energetics & remineralisation Flashcards

1
Q

equation to calculate energy content of trophic level n

A

energy entering trophic level n + energy leaving trophic level n (respiration, predation, decomposition etc)

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2
Q

what is ecological efficient (EE) and its formula

A
  • Amount of energy transfered between trophic levels
    Energy present in current trophic level
    ——————————————————-
    Energy in trophic level below x100
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3
Q

what 2 principles did Lindeman conclude after looking at energy in a complicated web of trophic interactions

A
  • Predator = more active than herbivorous prey, which in turn are more active than plants - % energy loss to respiration is progressively greater for higher levels (Decreasing productivity)
  • Consumers at higher levels are more efficient in using their food supply. (Increasing efficiency)
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4
Q

explain the Biomass pyramid patterns

A
  • Generally need around 10x the animal to support the level above
  • Size will decrease as going down the chain – phytoplankton = smallest (but most abundant)
  • Bigger organisms at the top e.g. whales, cod, will have a smaller total biomass due to the amount of energy/biomass they need to support
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5
Q

whats the Second Law of Thermodynamics

A

“no process involving an energy transformation will spontaneously occur unless there is degradation of energy from a concentrated into a dispersed form”

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6
Q

what is Respiration (R)

A

Energy -> heat loss due to 2nd law of thermo
- Carbon -> break down of OM releasing CO2

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7
Q

what is Growth (G)

A

Energy amassed as matter i.e. net gain from ingested energy

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8
Q

equation for Energy budgets

A

I = G + R + Exc + Exu + D

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9
Q

what is Ingestion (I)

A

energy entering the gut

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10
Q

wat is Defecation (D)

A

energy not crossing the gut

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11
Q

what is Excretion (Exc)

A

energy never assimilated, but crosses gut wall

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12
Q

what is Excuvation (Exu)

A

energy once assimilated, but later secreted e.g. mucus

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13
Q

what’s the Lowest/most dispersed form of energy

A

heat

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14
Q

equation for growth

A

G = I – R – Exc – Exu – D

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15
Q

why is the Classic food chain more efficient than the microbial loop

A

fewer steps

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16
Q

3 advantages that gives the microbial loop more of an energy efficiency

A

1) Digestion efficiency
2) Protozoa = energy not otherwise available to mesozoo
3) Match & miss-match

17
Q

what is Digestion efficiency and how could it give the microbial loop more of an energy efficiency

A

% of ingested food that is digested
Ingestion – Defecation * 100
——————————-
Ingestion
- Microzoo have higher digestion efficiencies than mesozoo - smaller organisms tend to have more efficiency

18
Q

what is Match & miss-match and how could it give the microbial loop more of an energy efficiency

A
  • The > size difference between trophic level, the longer it takes predator # to respond to prey #
  • Smaller the organism, faster the reproduction + adapt to changes in environment
19
Q

explain Miss-Match

A

disconnect between how much food is being produced + how quickly the organisms that eat them can react to exploit it
- Spring Diatom Bloom – large amount of nutrients + light is picking up
- Lasts 1-2 weeks
- Diatoms can react quickly + reproduce quickly
- Copepods graze, but # cannot respond fast enough to be an effective predator to diatoms
- Primary production sinks to benthos – not being recycled as there is nothing to eat them

20
Q

explain Match

A

more stable population
- Summer PNAN population
- Lower conc of nutrients in summer – smaller organisms make more use of it e.g. nanoflagellates
- Ciliate #’s respond quickly – feed on nanoflagellates
- PNAN productivity may be high, but # remain low due to grazing by ciliates
- Primary production: recycled within the water column

21
Q

in general, what feeds on what

A

HNAN -> bacteria
larger hetero flag -> NAN
ciliates -> NAN
hetero dinos -> diatoms
coastal copepods -> diatoms, NAN, ciliates

22
Q

what is Remineralisation

A

Transformation of organic (contain carbon atoms) molecules -> inorganic forms (used by phytoplankton to reproduce), typically mediated by biological activity

