Nutrients in the oceans

Question 1

What are examples of key macronutrients?

Answer 1

• Nitrogen
• Phosphorous
• Silicon

Question 2

What are key examples of micronutrients?

Answer 2

• iron
• Copper
• Manganese
• Zinc
• Many others

Question 3

What might the effect of lack of macronutrients be?

Answer 3

Lack of these often limits plant growth on a regional or seasonal scale
–– especially Nitrogen and phosphorus –– likewise presence of excess N&P encourages growth

Question 4

What might the effect of lack of micronutrients be?

Answer 4

Lack of these may limit growth locally but less frequently – presence of excess may be toxic

Question 5

What are the most common forms of fixed nitrogen?

Answer 5

• NO-3 - nitrate
• NH3 - ammonia
• Organic nitrogen compounds – dissolved or particulate

Question 6

Why is it difficult to ‘fix’ nitrogen?

Answer 6

Breaking the N-N bonds is very difficult and requires a great deal of energy

Question 7

What is the process of nitrogen fixation?

Answer 7

1. Nitrogen gas (product) is ‘fixed’ by nitrogen fixing bacteria (Cyanobacteria) into ammonia. Or the product is put through fertiliser product (Haber process) and oxidation to produce Nitrate.
2. Nitrate is utilised by primary production and consumption, to be ‘fixed’ into organic Nitrogen e.g. proteins

THIS IS VERY SIMPLE EXPLANATION ! U NEED TO KNOW THIS

Question 8

What is true of nitrate/nitrite concentration in the surface waters of the North Sea?

Answer 8

• Highest concentrations close to the land - the source of much of the nutrients
• Highest concentrations from areas with higher population in the catchment - these European rivers drain many countries

Question 9

What are the areas of increased surface nitrate concentrations around the globe?

Answer 9

1. Peru current
2. Canary current
3. Benguela current

ALSO note elevated concentrations around Antarctica

Question 9

What are the areas of increased surface nitrate concentrations around the globe?

Answer 9

1. Peru current
2. Canary current
3. Benguela current

ALSO note elevated concentrations around Antarctica

Question 10

What is subtropical convergence?

Answer 10

Subtropical convergence is the boundary between warm water to the North and cold waters to the South

Question 11

What happens to water at the Antarctic convergence?

Answer 11

Water sinks

Question 12

What happens at the Antarctic divergence?

Answer 12

Water rises to the surface from the deep – this is nutrient rich water

Question 13

Why is phosphorous important?

Answer 13

• Essential element for biological systems

(key form - dissolved inorganic phosphate PO4^2-)

Question 14

What is the ratio of N:P in phytoplankton?

Answer 14

16:1

Question 15

What are the sources of phosphorous?

Answer 15

• From weathering of rocks
• Agriculture
• Urban waste water (sewage)
• Recycling in the ocean

Question 16

What is eutrophication?

Answer 16

Disruption of ecosystem caused by excess nutrients - which may cause an increased accelerated growth of algae in the water column and higher forms of plants living on the bottom of the sea

Question 17

What causes phytoplankton blooms?

Answer 17

They may be natural or caused by pollution

Question 18

What is a key example of eutrophication?

Answer 18

Gulf of Mexico.

(The Mississippi delta is being deprived of sediment because of canalisation of the lower reaches of the river which speeds water into the Gulf – healthy wetlands would remove nutrients from water and reduce impacts of eutrophication)