View source for Ocean fertilization

{{Short description|Type of climate engineering}}
{{Use dmy dates|date=October 2021}}
{{for|information on ocean fertilization schemes with iron in particular|Iron fertilization}}
[[File:CO2 pump hg.svg|thumb|400px|{{chem|CO|2}} sequestration in the ocean]]

'''Ocean fertilization''' or '''ocean nourishment''' is a type of technology for [[carbon dioxide removal]] from the ocean based on the purposeful introduction of plant [[nutrient]]s to the upper [[ocean]] to increase marine food production and to remove [[carbon dioxide]] from the atmosphere.<ref>{{cite journal |author1=Matear, R. J. |author2=B. Elliott |name-list-style=amp |year=2004 |title=Enhancement of oceanic uptake of anthropogenic CO<sub>2</sub> by macronutrient fertilization |url=http://www.agu.org/pubs/crossref/2004/2000JC000321.shtml |url-status=live |journal=J. Geophys. Res. |volume=109 |issue=C4 |pages=C04001 |bibcode=2004JGRC..109.4001M |doi=10.1029/2000JC000321 |archive-url=https://web.archive.org/web/20100304053707/http://www.agu.org/pubs/crossref/2004/2000JC000321.shtml |archive-date=4 March 2010 |access-date=19 January 2009 |doi-access=free}}</ref><ref>{{cite journal |author1=Jones, I.S.F. |author2=Young, H.E. |name-list-style=amp |year=1997 |title=Engineering a large sustainable world fishery |journal=Environmental Conservation |volume=24 |issue=2 |pages=99–104 |doi=10.1017/S0376892997000167|bibcode=1997EnvCo..24...99J |s2cid=86248266 }}</ref> Ocean nutrient fertilization, for example [[iron fertilization]], could stimulate photosynthesis in [[phytoplankton]]. The phytoplankton would convert the ocean's dissolved carbon dioxide into [[carbohydrate]], some of which would sink into the deeper ocean before oxidizing. More than a dozen open-sea experiments confirmed that adding iron to the ocean increases [[photosynthesis]] in phytoplankton by up to 30 times.<ref>{{cite book |last=Trujillo |first=Alan |title=Essentials of Oceanography |publisher=Pearson Education, Inc. |year=2011 |isbn=9780321668127 |pages=157}}</ref>  

This is one of the more well-researched [[carbon dioxide removal]] (CDR) approaches, and supported by the [[Climate restoration]] proponents. However, there is uncertainty about this approach regarding the duration of the effective oceanic carbon sequestration. While surface ocean acidity may decrease as a result of nutrient fertilization, when the sinking organic matter remineralizes, deep ocean acidity could increase. A 2021 report on CDR indicates that there is medium-high confidence that the technique could be efficient and scalable at low cost, with medium environmental risks.<ref name=":1">{{Cite book |last=National Academies of Sciences |first=Engineering |url=https://nap.nationalacademies.org/catalog/26278/a-research-strategy-for-ocean-based-carbon-dioxide-removal-and-sequestration |title=A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration |date=2021-12-08 |isbn=978-0-309-08761-2 |language=en |doi=10.17226/26278|pmid=35533244 |s2cid=245089649 }}</ref> The risks of nutrient fertilization can be monitored. Peter Fiekowsky and Carole Douglis write "I consider iron fertilization an important item on our list of pottential climate restoration solutions. Given the fact that iron fertilization is a natural process that has taken place on a massive scale for millions of years, it is likely that most of the side effects are familiar ones that pose no major threat" <ref>{{cite book |last=Fiekowsky Peter |first= Douglis Carole |title=Climate Restoration: the only future that will sustain the human reace |publisher=Rivertown Bools, Inc. |year=2022 |isbn=978-1-953943-10-1|pages=241}}</ref>

