1. The ocean can be divided into horizontal and vertical zones based on depth and distance from land, with the epipelagic zone located at the top within 200 meters of the surface where sunlight and photosynthesis occur.
2. Below the epipelagic zone is the mesopelagic zone from 200-1000 meters where low light levels prevent photosynthesis, and many species have bioluminescence. The bathypelagic zone extends from 1000-4000 meters with no sunlight and low nutrients.
3. Marine organisms can be classified as plankton, nekton, or benthos depending on their lifestyle as floaters, swimmers, or bottom dwell
3. The ocean can be divided into zones based on depth (vertically)
and distance from land (horizontally)
• Horizontal- Neritic / Oceanic
• Vertical- 1.Epipelagic (top) / Euphotic (good)
2. Mesopelagic (middle) /Disphotic (low)
3. Bathypelagic (deep) / Aphotic (without)
4. Abyss pelagic (bottomless)
There are more than 250,000 identified marine species. Most live in sunlight surface
seawater. 16.7% of Earth’s animals are marine 2% inhabit pelagic environment
(most of the oceans are cold and dark) 98% are benthic.
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5. 1. Epipelagic Zone [Sunlight Zone]
This zone has the depth of about 200 meters (656 feet) below the ocean surface.
It has the most visbile light, ( most heat ). It ranges from 104 to 27º F. Enough light for
photosynthesis.
Example- Plant Species: Phytoplanktons, Seaweed or free-floating algae, red algae,
angiosperms, mangroves, sea grass.
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6. 2. Mesopelagic Zone [Twilight Zone]
This zone extends from epipelagic zone at about 200 meters (656 feet) to a depth of about 1000 meters
(3,280 feet).
Sunlight penetrates to a very little extent, which makes the process of photosynthesis impossible.
Many of the animals in this zone have bioluminescence.(This is when a fish has a certain chemical that
creates light to help them. Eg- viperfish). There is not enough light for photosynthesis so the organisms have
to eat food that is filtered down from above. There are filter feeders, grazers, and predators.
Supported Plant Species: No plants exist in this zone due to lack of light.
Supported Animal Species: Squid, crab, cuttlefish, swordfish, wolf eels, bigeye tuna. Most of the fish in
this zone are highly mobile with scaled, muscular bodies and rigid bones. They have big kidneys and hearts.
Their gills (respiratory organ) are well-developed.6
7. 3.Bathypelagic Zone [Midnight Zone]
This zone extends from mesopelagic zone at about 1000 meters (3,280 feet) to a depth of about
4000 meters (13,123 feet).
Sunlight doesn’t penetrate in this zone. This region is very low on nutrient levels.
Supported Plant Species: No plants exist in this zone due to lack of light.
Supported Animal Species: Squid, sea stars , large whale, octopus, frill shark. Most of the fish
have low metabolism rate as the zone lacks in nutrients. The fish have tiny eyes, huge mouths and
long jaws to help them swallow anything and fragile skin, faint muscles, and a slimy body.
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8. 4. Abyssopelagic or Abyssal Zone-
It lies in perpetual darkness. The name is Greek-based and means “bottomless”. It is from
2,000-6,000 meters.
Water pressure increases one atmosphere every 33 feet in depth, animals in the abyssal
zone must be able to withstand tremendous amounts of pressure, tempareture 2-3° C.
This layer is low in oxygen, food, and nutrients.
Example- Deep-Water Squids, Basket Stars, Seapigs, Sea Spiders,
Echinoderms, and Medusas. In the Abyss live the deep water squid is completely
transparent and has photophores on its tentacles to attract food and scare away
predators.
Unique and varities type of creatures find in this zone- eg (tube worms, that
have no mouth, no stomach, no intestines, and no excretory system).
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10. Classification of Marine Organisms by Lifestyle
1. Plankton (floaters) - Plankton are weak swimmers, and are
known as drifters, unable to counteract currents.
Phytoplankton (plants)
Zooplankton (animals)
2. Nekton (swimmers) - Nekton are active swimmers capable
of counteracting currents. Eg- adult fish and squid, Reptiles.
3. Benthos (bottom dwellers) - Benthos are most
abundant in shallower water. Many live in perpetual
darkness, coldness,
Eg- Epiflora or epifauna live on the sea bottom.
Nektobenthos swim or crawl through water above
the seafloor.
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11. Types of Marine Ecosystems –
Salt Marsh
Coastal wetlands that are flooded and drained by salt water brought in by the tides. Eg- Great Rann of
Kutch
Intertidal Zones
Intertidal zones are the areas that are visible during low tide and covered up by saltwater during high tide.
These areas have a higher salinity because salt is left behind after evaporation has occurred. Eg- Western
Indian ocean
Estuaries
Where change in salinity between saltwater and freshwater sources, for example, the confluence between a
river and an ocean. Eg- Mississippi River
Lagoons
The National Geographic Society defines lagoons as a "shallow body of water protected from a larger body
of water (usually the ocean) by sandbars, barrier islands, or coral reefs." There are two different types of
lagoons: coastal lagoons and atoll lagoons. Eg- The Blue Lagoon in Iceland11
12. Mangroves
Mangroves are a compilation of different mangrove tree species living together near the
coastline to create a forest.
Coral Reefs
The largest being that of the Great Barrier Reef. These reefs are composed of large coral
colonies of a variety of species living together..
Deep Sea and Sea Floor
The deep sea conquers up to 95% of the space occupied by living organisms. Combined with the
sea floor (or benthic zone), these two areas have yet to be fully explored.
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