SOES 2006 - Carbon cycle, DOM and microbial loop.單詞卡 | Quizlet

It's one of the carbon sinks that doesn't experience any affects from anthropogenic activities (not yet on a quantifiable level).

What is interesting about the anthropogenic impacts on marine biota?

Oceanic carbon pumps act to maintain a gradient of CO2 between the upper and lower ocean. This stores CO2 in the deep ocean, out of contact with the atmosphere, hence reducing atmospheric CO2.

How does the ocean generally reduce CO2 in the atmosphere?

Concentration differences between the atmosphere and the ocean.

What is air-sea CO2 flux driven by?

Chemical and physical processes.

What processes is the solubility pump driven by?

CO2 dissolves into the surface waters (solubility of CO2 is temperature dependant so cooler waters take up more) then when/if these waters sink into the interior, they take carbon with them (this is primarily how the oceans take up anthropogenic CO2).

How does the solubility pump work?

Organic carbon is produced in the surface - when a proportion of this carbon sinks into the interior, it takes carbon with it.

How does the biological pump work?

They maintain a sharp gradient of CO2 between the atmosphere and the deep ocean where 38,000 GtC of carbon is stored.

What is the point of the biological and solubility pump?

Particulate organic matter that isn't remineralised, converted back to CO2 and released into the atmosphere will sink to the deep ocean where it is remineralised back to CO2 by bacteria, but it can be stored here away from the atmosphere for as long as it takes to resurface through the circulation (for 1000 years)

What is export production?

- Amount of POC produced

- The food web structure

- Relative abundance of species

(All of which can be controlled by inorganic nutrients like nitrogen, phosphorous, silicon and iron).

What influences how much CO2 is pumped to the deep ocean?

Aggregates of marine material.

What is marine snow?

- Fixation of C, N by phytoplankton

- Grazing (zooplankton then fish etc)

- Respiration, egestion and excretion by grazers

- Aggregate formation and break up (more physical)

- Active vertical migration to below the euphotic zone

- Decomposition by bacteria

- Passive sinking of PIC, POC (determined by form and density of it)

What ecosystem interactions might be involved in the biological carbon pump?

The component of the upper ocean organic matter production which is supported by nutrients which are newly supplied to the euphotic zone.

What is new production?

The sinking of organic carbon to the aphotic zone (i.e. the flux of carbon to the deep ocean).

What is export production?

The carbon lost to the deep sea can be replaced by taking CO2 into the surface ocean from the atmosphere.

Over long time scales, new production and export production must balance. How can this be done?

uptake of new N (NO3)/ uptake of new N + regenerated N (NO3 + NH4)

Define the f-ratio with a formula.

- Ungrazed dead phytoplankton cells.

- Faecal pellets from copepods and larger organisms.

- Organic aggregates or marine snow.

- Dead metazoan organisms and moults.

There is a downwards flux of particulate organic material (POM). What 4 things might this be made up of?

(basically represents the biological pumps export of organic matter to the deep ocean).

The sinking flux of organic material (marine snow) can be collected using sediment traps and then analysed (eg: look at the POC)

A variety of types of trap are used (moored, surface tethered, free drifting)

How can the magnitude of export production in different regions of the ocean be estimated?

A funnel collects sinking particles and funnels these into collection cups. These cups are rotated to provide a time series of material. They are typically attached to a bottom weight with a release mechanism. Vertical spacing of sediment traps allows measurements of flux at different depths.

How do moored sediment traps work?

Tethered or moored sediment traps in the upper ocean can be influenced by artefacts. So some may therefore be free drifting.

For example the NERC with a biological pump.

How do free drifting sediment traps work?

It decreases as the POC is degraded.

(The zooplankton and bacteria use the supply of organic carbon 'raining' down from above for energy, respiring a proportion back to CO2 - only a small portion of the material leaving the surface reaches the sea floor).

What happens to the downwards flux of organic carbon with depth?

The water moves so that those in the upper ocean may get influenced by artefacts.

What is an issue with tethered or moored sediment traps?

Pelagra free drifting sediment traps.

NERC funded COMICS project.

Give some examples of free drifting sediment traps.

Collect materials, quantify organic carbon and if you know how long it took to form the organic carbon, you can estimate rate of organic material being lost out of the upper ocean.

The biological content can be biologically and chemically characterised.

What can be done with the biological material caught in sediment traps?