A number of techniques, including fertilization by the micronutrient [[iron]] (called iron fertilization) or with [[nitrogen]] and [[phosphorus]] (both macronutrients), have been proposed. Some research in the early 2020s suggested that it could only permanently sequester a small amount of carbon.<ref>{{Cite web |date=2021-06-23 |title=Cloud spraying and hurricane slaying: how ocean geoengineering became the frontier of the climate crisis |url=http://www.theguardian.com/environment/2021/jun/23/cloud-spraying-and-hurricane-slaying-could-geoengineering-fix-the-climate-crisis |url-status=live |archive-url=https://web.archive.org/web/20210623071321/https://www.theguardian.com/environment/2021/jun/23/cloud-spraying-and-hurricane-slaying-could-geoengineering-fix-the-climate-crisis |archive-date=23 June 2021 |access-date=2021-06-23 |website=The Guardian |language=en}}</ref>  More recent research publications sustain that iron fertilization shows promise. A NOAA special report rated iron fertilization as having "a moderate potential for cost, scalability and how long carbon might be stored compared to other marine sequestration ideas" <ref>{{Cite web |date=2023-11-13 |title=Is ocean iron fertilization back from the dead as a CO₂ removal tool?|url=https://news.mongabay.com/by/jeremy-hance/ |language=en}}</ref>
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== Rationale ==
The marine food chain is based on photosynthesis by marine [[phytoplankton]] that combine carbon with inorganic nutrients to produce organic matter. Production is limited by the availability of nutrients, most commonly nitrogen or [[iron]]. Numerous experiments<ref>{{cite journal  |vauthors=Coale KH, Johnson KS, Fitzwater SE, etal |title=A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean |journal=Nature |volume=383 |issue=6600 |pages=495–501 |date=October 1996 |pmid=18680864 |doi=10.1038/383495a0 |bibcode=1996Natur.383..495C|s2cid=41323790 }}</ref> have demonstrated how [[iron fertilization]] can increase phytoplankton productivity. Nitrogen is a limiting nutrient over much of the ocean and can be supplied from various sources, including fixation by [[cyanobacteria]]. Carbon-to-iron ratios in phytoplankton are much larger than carbon-to-nitrogen or [[carbon]]-to-[[phosphorus]] ratios, so iron has the highest potential for sequestration per unit mass added.

Oceanic carbon naturally cycles between the surface and the deep via two "pumps" of similar scale. The "solubility" pump is driven by ocean circulation and the solubility of CO<sub>2</sub> in seawater. The "biological" pump is driven by phytoplankton and subsequent settling of detrital particles or dispersion of dissolved organic carbon.&nbsp;The former has increased as a result of increasing atmospheric CO<sub>2</sub> concentration. This CO<sub>2</sub> sink is estimated to be approximately 2 GtC yr−1.<ref name="Lampitt 2008">{{Cite journal|last1=Lampitt|first1=R. S.|last2=Achterberg|first2=E. P.|last3=Anderson|first3=T. R.|last4=Hughes|first4=J. A.|last5=Iglesias-Rodriguez|first5=M. D.|last6=Kelly-Gerreyn|first6=B. A.|last7=Lucas|first7=M.|last8=Popova|first8=E. E.|last9=Sanders|first9=R.|date=2008-11-13|title=Ocean fertilization: a potential means of geoengineering?|journal=Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences|language=en|volume=366|issue=1882|pages=3919–3945|doi=10.1098/rsta.2008.0139|issn=1364-503X|pmid=18757282|bibcode=2008RSPTA.366.3919L|doi-access=free}}</ref>

The global phytoplankton population fell about 40 percent between 1950 and 2008 or about 1 percent per year. The most notable declines took place in polar waters and in the tropics. The decline is attributed to [[sea surface temperature]] increases.<ref>{{Cite news|url=https://www.scientificamerican.com/article/phytoplankton-population/|title=Phytoplankton Population Drops 40 Percent Since 1950|last=Morello|first=Lauren|date=29 July 2010|work=Scientific American|access-date=2018-07-19|language=en|archive-date=18 August 2018|archive-url=https://web.archive.org/web/20180818175045/https://www.scientificamerican.com/article/phytoplankton-population/|url-status=live}}</ref> A separate study found that diatoms, the largest type of phytoplankton, declined more than 1 percent per year from 1998 to 2012, particularly in the North Pacific, North Indian and Equatorial Indian oceans. The decline appears to reduce pytoplankton's ability to sequester carbon in the deep ocean.<ref>{{Cite news|url=https://www.nasa.gov/feature/goddard/nasa-study-shows-oceanic-phytoplankton-declines-in-northern-hemisphere|title=Study Shows Phytoplankton Declines in Northern Hemisphere|last=Morrow|first=Ashley|date=2015-09-22|work=NASA|access-date=2018-07-19|language=en|archive-date=16 October 2018|archive-url=https://web.archive.org/web/20181016111532/https://www.nasa.gov/feature/goddard/nasa-study-shows-oceanic-phytoplankton-declines-in-northern-hemisphere/|url-status=live}}</ref>

