Ocean Productivity

Question 1

the gulf stream has very high productivity due to:

Answer 1

the interaction between the gulf stream and neighboring colder waters (mixing/ turbulence)

Question 2

the center of gyres has __ (high/ low) productivity

Answer 2

very low b/c no mixing

Question 3

t/f
productivity in the oceans is driven entirely by plankton

Answer 3

false
mostly plankton, but also by coastal macroalgae such as kelp forests

Question 4

phytoplankton=

where do they live?

Answer 4

microscopic algal cells that use chlorophyll to photosynthesize, using sunlight and nutrients to make protein, fat, carbohydrates

they live in the upper part of the ocean where sunlight reaches

Question 5

zoopolankton=

Answer 5

microscopic or macroscopic animals that graze on phytoplankton

Question 6

does plankton occur uniformly around the ocean?

Answer 6

no
occurs in spatially discontinuous patches
(sometimes concentrated at interfaces b/w water bodies)

Question 7

what 4 things control plankton abundance/ patterns of productivity?

Answer 7

1. turbulence and ‘current transport’ at many spatial scales (mixing)
2. different physical conditions seasonally and spatially (light, temp, salinity)
3. spatially discontinuous levels of grazing by zooplankton
4. localized reproduction

Question 8

____ is the main cause for productivity

• currents and winds cause ____ and ___
• currents converging cause ___ ___
• currents and coastlines cause ___

Answer 8

turbulence (mixing)

• spreading and mixing
• langmuir circulation
• eddies

Question 9

Explain how Langmuir circulation works. What are some impacts of it?

Answer 9

currents converge, causing circular circulation & localized mixing

Results in higher productivity because of the mixing
- This is where you see lines of birds etc eating the plankton at the lines of convergence

Question 10

Seasonal patterns in plankton abundance differ depending on latitude.
Explain the plankton patterns in the arctic

Answer 10

Arctic:
1 bloom per year
- starting to get 2 blooms b/c waters are warming

phytoplankton bloom first, zooplankton bloom follows

Question 11

Seasonal patterns in plankton abundance differ depending on latitude.
Explain the plankton patterns in temperate locations

Answer 11

Temperate:
eg BC coast

• 2 plankton blooms
• zooplankton deplete the first phytoplankton bloom, but phytoplankton come back for a second bloom as zooplankton numbers drop

Question 12

Seasonal patterns in plankton abundance differ depending on latitude.
Explain the plankton patterns in tropical locations

Answer 12

Tropical:
- not enough mixing= no obvious blooms
- depends on nutrients

• can have localized blooms after a storm etc if there are enough nutrients

Question 13

In winter, storms mix to a ____ (greater/ lesser) depth that in spring

Answer 13

greater in winter

Question 14

Blooms and declines of phytoplankton are due to changes in mixing ____

Answer 14

depth

Question 15

Explain the differences in light and mixing depth in the winter vs spring

Answer 15

winter:
- storms= water mixes to a greater depth
- less light= light doesn’t reach as deep

spring:
- water is less mixed
- more light= it penetrates further

Question 16

Compensation depth=

Answer 16

where photosynthesis= respiration
- phytoplankton photosynthesize above this depth above

Question 17

Mixing depth=

Answer 17

depth to which the water column is mixed by winds
- determines the critical depth
- moves phytoplankton down

Question 18

Critical depth=

Answer 18

depth above which total oxygen produced in the water column= total oxygen consumed

Question 19

if the mixing depth is ____ (<, > or =) critical depth, then phytoplankton cells can photosynthesize –> bloom

Answer 19

mixing depth < (less than) critical depth

Question 20

mixing depth > critical depth= _____ (bloom/ no bloom)

Answer 20

no bloom

not sure why

Question 21

explain the steps that happen that allow a spring plankton bloom to occur

Answer 21

1. winter mixing brings nutrients to the surface
2. spring sun heats the water & less mixing by wind= a thermocline develops
3. phytoplankton cells are now in nutrient-rich, calmer water = BLOOM!

