View source for Chemistry:Ocean chemistry

{{short description|chemistry of marine environments}}
{| class="wikitable" style="float: right; margin: 0 0 1em 1em;"
|+'''Total Molar Composition of Seawater (Salinity = 35)'''<ref>{{
Cite book
|author=DOE
|year=1994
|chapter-url=http://cdiac.esd.ornl.gov/ftp/cdiac74/chapter5.pdf
|title=Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water
|publisher= ORNL/CDIAC-74
|version=2
|editor1=A.G. Dickson |editor2=C. Goyet
|chapter=5
}}</ref>
|-
! Component !! Concentration (mol/kg)
|-
| '''[[Chemistry:Water (molecule)|{{chem|H|2|O}}]]''' || 53.6
|-
| '''[[Chemistry:Chloride|{{chem|Cl|-}}]]''' || 0.546
|-
| '''[[Chemistry:Sodium|{{chem|Na|+}}]]''' || 0.469
|-
| '''[[Chemistry:Magnesium|{{chem|Mg|2+}}]]''' || 0.0528
|-
| '''[[Chemistry:Sulfate|{{chem|SO|2-|4}}]]''' || 0.0282
|-
| '''[[Chemistry:Calcium|{{chem|Ca|2+}}]]''' || 0.0103
|-
| '''[[Chemistry:Potassium|{{chem|K|+}}]]''' || 0.0102
|-
| '''[[Chemistry:Total inorganic carbon|C<sub>T</sub>]]''' || 0.00206
|-
| '''[[Chemistry:Bromide|{{chem|Br|-}}]]''' || 0.000844
|-
| '''[[Chemistry:Total boron|B<sub>T</sub>]]''' (total boron) || 0.000416
|-
| '''[[Chemistry:Strontium|{{chem|Sr|2+}}]]''' || 0.000091
|-
| '''[[Chemistry:Fluoride|{{chem|F|-}}]]''' || 0.000068
|}

'''Ocean chemistry''', also known as '''marine chemistry''', is influenced by [[Earth:Plate tectonics|plate tectonics]] and [[Earth:Seafloor spreading|seafloor spreading]], [[Biology:Turbidity|turbidity]] [[Earth:Ocean current|currents]], [[Earth:Sediment|sediment]]s, [[Chemistry:PH|pH]] levels, [[Astronomy:Atmosphere|atmospheric]] constituents, [[Earth:Metamorphic reaction|metamorphic activity]], and [[Earth:Ecology|ecology]]. The field of [[Chemistry:Chemical oceanography|chemical oceanography]] studies the chemistry of marine environments including the influences of different variables. [[Biology:Marine life|Marine life]] has adapted to the chemistries unique to [[Earth:Ocean|earth's oceans]], and [[Earth:Marine ecosystem|marine ecosystem]]s are sensitive to changes in ocean chemistry.

The impact of human activity on the chemistry of the earth's oceans has increased over time, with pollution from industry and various land-use practices significantly affecting the oceans. Moreover, increasing levels of carbon dioxide in the earth's atmosphere have led to [[Biology:Ocean acidification|ocean acidification]], which has negative effects on marine ecosystems. The international community has agreed that restoring the chemistry of the oceans is a priority, and efforts toward this goal are tracked as part of [[Earth:Sustainable Development Goal 14|Sustainable Development Goal 14]].

==History==
Chemistry is though to have to come from the oceans, beginning around 4 billion years ago, when it was released by carbon into the [[Astronomy:Atmosphere|atmosphere]].

==Marine chemistry on earth==
===Organic compounds in the oceans===
[[Biology:Colored dissolved organic matter|Colored dissolved organic matter]] (CDOM) is estimated to range 20-70% of carbon content of the oceans, being higher near river outlets and lower in the open ocean.<ref name=Coble>{{cite journal | last1 = Coble | first1 = Paula G. | year = 2007 | title = Marine Optical Biogeochemistry: The Chemistry of Ocean Color | journal = Chemical Reviews | volume = 107 | issue = 2| pages = 402–418 | doi =  10.1021/cr050350+| pmid = 17256912 }}</ref>