Fertilization offers the prospect of both reducing the concentration of atmospheric greenhouse gases with the aim of slowing [[avoiding dangerous climate change|climate change]] and at the same time increasing [[fish stocks]] via increasing [[primary production]]. The reduction reduces the ocean's rate of carbon sequestration in the deep ocean.

Each area of the ocean has a base sequestration rate on some timescale, e.g., annual. Fertilization must increase that rate, but must do so on a scale beyond the natural scale. Otherwise, fertilization changes the timing, but not the total amount sequestered. However, accelerated timing may have beneficial effects for primary production separate from those from sequestration.<ref name="Lampitt 2008" />

Biomass production inherently depletes all resources (save for sun and water). Either they must all be subject to fertilization or sequestration will eventually be limited by the one mostly slowly replenished (after some number of cycles) unless the ultimate limiting resource is sunlight and/or surface area. Generally, phosphate is the ultimate limiting nutrient. As oceanic phosphorus is depleted (via sequestration) it would have to be included in the fertilization cocktail supplied from terrestrial sources.<ref name="Lampitt 2008" />

== Approaches ==
Phytoplankton require a variety of nutrients. These include [[macronutrients]] such as nitrate and phosphate (in relatively high concentrations) and [[micronutrients]] such as iron and zinc (in much smaller quantities). Nutrient requirements vary across phylogenetic groups (e.g., diatoms require silicon) but may not individually limit total biomass production. Co-limitation (among multiple nutrients) may also mean that one nutrient can partially compensate for a shortage of another. Silicon does not affect total production, but can change the timing and community structure with follow-on effects on remineralization times and subsequent mesopelagic nutrient vertical distribution.<ref name="Lampitt 2008" />

[[High-nutrient, low-chlorophyll]] (HNLC) waters occupy the oceans' [[Ocean gyre|subtropical gyre]] systems, approximately 40 per cent of the surface, where wind-driven downwelling and a strong [[thermocline]] impede nutrient resupply from deeper water. Nitrogen fixation by [[cyanobacteria]] provides a major source of N. In effect, it ultimately prevents the ocean from losing the N required for photosynthesis. Phosphorus has no substantial supply route, making it the ultimate limiting macronutrient. The sources that fuel primary production are deep water stocks and runoff or dust-based.<ref name="Lampitt 2008" />

=== Iron ===
{{excerpt|Iron fertilization|paragraphs=1-2|file=no}}

=== Phosphorus ===
In the very long term, phosphorus "is often considered to be the ultimate limiting macronutrient in marine ecosystems"<ref>{{cite journal|first1=Adina|last1=Paytan|first2=Karen|last2=McLaughlin|title=The Oceanic Phosphorus Cycle|url=https://pdfs.semanticscholar.org/1b9a/68e192e02aaa8a1a8b910d16a937a883d666.pdf|archive-url=https://web.archive.org/web/20180816162138/https://pdfs.semanticscholar.org/1b9a/68e192e02aaa8a1a8b910d16a937a883d666.pdf|url-status=dead|archive-date=2018-08-16|journal=Chemical Reviews|date=2007|issn=1520-6890|pages=563–576|volume=107|issue=2|doi=10.1021/cr0503613|pmid=17256993|citeseerx=10.1.1.417.3956|s2cid=1872341}}</ref> and has a slow natural cycle. Where phosphate is the limiting nutrient in the [[photic zone]], addition of phosphate is expected to increase primary phytoplankton production. This technique can give 0.83&nbsp;W/m<sup>2</sup> of globally averaged negative forcing,<ref name="atmos-chem-phys-discuss.net">{{cite journal |last1=Lenton |first1=T. M. |last2=Vaughan |first2=N. E. |title=The radiative forcing potential of different climate geoengineering options |journal=Atmos. Chem. Phys. |volume=9 |issue=15 |pages=5539–5561 |year=2009 |doi=10.5194/acp-9-5539-2009|bibcode=2009ACP.....9.5539L |doi-access=free }}</ref> which is sufficient to reverse the warming effect of about half the current levels of [[human impact on the environment|anthropogenic]] {{chem|CO|2}} emissions. One water-soluble fertilizer is [[diammonium phosphate]] (DAP), {{chem|(NH|4|)|2|HPO|4}}, that as of 2008 had a market price of 1700/tonne−1 of phosphorus. Using that price and the C : P Redfield ratio of 106 : 1 produces a sequestration cost (excluding preparation and injection costs) of some $45 /tonne of carbon (2008), substantially less than the trading price for carbon emissions.<ref name="Lampitt 2008" />

