Primary Productivity and Nutrients

Question 1

What are nutrients?

Answer 1

Chemical substances required to support life, present as dissolved salts, used by PP for synthesis of energy-rich organic compounds and for synthesis of cells walls and skeletons

Question 2

Why are nutrients important?

Answer 2

Regulate PP

Question 3

What are some major nutrients used in metabolic processes?

Answer 3

N, P, Na, Mg, S, Cl, K, Ca, I, Si, Fe, Cu, Zb

Question 4

How can nutrients affect community composition?

Answer 4

Different phytoplankton species have different nutrient requirements

Question 5

What are some essential elements for phytoplankton growth?

Answer 5

C, N, Fe, Zn, H, P, Cu, Mo, O, Mg, Mn

Question 6

What are some nutrients essential for only some phytoplankton?

Answer 6

Na, Se, B, Co, Si, I, Vn, Cl

Question 7

What are some vitamins that phytoplankton require?

Answer 7

Vitamin B12, B1, Biotin

Question 8

What are macronutrients?

Answer 8

Nutrients that are typically present in micronolar concentrations (C, N, P, H, O, Si)

Question 9

What are micronutrients?

Answer 9

Nutrients that are typically present in the nanomolar range (Fe, Zn, Cu, Mn)

Question 10

Are macronutrients more important than micronutrients?

Answer 10

No, they’re just more abundant than micronutrients

Question 11

What are some limiting nutrients?

Answer 11

N, P, Si, Fe, organic substances (i.e. vitamins)

Question 12

How are nutrients biolimited?

Answer 12

Photosynthetic organisms deplete nutrient concentrations in sunlit surface waters.

Question 13

How are nutrients added back into the water?

Answer 13

Bacterial degradation of organic matter.

Question 14

Where does accumulation of nutrients occur?

Answer 14

At depth, where nutrients are not used by primary producers

Question 15

What is the redfield ratio?

Answer 15

The ratio of carbon, nitrate and phosphate (106:16:1mol/mol) from linear regression analysis of dissolved [nutrient] and the analysis of particulate matter from photosynthesis and respiration

Question 16

What are biogeochemical cycles?

Answer 16

Nutrient, mineral cycles. The flow of nutrients between the land, atmosphere and ocean.

Question 17

What are the components of the biogeochemical cycle?

Answer 17

Inorganic matter -> organic matter (photosynthesis) -> up through food web -> through microbial loop -> back into photosynthetic zone -> inorganic matter

Question 18

What are biotic processes of the biogeochemical cycles?

Answer 18

Conversion of inorganics (CO2, Si(OH)4, NO3) into organics by photoplankton, decomposition of sinking organic organic matter by bacteria returns inorganic nutrients to water column

Question 19

What are the abiotic processes of the biogeochemical cycle?

Answer 19

Wind mixing and upwelling bringing nutrient-rich deep water to surface, river discharge and water runoff from land sewage outfalls

Question 20

What are the forms of nitrogen and their sources (in decreasing concentration)

Answer 20

Inorganic: N2, NO3, NO2,NH4,NH3; Organic: CO(NH2)2, Amino acids, other forms

Question 21

What is the most cited cause of limitation of PB and PP in marine ecosystems?

Answer 21

Nitrogen

Question 22

What is nitrogen used for?

Answer 22

Amino acids, building enzymes and proteins, nucleotides, ATP, chlorophyll

Question 23

What form of N is used in amino acids?

Answer 23

NH4, if phytoplankton takes in N in other forms, they must be reduced to NH4.

Question 24

How is NH4 produced?

Answer 24

Organisms use ATP and enzymes (nitrate reductase and nitrite reductase) to reduce other compounds to NH4, it can be produced as an excretory product of zooplankton, fish and other heterotrophs.

Question 25

What form of N do phytoplankton take in the most?

Answer 25

NH4 is the easiest, but NO3 is present in higher concentrations,

Question 26

What are some processes that bring N into the surface ocean?

Answer 26

Atmospheric inputes (Precipitation, N2 fixation by cyanobacteria), runoff (rivers, coastal waters, farm runoff, sewage), advection (upwelling, wind mixing), nitrification

Question 27

What are processes that contribute to loss of N from the surface ocean?

Answer 27

Sedimentation of phytoplankton, zooplankton, fecal pellets, marine snow to deep waters, and seafloor basin, denitrification (formation of reduced N compounds from NO3 - bacterial process where they use nitrogen as an oxygen source)

Question 28

What affects the location of the nutricline?

Answer 28

Physical properties of the water column

Question 29

What is new production?

Answer 29

The portion of primary production that results from the utilization of new nitrogen (NO3, N2)

Question 30

What is regenerated production?

Answer 30

The portion of primary production that results from the utilization of regenerated nitrogen

Question 31

What does new production equal?

Answer 31

Export production (over the long term, in a steady state ocean)

Question 32

What affects the proportion of new/regenerated production?

Answer 32

The type of system there is: if there is more regenerated production, small organisms dominate (greater SA:V ratio), if there is more new production, larger organisms dominate (i.e diatoms)

Question 33

What are some sources of silicon to the surface ocean?

Answer 33

River input, groundwater, weathering, hydrothermal vents, deposits, upwelling/wind mixing

Question 34

What are some processes that contribute to the loss of Si from surface waters?

Answer 34

Sedimentation of diatoms and other silica-containing organisms (radiolarians, silicaflagellates) which go to deeper waters/seafloor burial

Question 35

What are the main biogeochemical fluxes internall cycling Si in the oceans?

Answer 35

Production and dissolution of biogenic Si

Question 36

What affects the rate of nutrient uptake?

Answer 36

Transport mechanism

Question 37

What is the rate of nutrient uptake in passive diffusion?

Answer 37

Uptake rate is proportional to the concentration of the nutrient (nutrients go from [low] to [high]

Question 38

What is the rate of nutrient uptake in facilitated diffusion/active transport?

Answer 38

Carriers of nutrients can be saturated as the concentration of the nutrient increases (different nutrients have different carriers)

Question 39

What is Ks?

Answer 39

The concentration of nutrients at Vmax/2

Question 40

What does it mean if a nutrient has a low Ks?

Answer 40

There is a higher affinity of the carrier for a particular molecule/iron (faster at uptake)

Question 41

What is the paradox of the plankton?

Answer 41

Why are there so many different phytoplankton species coexisting at one time in the oceans?

Question 42

How to answer the paradox of the plankton?

Answer 42

Although the auphotic zone appears homogeneous, there are vertical gradients in temperature, salinity, light, nutrients, and miximing moves phytoplankton throughout the surface layer, so they experience average conditions.

Question 43

Why don’t phytoplankton outcompete each other since they need the same things?

Answer 43

Each species has slightly different nutrient requirements, Ks, Kl, so at any time some species will do better than others. But nutrient concentrations and phystical characteristics can change quickly, making favorable conditions for different species, so the balance can go back and forth (Contemporaneous disequilibrium)