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Marine biology > Primary + secondary production > Flashcards

Primary + secondary production Flashcards

1
Q

What is primary production?

A

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

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2
Q

Benthic primary producers?

A

Microalgae (seaweed) + seagrass.

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3
Q

Pelagic primary producers?

A

Phytoplankton.

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4
Q

Percentage of photosynthesis

on Earth from phytoplankton?

A

50%.

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5
Q

Difference between holoplankton + meroplankton?

A

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

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6
Q

Types of phytoplankton?

A

Diatoms, dinoflagellates, + coccolithophores.

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7
Q

Features of diatoms?

A

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).

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8
Q

Features of dinoflagellates?

A

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.

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9
Q

Features of coccolithophores?

A

Calcium carbonate plates (coccoliths).

Eg: Emiliana huxleyi.

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10
Q

Where is microalgae dominant + 3 types?

A

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

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11
Q

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

A

Tropics.

Stabilise seabeds.

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12
Q

Vegetated coastal habitats + carbon storage?

A

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.

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13
Q

What does productivity depend on?

A

Water, light, CO2, + nutrients.

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14
Q

What are the two reactions in photosynthesis?

A

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

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15
Q

Why isn’t chlorophyll used in the tropics?

A

Use different accessory pigments to avoid light damage.

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16
Q

What is compensation depth?

A

Depth where photosynthesis = respiration. Varies.

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17
Q

What is the average depth for max primary production?

A

25m - not at surface because UV damage.

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18
Q

What side of the ocean is usually clearer?

A

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

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19
Q

What is net primary production?

A

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

20
Q

What are the main growth-limiting nutrients of algae?

A

Nitrogen + phosphorous.

Sometimes iron.

21
Q

How is nitrogen fixed?

A

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

22
Q

How do nutrients vary spatially?

A

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).

23
Q

What is the biological carbon pump?

A

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

24
Q

Why do oceans have high net primary productivity?

A

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

25
Q

What areas of the ocean have the highest primary productivity?

A

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

26
Q

Eutrophic vs oligotrophic zones?

A 
Eutrophic = High net primary production. 
Oligotrophic = Low net primary production.
27
Q

How does primary production vary temporally?

A

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).

28
Q

How are nutrients cycled?

A

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.

29
Q

Hinder et al (2012)

A

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.

30
Q

What is secondary production?

A

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

31
Q

2 components of secondary production?

A

Somatic production + gonad production.

32
Q

Secondary production functional groups?

A

Grazers, suspension feeders, + predators.

33
Q

Types of microzooplankton?

A 
Phagotrophic protists (eg: dinoflagellates).
Metazoans (eg: copepod nauplii).
34
Q

Diel vertical migration?

A

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

35
Q

Types of pelagic grazers?

A

Copepods, pteropods, + krill.

36
Q

Copepods?

A

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

37
Q

Pteropods?

A

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

38
Q

Krill?

A

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

39
Q

Types of benthic secondary producers?

A

Bivalves, barnacles, polychaete worms, deposit feeders.

40
Q

Bivalves?

A

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

41
Q

Barnacles?

A

Cirri (feeding appendages) sweep water.

42
Q

Polychaete worms?

A

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.

43
Q

Deposit feeders?

A

Directly assimilate photo-detritus.

Influence mineralisation + nutrient-return to water column.

44
Q

Role of detritus?

A

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

45
Q

How is secondary production measured?

A

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.

46
Q

Importance of secondary production info?

A

Fishery management + modelling climate change impacts.

Marine biology (13 decks)

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