=== Nitrogen (urea) ===

This technique proposes to fertilize the ocean with [[urea]], a [[nitrogen]] rich substance, to encourage [[phytoplankton]] growth.<ref>{{cite journal |last=Jones |first=Ian S. F. |title=Enhanced Carbon Dioxide Uptake by the World's Oceans |journal=Energy Conversion & Management |volume=37 |issue=6–8 |pages=1049–1052 |doi=10.1016/0196-8904(95)00296-0 |year=1996|bibcode=1996ECM....37.1049J }} Note typo in paper Fig. 1.</ref><ref>{{cite journal |author1=Karl, D. M. |author2=Letelier, R. |title=Nitrogen fixation-enhanced carbon sequestration in low nitrate, low chlorophyll seascapes |journal=Mar. Ecol. Prog. Ser.|volume=364 |pages=257–268 |year=2008 |doi=10.3354/meps07547|bibcode=2008MEPS..364..257K |doi-access=free }}</ref><ref>{{Cite news |date=February 19, 2007 |title=Multiplying the ocean's CO2 guzzlers |url=http://news.bbc.co.uk/1/hi/programmes/6369401.stm |url-status=live |access-date=January 15, 2018 |archive-url=https://web.archive.org/web/20070301002344/http://news.bbc.co.uk/1/hi/programmes/6369401.stm |archive-date=March 1, 2007 |via=news.bbc.co.uk}}</ref> Concentrations of macronutrients per area of ocean surface would be similar to large natural upwellings. Once exported from the surface, the carbon remains sequestered for a long time.<ref name="RichmondHu2013">{{cite book |last1=Jones |first1=Ian S F |last2=Harrison |first2=D P |url={{google books |plainurl=y |id=gFuYygAACAAJ}} |title=Handbook of Microalgal Culture: Applied Phycology and Biotechnology|edition=2|date=4 June 2013|publisher=Wiley|isbn=978-0-470-67389-8|editor-first1=Amos |editor-last1=Richmond |editor-first2=Qiang |editor-last2=Hu}}</ref>

An Australian company, Ocean Nourishment Corporation (ONC), planned to inject hundreds of tonnes of urea into the ocean, in order to boost the growth of {{chem|CO|2}}-absorbing phytoplankton, as a way to combat climate change. In 2007, Sydney-based ONC completed an experiment involving one tonne of nitrogen in the [[Sulu Sea]] off the Philippines.<ref>{{cite web |author=Anna Salleh |title=Urea 'climate solution' may backfire |date=9 November 2007 |work=ABC Science: In Depth |publisher=Australian Broadcasting Commission |url=http://www.abc.net.au/science/articles/2007/11/09/2085584.htm |access-date=31 January 2009 |archive-date=2 February 2009 |archive-url=https://web.archive.org/web/20090202045803/http://www.abc.net.au/science/articles/2007/11/09/2085584.htm |url-status=live }}</ref> This project was criticized by many institutions, including the [[European Commission]],<ref>{{Cite journal |last1=El-Geziry |first1=T M |last2=Bryden |first2=I G |date=January 2010 |title=The circulation pattern in the Mediterranean Sea: issues for modeller consideration |journal=Journal of Operational Oceanography |volume=3 |issue=2 |pages=39–46 |doi=10.1080/1755876x.2010.11020116 |issn=1755-876X |doi-access=free |bibcode=2010JOO.....3...39E |s2cid=130443230}}</ref> due to lack of knowledge of side effects on the marine ecosystem.<ref name="mayo">{{Cite journal |last=Mayo-Ramsay |first=Julia |date=September 2010 |title=Environmental, legal and social implications of ocean urea fertilization: Sulu sea example |journal=Marine Policy |volume=34 |issue=5 |pages=831–835 |doi=10.1016/j.marpol.2010.01.004 |bibcode=2010MarPo..34..831M |issn=0308-597X}}</ref>

