Deep Sea Flashcards
Many environments
Mid-water dysphotic and aphotic
Continental slopes
Soft sediment benthos
Has-substratum benthos
Ephemera, food falls
Chemosynthetic environments
Dysphotic Zone
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
Aphotic Zone
No more downwelling sunlight
Bioluminescence
Prey can be increasingly scarce
Continental slope
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.
Abyssal plains
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
Seamounts
Rise more than 1000m.
>43000 worldwide
bare rock surface for filter feeders.
Enhanced flow around them, increases food.
MORs
> 60000km long undersea rift
Rocky habitat
Non-chemosynthetic fauna
Ocean trenches
ROVs and HOVs.
Funnel organic input.
Seismic activity leads to smothering events
Adaptations to high P
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
Predation
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
Scavenging
Benthic scavengers have olfactory and other sensory adaptations to find larger food falls.
Arrive quickly and remove flesh rapidly.
Exploiting food falls
Skeletons and wood.
Osedax spp. Bone eating polychaetes, symbiotic bacteria digest lipids and bone.
Xylophagidae wood eating bivalves, symbiotic bacteria.
Finding a mate
Opportunistic, stick sperm packet to female.
Pairing behaviour.
Accessory dwarf male
Sensory and camouflage adaptations
Faint downwelling sunlight present in the dysphotic zone
biolumiscence
Eyes
Bioluminescence
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
Catching prey
Illuminate lures
Suborbital photophores
Attracting mates
Nearest neighbour distances generally beyond signal range
Pheromones.
To evade or deter
Light reactions to distract
Burglar alarm, big display alarm
Counter illumination
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.
Other camouflage
Red bodies appear black under blue light.
Red cheaper than black
Ultra black in some aphoticE
Evo history of deep-sea taxa
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.
Fisheries
On slope and seamount habitats
Slow growth and maturity of deep species
Collateral to seabed habitats
Litter
Burned coal in historic steamship areas
Modern litter ubiquitous in deep sea
Microplastics
Accumulate in deep sediments
~10,000x conc found at surface
Pollution
Oil spills and gas
Deep sea dumping of radioactive and industrial waste.
Mining
Initial exploratory mining claims already approved by UN
Potential impacts poorly understood
Climate change
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
