The Ocean Depths

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THE OCEAN DEPTHS

2.

THE OCEAN DEPTHS
From 100-200 m (600 ft) to the deepest part
Mesopelagic (to depth of 3300 ft -1000 m)
Twilight
THE DEEP - Bathypelagic, Abyssopelagic &
Hadopelagic
No sunlight at all

3.

THE MESOPELAGIC
From 100-200 m to depth of 3300 ft (1000 m)
Not enough light for photosynthesis, no primary
productivity
Enough light to see by – like twilight
Chronically short of food
High pressure

4.

THE MESOPELAGIC - ADAPTATIONS
Small size
Large mouths
Hinged, extendable jaws
Needle-like teeth
Unspecialized diets
Flabby watery flesh – no swim bladder
Large sensitive eyes
Countershading & bioluminescence

5.

THE MESOPELAGIC - ADAPTATIONS

6.

THE DEEP
From 1000 m – deepest trenches
No light
Cold
High pressure (up to 1000 atm)
Lack of food
Lack of mates

7.

THE DEEP - ADAPTATIONS
Small size (but larger than mesopelagic)
Black
Small eyes
Sluggish & sedentary
Large mouths (consume prey larger than
themselves)
Expandable stomachs
Flabby watery flesh – no swim bladder
Hermaphroditism / Male parasitism /
Bioluminescence

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THE DEEP- ADAPTATIONS

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Characteristics of the benthic zone:
- 90% of the organisms are found on the continental shelf, others
are in the abyss
- deep sea benthhic fishes dark brown or black
- meso- and deep pelagic zone 99% of the organisms are
bioluminescent (produce light by chemical reaction)
- very stable environment - increases with depth
- lack of light is a major limiting
factor - reducing food, predation
and mating
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10.

- oxygen is supplied from cold, saline waters of the poles
- biomass decreases with depth - this low population density is
directly related to food scarcity
NOAA
- communities entirely composed of consumers and scavengers
- producers are found only in photic zones; decomposers like
bacteria are more common in mid-water mesopelagic zone
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11.

Hydro-Thermal Vent Communities
The exception in benthic communities’ producers are the
chemosynthetic bacteria around hydrothermal vent.
In 1977, scientists working in the DSV
Alvin with project FAMOUS (Robert
Ballard), discovered unique
hydrothermal vent communities of
previously unknown organisms.
Since then, vent communities have been
found in all oceans at depths varying
from 1 to 2 miles down.
NOAA
Bacteria living near the vent use
hydrogen sulfide dissolved in
seawater to build organic
molecules in a process called
chemosynthesis.
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Animals clustered near the vents grow to huge sizes;
can withstand temperature differences from 36o to 662o.
The community also has many suspension-feeders attached to the
hard rock bottom which is unusual in the deep sea.
Geologist estimate that the vents probably last for 100 years;
when supply of H2S is exhausted, the ecosystem dies.
NOAA
In other areas, called Cold Seeps, also have
chemosynthesis. Here methane and
sulfide-rich fluids seep into the ocean floor
where symbiotic bacteria use sulfuroxidation for survival.
Cold Seeps are home to millions of benthic
worms, crabs and mollusks.
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13.

OCEAN FLOOR - SEDIMENTS
Continental shelf - terrigenous sediment
derived from eroded continent
erosion, volcanic eruption, wind-blown dust
Ocean floor – biogenous sediment
Derived from once living organisms (plankton)
foraminifera, coccolithophores, radiolarians,diatoms

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Radiolarians – equatorial regions
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Diatoms – polar regions
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