Adaptations in Phytoplankton

Question 1

Advantages of Phytoplankton Shell

Answer 1

Protection from grazing
Protection from pathogen/enzyme
Buoyancy control – helps sink a bit

Question 2

Effect of thicker diatom shell on growth

Answer 2

Thicker shelled diatoms tend to grow more slowly even when Si is not limited
May be due to energy intensive formation, lack of nutrients or light

Question 3

Shell thickness effect on predation

Answer 3

Copepods show a preference for thinner-shelled diatoms

Dinoflagellates do not select diatoms based on shell thickness, but rather on cell size

Dinoflagellates eat non-calcified coccolithophores more often

Question 4

Effects of sinking in phytoplankton

Answer 4

Phytoplankton take up nutrients around their cell, depleting nutrients directly adjacent
Sinking causes turbulence to mix water, and increase nutrient levels around cell
This increase nutrient uptake rate

However sinking removes phytoplankton from photic zone

Question 5

Mechanisms to Prevent Sinking

Answer 5

Gas Vacuole – mostly freshwater species

Flagella and Cilia

Lipids and Fats

Remove Dense Material

Colony or Chain Formation

Ion Regulation

Spine Formation

Small Size

Question 6

What controls sink rate of sphere

Answer 6

Density of cell and Density of water
Viscosity
Gravity
Radius of cell squared

Cell size is incredibly important for the sinking rate
Small size slows sinking drastically

Question 7

3rd Hypothesis for Deep Chlorophyll Max

Answer 7

Deep Chl a max can occur at density shifts in the water column where phytoplankton stop sinking

This is especially true for thin layers

Question 8

Importance of Spines and Colony Formation for Sinking Rate

Answer 8

Spines increase drag on the cell and colonies increase SA

These both have the effect of slowing sinking

Question 9

Flagella Importance for Sinking

Answer 9

Helps to move towards light and upwards – very small movements
Some have photoactive cells

Question 10

On average how does a phytoplankton vacuole compare to the seawater

Answer 10

Vacuoles are usually less dense than the seawater

Question 11

Ion Regulation

Answer 11

Phytoplankton actively transport salt ions out of the cell and lower the density

They can do this over very quick time periods, to increase turbulence and increase nutrient uptake (bursts)

More rapid sink burst cycles in nutrient-poor waters