Photosynthesis

Question 1

(1) What are Redfield ratios?

Answer 1

The ratio of carbon to nitrogen to phosphorus is a nearly constant 106:16:1 throughout the world’s oceans, in both phytoplankton biomass and in dissolved nutrient pools. Under optimal growth conditions it is the amount removed by phytoplankton from seawater, it is also the amount released back into the seawater when an organism dies and decomposes. It defines the stoichiometry of photosynthesis and remineralization reactions.

C:N:P 106:16:1

The Redfield ratio can be extended to include most of the essential elements, so instead of writing the plankton composition as C106H263O110N16P, it can be written as C106H263O110N16P(Fe, Mn, Zn)0.01(Cu, Ni, Cd…)0.001

Question 2

What is the formula for photosynthesis?

Answer 2

6 H2O + 6 CO2 + light energy → C6H12O6 + 6 O2

Question 3

(8) Name four parameters which affect the growth rate of phytoplankton and what the effect is.

Answer 3

Carbon dioxide – needed for growth. Less amount -> less growth.
Sunlight – needed for photosynthesis as they have chlorophyll. Needed for growth. Less sunlight -> less growth
Iron - plays a central role in energy production and biochemical catalysis within phytoplankton cells. Less iron -> less growth (until a certain amount)
Phosphorus – a needed macronutrient. Less phosphorus -> less growth

Question 4

(9) Describe how an algal bloom is created, and explain why it is unwanted, both in short and long term

Answer 4

Algal blooms are the result of excess nutrients, like nitrogen or phosphorus from various sources (for example fertilizer runoff or other forms of nutrient pollution), entering the aquatic system and causing growth of algae. An algal bloom affects the whole ecosystem.
Consequences range from the benign feeding of higher trophic levels to more harmful effects like blocking sunlight from reaching other organisms, causing a depletion of oxygen levels in the water, and, depending on the organism, secreting toxins into the water. Blooms that can injure animals or the ecology are usually called “harmful algal blooms” (HAB), and can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries. The process of the oversupply of nutrients leading to algae growth and oxygen depletion is called eutrophication.
Algal blooms cause higher pH which can change metal speciation in the water.

Question 5

What is the plankton formula?

Answer 5

C(106)H(263)O(110)N(16)P

Question 6

What is Photosynthetically active radiation?

Answer 6

the amount of light available for photosynthesis, which is light in the 400 to 700 nanometer wavelength range.
Chlorophyll A vs Chlorophyll B absorbing the sunlight in different wavelength, mainly A

Question 7

What is the euphotic zone?

Answer 7

Depth with 1% of initial PAR.