Landers with camera systems and buoyancy aids can be deployed to observe the changes and composition of sediments on the sea floor.

EG: sediment can get completely covered by green fluffy matter at the end of summer which is organic material (phytodetritus) sinking from a phytoplanktonic spring bloom. Benthic organisms can then use this material.

How can variations in export flux be observed with cameras.

Using variance methods such as satellite imaging, variability in new and export production can be estimated across the oceans.

How can variations in export be observed through production gradients?

In higher productivity systems (coastal, upwelling etc) - more produced at surface = more lost to depth.

The proportion of organic carbon in the surface exported to depth can also be higher in higher productivity systems.

Where is export of organic carbon from the surface ocean higher?

Changes in primary production (particularly new) can ultimately result in altered export production. Variations can occur over multiple scales in response to physical forcing perturbing the environment eg: in response to the seasonal cycle, passage of cyclonic eddies etc.

How might export production vary?

Autotrophic heterotrophic coupling.

Balancing of the photosynthesis/primary production done by autotrophs can be balanced and counter-acted by autotrophs, changing nutrient levels.

What is A-H coupling?

There is weak A-H coupling at it is more autotrophic dominated, using the nutrients but not being grazed upon (particularly as high nutrients means these diatoms that have defences against being grazed on). This then allows for high export production as the organisms die and sink instead of being grazed upon. Here, there are greater organic particulate nutrients than dissolved nutrients because there is high organic matter.

What happens to A-H coupling in high productivity systems?

There is weaker A-H coupling as it is more heterotroph dominated - there are lower nutrients meaning smaller phytoplankton cells utilising the nutrients. This causes lower export production as cells are grazed upon instead of sinking and demineralising. Here, there are greater dissolved inorganic nutrients because there is low organic matter.

What happens to A-H coupling in low productivity systems?

Microbial degradation in the mesopelagic layer in low productivity systems.

Zooplankton degradation in the mesopelagic layer in high productivity systems.

How does degradation change as a system gets more productive?

Dissolved organic matter of less than 0.2µm in size. It includes a spectrum of material ranging from low molecular weight amino acids and sugars to large complex molecules, viruses and sub micron detrital remnants of previously consumed biota.

Includes DOC (carbon), DON (nitrogen), DOP (phosphorous)

Can be labile (easily metabolised) or refractory (less easily assimilated and decomposed.

What is DOM?

natural sources of terrestrial or benthic origin.

Can also be anthropogenic - sewage effluent, oil pollution, wood pulp, industrial effluents.

Where does coastal waters autochthonous DOm come from?

- Phytoplankton excretion or exudation (leakage of low molecular weight compounds across cell membrane).

- Zooplankton feeding and excretion (soluble and faecal breakdown)

- Viral lytic cycle when infected cells burst and release DOM

Where does DOM come from in the open ocean?

Unicellular prokaryotic plankton (less than -0.5-1um in length).

They are highly abundant but small sizes meaning they never really dominate biomass. They change over a seasonal cycle.

Abundance can be measured by flow cytometry and epifluorescent microscopy.

Activity can be measured using radiotracer methods.

Diversity can be investigated using modern molecular biological (genomic) techniques.

What are marine backteria?

The cycling of carbon and nutrients through DOM and bacteria (and their grazers, microzooplankton such as ciliates and heterotrophic flagellates.

What is the microbial loop?

Mixotrophy - the combining heterotrophic and autotrophic metabolism.

It is key in oceanic microbial systems.

It has also influenced the evolution of phytoplankton and the biogeochemistry of marine systems.

What had to be considered and incorporated into the microbial foodweb?

Microbial carbon and nutrient cycling involves the transfer of different forms of carbon between organisms. However, the net effect appears to be "pumping" some of the DOM into refractory forms - different forms of carbon that basically cannot be used/ metabolised by organisms as easily.

What is the microbial pump?

- Production of new organic material in the surface by phytoplankton.

- Packaging of particulate material into sinking forms (large cells, aggregates, faecal pellets.

- Sinking of POC to depth.

- Remineralisation of POC back to CO2 and storage in the deep ocean.

What are the 4 key components of the biological carbon pump?

- Production of new organic material in the surface by phytoplankton.

- Transformation of organic material into refractory dissolved organic matter (rDOM), allowing long term storage.

What are the 2 key components of the microbial carbon pump?