2.2 Types of Aquatic Ecosystems
9
Table 2.4 Different zones of the ocean
Ocean zones
Depth range
Organisms and features
Epipelagic zone (Sunlight
zone)
Surface to 200 m
Abundant sunlight, minimal
pressure, higher
temperatures. Coral reefs and
photosynthetic organisms,
more ocean life and human
activities
Mesopelagic zone (Twilight
zone)
200–1000 m
Lower light intensity (mostly
blue light). Zooplankton and
rarer sea life such as the
Barreleyes, ribbonfish and
snipe eels. Vertical migration
of organisms and gradient of
oxygen level, light intensity,
temperature and salinity
Bathypelagic zone (Midnight
zone)
1000–2000 m
Dark, pressure up to
5.858 lbs/square inch,
bioluminescent organisms.
Nematodes, bivalve molluscs,
polychaetes, crustaceans,
sipunculid worms and
gastropods
Abyssopelagic zone (Abyssal
zone)
2000–6000 m
Near freezing point, high
pressure, rare species and
invertebrates such as the giant
squid. Includes some parts of
the ocean floor
Hadalpelagic zone (The
trenches)
6000–11,000 m (valleys
below the ocean floors)
Deepest known is the
Mariana Trench in Japan.
temperature and pressure,
few rare species recently
discovered include the
Mariana Snailfish and
Ethereal snailfish
2.2.1 Estuaries
Estuaries are very important in the maintenance of the aquatic biodiversity. They are
water bodies which are enclosed by structures such as vegetation and the organisms;
they have easy access to the sea (Dame 2008). The water in the estuaries is brackish as
a result of ocean water mixing with freshwater. There is also variation in turbulence
depending on the contact with the sea. These estuaries serve as nurseries for young
species. The underwater plant roots protect them from bigger prey simply by serving
as a hiding place that only allows entry of organisms below a certain size. This allows
them a better chance of survival and growing to a safer size after which they can then
easily access the sea and begin their journey to their final home in the deeper waters.
9
Table 2.4 Different zones of the ocean
Ocean zones
Depth range
Organisms and features
Epipelagic zone (Sunlight
zone)
Surface to 200 m
Abundant sunlight, minimal
pressure, higher
temperatures. Coral reefs and
photosynthetic organisms,
more ocean life and human
activities
Mesopelagic zone (Twilight
zone)
200–1000 m
Lower light intensity (mostly
blue light). Zooplankton and
rarer sea life such as the
Barreleyes, ribbonfish and
snipe eels. Vertical migration
of organisms and gradient of
oxygen level, light intensity,
temperature and salinity
Bathypelagic zone (Midnight
zone)
1000–2000 m
Dark, pressure up to
5.858 lbs/square inch,
bioluminescent organisms.
Nematodes, bivalve molluscs,
polychaetes, crustaceans,
sipunculid worms and
gastropods
Abyssopelagic zone (Abyssal
zone)
2000–6000 m
Near freezing point, high
pressure, rare species and
invertebrates such as the giant
squid. Includes some parts of
the ocean floor
Hadalpelagic zone (The
trenches)
6000–11,000 m (valleys
below the ocean floors)
Deepest known is the
Mariana Trench in Japan.
temperature and pressure,
few rare species recently
discovered include the
Mariana Snailfish and
Ethereal snailfish
2.2.1 Estuaries
Estuaries are very important in the maintenance of the aquatic biodiversity. They are
water bodies which are enclosed by structures such as vegetation and the organisms;
they have easy access to the sea (Dame 2008). The water in the estuaries is brackish as
a result of ocean water mixing with freshwater. There is also variation in turbulence
depending on the contact with the sea. These estuaries serve as nurseries for young
species. The underwater plant roots protect them from bigger prey simply by serving
as a hiding place that only allows entry of organisms below a certain size. This allows
them a better chance of survival and growing to a safer size after which they can then
easily access the sea and begin their journey to their final home in the deeper waters.