Primary + secondary production

Question 1

What is primary production?

Answer 1

Autotrophs (eg: cyanobacteria + kelp) create energy from sunlight, nutrients, + CO2.

Question 2

Benthic primary producers?

Answer 2

Microalgae (seaweed) + seagrass.

Question 3

Pelagic primary producers?

Answer 3

Phytoplankton.

Question 4

Percentage of photosynthesis

on Earth from phytoplankton?

Answer 4

50%.

Question 5

Difference between holoplankton + meroplankton?

Answer 5

Holoplankton: Whole life as plankton.
Meroplankton: Part of life as plankton.

Question 6

Types of phytoplankton?

Answer 6

Diatoms, dinoflagellates, + coccolithophores.

Question 7

Features of diatoms?

Answer 7

Unicellular. Mostly pelagic, some benthic.
Divide asexually up to 4 times a day = rapid blooms.
Some cause harmful algal blooms + produce domoic acid (shellfish poisoning).

Question 8

Features of dinoflagellates?

Answer 8

Unicellular protists.
Flagella for movement = active decisions.
Numerous in warmer seas.
Most photosynthetic, some mixotrophic/heterotrophic.
Can cause harmful algal blooms (eg: Karenia brevis causes red tides = produce brevetoxins). Common when nutrients runoff land.

Question 9

Features of coccolithophores?

Answer 9

Calcium carbonate plates (coccoliths).

Eg: Emiliana huxleyi.

Question 10

Where is microalgae dominant + 3 types?

Answer 10

Dominant in temperate regions.
Green (eg: Ulva lactuca).
Red (eg: Palmaria palmata).
Brown (eg: Fecus vesiculosus).

Question 11

Where are seagrass, salt marshes, + mangroves dominant, + functions.

Answer 11

Tropics.

Stabilise seabeds.

Question 12

Vegetated coastal habitats + carbon storage?

Answer 12

Cover 0.5% global marine system, but 50-71% total marine sediment carbon storage.
Bury carbon 40 times faster than tropical forests - sediment buildup = slow decay = more carbon stored.

Question 13

What does productivity depend on?

Answer 13

Water, light, CO2, + nutrients.

Question 14

What are the two reactions in photosynthesis?

Answer 14

Light dependent: Chlorophyll + accessory pigments gather photons + make chemical energy.
Light independent: CO2 reduced to high-energy carbohydrates = growth.

Question 15

Why isn’t chlorophyll used in the tropics?

Answer 15

Use different accessory pigments to avoid light damage.

Question 16

What is compensation depth?

Answer 16

Depth where photosynthesis = respiration. Varies.

Question 17

What is the average depth for max primary production?

Answer 17

25m - not at surface because UV damage.

Question 18

What side of the ocean is usually clearer?

Answer 18

East clearer than west - water speed higher in East Atlantic than West Atlantic = particulate matter moved through quicker.

Question 19

What is net primary production?

Answer 19

Difference between primary production + respiration = how much energy + organic matter available to heterotrophs.

Question 20

What are the main growth-limiting nutrients of algae?

Answer 20

Nitrogen + phosphorous.

Sometimes iron.

Question 21

How is nitrogen fixed?

Answer 21

Mostly by free-living, symbiotic bacteria (eg: Trichodesmium).

Question 22

How do nutrients vary spatially?

Answer 22

30% ocean surface = high macronutrient, iron-limited.
70% = nitrogen/phosphorous limited.
Tropics = nitrogen-limited. Polar (esp South Pole) high nitrogen (mixing).
Sub-tropical gyre = nitrates increase w/ depth (phytoplankton take nitrates in shallow water).

Question 23

What is the biological carbon pump?

Answer 23

Primary production assimilates carbon from surface waters/atmosphere to deep water/sediments.

Question 24

Why do oceans have high net primary productivity?

Answer 24

Low rate of primary production per m2, but large area overall.

