pelagic demersal zones
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PELAGIC & DEMERSAL ZONES
Issa Agustin Alex Aldaba
Benedict Jr Evangelista Christine Magpayo
Yenyen Te
POP QUIZ! Identify
this animal:
POP QUIZ! Identify
this animal:
POP QUIZ! Identify
this animal:
Answer:Lophiiformes a.k.a. Anglerfish
Pelagic Zone: • part of the water near the surface/from the surface
to almost the bottom • has the largest volume, 1,370,000,000 cubic
kilometres (330,000,000 cubic miles), and the greatest vertical range (36,000 feet)
• constantly changing due to ocean currents and other conditions
• popularly referred to as “open water” !
Demersal Zone: • nearer to the bottom of the ocean (seabed or
benthos) • right above the benthic zone
Features of Different Pelagic Zones
Epipelagic Zone
• from the surface down to the depth where photosynthesis can no longer occur because of the limited light, generally about 200 meters
• nearly all primary production of the ocean occurs here
• where most pelagic animals are found
• dominated by phytolankton, diatoms and dinoflagellates
Mesopelagic Zone • “The Twilight Zone” • no longer enough light for photosynthesis
and low oxygen levels too • example of species: squids, nautilus shells
and swordfish !!Bathypelagic Zone • no light can ever reach except for
bioluminescence • the pressure is great; therefore organisms
need special adaptive features • source of food for organisms are dead
ones or each other
Abyssopelagic Zone • where the continental slope slopes off;
more than 30% of the bottom of the ocean is here
• freezing temperatures and crushing weight
• surprisingly, however, the oxygen level is higher than in the shallower zones because the low temperatures make dissolving of gasses easier. !
Hadopelagic Zone • deep trenches that can reach several
kilometers deeper than the surrounding ocean floor
Features of the Demersal Zone
Similar to the deeper levels of the pelagic zone, the demersal zone has high hydrostatic pressure and low temperature.
!• Most inhabitants of the demersal zone are highly
specifically evolved according to their environment and ecological conditions of the deep sea.
• Some examples are: • Bioluminescent organs • Specialized eyes (e.g. anglerfish) • Elaborate gas glands and specialized swim bladder
construction • Remarkable jaws and teeth
Importance of Oceanic Zones
How do these zones benefit us? !
Pelagic and Demersal Fishing • For pelagic zone: catching and pelagic trawling • For demersal zone: demersal trawling
!However, it is a point for us to be careful because large-scale pelagic fishing has been linked to overfishing and large-scale demersal trawling has been linked to the destruction of seabeds/habitats.
POP QUIZ!
POP QUIZ! Name the pelagic zone
where most of the Pelagic Animals can be found!
Epipelagic, Mesopelagic, Bathypelagic, Abyssopelagic, or Hadopelagic Zone
POP QUIZ! Name the pelagic zone
where most of the Pelagic Animals can be found!
Answer: Epipelagic Zone
Epipelagic, Mesopelagic, Bathypelagic, Abyssopelagic, or Hadopelagic Zone
CHALLENGES AND OPPORTUNITIES
PELAGIC ZONE OR OPEN OCEANEPIPELAGIC ZONE
• meets the photic zone above and becomes very dark as depth increases
• because nutrients are limited here, some animals rise to the photic zone at night for food
• people can easily go scuba diving • packed with ocean life because of the
sunlight that penetrates the surface • Much of the life in the aphotic zone
depends on detritus floating down from the epipelagic zone.
MESOPELAGIC ZONE
PELAGIC ZONE OR OPEN OCEANBATHYPELAGIC ZONE
• freezing temperatures and incredible pressures • only a few organisms adapted to survive • Deep-water squid, octopus, basket stars,
seapigs, and seaspiders • Other crustaceans living at these depths have
adapted by becoming transparent and have evolved without eyes because they serve no purpose at these depths.
ABYSSOPELAGIC ZONE
• Animals rely on detritus for food or on eating other animals in this zone (fish, mollusks, crustaceans, and jellyfish)
• Sperm whale, Amphipods, Vampire Squid
Other issues…Increases the amount of primary
production available, but the increase is not transferred throughout the food web
with linearity or proportionality EUTROPHICATION
Microplastic ingestion appears to be common, in relatively small quantities,
across a range of fish species irrespective of feeding habitat
MARINE POLLUTION
POP QUIZ! Identify this
animal:
POP QUIZ! Identify this
animal:
POP QUIZ! Identify this
animal:
Answer: Vampire Squid
PELAGIC AND DEMERSAL
ORGANISMS
Herring (Clupea harengus)
Mullet (Mugil cephalus)Tuna (Thunnus sp.)
