Ocean Biology

Question 1

What is the primary long term removal pathway for volcanic CO2?

Answer 1

Production and burial of organic carbon and calcium carbonate shells/skeletons

Question 2

Give an example of a tertiary, secondary and primary producer in the ocean.

Answer 2

Tertiary - fish, dolphins, squids, sharks and whales
Secondary - zooplankton, shrimps, krills.
Primary - phytoplankton

Question 3

Photosynthesis uses energy from sunlight. Where do algae get this from in the ocean? show this in the overall equation.

Answer 3

Light energy from chlorophyll in algae. CO2+H20 —> chlorophyll —-> O2 and Organic matter

Question 4

Coccolithophores are large phytoplankton. What is their defining feature and what is it used for?

Answer 4

CaCO3 shell to protect from viruses and grazing.

Question 5

How big are Coccolithophores?

Answer 5

Unicellular 5-100 µm (micro meters).

Question 6

What do coccolithophores contribute to the ocean?

Answer 6

After death, their shells sink to the bottom of the ocean, forming chalky sediments.

Question 7

Diatoms are also large phytoplankton. How big are they and what is their defining feature?

Answer 7

Form Silicate (SiO2) shell. 2 - 200µm.

Question 8

Name the other two smaller, unicellular phytoplankton abundant in the ocean. Where do they live and how do they differ in size?

Answer 8

Prochlorococcus 0.5-0.7µm and Synedococcus 0.8-1.5µm occupy the tropics and sub tropics.

Question 9

What is the distribution of Coccolithophores and diatoms in the ocean?

Answer 9

Coccolithophores - 30-60 degrees north

Diatoms - 40-80 degrees south

Question 10

Where is total biomass in the oceans highest and why?

Answer 10

At the coast nutrients are brought to the surface waters by tidal and wave turbulence as well as freshwater runoff from the land. Freshwater runoff also creates a low-density surface water layer that keeps phytoplankton near the surface.

Question 11

Why does primary production occur at the ocean surface?

Answer 11

Sunlight is strongly attenuated in water - only 25% reaches 10m depth in clear water.

Question 12

What is the assimilation number for phytoplankton photosynthesis and what two properties of phytoplankton is this related to?

Answer 12

assimilation number - the rate of photosynthetic carbon assimilation per weight of chlorophyll, determined by the carbon/chlorophyll ratio and growth rate of the phytoplankton.

Question 13

Why do tropical seas and temperate waters show low summer assimilation rates, whilst coastal estuaries show seasonal variation?

Answer 13

Low summer assimilation = low ambient nutrient concentrations. Seasonal variation is due to temperature, as nutrients constantly supplied from freshwater of rivers.

Question 14

Where do the C, N and P required for phytoplankton in the ocean come from.

Answer 14

C from DIC (rarely limiting)
N from No3- and NH4+
P from PO43-

Question 15

Which phytoplankton type does not get nitrogen from NO3-?

Answer 15

Prochlorococcus

Question 16

Where is nitrate concentration highest, andhow does this relate to phosphate and chlorophyll concentrations?

Answer 16

Highest in polar south, with concentrations in N high latitudes, particularly in the Pacific, and off the western coast of S America - both phosphate and chlorophyll presence reflect this.

Question 17

What is the redfield ratio including Fe?

Answer 17

P : N : C : Fe

1 : 16 : 106 : 5x10-4

Question 18

What is the condition for nitrogen limitation, and where do nitrogen fixers grow in response to this?

Answer 18

[NO3- + NH4+] < 16x[PO43-]

Nitrogen fixers found in tropics and sub-tropics (of the atlantic and indian oceans - less so in the pacific)

Question 19

What does the distribution of diatoms in the ocean correspond to?

Answer 19

High Silicate levels (Si04)

Question 20

Where is average dissolved total iron lowest in the surface ocean?

Answer 20

Southern and Pacific oceans

Question 21

What are HNLC regions and where are they found?

Answer 21

High Nitrate, Low Chlorophyll regions, where biomass of phytoplankton is low despite high nutrient levels - caused by iron limitation. Found in equatorial east pacific and southern oceans.

Question 22

Sediment burial is a sink which nutrients? what are the two ‘exceptions’?

Answer 22

Sink for Phosphorus, Carbon, Nitrogen and Silica. However, nitrogen also ‘sunk’ by denitrification whilst decomposition is the sink for Oxygen.

Question 23

Rivers are a source of which 4 nutrients? in what form?

Answer 23

Phosphorus (PO43-)
Carbon (DIC, DOC)
Nitrogen (DIN, ON)
Silica (SiO4)

Question 24

Which two nutrients can be obtained by air-sea gas exchange?

Answer 24

Carbon and Oxygen