Week 4

Question 1

What is the equation for exponential growth of biomass?

Answer 1

C(t)=C(0)e^μt, where μ is the growth rate.

Question 2

How is the growth rate (μ) determined from biomass data?

Answer 2

Fit a straight line to the natural log of biomass during the exponential growth phase.

Question 3

How does the O2 Light-Dark method calculate photosynthesis and respiration?

Answer 3

Gross photosynthesis: ([O2]light - [O2]dark)/time. Net photosynthesis: ([O2]light - [O2]initial)/time. Respiration: ([O2]initial - [O2]dark)/time.

Question 4

What are the advantages of in situ O2/Ar measurements?

Answer 4

No bottle incubations, continuous measurement, and longer integration times.

Question 5

What is the H2^18O method for measuring production?

Answer 5

Tracks O2 produced from water enriched with 18O, directly measuring GPP.

Question 6

What are the limitations of the H2^18O method?

Answer 6

Requires specialized equipment and is not commonly used.

Question 7

How do satellites estimate global primary production?

Answer 7

By measuring ocean color to infer chlorophyll concentration and light penetration.

Question 8

Why is global primary production difficult to estimate?

Answer 8

Sparse in situ measurements and variability in regional productivity.

Question 9

How does water influence light attenuation?

Answer 9

Water absorbs red and infrared light strongly, limiting depth penetration.

Question 10

What is the significance of CDOM in light attenuation?

Answer 10

Absorbs blue and UV light, shaping the underwater light spectrum.

Question 11

How do phytoplankton particles affect light attenuation?

Answer 11

Pigments like chlorophyll absorb light, while cell structures scatter it.

Question 12

What is the attenuation coefficient for pure water?

Answer 12

Approximately k=0.015 m−1, allowing deep light penetration.

Question 13

How do light attenuation rates vary in coastal and oceanic waters?

Answer 13

Coastal waters attenuate light faster due to higher CDOM and particles.

Question 14

How can Secchi disk data estimate k?

Answer 14

Using k≈1.7/Secchi depth.

Question 15

What is the relationship between wavelength and light attenuation?

Answer 15

Short (UV) and long (infrared) wavelengths attenuate faster than visible light.

Question 16

What is the equation for light attenuation with depth?

Answer 16

E_z = E_o e^(-kz), where E_z is irradiance at depth z.

Question 17

How are the 1% and 0.1% light depths calculated?

Answer 17

z_1% = (ln(100) - ln(1))/k. z_0.1% = (ln(100) - ln(0.1))/k.

Question 18

What adaptations help Prochlorococcus thrive in nutrient-poor waters?

Answer 18

Unique pigments like divinyl chlorophyll and efficient resource use.

Question 19

How does Synechococcus adapt to varying light conditions?

Answer 19

Uses phycoerythrin and zeaxanthin pigments to optimize light absorption.

Question 20

What are the key features of diatom reproduction?

Answer 20

Asexual divisions reduce size, restored by periodic sexual reproduction.

Question 21

How do coccolithophores impact carbon cycling?

Answer 21

By forming calcium carbonate plates and sequestering CO₂ in ocean sediments.

Question 22

Why is Trichodesmium important in tropical ecosystems?

Answer 22

Fixes nitrogen in nutrient-poor waters, supporting other organisms.

Question 23

What is the ecological significance of mixotrophy?

Answer 23

Allows phytoplankton to adapt to nutrient variability by combining autotrophy and heterotrophy.

Question 24

How does endosymbiosis explain phytoplankton evolution?

Answer 24

Primary and secondary endosymbiosis led to diverse phytoplankton lineages.

Question 25

What role does fluorescence play in measuring productivity?

Answer 25

Tracks photosynthetic efficiency using chlorophyll fluorescence.

Question 26

What are auxiliary pigments, and why are they important?

Answer 26

Pigments like carotenoids and biliproteins expand light absorption range for photosynthesis.

Question 27

Why is light scattering significant in underwater ecosystems?

Answer 27

Redistributes light, enabling photosynthesis in shaded areas.

Question 28

What challenges do researchers face when measuring production at scale?

Answer 28

Variability in methods, regional conditions, and sparse in situ data.

Question 29

How do molecular techniques enhance phytoplankton studies?

Answer 29

Provide insights into genetic diversity and ecological roles through RNA analysis.

Question 30

What is the significance of measuring net and gross production?

Answer 30

Differentiates between immediate carbon fixation and overall ecosystem respiration.

Question 31

What is Gross Primary Production (GPP)?

Answer 31

The total rate of photosynthesis over time, uncorrected for respiration.

Question 32

Define Net Primary Production (NPP).

Answer 32

GPP minus autotrophic respiration, representing the carbon available for growth and reproduction. ## Footnote P_np = P_g - R_phyto.