Mackerel (Scomber scombrus)
Pelagic
Demersal
Flatfish (Order: Pleuronectiformes)
Manta ray (Order: Rajiformes)
Cod (Gadus sp.)
Nurse shark (Ginglymostoma sp.)
Adaptations: PelagicHighly forked to lunate tail —> decreases turbulence and drag because the surface area is smaller; facilitates their constant swimming and migration in open water
Adaptations: PelagicFusiform/Spindle shaped body —> For streamlined motion; Fast swimming in open water
Adaptations: PelagicFor tunas and sharks: caudal keel —> For balance and stability during gliding
Adaptations: DemersalDorso-ventrally flattened or depressiform body shape
—>Bottom-dwelling habit; Food source found on sea floor
Adaptations: DemersalInferior mouth: Upper jaw longer than lower jaw or mouth is found on their underside —> Food source on sea floor or below them
Adaptations: Demersal
Oil-rich liver —> Neutral buoyancy; To move just off the surface of the ocean floor
SUPER POP QUIZ!
SUPER POP QUIZ! Describe the proper
streamline position when diving into the water like
that of pelagic fish
TROPHIC STRUCTURES OF PELAGIC AND
DEMERSAL ORGANISMS
Review on the Definition of Trophic Structure
It is simply the position that an organism occupies in a food chain - what it eats, and what eats it. !
Pelagic (Primary Producers, Herbivorous Zooplankton, Carnivorous Zooplankton, Small Pelagic fish, Large Pelagic Fish) !
Demersal (Primary Producers, Herbivorous Zooplankton, Benthic Detritivores, Demersal fish, Large Fish)
Common Trophic Structure: Primary Producers
a. Dinoflagellates
b. Diatoms c. Microflagellates
Common Trophic Structure : Primary Consumers
!
!
Herbivorous Zooplankton
a. Microzooplankton b. Herbivorous Krills and Copepodsc. Pteropodsd. Larvaee. Chordates
Pelagic Trophic Structure: Secondary Producers
Carnivorous Zooplankton
a. Gelatinous Zooplankton b. Carnivorous krill and Predatory copepods c. Fish juveniles
Pelagic Trophic Structure: Small Pelagic Fish
Small fish (prey on herbivorous and carnivorous zooplankton) —> herring, anchovy, sardine, smelt, sand lance
Pelagic Trophic Structure: Large Pelagic Fish
Large fish (Which is eaten by main predators like birds, mammals)
Coho Salmon, Tuna, Sharks, Billfish
Demersal Trophic Structure: Benthic Detritivores
Demersal Trophic Structure: Demersal Fish
Which in turn is eaten by the main predators like mammals
Interaction between species
Predation (big pelagic
fish and small pelagic
fish)
Competition (Young Cods
and small herring fish)
Reference• Bone, Q. & Moore, R. Biology of Fishes, 3rd ed. 2008. New York, N.Y.: Taylor & Francis Group • http://marinebio.org/oceans/open-ocean/ • http://marinebio.org/oceans/open-ocean/ • Some Effects of Eutrophication on Pelagic and Demersal Marine Food Webs (R. Eugene Turner,
2001) h"p://www.agu.org/books/ce/v058/CE058p0371/CE058p0371.pdf
• Occurrence of microplastics in the gastrointestinal tract of pelagic and demersal fish from the English Channel (A.L. Lushera, M. McHughb, R.C. Thompsona) from the Marine Pollution Bulletin 15 February 2013 h"p://www.sciencedirect.com/science/arAcle/pii/S0025326X12005668
• The Open Ocean. (n.d.). MarineBio Conservation Society ~ Marine Biology, Ocean Life Conservation, Sea creatures, Biodiversity, Research.... Retrieved from: <http://marinebio.org/oceans/open-ocean/>
• Editors of Encyclopædia Britannica. (n.d.). Pelagic zone (Oceanography). Encyclopedia Britannica Online. Retrieved from: <http://www.britannica.com/EBchecked/topic/449062/pelagic-zone>
• No author, (n.d.). Pelagic Zone, Palaeos.org. Retrieved from: <http://www.palaeos.org/Pelagic> • The Difference Between Pelagic and Demersal Fishing. (2010, July 6). eHow. Retrieved from:
<http://www.ehow.com/about_6539821_difference-pelagic-_amp_-demersal-fishing.html>
Thank you!
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