User:Benjah-bmm27/degree/2/RDP

Marine chemistry, RDP
"Marine Chemistry"
 * Physical oceanography
 * Chemical oceanography
 * Seawater, salinity: conservative ions (99.8% of ocean solutes) are nacklecamgsok: Na+, Cl−, Ca2+, Mg2+, SO42−, K+
 * Ocean current, hydrothermal circulation
 * Thermohaline circulation: halocline, thermocline, pycnocline, sea surface temperature
 * Upwelling
 * Carbon cycle
 * Redfield–Richards ratio in marine plankton – C:H:P – 106:16:1
 * Nitrification, Anammox, Sulfur assimilation, Denitrification, Methanogenesis
 * Remineralisation
 * Biological pump - faecal pellet packaging (particulate) and downwelling (dissolved) transport organic carbon from the surface to the deep ocean
 * Paleocene–Eocene Thermal Maximum
 * Methane clathrate
 * Archaeol
 * Sulfate-reducing bacteria
 * Dissolved inorganic carbon: CO2, CO32−, HCO3−, H2CO3, CaCO3
 * Lysocline, Carbonate Compensation Depth
 * Ocean acidification, UNESCO ocean acidification FAQ
 * Biomarkers, haptophytes, dinoflagellates, diatoms, maitotoxin
 * Methanogens and methanotrophs are archaea and have ether lipid membranes
 * they probably developed in warm conditions, so needed lipids resistant to acid hydrolysis – an ester lipid would not do
 * ether lipids are used to trace methanogenic and methanotrophic archaea

Isorenieratene

 * Anoxygenic photosynthesis by Chlorobium (green sulfur bacteria):
 * H2S + CO2 + hν → SO42− + organic C
 * needs reduced sulfur so strictly anaerobic, but also needs light – rare combination of conditions, found in very stratified water columns (constrained basin with fresh water flowing in to achieve sharp density gradient), e.g. the Black Sea
 * Lives ~100 m depth, so wavelength of sunlight is altered, ∴ uses its own special light harvesting pigment, isorenieratene: Isorenieratene-2D-skeletal.png
 * Brocks & Summons, Nature 437, 866-870: "Biomarker evidence for green and purple sulphur bacteria in a stratified Palaeoproterozoic sea"
 * Indicator of photic zone anoxia (Isorenieratene Biosynthesis in Green Sulfur Bacteria (2008))
 * Anoxic event

Anammox

 * Also from the anoxic Black Sea – anammox:
 * NH4+ + NO2− → (intermediates: N2H4, NH2OH) → N2 + 2H2O
 * Membrane lipids of planctomycetes: ladderanes e.g. pentacycloanammoxic acid from Brocadia anammoxidans, stack flat making an impermeable membrane to keep toxic intermediates isolated inside anammoxosome

Alkenones
E. huxleyi (a haptophyte) uses alkenones as membrane lipids:
 * In colder seas, it makes more triunsaturated alkenone (37:3) which is more kinked as so remains fluid at low temperatures
 * In warmer seas, it makes for diunsaturated alkenone (37:2), which is less kinked and would solidify in the cold
 * Use ratio of the two alkenones as a proxy for sea surface temperature: $$U_{37}^K = \frac$$
 * First work on alkenones for SST done in Bristol in the 1980s:
 * Br. Phycol. J. (1980) 19, 2619-2622
 * Phys. Chem. Earth (1980) 12, 219-227
 * Nature (1986) 320, 129-133
 * Org. Geochem. (1988) 13, 727-734 – C37 alkenones unexpectedly have all-trans (E) stereochemistry
 * Further reading:
 * http://chemoc.coas.oregonstate.edu/~fprahl/alkdesc.html
 * Marine Chem. (1999) 64, 301-313
 * Paleoceanography (2001) 16, 226–232
 * Geochem. Geophys. Geosys. (2003) 4, 1014]
 * Paleoceanography (2006) 21, PA1005
 * Anal. Chem. (2008) 80, 2161–2170
 * Geochim. Cosmochim. Acta (2008) 72, 4035-4046

37:2 (15E,22E)-heptatriaconta-15,22-dien-2-one, C37H70O:



37:3 (8E,15E,22E)-heptatriaconta-8,15,22-trien-2-one, C37H68O:



Tetraether lipids

 * Pelagic crenarchaea use tetraether lipids, which they adapt to different temperatures:
 * more rings help membranes stack at stay well-ordered at high temperatures
 * fewer rings help disorder membranes, so they don't freeze at low temperatures

News reports

 * Nature's own acidic ocean, BBC News Online, 10 March 2009
 * Threats from ocean acidification, BBC News Online, 11 March 2009
 * UK funds sea acidification study, BBC News Online, 28 April 2009
 * Shrimp tuned to ocean temperature, BBC News Online, 7 May 2009