage

Question 16

Catching prey

Answer 16

Illuminate lures
Suborbital photophores

Question 17

Attracting mates

Answer 17

Nearest neighbour distances generally beyond signal range
Pheromones.

Question 18

To evade or deter

Answer 18

Light reactions to distract
Burglar alarm, big display alarm

Question 19

Counter illumination

Answer 19

Break/mask silhouette.
Eyes of some species have yellow lenses
yellow lens filters out blue
Upward and down looking eyes.
Large eye upwards.
Transparent to avoid shadows.

Question 20

Other camouflage

Answer 20

Red bodies appear black under blue light.
Red cheaper than black
Ultra black in some aphoticE

Question 21

Evo history of deep-sea taxa

Answer 21

Few exhibit gigantism
Deep ocean may be an island for evolution of body size among colonists
Some groups radiated into deep oceans via polar, no thermal barrier with depth.

Question 22

Fisheries

Answer 22

On slope and seamount habitats
Slow growth and maturity of deep species
Collateral to seabed habitats

Question 23

Litter

Answer 23

Burned coal in historic steamship areas
Modern litter ubiquitous in deep sea

Question 24

Microplastics

Answer 24

Accumulate in deep sediments
~10,000x conc found at surface

Question 25

Pollution

Answer 25

Oil spills and gas
Deep sea dumping of radioactive and industrial waste.

Question 26

Mining

Answer 26

Initial exploratory mining claims already approved by UN
Potential impacts poorly understood

Question 27

Climate change

Answer 27

Warming water
Acidification
Changes in particulate organic C flux
Reduction in O supply to deep:
- decreased solubility in warmer water
- Increased respiration rates
- Weaking ocean circulation