Productivity

Question 1

what drives the productivity in the ocean?

Answer 1

plankton and coastal macroalgae (kelp forests)

Question 2

what are phytoplankton?

Answer 2

• microscopic algal cells that use chlorophyll to photosynthesize, uses sunlight and nutrients to make proteins, fats and carbs
• live in upper part of ocean where sunlight hits

Question 3

what are zooplankton?

Answer 3

microscopic to macroscopic animals that graze on phytoplankton

Question 4

how are phytoplankton distributed?

Answer 4

discontinuous patches
- non-random clumped population
- concentrated at interfaces between water bodies

Question 5

what color on a map shows the highest productivity?

Answer 5

• red
• most nutrients

Question 6

why are there patterns of productivity?

Answer 6

• turbulence and current transport at many spatial scales (conveyor belt, marginal seas)
• different physical conditions seasonally and spatially
  ->light, temp, salinity
• spatially discontinuous levels of grazing by zooplankton - food is patchy
• localized reproduction -> max and min productivity depends on sunlight

Question 7

what is the main cause of productivity?

Answer 7

turbulence or mixing

Question 8

what causes spreading and mixing?

Answer 8

currents and wind

Question 9

what causes Langmuir circulation?

Answer 9

currents converging

Question 10

what causes eddies?

Answer 10

currents and coastlines

Question 11

what do seasonal patterns depend on to cause differences?

Answer 11

latitude
- depending on the sunlight phytoplankton are either abundant or non-existent which causes zooplankton to fluctuate

Question 12

which latitude has consistent levels of phytoplankton?

Answer 12

tropical

Question 13

describe the mixing depth in the winter

Answer 13

• storms mix water to a greater depth
• less light
• light doesn’t reach as deep so nutrients are deeper

Question 14

describe the mixing depth in spring

Answer 14

• water is mixed less
• more light
• light penetrates further

Question 15

what changes as a result of mixing depth?

Answer 15

blooms and declining phytoplankton

Question 16

compensation depth

Answer 16

photosynthesis = respiration
- above this depth is where phytoplankton photosynthesize

Question 17

mixing depth

Answer 17

depth to which water column is mixed by winds
determines critical depth
-> more respiration than photosynthesis

Question 18

critical depth

Answer 18

depth above which total oxygen produced in the water column = total oxygen consumed
- more respiration = more zooplankton to control phytoplankton = no bloom

Question 19

what happens when the mixing depth is less than critical depth?

Answer 19

bloom

Question 20

what happens when the mixing depth is more than the critical depth?

Answer 20

no bloom

Question 21

what happens as a result of winter mixing?

Answer 21

brings nutrients to the surface

Question 22

what happens in spring sun to the bloom?

Answer 22

heats water and less mixing by wind so thermocline develops and cells are in nutrient rich calmer water = bloom

Question 23

how do you catch plankton?

Answer 23

plankton net
- cod end - name of tube at the end that catches plankton

Question 24

why do we study plankton?

Answer 24

carbon cycle -> phyto = uptake
zoo -> respiration

Question 25

what nutrients do phytoplankton need for growth?

Answer 25

- nitrogen - phosphorus - silicon - iron

Question 26

what is nitrogen used for?

Answer 26

make proteins

Question 27

what 3 forms does N come in?

Answer 27

ammonium -> excretion by animals in water column (taken up the fastest) nitrate - most abundant nitrite - less common

Question 28

what does nitrate and nitrite need?

Answer 28

need enzymatic reduction to convert to ammonium - nitrate reductase and nitrite reductase

Question 29

how is N formed?

Answer 29

new production - deep waters by mixing or upwelling regenerated production - nutrients derived from excretion in surface waters nitrogen fixation - some algal phytoplankton cells

Question 30

purpose of P

Answer 30

- synthesis of ATP - required for lipids, DNA, fats/oils

Question 31

what forms do P come in?

Answer 31

- dissolved inorganic phosphate - particulate phosphorus from sediments/rivers - some dissolved P in organic molecules

Question 32

redfield rations

Answer 32

- constant ratio of N:P = 16:1 in oceans - phyto have 16:1 ratio - ocean have 14.7:1 ratio - nitrogen fixation by some plankton might make difference

Question 33

why is the ratio of N to P constant in all ocenas?

Answer 33

residence time of nutrients way longer than mixing time of oceans

Question 34

where does P come from?

Answer 34

land

Question 35

why is Si needed?

Answer 35

for diatom skeletons - from land by weathering

Question 36

what is Fe used for?

Answer 36

cofactor in oxygen production step of photosynthesis - crucial in parts of ocean where N is not limited

Question 37

what are the areas of where N is not limited called?

Answer 37

high nutrient/low productivity areas (HNLP)

Question 38

where are HNLP found?

Answer 38

antarctic ocean north Pacific

Question 39

how do Si and Fe enter oceans?

Answer 39

by wind as dust

Question 40

where is a major source of iron dust?

Answer 40

Sahara

Question 41

what controls phytoplankton growth?

Answer 41

bottom up feeding

Question 42

what are organic trace substances important for?

Answer 42

auxotrophic

Question 43

how is C produced at the ocean surface taken deep?

Answer 43

physical: mixing at poles - taking dissolving CO2 down with cold saline water - bringing up CO2 from deep biological: productivity - taken up into phytoplankton by photosynthesis - eaten and moved down as organic matter

Question 44

who eats most of the carbon?

Answer 44

zooplankton and nekton

Question 45

carbon sink

Answer 45

sinking water - ecosystems where C is sequestered

Question 46

what are Larvacean houses?

Answer 46

big structures of mucus and cellulose that allow filter feeders to get C

Question 47

how is C transported to the seafloor?

Answer 47

larvaceans

Question 48

how is C caught?

Answer 48

- put traps for sediment - caught larvacean houses

Question 49

how many blooms do polar regions have?

Answer 49

1

Question 50

how many blooms do temperate regions have?

Answer 50

2