Macronutrient nourishment can give 0.38&nbsp;W/m<sup>2</sup> of globally averaged negative forcing,<ref name="atmos-chem-phys-discuss.net" /> which is sufficient to reverse the warming effect of current levels of around a quarter of [[human impact on the environment|anthropogenic]] {{chem|CO|2}} emissions.

The two dominant costs are manufacturing the nitrogen and nutrient delivery.<ref>{{Cite journal|last=Ian S.F. Jones|date=2014-11-10|title=The cost of carbon management using ocean nourishment|journal=International Journal of Climate Change Strategies and Management|volume=6|issue=4|pages=391–400|doi=10.1108/ijccsm-11-2012-0063|bibcode=2014IJCCS...6..391S |issn=1756-8692}}</ref>
[[File:Coral_reef_in_Tubbataha_Natural_Park.jpg|thumb|286x286px|According to Ramsay et al.,<ref name="mayo" /> urea fertilization could cause damage to the rich marine biodiversity of the Sulu sea (including its coral reefs).]]
In waters with sufficient iron micro nutrients, but a deficit of nitrogen, [[urea]] fertilization is the better choice for algae growth.<ref name=":0b">{{Cite book |last=Mingyuan |first=Glibert, Patricia M. Azanza, Rhodora Burford, Michele Furuya, Ken Abal, Eva Al-Azri, Adnan Al-Yamani, Faiza Andersen, Per Anderson, Donald M. Beardall, John Berg, Gry M. Brand, Larry E. Bronk, Deborah Brookes, Justin Burkholder, JoAnn M. Cembella, Allan D. Cochlan, William P. Collier, Jackie L. Collos, Yves Diaz, Robert Doblin, Martina Drennen, Thomas Dyhrman, Sonya T. Fukuyo, Yasuwo Furnas, Miles Galloway, James Graneli, Edna Ha, Dao Viet Hallegraeff, Gustaaf M. Harrison, John A. Harrison, Paul J. Heil, Cynthia A. Heimann, Kirsten Howarth, Robert W. Jauzein, Cecile Kana, Austin A. Kana, Todd M. Kim, Hakgyoon Kudela, Raphael M. Legrand, Catherine Mallin, Michael Mulholland, Margaret R. Murray, Shauna A. O’Neil, Judith Pitcher, Grant C. Qi, Yuzao Rabalais, Nancy Raine, Robin Seitzinger, Sybil P. Salomon, Paulo S. Solomon, Caroline Stoecker, Diane K. Usup, Gires Wilson, Joanne Yin, Kedong Zhou, Mingjiang Zhu |title=Ocean urea fertilization for carbon credits poses high ecological risks |date=2008-08-14 |oclc=1040066339}}</ref> Urea is the most used fertilizer in the world, due to its high content of nitrogen, low cost and high reactivity towards water.<ref name=":12">{{Cite journal |last1=Azeem |first1=Babar |last2=KuShaari |first2=KuZilati |last3=Man |first3=Zakaria B. |last4=Basit |first4=Abdul |last5=Thanh |first5=Trinh H. |date=May 2014 |title=Review on materials & methods to produce controlled release coated urea fertilizer |journal=Journal of Controlled Release |volume=181 |pages=11–21 |doi=10.1016/j.jconrel.2014.02.020 |issn=0168-3659 |pmid=24593892}}</ref> When exposed to ocean waters, urea is metabolized by phytoplankton via [[urease]] enzymes to produce [[ammonia]].<ref>{{Cite journal |last1=Collins |first1=Carleen M. |last2=D'Orazio |first2=Sarah E. F. |date=September 1993 |title=Bacterial ureases: structure, regulation of expression and role in pathogenesis |journal=Molecular Microbiology |volume=9 |issue=5 |pages=907–913 |doi=10.1111/j.1365-2958.1993.tb01220.x |issn=0950-382X |pmid=7934918 |s2cid=21192428}}</ref>

