2 of 24

pelagic zone

The pelagic zone refers to the open water column in the ocean, away from the sea floor and shore.
It is divided into different layers based on depth, light availability, and ecological conditions. �

3 of 24

1. Epipelagic Zone (Sunlit Zone)

�

Depth: 0–200 meters.

Characteristics:

Receives ample sunlight, enabling photosynthesis.
Warm temperatures compared to deeper zones.
High primary productivity due to the presence of phytoplankton.

Organisms:

Phytoplankton, zooplankton, small fish, jellyfish, and large predators like sharks and tuna.

4 of 24

2. Mesopelagic Zone (Twilight Zone)

�

Depth: 200–1000 meters.

Dim light penetrates this layer, insufficient for photosynthesis.
Transitional zone between the sunlit and dark zones.

Characteristics:

Bioluminescence is common for communication, camouflage [HIDE], and predation.

Adaptations:

Lanternfish, squid, bristle mouths, and hatchetfish.

Organisms:

5 of 24

3. Bathypelagic Zone (Midnight Zone)

�

Depth: 1000–4000 meters.

Characteristics:

Completely dark except for bioluminescent organisms.
High pressure and cold temperatures.

Organisms:

Anglerfish, gulper eels, and other deep-sea creatures.

6 of 24

4. Abyssopelagic Zone

�

Depth: 4000–6000 meters.

Extreme cold and high pressure.
Lacks light entirely.

Characteristics:

Brittle stars, sea cucumbers, and some species of deep-sea fish.

Organisms:

7 of 24

5. Hadalpelagic Zone

Depth: Below 6000 meters (oceanic trenches).

Characteristics:

Found in the deepest parts of the ocean, like the Mariana Trench.
Extreme pressure and low temperatures.

Organisms:

Amphipods, deep-sea fish, and extremophiles.

9 of 24

NERITIC ZONE

10 of 24

INTRODUCTION

Marine habitats are broadly classified into pelagic (open ocean) and benthic (ocean floor) zones. The neritic zone falls within the pelagic system but has its unique features:

Pelagic Zone (Open Water)

Neritic Zone:

Shallow waters over the continental shelf.
Extends from the intertidal zone to about 200 meters in depth.
Includes sub-habitats such as coral reefs, seagrass beds, and kelp [a type of brown algae] forests.

Kelp forests

11 of 24

Characteristics of the Neritic Zone

Location:

Found along the continental shelf.
Typically extends to depths of about 200 meters (656 feet).

Sunlight:

High penetration of sunlight (photic zone) supports photosynthesis, making it ideal for plant and algal growth.

Temperature:

Generally warmer than deeper ocean zones due to sunlight exposure.

Water Quality:

Rich in nutrients due to runoff from land and upwelling currents.

12 of 24

Flora

Phytoplankton: Microscopic algae serve as the base of the food chain.

Seaweeds and Algae: Include kelp and other macroalgae.

Seagrasses: Found in shallower parts of the zone.

13 of 24

Fauna

Zooplankton: Serve as primary consumers.
Fish: Includes commercial species like cod [panna], tuna, and sardines [chalai].
Invertebrates: Crustaceans (e.g., crabs, lobsters), mollusks (e.g., clams, oysters), and coral.
Marine Mammals: Dolphins, seals, and other species frequent this zone.
Reef Builders: Coral reefs thrive in warm, shallow parts of the neritic zone.

seals

14 of 24

Ecological Importance

Biodiversity Hotspot: Supports a diverse range of species, including commercially valuable fish.

Primary Productivity: Contributes significantly to the global oxygen supply through photosynthesis.

Breeding Ground: Many marine organisms raise its young ones in this area.

15 of 24

Human Impact

Fishing: Overfishing can deplete fish stocks in this biologically rich zone.

Pollution: Runoff from agriculture and industries introduces pollutants, affecting marine life.

Habitat Destruction: Activities like dredging and coral reef destruction threaten biodiversity.

16 of 24

Classification Based on Depth and Distance

Intertidal Zone: Transition between land and neritic waters.

Shallow Neritic Zone: Up to 50 meters; includes seagrasses and coral reefs.

Deep Neritic Zone: 50–200 meters; dominated by pelagic fish and deeper benthic species.

17 of 24

Oceanic province

The oceanic province refers to the vast open ocean beyond the continental shelf, encompassing the majority of Earth's marine environment.
It contrasts with the neritic zone, which lies over the continental shelf. This province is characterized by deep waters, limited nutrient availability, and distinct zones based on depth and light penetration.

18 of 24

Key Characteristics of the Oceanic Province

Location:

Begins at the edge of the continental shelf and extends into the open ocean.
Covers areas with depths often exceeding 200 meters.

Depth and Zones:

Divided into distinct zones based on depth and light availability:

Epipelagic Zone (0–200 m): Sunlit, supports photosynthesis, and is home to most marine life.
Mesopelagic Zone (200–1,000 m): Twilight zone with limited light, home to bioluminescent organisms.
Bathypelagic Zone (1,000–4,000 m): Midnight zone, no light, pressure increases, sparse life.
Abyssopelagic Zone (4,000–6,000 m): Cold, dark, with unique deep-sea species.
Hadalpelagic Zone (>6,000 m): Found in deep ocean trenches, extreme environments.

Light Availability:

Only the epipelagic zone receives sunlight, making it the primary site for photosynthesis.

Nutrient Levels:

Generally lower than in the neritic zone, except in areas of upwelling or near hydrothermal vents.

19 of 24

Flora and Fauna

The oceanic province supports diverse life forms, adapted to varying conditions across its zones.

Flora:

Phytoplankton: The primary producers in the epipelagic zone.

Algae: Restricted to the upper, sunlit layers.

Fauna:

Epipelagic Zone: Large predators like tuna, sharks, and dolphins; zooplankton; and small schooling fish.

Mesopelagic Zone: Bioluminescent organisms like lanternfish and jellyfish.

Bathypelagic and Abyssopelagic Zones: Anglerfish, gulper eels, and other specialized deep-sea creatures.

Hadalpelagic Zone: Extreme organisms such as amphipods and snailfish.

20 of 24

Ecological Importance

Carbon Cycle:

The oceanic province plays a vital role in carbon sequestration through the biological pump.

Global Climate Regulation:

Absorbs a significant portion of atmospheric CO₂.

Biodiversity Reservoir:

Home to unique ecosystems like hydrothermal vents and deep-sea trenches.

21 of 24

Human Interaction

Exploration

Advances in deep-sea exploration have revealed new species and ecosystems.

Resource Extraction

Mining for minerals and oil is an emerging concern.

Pollution

Microplastics and chemical contaminants are accumulating in even the deepest zones.

22 of 24

Benthic zonation

Benthic zonation refers to the ecological division of the ocean floor into distinct zones based on depth, light availability, and environmental conditions. The benthic zone encompasses all areas of the ocean floor, from shallow coastal regions to the deepest ocean trenches.

23 of 24

Zones of Benthic Zonation

The benthic zone is divided into several regions, each with unique physical, chemical, and biological characteristics:

24 of 24

Supralittoral Zone (Splash Zone)

Found above the high tide line.
Periodically wetted by wave spray but not submerged.
Fauna: barnacles, and crabs.