Question 22

How do we catch plankton to study it?

Answer 22

Plankton nets
-“Cod End”= the name of the tube at the bottom of the net that catches plankton

Question 23

List 4 of the main nutrients (+2) that phytoplankton need for growth

Answer 23

1. Nitrogen
2. Phosphorous
3. Silicon
4. Iron
5. Trace elements like Mn, Zn, etc
6. Organic trace substances (vitamins etc)

Question 24

Nitrogen is used by phytoplankton for making ____ and it occurs in 3 dissolved forms:
1
2
3

which of these 3 is taken up the fastest?

Answer 24

proteins

1. ammonium (NH4): excretion products (TAKEN UP FASTEST)
2. nitrate NO3: most abundant dissolved form
3. nitrite (NO2): less common form

Question 25

ammonium is the easiest form of nitrogen to be taken up. How are nitrate and nitrate taken up?

Answer 25

Both require enzymatic reduction to convert to ammonium

Nitrate + nitrate reductase = nitrite
Nitrite + Nitrite reductase = ammonium

Then ammonium is the usable form

Question 26

What are 3 ways nitrogen can be acquired for use?

Answer 26

1. new production: from deep waters (mixing or upwelling)
2. regenerated production: nutrients derive from excretion in surface waters
3. nitrogen fixation: by some algal phytoplankton cells

Question 27

_____ is required by phytoplankton for lipids, DNA, fats/ oils, and synthesis of ATP

It occurs in water mainly as dissolved inorganic ____ (___)

Answer 27

phosphorus

inorganic phosphate (PO4 3-)

Question 28

where does oceanic phosphorus mainly come from?

Answer 28

the land! plants and soil
also
bubbles/ foam in ocean= broken up lipids of planktons (phosphorous)

Question 29

The ratio of nitrogen to phosphorous is constant in all the oceans. Why?
What is the ratio?

Answer 29

Because the residence time of all these nutrients is way longer than the mixing time of the oceans (~1000yrs)

Ratio is 16N: 1P

Question 30

Silicon is required for diatom ___ and it’s a ___ nutrient in the oceans
Where does it come from?

Answer 30

skeletons
limiting

Comes from the land (rocks) by weathering

Question 31

Iron and silicon often enter the ocean as ___

Answer 31

dust

Question 32

___is a cofactor required in the oxygen production step of photosynthesis

Answer 32

iron

Question 33

Iron may be crucial in parts of the ocean where ___ appears not limited
- this means iron is a ____ factor
- these areas are called:
list 2 examples of areas that fall into this category

Answer 33

nitrogen

limiting

high nutrient/ low productivity areas (HNLP)

eg
-parts of the Antarctic ocean
- north pacific

Question 34

Explain the controversial experiment with iron that took place off Canada’s west coast

Answer 34

they dumped iron into the ocean to increase productivity (because iron was a limiting nutrient)
- fishery success and productivity sky rocketed, but it was not sustainable (eventually Si becomes the limiting factor)

Question 35

T/F
phytoplankton cannot synthesize organic compounds

Answer 35

true
organic trace substances still important for auxotrophic etc

Question 36

Carbon produced at the ocean surface is taken into the deep by 2 different methods: physical and biological. Explain each

Answer 36

Physical: mixing at the poles takes dissolved CO2 down with cold saline water

Biological: (productivity)
- taken up into phytoplankton by photosynthesis
- they’re eaten and moved down as organic matter (falls as marine snow/ in diatoms etc)

Question 37

Not all carbon produced makes it to the deep sea. Where is the missing carbon?

Answer 37

Larvacean houses!
these houses filter out food from the water column, and when they get full, the animal abandons the house and it drops to the seafloor, brining with it all the food (carbon!) caught in it

Question 38

Phosphorous in the oceans comes from ___ and ____. Redfiled ratios are ratio of __ to __ (16:1 near shore) .
Redfeild ratios are constant due to short ___ time of oceans relative to ___ of the nutrients from ____ and ____

Answer 38

land and rivers

N to P (16:1)

mixing
input
land and rivers