General biogeochemistry Flashcards
Effect of Fe fertilization on ___ to ___ uptake ratio
Lowers the silicate to nitrate uptake ratio in diatoms (Hutchns and Bruland, 1988; Takeda, 1998), allowing for diatom-driven nitrate consumption to proceed to a much higher degree
Depth of MLD in Antarctica during summer sea ice retreat
Shoals from to 20 m (from 60 m). (e.g., Robinson and Sigman 2008)
BATS coordinates
31º40’ N 64º10’ W
Chl.a concentration at BATS mg m-3
0.10 ± 0.08 mg m-3 (std deviations of the mean, not measurement error)
(vs. 0.8 ± 0.5 in SNA)
REF: see Biogeochemical Dynamics chapter 4
Nitrate µmol kg-1 at BATS
0.04 ± 0.11 mg m-3 (std deviations of the mean, not measurement error)
(vs. 9 ± 6 in SNA)
(vs. 25 ± 2 at Antarctic Polar Front)
REF: see Biogeochemical Dynamics chapter 4
Phosphate at BATS µmol kg-1
0.01 ± 0.02 mg m-3 (std deviations of the mean, not measurement error)
(note, vs. 1.8 ± 0.1 at Antarctic Polar Front)
REF: see Biogeochemical Dynamics chapter 4
Silicic acid at BATS µmol kg-1
0.8 ± mg m-3 (std deviations of the mean, not measurement error) (note, vs. 14 ± 4 at Antarctic Polar Front)
REF: see Biogeochemical Dynamics chapter 4
Definition of “high nutrients” in terms of nitrate and HNLC
> 2 mmol m-3 (i.e., greater than 2 mM)
Ecumenical Hypothesis
Morel et al 1991
Combination of top down versus bottom up for different parts of the ecocystem i.e., parts of the system are controlled by grazing but the system as a whole is controlled by Fe limitation…
C:N:P ratio variability as pertains to diatoms
Specifically: C:N:P of 80.5:10:1 for diatoms vs 134:18.6:1 for dinoflagellates., e.g., Sweeney et al 2000 (see also Arrigo 94:10:1 for diatoms; 150:20:1 for Phaeocystis)
Generally: Diatoms have lower than redfield proportions for C:N and N:P
REF: see Biogeochemical Dynamics chapter 4
Average C:N ratio
6.6, but the net photosynthetic uptake if often ~ 10 to 12 (in “considerable excess” of 6.6) in Bering Sea, SNA, and Antarctic, e,g.
REF: Sambratto et al 1993, Biogeochemical Dynamics chapter 4
IMPORTANT FIGURE
p. 120, Biogeochemical Dynamics chapter 4, Nitrate runs out before Phosphate; slope of the line is miraculously close to 16:1
A) Why is there so little remineralization of nitrate in the euphotic zone?
nitrifying bacteria are inhibited by light
Ammonium in the surface ocean
has a really low residence time! only measurable = from local remineralization of OM (REF: Sarmiento chpt 4) p 120
Percentage of DOM cycled through bacteria (microbial loop) in the global surface ocean?
50% (Carlson, 2002)
Percentage of total exported OM that is in the form of DOC?
10-30% (11% in Ross Sea to 52% in subtropical Pacific; Carlson et al 2002; Emerson et al., 1997). (33% in SS; Carlson et al., 1994) I.e., microbial loop is really important!
Specific to the subtropical North Atlantic, Percentage of total exported OM that is in the form of DOC?
33% in SS; Carlson et al., 1994.
i.e., microbial loop is really important!
REF: Sarmiento chpt 4 p 122
Two primary reasons microbial life = important for recycling of OM in the surface?
1) primary consumers of DOM
2) excrete of enzymes capable of breaking down the pool of OM into smaller soluble molecules
(Cho & Azam, 1988)
e-ratio = ? (from Sarmiento text)
e-ratio = export ratio. e = (export production)/(primary production)
in contrast to f-ratio, which is (new prod)/(new+regen’d prod)
relationship between e- and f-ratios over time and space?
supposed to equal one another, if you include lateral transport. Mass balance.
why do e- and f-ratios have to = one another over space and time?
write eq for both ratios… primary prod cancels out…
BATS nitrite concentration at 100m and at PNM
60 ±8 nmols 100m, peaked at 64 ± 14 nM at 120 m (PNM) (DECEMBER, 2009, Newell et al 2013)
BATS nitrate concentration at surface, 100m, and 1000 m
0-10 nM in surface, up to 21 µM at 100m (DECEMBER 2009, Newell et al 2013)
Ammonium concentrations at BATS in December
highest at 30 m – 26.2 ± 1.4 nM. Overall, = variable, but up to 26 nM in the upper 200 m. Undetectable below 300 m! (Newell et al 2013, December 2009)
side effect of light limitation by phytoplankton
nitrite excretion during assimilation of NO3- (Lomas and Lipschultz 2006)
Theorized percentage of nutrients supplied by subantarctic mode water in the southern ocean to productivity north of >30ºS in the Atlantic?
~75%! This from Sarmiento, Gruber, Dunne, Brezinski 2004 Nature paper
ratio of Si to N in diatoms that are not Fe stressed or light stressed
1:1
definition of Si* as a tracer
Si* = [Si(OH)4] - [NO3-]
Basically, Si in excess of NO3 assuming a 1:1 ratio of Si to NO3 (Sarmiento, Gruber, Dunne, Brezinski 2004 Nature Paper)…
In SAMW, concentrations of Si*= -10 µmol kg-1 to -15 µmol kg-1 are the lowest we were able to find anywhere at the surface of the ocean.