<chem>CO(NH_2)_2 + H_2O ->[urease] NH_3 + NH_2COOH </chem>

<chem>NH_2COOH + H_2O -> NH_3 + H_2CO_3</chem>

The intermediate product [[carbamate]] also reacts with water to produce a total of two ammonia molecules.<ref name=":2">{{Cite journal |last1=Kugino |first1=Kenji |last2=Tamaru |first2=Shizuka |last3=Hisatomi |first3=Yuko |last4=Sakaguchi |first4=Tadashi |date=2016-04-21 |title=Long-Duration Carbon Dioxide Anesthesia of Fish Using Ultra Fine (Nano-Scale) Bubbles |journal=PLOS ONE |language=en |volume=11 |issue=4 |pages=e0153542 |bibcode=2016PLoSO..1153542K |doi=10.1371/journal.pone.0153542 |issn=1932-6203 |pmc=4839645 |pmid=27100285 |doi-access=free}}</ref> 

Another cause of concern is the sheer amount of urea needed to capture the same amount of carbon as eq. iron fertilization. The nitrogen to iron ratio in a typical algae cell is 16:0.0001, meaning that for every iron atom added to the ocean a substantial larger amount of carbon is captured compared to adding one atom of nitrogen.<ref name=":0">Caldeira, Ken, et al. “IPCC Special Report on Carbon Dioxide Capture and Storage: Ocean Storage.” International Panel on Climate Change, 2005.</ref> Scientists also emphasize that adding urea to ocean waters could reduce oxygen content and result in a rise of toxic marine algae.<ref name=":0" /> This could potentially have devastating effects on fish populations, which others argue would be benefiting from the urea fertilization (the argument being that fish populations would feed on healthy [[phytoplankton]]).<ref>{{Citation |last1=Jones |first1=Ian S.F. |title=Lowring the cost of carbon sequestration by ocean nourishment |date=1999 |work=Greenhouse Gas Control Technologies 4 |pages=255–259 |publisher=Elsevier |doi=10.1016/b978-008043018-8/50041-2 |isbn=9780080430188 |last2=Cappelen-Smith |first2=Christian}}</ref>

===  Pelagic pumping ===
Local [[wave power]] could be used to pump nutrient-rich water from hundred- metre-plus depths to the euphotic zone. However, deep water concentrations of dissolved CO<sub>2</sub> could be returned to the atmosphere.<ref name="Lampitt 2008" />

The supply of DIC in upwelled water is generally sufficient for photosynthesis permitted by upwelled nutrients, without requiring atmospheric CO<sub>2</sub>. Second-order effects include how the composition of upwelled water differs from that of settling particles. More nitrogen than carbon is remineralized from sinking organic material. Upwelling of this water allows more carbon to sink than that in the upwelled water, which would make room for at least some atmospheric CO<sub>2</sub> to be absorbed. the magnitude of this difference is unclear. No comprehensive studies have yet resolved this question. Preliminary calculations using upper limit assumptions indicate a low value. 1,000 square kilometres (390&nbsp;sq mi) could sequester 1 &nbsp;gigatonne/year.<ref name="Lampitt 2008" />

Sequestration thus depends on the upward flux and the rate of lateral surface mixing of the surface water with denser pumped water.<ref name="Lampitt 2008" />

