Final-Light and Nutrients

Question 1

What are the pathways of energy in the ocean?

Where does the energy come from and where does it ultimately go?

Answer 1

sunlight transformed into chemical energy by photosythesizers (green plants, algae, specialized bacteria), chemical energy used by respirers (animals, decomposers, plants at night), energy eventually lost to heat and entropy

Question 2

What are some of the main “building materials” of life in the ocean?

Answer 2

Carbon, Oxygen, Hydrogen, Nitrogen

Question 3

What is photosynthesis? What are the light reactions? What are the light-independent (or dark) reactions?

Answer 3

Photosynthesis Light energy is converted into chemical energy for use in living cells

Light Reactions Water is split into hydrogen and oxygen, energy is stored in phosphate and hydrogen bonds

Dark Reactions Inorganic carbon is fixed via the Calvin-Benson cycle, Energy supplied by phosphate and hydrogen bonds

Question 4

What is

the Calvin-Benson Cycle?

Answer 4

series of biochemical redox reactions that take place in the stroma of chloroplast in photosynthetic organisms.
(light-independent reactions)

Question 5

What are limiting factors of photosynthesis in the ocean?

Answer 5

Nutrients: Macronutrients (ammonium), micronutrients (iron)

-light scattering and absorption with depth

Question 6

How is light differentially absorbed in the ocean as a function of wavelength? Do shorter or longer wavelengths penetrate deeper into the ocean? What factors determine the quantity of
light in the ocean?

Answer 6

• Shorter wavelengths penetrate deeper (blue shortest 400 nm)
• penetration of ocean depends on: angle of sun,
• absorption&scattering in the atmosphere, roughness of the water surface, water clarity

Question 7

What are some macro- and micronutrients in the ocean?

Answer 7

Micronutrients of the ocean Iron, copper, zinc, manganese

Macronutrients of the ocean sodium, magnesium, phosphorus, sulfur, chlorine, potassium, calcium, iodine, silicon

Question 8

How do nutrients enter the ocean?

Answer 8

• enter via: riverine flux, aeolian flux
• behave as non-conservative consituents
• recycled short term

Question 9

Why are nutrients relatively depleted in the deep Atlantic Ocean compared to the deep Pacfic and Indian Oceans?

Answer 9

Concentrations of nutrients in the depths of the Indian and Pacic Oceans,are so much greater than they are in the abyssal Atlantic Ocean because the Indian and Pacic deep waters has had more time to accumulate nutrients from oxidation of organic matter.

Question 10

What is the `Law of the Minimum’?

Answer 10

ocean growth is not controlled by the total amount of resources available but by the scarcest resource (limiting factor)

Question 11

What are the main forms of nitrogen in the ocean? What organisms use which
forms of nitrogen? In what regions is iron limiting?

Answer 11

Nitrogen in the ocean

• macronutrients
• dinitrogen gas (used by few microbes), nitrate/nitrite (consumed by some marine microbes [assimilation]), ammonium (limiting) (most easily consumed by microorganisms)

Iron limiting -equatorial pacific, southern ocean, central north pacific
-iron fertilization potential remediation strategy for CO2 buildup in atmosphere