oceans C

the ocean floor is near

shores, sediments of terrestrial origins

abyssal plain

3-6.5 km, VAST, 70 of 70% = 50% of Earth surface

above 4000 m

sediments consist primarily of calcareous shells (carbonate)

below 4000m

- calcareous shells dissolve (high pressure)

- sediments = clay and silica

what is the average sediment layer thickness?

1 km thick

sediment layer thickness at shore

15 km

what is life like in the abyssal zone?

- complete darkness

- bioluminescent communication

- cold, -2 to +2 C

- increasing pressure (750 ATM, 11000 PSI)

- water aerobic except for isolated areas

what is the benthic diversity of oceans?

surprisingly high

benthic diversity is

poorly studied, yet on same order of magnitude of high diversity communities

benthic diversity has

mostly tiny organisms, "dwarfism," low food supply

some benthics are

HUGE, 'gigantism' high oxygen, cold water, long life

benthics depend on

marine snow (shower of organic matter from upper waters)

herbivores

filter feeders

what accounts for high benthic diversity?

1. equilibrium

2. non-equilibrium

equilibrium

- stability time Ho

- very low currents

- low levels of physical disturbance

- long periods of evolutionary stability

non-equilibrium

- disturbances and top predators

- keystone preds (higher diversity)

- intermediate disturbance (higher diversity)

- preds and small scale disturbances (spatial-temporal mosaics)

what is an example of non-equilibrium

whale carcasses

- several now found - huge accumulation of organisms

- enough for one very few kms1 close enough for dispersal

methane seeps

support chemoautotrophic food webs

seamounts

- underwater mountains

- volcanic in origin, geographically active areas (tectonic plate edges = 'chain')

- common (> 1000 that are 1000m)

- diversion of UW currents

seamounts provide

habitat diversity in area with little diversity

very high diversity =

poorly studied

worlds deepest fish

- 8336 m

- near theoretical maxima for vertebrates

- snailfish

what are the threats to deep communities?

- overfishing of large marine organisms

- plastics

- acidification, changes to mineral composition of food

- mining

- climate change to deep ocean circulation

dark oxygen

- produced in the deep ocean

- made by lumps of metal on seafloor

who owns deep ocean?

- no one??

- likely huge mineral deposits...and lots of $$ to be made

hadal zone

- 6000 to 11000 m

- plums of chemicals from volcanically active areas

-- hot plumes

-- cold seeps

chemoautotrophy

- based on flow of highly reduced sulphur or carbon

- base of food chain

- endosymbionts

chemoautotrophy was first seen in

1977

>600 species of

chemoautotrophs