=== Volcanic ash ===
[[Volcanic ash]] adds nutrients to the surface ocean. This is most apparent in nutrient-limited areas. Research on the effects of anthropogenic and [[Aeolian processes|aeolian]] iron addition to the ocean surface suggests that nutrient-limited areas benefit most from a combination of nutrients provided by anthropogenic, eolian and volcanic deposition.<ref>{{cite journal| last1=Duggen| first1=Svend| last2=Croot| first2=Peter| last3=Schacht| first3=Ulrike| last4=Hoffmann| first4=Linn| year=2007| title=Subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth: Evidence from biogeochemical experiments and satellite data| journal=Geophysical Research Letters| volume=34| issue=1| url=http://oceanrep.geomar.de/4138/| access-date=2012-08-27| doi=10.1029/2006GL027522| s2cid=44686878| archive-date=10 August 2014| archive-url=https://web.archive.org/web/20140810215838/http://oceanrep.geomar.de/4138/| url-status=live| doi-access=free| bibcode=2007GeoRL..34.1612D}}</ref> Some oceanic areas are comparably limited in more than one nutrient, so fertilization regimes that includes all limited nutrients is more likely to succeed. Volcanic ash supplies multiple nutrients to the system, but excess metal ions can be harmful. The positive impacts of volcanic ash deposition are potentially outweighed by their potential to do harm.{{citation needed|date=April 2012}}

Clear evidence documents that ash can be as much as 45 percent by weight in some deep marine sediments.<ref>{{cite journal| last1= Peters| first1= J.L.| last2= Murray| first2=R.W. | last3= Sparks, J.W| last4= Coleman| first4= D.S.|year=2000| title= Terrigenous matter and dispersed ash in sediment from the Caribbean Sea; results from Leg 165| journal= Proceedings of the Ocean Drilling Program, Scientific Results| volume= 165 | pages= 115–124 | doi=10.2973/odp.proc.sr.165.003.2000| series= Proceedings of the Ocean Drilling Program}}</ref><ref>{{Cite journal|last1=Scudder|first1=Rachel P.|last2=Murray|first2=Richard W.|last3=Plank|first3=Terry|date=2009-07-15|title=Dispersed ash in deeply buried sediment from the northwest Pacific Ocean: An example from the Izu–Bonin arc (ODP Site 1149)|journal=Earth and Planetary Science Letters|volume=284|issue=3–4|pages=639–648|doi=10.1016/j.epsl.2009.05.037|bibcode=2009E&PSL.284..639S}}</ref> In the Pacific Ocean estimates claim that (on a millennial-scale) the atmospheric deposition of air-fall volcanic ash was as high as the deposition of desert dust.<ref>{{Cite journal|last1=Olgun|first1=Nazlı|last2=Duggen|first2=Svend|last3=Croot|first3=Peter Leslie|last4=Delmelle|first4=Pierre|last5=Dietze|first5=Heiner|last6=Schacht|first6=Ulrike|last7=Óskarsson|first7=Niels|last8=Siebe|first8=Claus|last9=Auer|first9=Andreas|date=2011-12-01|title=Surface ocean iron fertilization: The role of airborne volcanic ash from subduction zone and hot spot volcanoes and related iron fluxes into the Pacific Ocean|journal=Global Biogeochemical Cycles|language=en|volume=25|issue=4|pages=GB4001|doi=10.1029/2009gb003761|issn=1944-9224|bibcode=2011GBioC..25.4001O|url=http://oceanrep.geomar.de/10133/1/2009GB003761.pdf|doi-access=free|access-date=7 September 2020|archive-date=10 August 2021|archive-url=https://web.archive.org/web/20210810122119/https://oceanrep.geomar.de/10133/1/2009GB003761.pdf|url-status=live}}</ref> This indicates the potential of volcanic ash as a significant iron source.

