Lecture 14- Carbon flux and Biological Pump- BIO OCE

what is the net carbon flux in the ocean

net carbon into ocean than going out

what are the two reasons to study vertical flux material

1. the ocean is a sink of carbon dioxide

2. to understand deep sea ecosystems

when is the ocean a sink of carbon dioxide

when you remove carbon from the surface

why is the ocean a sink of carbon when you remove it from the surface

because carbon dioxide between the atmosphere and ocean are in equilibrium at the surface

why is studying vertical fluxes important for deep sea ecosystems

most organisms in the deep sea are dependent on nutrients from the surface

highest biomass in open ocean and why

bacteria and archaea because they require less nutrients and their large surface area to volume ratio helps the uptake of limiting nutrients

where are eukaryotic organisms more abundant

more coastal areas with more nutrients

three biological carbon pumps

1. mixing pump

2. gravitational pump (archimedian pump)

3. migrant pump (reciprocating pump)

rotary pump

circulation of material in microplankton food web where there is no vertical flux

other two types of pumps

solubility pump and changes of alkalinity

5 types of pumps

1. mixing

2. gravitational

3. migrant

4. solubility

5. changes in alkalinity

how does the mixing pump work

advection of DOM, colloids, small particles

how does the gravitational pump work

flux of fecal material and marine snow due to gravity

how does the migrant pump work

drawdown of material due to migrating organisms which releases CO2 and defecation at diff depths

how does the solubility pump work

sinking water that holds lots of CO2

how does changes in alkalinity contribute to carbon flux

changes in alkalinity of seawater due to phytoplankton influencing air-sea exchanges

synonym for gravitational pump

archimedian pump

synonym for migrant pump

reciprocating pump

marine snow

>500um amorphous aggregates of mixed composition

particles that mediate carbon flux

1. phytoplankton aggregates and marine snow

2. gelatinous excretions of zooplankton

3. fecal pellets of zooplankton and fish

4. carcassess

what is needed for plankton aggregates and excretions to sink

ballast by attached diatoms and calcium carbonate shells of coccoliths

examples of gelatinous excretions that contribute to gravitational flux

appendicular and pteropods

what pump needs ballast

gravitational so that they sink

what does the microbial carbon pump produce

refractory dissolved organic carbon

4 ways to determine vertical fluxes

1. new production/ export models

2. radionuclide disequilibrium models

3. sediment traps

4. particle numbers and sizes and stoke’s equation

main 2 methods of radionuclide disequilibrium methods

thorium in weeks and polonium in months

what is the only direct measurement to determine vertical fluxes

sediment traps

why is nitrogen good for studying elemental dynamics

there is a distinction between old and new N and it is limiting

how does new and old nitrogen tell us about elemental dynamics

dividing it tells us exactly where it came from and getting ratio can tell us the net flux

new nitrogen

No3 nitrate upwelling, from nitrification, can be NH3 and NO3

recycled nitrogen

ammonium NH3, excreted

how does nitrogen being limiting help us estimate fluxes

because when it is high we can tell where there is upwelling

what other elements are limiting

iron and phosphorus

where is limiting phosphorus important

subtropical North Atlantic

where does recycled nitrogen come from

excretion from PP done by microzooplankton, protists, bacteria

F ratio

new production/ (new + regenerated production)

method to measure f ratio

stable isotope of NO3 uptake vs C14 primary production

range of f ratio

0.1 in coral reefs and 0.8 in upwelling systems

steps of using f ratio equation

1. stable isotope N15 and radioactive isotope C14 added to water sample

2. measurement in mass spectrometer to determine N15/N14 ratio

3. C/N ratio from CHN analyzer

4. C14 uptake to measure primary production

why would we use C13 instead of C14

can be done simultaneously with N15/N14

3 issues with the F ratio concept

1. some bacterial production should be added to primary production because they represent a sink not a source of nitrogen

2. tracking chemical nitrogen species (nitrate vs. ammonium) does not cleanly or reliably translate into the actual biological structure or energy pathway of the food web

3. nitrogen fixation is a new source of nitrogen but not accounted for with this method

what does it mean that some bacterial production should be added to primary production because they represent a sink not a source of nitrogen being an issue for f ratio

Bacteria act as a "sink," not just a recycler

what does it mean that tracking chemical nitrogen species (nitrate vs. ammonium) does not cleanly or reliably translate into the actual biological structure or energy pathway of the food web being an issue for f ratio

Chemical "currency" doesn't match the user:
You cannot guess the size of a marine creature or who will eat it just by looking at the type of nitrogen it consumes. Large algae frequently eat "recycled" ammonium, and tiny microbes routinely eat "new" nitrate. The chemical label does not dictate how energy actually moves through the food chain

what does it mean that “nitrogen fixation is a new source of nitrogen but not accounted for with this method” being an issue for f ratio

certain microbes can grab nitrogen gas straight from the air and turn it into food (nitrogen fixation). Because the f-ratio method completely ignores this massive overhead source, it misses a huge chunk of "new" production.

upwelling f ratio

0.8

estimated whole ocean annual f ratio

0.3-0.5

photosynthetic quotient

PQ = O2 released/CO2 assimilated

eppley and peterson hypothesis

over large time scales production is balanced by new production

new production example

upwelling

evidence of eppley and peterson hypothesis

direct dependence of primary production on NO3 nitrate input

what does it mean that there is a hyperbolic increase of primary production and f ratio with nitrate (assimilation) and primary production