23
Q

how do Bacteria make nutrients available to other organisms

A

through decomposition

24
Q

what is nutrient remineralisation

A

photosynthesis - collection of energy to organic molecules

25
Q

explain how Remineralisation works

A

1.Phytoplankton uptake energy from sun
2.Zooplankton feed on phyto
3.Zooplankton excrete/die - put organic material (POM/DOM) into water
4.Bacteria break these down into usable inorganic material

26
Q

how do Bacteria break down POM/DOM from dead zooplankton into usable inorganic material

A
  1. Direct uptake of LMW (low molecular weight) DOM
  2. Exoenzymatic activity to break down complex DOM and POM (macromolecules)
  3. Also require inorganic nutrients; hence, dual role of nutrient regenerator and competitor for phytoplankton
27
Q

how are bacteria good at making use of material

A
  • Their small size means they are able to make use of small amounts of inorganic material
  • Can switch from making use of organic and inorganic molecules depending on the concentration/availabilty
28
Q

2 main factors that keep the bacterial population in check

A
  • Bacterivory – things that eat them e.g. nanoplankton
  • Viral lysis
29
Q

what happens when N is limiting

A
  • bacteria can compete with phytoplankton for DIN
  • Bacteria = better competitors due to large surface area/volume ratio
  • When this occurs: protozoa = most important remineralizers
30
Q

explain the High efficiency of N transfer up food web by protozoa (LINK)

A

1.Bacteria feed on POM + DOM also inorganic nutrients (competing with the phyto)
2.Protozoa feed on bacteria
3.Zooplankton feed on protozoa
4.Zooplankton excretion + death = more inorganic material
- OM incorporated into bacteria
- Protozoa incorporate majority of bacterial N
- Protozoa provide N link bact -> mesozoo
- N remineralization dominated by mesozoo
- High efficiency of transfer

31
Q

explain the low efficiency of N transfer up food web by protozoa (SINK)

A
  • Bacteria remineralize POM & DOM
  • Protozoa remineralize remaining nutrients
  • Low efficiency of transfer – organic material in protozoa gets remineralised to DIN and gets taken up by phytoplankton rather than zooplankton
  • Little PON for mesozoo
  • Microbial loop = PON sink
  • Provide DIN to phyto
32
Q

how does the microbial loop occur

A
  • If coupling between microplankton and higher organisms is weak and there are low conc of inorganic nitrogen in the water, organic matter can be recycled multiple times between the microbes and microplankton without moving up the food chain – organic matter is trapped in a “loop”
  • Microbial loop is somewhere in between acting as a PON link or sink
  • low N conc = protozoans will be more important in remineralising organic material (microbial loop) – avoids losing N into the seabed
33
Q

how do we determine if predators will incorporate or excrete nitrogen

A

C:N ratio - Pred feeding on N rich prey will excrete excess N as NH4+
- Bacterivorous protozoa N poor compared to their bact prey -> excrete excess NH4+
- Copepods N rich compared to their phyto prey -> incorporate N

34
Q

what does a large C:N ratio mean

A

nitrogen poor body

35
Q

explain the biological pump (carbon)

A

1.Gas gets dissolved into water
2.Phytoplankton takes in the material
3.Organisms eat those phyto – turns into DOC that goes to deeper waters

36
Q

what determines if the carbon export in biological pumps are high or low

A
  • Export fluxes depends on where you are
  • In general: Low export of POC relative to PP
  • Exceptions:
    Episodic events e.g. Spring Bloom, N. Atlantic
    Export pulses e.g. SW monsoon, Arabian Sea
  • High Export = ‘classical food chain’
  • Low Export = ‘microbial loop’
37
Q

high export environments characteristics

A
  • Large phytoplankton: diatoms – can’t swim, fall out of surface waters
  • Large zooplankton:
    POC: faecal pellets
    DIC/DOC: vertical migration
  • High miss-match
  • Classic food chain: major export C to deep ocean
  • High conc of organic material in deep waters will decrease the amount at the surface, drawing more carbon from atmos
38
Q

low export environments characteristics

A
  • Microbial loop organisms
  • Dominate most of world’s oceans
  • OM remineralized & recycled: SML
  • V little export to deep ocean
  • F-ratio = LOW (nitrate : uptake of nitrate + amonium) - lots of uptake of recycled nutrients e.g. amonium instead of new nitrogen from external sources