energetics & remineralisation

Question 1

equation to calculate energy content of trophic level n

Answer 1

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

Question 2

what is ecological efficient (EE) and its formula

Answer 2

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

Question 3

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

Answer 3

• 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)

Question 4

explain the Biomass pyramid patterns

Answer 4

• 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

Question 5

whats the Second Law of Thermodynamics

Answer 5

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

Question 6

what is Respiration (R)

Answer 6

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

Question 7

what is Growth (G)

Answer 7

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

Question 8

equation for Energy budgets

Answer 8

I = G + R + Exc + Exu + D

Question 9

what is Ingestion (I)

Answer 9

energy entering the gut

Question 10

wat is Defecation (D)

Answer 10

energy not crossing the gut

Question 11

what is Excretion (Exc)

Answer 11

energy never assimilated, but crosses gut wall

Question 12

what is Excuvation (Exu)

Answer 12

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

Question 13

what’s the Lowest/most dispersed form of energy

Answer 13

heat

Question 14

equation for growth

Answer 14

G = I – R – Exc – Exu – D

Question 15

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

Answer 15

fewer steps

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

• 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

Question 19

explain Miss-Match

Answer 19

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

Question 20

explain Match

Answer 20

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

Question 21

in general, what feeds on what

Answer 21

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

Question 22

what is Remineralisation

Answer 22

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

Question 23

how do Bacteria make nutrients available to other organisms

Answer 23

through decomposition

Question 24

what is nutrient remineralisation

Answer 24

photosynthesis - collection of energy to organic molecules

Question 25

explain how Remineralisation works

Answer 25

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

Question 26

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

Answer 26

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

Question 27

how are bacteria good at making use of material

Answer 27

• 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

Question 28

2 main factors that keep the bacterial population in check

Answer 28

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

Question 29

what happens when N is limiting

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

• 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

Question 32

how does the microbial loop occur

Answer 32

• 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

Question 33

how do we determine if predators will incorporate or excrete nitrogen

Answer 33

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

Question 34

what does a large C:N ratio mean

Answer 34

nitrogen poor body

Question 35

explain the biological pump (carbon)

Answer 35

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

Question 36

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

Answer 36

• 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’

Question 37

high export environments characteristics

Answer 37

• 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

Question 38

low export environments characteristics

Answer 38

• 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