When you add nitrate (a key nutrient) to the ocean, both the total amount of organic matter made by marine life (primary production) and the proportion of that life that sinks into the deep ocean (the \(f\)-ratio) will rapidly shoot up at first, but eventually flatten out as the ecosystem hits its maximum capacity

least to greatest nitrogen new production over total production in areas of ocean

central N Pac< eastern med< socal < eastern tropical pac< costa rica< peru upwelling

where is f ratio the highest

where there are new inputs of nitrate

example of areas with high f ratio

coastal and upwelling regions

what percent is of upwelling and coastal regions in the ocean

11%

what fraction of ocean’s primary production is done by coastal and upwelling region

1/3 to ½ of total PP

e ratio

export/ net primary production

export in terms of carbon

carbon flowing down driven by gravity

ef ratio

export production over NPP in combination with f ratio model

NPP

net primary production corrected for respiration and loses

Gt of upwelled nitrate year

7.2 GtC/yr

Gt of dissolved inorganic carbon inventory corrected for CO2 air-sea exchanges

9.1-10.8 Gt C/yr

problems with eppley and peterson hypothesis

1. assumes N2 fixation is not significant

2. vertical migration of organisms not taken into account

3. assume production and export occur at same time scales

4. ignores any ammonium input from atmosphere

5. assumes steady state

6. net community production and export production can be decoupled

what is the issue with assuming N2 fixation is not significant

N2 fixation injects substantial amounts of new nitrogen into the surface layer that do not come from deep-water nitrate

what is the problem with assuming no vertical migration of organisms

This active transport bypasses simple diffusive/upwelling flux calculations and breaks the clean separation between surface uptake and deep export

what is the issue with assuming production and export occur at same time scales

In reality, surface production often decouples from export over days to weeks.

what is the issue with ignoring any ammonium input from atmosphere

Treating all ammonium as recycled misses this exogenous "new" nitrogen source, biasing new production estimates

what is the problem with the steady state assumption

In transient conditions, carbon and nitrogen accumulate or deplete in the upper layer, meaning export does not equal new production on short or seasonal time scales

what is the problem with decoupling net community production and export production

Not all net organic matter produced is exported downward; a large portion can be respired by heterotrophic bacteria, stored as dissolved organic carbon (DOC), or consumed and recycled horizontally. Conversely, physical advection and non-sinking pathways mean NCP and particle export can decouple in space and time

Th 234 method

Th 234 is produced by decay of long lived U238

half life of Th

21.4 days

half life of U238

4.46 billion years

what does it mean that Th attaches to particles

it acts as a tracking tag that allows scientists to measure how fast carbon and organic matter sink out of the upper ocean, sticks (adsorbs) onto the surfaces of sinking marine particles, such as phytoplankton, fecal pellets, and organic aggregates

what does it mean that 238 stays in solution because it is neither biologically reactive or absorbed on surfaces

because it is not biologically reactive or adsorbed on surfaces, they mean that ²³⁸U behaves as a "conservative" element in seawater

what does thorium react with

OH hydroxyl ion causes them to be unstable and cling to negatively charged materia;

why does thorium attach to particles

due to large ionic charge +4, it forms strong chemical bonds with their surfaces

what does it mean that thorium is removed proportionally to sinking fluxes

the amount of Thorium-234 (²³⁴Th) escaping the upper ocean directly scales with the physical mass of the debris sinking out

why is U238 evenly distributed with depth

because long half life and no particle reactivity

what does the disequilibrium between Th and U tell us

indicates sinking fluxes at certain depths

what does it mean if Th is absent

thorium is gone because heavy, sinking debris swept through the water like a sticky broom, gathered up the thorium, and carried it down to the deep ocean

what does it mean if Th is present

There is NO sinking mass

problems with Th234 approach

1. needs statistically significant deficit in Th

2. correction through models and calibration by drifting neutrally buoyant sediment traps is necessary

why is it a problem that we need significant deficit of Th234

issue in oligotrophic waters because the sinking flux there is so incredibly low that a clear deficit rarely forms

why do we need correction through models and calibration of sediment traps for Th approach

²³⁴Th water profile provides the broad, large-scale speed of the downward conveyor belt, while sediment traps provide the specific carbon chemical composition of what is riding the belt

most direct way of determining fluxes

sediment traps

2 basic designs of sediment traps

1. cone shapes (honjo) traps

2. straight tubes (particle interceptor traps PITS)

two problems with sediment traps

1. only small part of ocean is measured at any given time

2. statistical funnel

statistical funnel

what ends up in the trap are particles from different surface waters due to current direction

stoke’s equation

u = 2gr²(ρ’ - ρ)/9ƞ

u

sinking velocity

ƞ

coefficient of dynamic viscosity

ρ’

density of particle

ρ

density of water

hardest thing to measure from stoke’s equation

ρ’

mechanisms that make particles collide and aggregate

differential sinking, turbulence, and brownian motion

brownian motion

random, erratic, zigzag movement of microscopic particles suspended in a fluid

problems of particle inventory method

excess density is difficult to guess, there is a very poor correlation between particle size and sinking velocity, needs to be calibrated with sediment traps or Th234 locally

settling velocity

approx relationship between size and sinking velocity

what size particles contribute the most to mass flux

500um and 2mm

what is the best prediction size for stokes equation

500um