L03 - Water Zones

Question 1

What are the two major water zones?

Answer 1

There are two water zones that break up into two smaller ones:

1. Coastal (Neritic/sub-littoral)
2. Open Sea (oceanic/pelagic)

Question 2

Explain the coastal zone:

Answer 2

The coastal zone breaks into the Neritic/sub-littoral zone:

It is the region of shallow water (200 m depth) above the continental shelf. Due to light and nutrient, very productive part of the coast.

Question 3

Explain the Open Sea zone:

Answer 3

The Open Sea zone is also the Oceanic (Pelagic) zone:

It is typically defined as the area of the ocean beyond the continental shelf. Usually, it begins where the water depths drop to below 200m. It is in turn divided into subzones based on amount of sunlight.

Question 4

What is the Euphotic Zone (5)

Answer 4

The Open Sea//Oceanic//Pelagic Zone is divided into three subzones based on the amount of sunlight.

The first is the euphotic (Photic) zone:

1. Lots of light (the sunlight layer).
2. From 0 - 200 meters (top
   layer).
3. Photosynthesis takes place
   here.
4. Sea-surface microlayer (0-1mm) very important with:
5. Lots of planktons, and micro organisms such as bacteria, etc.

Question 5

What is the Bathyal Zone? (5)

Answer 5

1. The dimly lit part of ocean below the Photic Zone
2. From 200 - 1500 meters.
3. Also called the twilight layer.
4. In this zone only a small
   amount of light penetrates the water.
5. Plants do not grow here due to the insufficient amount of light.

Question 6

What is the Abyssal Zone

Answer 6

1. Completely dark. (Aphotic)
2. Extends to a depth of 4000 to 6000 meters.
3. Water here is very cold &
   has little dissolved oxygen.
4. About 90% of the ocean is
   in this layer.

Question 7

What is the Benthic Zone?

Answer 7

This is the Ocean floor

1. The ocean floor consists partly of
   sediments (mostly sand and mud)
2. Many marine animals like worms and
   clams, burrow, .. (living in mud and
   soil of ocean floor)
3. Bacteria are common & can go down
   500 meters below ocean floor.
4. The Benthic environment extends
   from the shore to the deep.

Question 8

Describe the marine life in different zones:

Answer 8

1. Based on level of lights received,
   temperature, salinity, etc., different
   zones support different species.
2. Photic zone is to a large extent home to marine plants where they carry out a lot of photosynthesis activities.
3. In particular they are rich in plankton
   including both animal and plant type
   planktons