Topic 12: Marine Productivity

Question 1

How much of earths surface is covered by oceans?

Answer 1

70%

Question 2

Why is only a small amount of the ocean biologically productive?

Answer 2

Limiting factors restrict the frown of the most important photosynthetic organisms: algae
Limiting factors: light levels, nutrient availability

Question 3

How light affects marine productivity

Answer 3

Little light penetrates water at a greater depth than 100m- less if water is turbid
So photosynthesis is limited to surface water layers- photic zone
Life at greater depths, in the aphotic zone, relies on food produced near the surface

Question 4

Give an example of how life in the aphotic zone gets food

Answer 4

Planktonic algae is carried down by the water currents
The bodies of dead organisms sink

Question 5

How do algae get nutrients in the oceans?

Answer 5

They absorb it directly from the water because there is no soli and they have no roots
Some nutrients are readily available e.g. co2
Some are less available so are limiting to biological productivity e.g. phosphates

Question 6

How do algae gain nutrients like phosphates?

Answer 6

Phosphate in the photic zone can be increased by runoff from rivers
Usually done by upwelling
Neither of these are found in most sewage of open ocean

Question 7

Upwelling

Answer 7

Surface currents caused by strong winds, nutrients are drawn up from deep water by upwelling