Question 25

What areas of the ocean have the highest primary productivity?

Answer 25

Polar/mid-latitudes - high nutrients + enough light for phytoplankton.

Question 26

Eutrophic vs oligotrophic zones?

Answer 26

Eutrophic = High net primary production. 
Oligotrophic = Low net primary production.

Question 27

How does primary production vary temporally?

Answer 27

Arctic + North Pacific: Light-limited = high summer productivity.
North Atlantic: Spring bloom (nutrient mixing + increased light). Summer = nutrient-limited. Second autumn bloom.
Tropics: Nutrient-limited (nutrients deeper down = bigger storms needed to reach them).

Question 28

How are nutrients cycled?

Answer 28

Phytoplankton assimilate nutrients from surface layers + form particulate organic matter = transported down.
Microbes remineralise POM = enhance nutrients below photic zone.
Nutrient-rich water brought up to surface by storms etc.

Question 29

Hinder et al (2012)

Answer 29

92,263 samples over 50yrs from Continuous Plankton Recorder Survey. Increased SST + windy summers =
dinoflagellate abundance declined, diatoms increased.
Even dinoflagellates that fed on diatoms declined = caused by mechanisms other than trophic status.

Question 30

What is secondary production?

Answer 30

Biomass production by heterotrophs through consumption of primary producers or other heterotrophs.

Question 31

2 components of secondary production?

Answer 31

Somatic production + gonad production.

Question 32

Secondary production functional groups?

Answer 32

Grazers, suspension feeders, + predators.

Question 33

Types of microzooplankton?

Answer 33

Phagotrophic protists (eg: dinoflagellates).
Metazoans (eg: copepod nauplii).

Question 34

Diel vertical migration?

Answer 34

Largest biomass migration. Zooplankton migrate from surface during day to avoid visual predators.

Question 35

Types of pelagic grazers?

Answer 35

Copepods, pteropods, + krill.

Question 36

Copepods?

Answer 36

Largest oceanic contributors to secondary production.
Trophic link between phytoplankton + juvenile fish.
Excrete ammonia = sustains phytoplankton blooms.
Export carbon into deep sea (faecal pellets).

Question 37

Pteropods?

Answer 37

Pelagic molluscs.
Feed on plankton using mucous web.
Ocean acidification = can’t integrate carbon into shells.

Question 38

Krill?

Answer 38

Crustaceans. Eat phytoplankton + copepods.
Antarctic krill (Euphausia superba) = 500,000 tonne biomass.
Food source for key species.

Question 39

Types of benthic secondary producers?

Answer 39

Bivalves, barnacles, polychaete worms, deposit feeders.

Question 40

Bivalves?

Answer 40

Mytilus edulis suspension feeding = bentho-pelagic coupling.
Produce faeces + pseudofaeces = food for others.
Release nutrients into water column = fertilises algal growth.

Question 41

Barnacles?

Answer 41

Cirri (feeding appendages) sweep water.

Question 42

Polychaete worms?

Answer 42

Live in shallow, soft-botttom habitats (high nutrients).
Eg: N. diversicolor.
Convert detritus + microbes into complex carbons (eg: proteins).
Food for wading birds + benthic fish.

Question 43

Deposit feeders?

Answer 43

Directly assimilate photo-detritus.

Influence mineralisation + nutrient-return to water column.

Question 44

Role of detritus?

Answer 44

Marine snow. Exports energy from photic zone to aphotic zone.
Bacteria change organic carbon to CO2, water, + mineral nutrients.

Question 45

How is secondary production measured?

Answer 45

Ratio of production to biomass gained. Higher ratio in smaller organisms.
- Over 1 yr, marine system biomass can multiply by 100-300.
- Higher production on sea than land.
Stable isotope analysis (C + N) follows energy flow through food web.

Question 46

Importance of secondary production info?

Answer 46

Fishery management + modelling climate change impacts.