Marine life is largely similar in biochemistry to terrestrial organisms, except that they inhabit a saline environment. One consequence of their adaptation is that marine organisms are the most prolific source of halogenated organic compounds.<ref>{{cite journal | last1 = Gribble | first1 = Gordon W. | year = 2004 | title = Natural Organohalogens: A New Frontier for Medicinal Agents? | journal = Journal of Chemical Education | volume = 81 | issue = 10| page = 1441 | doi = 10.1021/ed081p1441 | bibcode = 2004JChEd..81.1441G }}</ref>

===Chemical ecology of extremophiles===
[[File:Deep_Sea_Vent_Chemistry_Diagram.svg|thumb|upright=1.75|A diagram showing ocean chemistry around deep sea hydrothermal vents|alt=]]The ocean provides special marine environments inhabited by extremophiles that thrive under unusual conditions of temperature, pressure, and darkness.  Such environments include hydrothermal vents and black smokers and cold seeps on the ocean floor, with entire ecosystems of organisms that have a symbiotic relationship with compounds that provided energy through a process called [[Earth:Chemosynthesis|chemosynthesis]].

===Plate tectonics===
[[File:MgCaRatioChanges.jpg|alt=|thumb|upright=1.5|Magnesium to calcium ratio changes associated with hydrothermal activity at mid-ocean ridge locations]]

Seafloor spreading on [[Earth:Mid-ocean ridge|mid-ocean ridge]]s is a global scale ion-exchange system.<ref name=":0">{{cite journal | last1 = Stanley | first1 = S.M. | last2 = Hardie | first2 = L.A. | year = 1999 | title = Hypercalcification: paleontology links plate tectonics and geochemistry to sedimentology | journal = GSA Today | volume = 9 | issue = 2| pages = 1–7 }}</ref> Hydrothermal vents at spreading centers introduce various amounts of [[Chemistry:Iron|iron]], [[Chemistry:Sulfur|sulfur]], [[Chemistry:Manganese|manganese]], [[Chemistry:Silicon|silicon]] and other elements into the ocean, some of which are recycled into the [[Earth:Oceanic crust|ocean crust]]. [[Physics:Helium-3|Helium-3]], an isotope that accompanies volcanism from the mantle, is emitted by hydrothermal vents and can be detected in plumes within the ocean.<ref>{{Cite journal|last=Lupton|first=John|date=1998-07-15|title=Hydrothermal helium plumes in the Pacific Ocean|journal=Journal of Geophysical Research: Oceans|volume=103|issue=C8|pages=15853–15868|doi=10.1029/98jc00146|issn=0148-0227|bibcode=1998JGR...10315853L|doi-access=free}}</ref>

Spreading rates on mid-ocean ridges vary between 10 and 200&nbsp;mm/yr. Rapid spreading rates cause increased [[Earth:Basalt|basalt]] reactions with seawater. The [[Chemistry:Magnesium|magnesium]]/[[Chemistry:Calcium|calcium]] ratio will be lower because more magnesium ions are being removed from seawater and consumed by the rock, and more calcium ions are being removed from the rock and released to seawater. Hydrothermal activity at ridge crest is efficient in removing magnesium.<ref name=":2">{{Cite journal|last1=Coggon|first1=R. M.|last2=Teagle|first2=D. A. H.|last3=Smith-Duque|first3=C. E.|last4=Alt|first4=J. C.|last5=Cooper|first5=M. J.|date=2010-02-26|title=Reconstructing Past Seawater Mg/Ca and Sr/Ca from Mid-Ocean Ridge Flank Calcium Carbonate Veins|journal=Science|language=en|volume=327|issue=5969|pages=1114–1117|doi=10.1126/science.1182252|pmid=20133522|issn=0036-8075|bibcode=2010Sci...327.1114C|s2cid=22739139}}</ref> A lower Mg/Ca ratio favors the precipitation of low-Mg calcite polymorphs of [[Chemistry:Calcium carbonate|calcium carbonate]] (calcite seas).<ref name=":0" />

Slow spreading at mid-ocean ridges has the opposite effect and will result in a higher Mg/Ca ratio favoring the precipitation of aragonite and high-Mg calcite polymorphs of calcium carbonate ([[Earth:Aragonite sea|aragonite sea]]s).<ref name=":0" />

Experiments show that most modern high-Mg calcite organisms would have been low-Mg calcite in past calcite seas,<ref name=":1">{{Cite journal|last=Ries|first=Justin B.|date=2004|title=Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic|journal=Geology|language=en|volume=32|issue=11|pages=981|doi=10.1130/G20851.1|issn=0091-7613|bibcode=2004Geo....32..981R}}</ref> meaning that the Mg/Ca ratio in an organism's skeleton varies with the Mg/Ca ratio of the seawater in which it was grown.

