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!