Question 33

What is Net Community Production (NCP)?

Answer 33

GPP minus all respiration (autotrophic and heterotrophic). ## Footnote P_nc = P_g - R_phyto - R_hetero.

Question 34

How can primary production be measured?

Answer 34

By quantifying organic carbon increase, CO₂ decrease, or O₂ increase.

Question 35

What is the role of the O₂ Light-Dark method?

Answer 35

Measures oxygen changes in light and dark conditions to estimate photosynthesis and respiration.

Question 36

What are the advantages of the O₂ Light-Dark method?

Answer 36

Simple and provides direct estimates of photosynthesis and respiration.

Question 37

What are the limitations of the O₂ Light-Dark method?

Answer 37

Insensitive in oligotrophic waters and prone to temperature and bubble formation issues.

Question 38

How does the O₂/Ar method improve precision?

Answer 38

Corrects O₂ measurements by using Ar as a reference to account for physical processes.

Question 39

What is the 14C method for measuring production?

Answer 39

Adds 14CO₂ as a tracer to track carbon fixation during photosynthesis.

Question 40

Why is the 14C method widely used?

Answer 40

It is highly sensitive, allowing high spatial and temporal resolution.

Question 41

What are the disadvantages of the 14C method?

Answer 41

Requires radioactive materials, complicating lab work, and interpretation of gross vs. net production.

Question 42

What is Photosynthetic Active Radiation (PAR)?

Answer 42

Light in the 400-700 nm range that phytoplankton can use for photosynthesis.

Question 43

What factors affect sea surface irradiance?

Answer 43

Time of day, season, latitude, and cloud cover.

Question 44

How does light attenuation occur in water?

Answer 44

Through exponential decrease with depth due to absorption and scattering.

Question 45

What is the attenuation coefficient (k)?

Answer 45

A measure of how quickly light diminishes with depth, with units of m−1.

Question 46

How is the 1% light depth calculated?

Answer 46

Using the formula z=(ln(E_0)−ln(E_z))/k.

Question 47

What does a Secchi disk measure?

Answer 47

Water clarity and approximate light penetration depth.

Question 48

How does CDOM influence light in the ocean?

Answer 48

Absorbs blue and UV light, reducing light penetration and affecting color.

Question 49

Why is pigment composition critical for phytoplankton?

Answer 49

Different pigments allow absorption of various light wavelengths, optimizing photosynthesis.

Question 50

What is the euphotic zone?

Answer 50

The ocean layer where light supports photosynthesis.

Question 51

How does light attenuation vary with wavelength?

Answer 51

UV and red light attenuate quickly, while blue-green penetrates deeper.

Question 52

What is the importance of light scattering?

Answer 52

Scattering redistributes light in water, creating a diffuse light field.

Question 53

How do phytoplankton pigments affect ocean color?

Answer 53

Pigments like chlorophyll absorb blue light, giving the water a greenish hue.

Question 54

What are the benefits of molecular tools in studying phytoplankton?

Answer 54

Tools like RNA analysis reveal genetic diversity and evolutionary relationships.

Question 55

How do picoeukaryotes dominate in nutrient-poor regions?

Answer 55

They efficiently use resources and have high photosynthetic capacity despite their small size.

Question 56

What is the ecological role of Prochlorococcus?

Answer 56

Dominates low-nutrient waters, contributing significantly to global primary production.

Question 57

Why is Synechococcus abundant in nutrient-rich boundaries?

Answer 57

It adapts to moderate nutrients and light variability with diverse pigments.

Question 58

What is the role of diatom frustules?

Answer 58

Provide protection and contribute to carbon sequestration when they sink.

Question 59

How does sexual reproduction benefit diatoms?

Answer 59

Restores size and ensures genetic diversity after repeated asexual divisions.

Question 60

What is the importance of coccolithophores?

Answer 60

Contribute to carbon cycling via calcium carbonate plate formation and CO₂ sequestration.

Question 61

How do Trichodesmium blooms support ecosystems?

Answer 61

Fix atmospheric nitrogen, aiding productivity in nutrient-poor tropical waters.

Question 62

What is kleptoplasty?

Answer 62

Temporary photosynthesis using stolen chloroplasts from algae.

Question 63

What is the function of auxiliary pigments?

Answer 63

Expand light capture range, improving photosynthesis in varied environments.

Question 64

Why is light measurement important in primary production studies?

Answer 64

Determines energy availability for photosynthesis across depths.

Question 65

Why are molecular techniques vital for phytoplankton classification?

Answer 65

They provide detailed insights into genetic diversity and evolutionary relationships.

Question 66

What is the role of active fluorescence in primary production?

Answer 66

Measures real-time photosynthetic activity for higher-resolution data.