Three things you need to know in order to set up an 15N experimentt
incubation time determination: need to know
◦ size of pool
◦ turnover rates
◦ detection limits of analytical methods
types of amino acids that undergo transaminations; ones that don’t
alanine, aspartate, glutamate are the usual products of transaminations; serine and threonine do not undergo transaminations (but do undergo dehydrogenation) (ref: wiki)
transamination
important for synthesis of non-essential amino acids; an amine group is switched with an O between a keto acid and an existing amino acid, resulting in a new keto and a new amino; this process accomplished by transamines (enzymes). The chirality of an enzyme is determined in these reactions (ref: wiki)
Diffusion - as defined by Jorge
occurs due to random motion of tracer molecules (molec diffusion) and also generally includes eddy diffusion - net effect of small-scale motion of water parcel that do not result in net advection. If one face of the cube has equal amounts of water flowing in and out, but if the water flowing in has a higher tracer concentration than the water flowing out, net accum of tracer will occur without net movement of water (advection)
Molecular diffusion
not proportional to the gradient in tracer concentration
Ekman transport
. great description, jorge’s book p 23
What are the basic wind patterns respectively in the tropics, the mid-latitudes, and the high latitudes?
Trade winds in the tropics, westerlies in the mid-lats, polar easterlies in the high lats
Ekman transport
Water that is set directly into motion by the wind that feels the effect of th erth’s rotation. Only extends to top 10-1000m of water column. 90º to the right of the wind in Nn Hemi, 90º to the left of the wind in Sn Hemi
Question - why doesn’t surface water go in the same direction as the wind?
It feels the effects of the earth’s rotation, resulting in 90º to the R ofthe wind, and to the L of the wind in Nthn and Sth respectively.
Fact: Ekman transport causes accum. of water on the western boundaries of oceans, resulting in a horizontal gradient of sea surface height.a Question - why doesn’t downslope flow of surface ocean currents occur as a result?
Earth’s rotation intervenes, causing the resulting flow instead to flow at a 90º angle to the expected down-gradient flow of water. Note: Gulf Stream results. Th western boundary flows are extremely concentrated and intense (because the water is piled up on the Western sides?)
Newton’s 2nd Law
F = ma
F = force in newtons
m is mass in kg
a is acceleration in m s-2
equation for m: m=volume V times density p (jess note - “p” = rho sign actually)
Mechanism 1 of 3 for how Ekman transport can lead to upwelling or downwelling
Continent Margins. Winds that run parallel to coastline - if wind blows in such a way as to drive Ekman trasnport away from the coast, then = upwelling of deep waters (e.g., if wind is blowing north along the western boundary of a continent in the southern hemisphere)
Mechanism 2 of 3 for how Ekman transport can lead to upwelling or downwelling
Equator. Winds that blow along the equator can give rise to upwelling or downwelling via Ekman Transport (ET) – trade winds have a strong easterly component… due to Coriolis, this results in R-ward turning currents in the Nthn Hemisphere, and L-ward turning currents in the Sthn Hemisphere, driving upwelling through Ekman Suction
Mechanism 3 of 3 for how Ekman transport can lead to upwelling or downwelling
Open Ocean. In regions wehre the direcition fo the prevailing winds switches from being easterlies to westerlies or vice versa (e.g., between 20º and 50º), Ekman Transport in the westerlies region will cause flow to go south; ET in the easterlies will cause flow to go north. In this way, IT will drive currents that will be convergent flow – in this case, resulting in currents going towards each other, resulting in downwelling where they meet, in the subtropical gyres. The opposite occurs, because there are two currents going away from one another, resulting in upwelling in the subpolar gyres.
Question: why are the subtropics so “devoid” of life?
Due to Ekman processes! Aka, little upwelling to bring nutrients to the surface! The subtropical gyres experience Ekman mechanism in which wind patterns (easterlies switching to westerlies with latitude for subtropical gyres) results in Ekman Convergence where northward-marching Ekman-derived currents meet southward-marching Ekman-derived currents and subsequently cause downwelling in subtropical gyres. In contrast, subpolar gyre experience southward flowing currents running in the opposite direction of northward flowing currents, resulting in upwelling Ekman convergence! Also, equatorial convergence and coastal upwelling are and example of Ekman transport causing nutrient-rich regions. p 30 Jorge
Ekman Transport accumulates water, causing mounding up of water in ___ gyres and ____ clockwise circulation
Northern subtropical gyre, clockwise circulation
Counterclockwise circulation = anticylonic or cyclonic?
Anticyclonic
Northern Hemisphere subtropical gyre has ___ circulation (counterclockwise or clockwise?)
Clockwise, anticyclonic
Geostrophic
The balance between the Coriolis Effect and the effect of pressure gradients (which themselves are the results of “mounding” up of water due to Ekman transport) result in observed geostrophic flow. Note on pressure gradients – in the north atlantic subtropical gyre, for example, which rotates clockwise, the effect of Ekman Transport (and because the 0 to 30ºN trade winds are easterlies i.e. west-going, creating northward flowing currents, which then meet the Ekman Transport-created southward-flowing currents from the westerlies, which are flowing from north to south, creating converging i.e. mounding waters. The mounding would create currents going DOWN the pressure gradient, but the rotation of the earth, the Coriolis forces, interferes, resulting in the clockwise rotating gyre in this case.
What is the symbol for density?
rho (ρ) as the symbol for density
1 cubic meter (m3) = ? liters
1 cubic meter (m3) = 1000 liters (L)