Nutrient Cycles in Marine

Ecosystems Part II

Section 4

Limited Productivity

• Inorganic nutrients (ex: nitrate and phosphate

ions) are essential for growth of primary

producers

• Productivity of

primary producers

will affect

productivity of

higher trophic

levels

Example: upwelling

– high productivity

Benguela upwelling system

Removal of Nutrients

1. Sink to sea floor

• In feces

• Detritus (decaying organic

materials); organisms die

• Loss of nutrients from surface

water

• Will only return to surface by

upwelling

• Slow decomposition on sea bed

(floor) due to cold/lack of

oxygen

Removal of Nutrients

2. Incorporated into coral reefs

• Deposition of calcium carbonate for

growth of corals

Removal of Nutrients

3. Removed by harvesting

• Removing/eating fish and other marine

organisms

Nutrient Biological UsesNutrient Biological Use

Nitrogen Make proteins; synthesis of

amino acids

Carbon Synthesis of all organic

materials (ex: carbohydrates,

proteins)

Magnesium Make chlorophyll for plants

Calcium Production of bones, corals

and shells

Phosphorus Production of bones and

synthesis of DNA

• Summary of ways in nutrients are

cycled in marine systems

Nutrients derived from both

Removal (3)

In Summary• Fertilizers, like nitrogen (N), phosphorous (P), and potassium

(K), are important for plant growth and are called 'nutrients.'

The level of dissolved nutrients increases from animal feces

and decomposition (bacteria, fungi). Surface water often may

be lacking in nutrients because feces and dead matter tend to

settle to the bottom of the ocean. Most decomposition is thus at

the bottom of the ocean. In the oceans most surface water is

separated from bottom water by a thermocline (seasonal in

temperature and marginal polar regions, constant in tropics)

which means that once surface nutrients get used up (by the

plants there) they become a limiting factor for the growth of new

plants. Plants must be at the surface for the light. Nutrients are

returned to surface waters by a special type of current called

'upwelling' and it is in these areas of upwelling that we find the

highest productivity of marine life.

Website References

• http://www.seafriends.org.nz/oceano/se

awater.htm#composition

• http://www.marinebio.net/marinescience

/02ocean/swcomposition.htm

Nutrient Cycle BookletCreate a booklet highlighting the 5 major biogeochemical

Cycles in

the Marine Environment

Including:

Biological use of each nutrient processes in the

ecosystem that effect its availability

A diagram of the cycle

1. Nitrogen- 2 pages

2. Carbon- 2 pages

3. Phosphorus- 1 page

4. Magnesium- 1 page

5. Calcium- 1 page