The mineralogy of reef-building and sediment-producing organisms is thus regulated by chemical reactions occurring along the mid-ocean ridge, the rate of which is controlled by the rate of sea-floor spreading.<ref name=":2" /><ref name=":1" />

== Human impacts ==

=== Marine pollution ===
{{Excerpt|Marine pollution|paragraphs=1-2|file=no}}

===Climate change===
{{Further|Earth:Effects of climate change on oceans}}
Increased [[Chemistry:Carbon dioxide|carbon dioxide]] levels, resulting from anthropogenic factors or otherwise, have the potential to impact ocean chemistry.   [[Earth:Global warming|Global warming]] and changes in [[Earth:Salinity|salinity]] have significant implications for [[Earth:Ecology|ecology]] of marine environments.<ref>{{cite journal | last1 = Millero | first1 = Frank J. | year = 2007 | title = The Marine Inorganic Carbon Cycle | journal = Chemical Reviews | volume = 107 | issue = 2| pages = 308–341 | doi = 10.1021/cr0503557 | pmid = 17300138 }}</ref> One proposal suggests dumping massive amounts of [[Chemistry:Lime (material)|lime]], a [[Chemistry:Base|base]], to reverse the acidification and "increase the sea's ability to absorb carbon dioxide from the atmosphere".<ref>{{Cite news|url=https://www.theguardian.com/environment/2009/jul/13/manchester-report-cquestrate|title=Cquestrate: adding lime to the oceans|last=Clark|first=Duncan|date=2009-07-12|work=The Guardian|access-date=2019-07-16|language=en-GB|issn=0261-3077}}</ref><ref>{{Cite news|url=https://www.theguardian.com/environment/2009/jul/13/manchester-report-climate-change|title=Twenty ideas that could save the world|last=Katz|first=Ian|date=2009-07-12|work=The Guardian|access-date=2019-07-16|language=en-GB|issn=0261-3077}}</ref><ref>[http://www.infrastructurist.com/2009/07/14/from-the-uk-20-bold-schemes-that-could-save-us-from-global-warming/ http://www.infrastructurist.com/2009/07/14/from-the-uk-20-bold-schemes-that-could-save-us-from-global-warming/] {{Webarchive|url=https://web.archive.org/web/20090718092540/http://www.infrastructurist.com/2009/07/14/from-the-uk-20-bold-schemes-that-could-save-us-from-global-warming/ |date=2009-07-18 }} July 14, 2009 Infrastructurist</ref>

==== Ocean acidification ====
{{Excerpt|Ocean acidification|paragraphs=1-2|file=no}}

==Marine chemistry on other planets and their moons==
A planetary scientist using data from the Cassini spacecraft has been researching the marine chemistry of [[Astronomy:Saturn|Saturn]]'s [[Astronomy:Moon|moon]] Enceladus using geochemical models to look at changes through time.<ref name="Enceladus">Pete Spotts [http://features.csmonitor.com/discoveries/2009/06/25/cassini-spacecraft-finds-evidence-for-liquid-water-on-enceladus/ Cassini spacecraft finds evidence for liquid water on Enceladus] June 25, 2009 Christian Science Monitor</ref> The presence of salts may indicate a liquid ocean within the moon, raising the possibility of the existence of life, "or at least for the chemical precursors for organic life".<ref name="Enceladus" /><ref>{{Cite journal|last1=Postberg|first1=F.|last2=Kempf|first2=S.|last3=Schmidt|first3=J.|last4=Brilliantov|first4=N.|last5=Beinsen|first5=A.|last6=Abel|first6=B.|last7=Buck|first7=U.|last8=Srama|first8=R.|year=2009|title=Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus|journal=Nature|volume=459|issue=7250|pages=1098–1101|bibcode=2009Natur.459.1098P|doi=10.1038/nature08046|pmid=19553992|s2cid=205216877}}</ref>

==See also==

* [[Earth:Seawater|Seawater]]
*[[Earth:RISE project|RISE project]]

==References==
{{Reflist}}{{Branches of chemistry}}

[[Category:Chemical oceanography]]
[[Category:Oceanographical terminology]]
[[Category:Geochemistry]]

{{Sourceattribution|Ocean chemistry|1}}