In August 2008 the [[Kasatochi Island|Kasatochi]] volcanic eruption in the [[Aleutian Islands]], Alaska, deposited ash in the nutrient-limited northeast Pacific. This ash (including iron) resulted in one of the largest phytoplankton blooms observed in the subarctic.<ref name="Olgun 2013">{{Cite journal|last1=Olgun|first1=N|last2=Duggen|first2=S|last3=Langmann|first3=B|last4=Hort|first4=M|last5=Waythomas|first5=CF|last6=Hoffmann|first6=L|last7=Croot|first7=P|date=2013-08-15|title=Geochemical evidence of oceanic iron fertilization by the Kasatochi volcanic eruption in 2008 and the potential impacts on Pacific sockeye salmon|journal=Marine Ecology Progress Series|language=en|volume=488|pages=81–88|doi=10.3354/meps10403|issn=0171-8630|bibcode=2013MEPS..488...81O|url=http://oceanrep.geomar.de/21945/1/m488p081.pdf|access-date=12 August 2019|archive-date=19 July 2018|archive-url=https://web.archive.org/web/20180719114513/http://oceanrep.geomar.de/21945/1/m488p081.pdf|url-status=live}}</ref><ref>{{cite journal| last1=Hemme| first1=R| year=2010| title=Volcanic ash fuels anomalous plankton bloom in subarctic northeast Pacific| journal=Geophysical Research Letters| volume=37| issue=19| pages=L19604| doi=10.1029/2010GL044629| url=http://www.agu.org/pubs/crossref/2010/2010GL044629.shtml| access-date=2012-08-27| bibcode=2010GeoRL..3719604H| display-authors=etal| doi-access=free| archive-date=5 July 2012| archive-url=https://web.archive.org/web/20120705011856/http://www.agu.org/pubs/crossref/2010/2010GL044629.shtml| url-status=live}}</ref> Fisheries scientists in Canada linked increased oceanic productivity from the volcanic iron to subsequent record returns of salmon in the Fraser River two years later<ref name="Parsons 2012">{{Cite journal|last1=Parsons|first1=Timothy R.|last2=Whitney|first2=Frank A.|date=2012-09-01|title=Did volcanic ash from Mt. Kasatoshi in 2008 contribute to a phenomenal increase in Fraser River sockeye salmon (Oncorhynchus nerka) in 2010?|journal=Fisheries Oceanography|language=en|volume=21|issue=5|pages=374–377|doi=10.1111/j.1365-2419.2012.00630.x|bibcode=2012FisOc..21..374P |issn=1365-2419}}</ref>

=== Monitored nutrients ===
The approach advocated by Ocean Nutrition Corporation is to limit the distribution of added nutrients to allow phytoplankton concentrations to rise only to the values seen in upwelling regions (5–10&nbsp;mg Chl/m<sup>3</sup>). Maintaining healthy phytoplankton levels is claimed to avoid harmful [[algal blooms]] and oxygen depletion. [[Chlorophyll]] concentration is an easily measured proxy for phytoplankton concentration. The company stated that values of approximately 4&nbsp;mg Chl/m<sup>3</sup> meet this requirement.<ref>{{Cite web|title=Ocean Solutions|url=http://www.oceannourishment.com/ocean-solutions|access-date=2021-08-14|website=ocean nourishment|language=en-US|archive-date=14 August 2021|archive-url=https://web.archive.org/web/20210814063358/http://www.oceannourishment.com/ocean-solutions|url-status=live}}</ref> SS

== Complications ==
While manipulation of the land [[ecosystem]] in support of [[agriculture]] for the benefit of humans has long been accepted (despite its side effects), directly enhancing ocean productivity has not. Among the reasons are:

=== Outright opposition ===
According to Lisa Speer of the Natural Resources Defense Council, "There is a limited amount of money, of time, that we have to deal with this problem....The worst possible thing we could do for climate change technologies would be to invest in something that doesn't work and that has big impacts that we don't anticipate."<ref name="Oceanus Fertilizing" />

In 2009 Aaron Strong, Sallie Chisholm, Charles Miller and John Cullen opined in ''Nature'' "...fertilizing the oceans with iron to stimulate phytoplankton blooms, absorb carbon dioxide from the atmosphere and export carbon to the deep sea – should be abandoned."<ref>{{Cite journal|last1=Strong|first1=Aaron|last2=Chisholm|first2=Sallie|last3=Miller|first3=Charles|last4=Cullen|first4=John|title=Ocean fertilization: time to move on|journal=Nature|volume=461|issue=7262|pages=347–348|doi=10.1038/461347a|pmid=19759603|bibcode=2009Natur.461..347S|year=2009|s2cid=205049552}}</ref>

In ''Science'', Warren Cornwall mentions "Tests have shown the iron does stimulate plankton growth. But key questions remain,says Dave Siegel, a marine scientist at the University of California, Santa Barbara, who served on the NASEM panel. How much of the absorbed carbon makes it to the deep
ocean is uncertain", while Wil Burns, an ocean law expert at Northwestern University declares that "...making iron fertilization a research priority is "barking mad" since "...a recent survey of 13 past fertilization experiments found only one that increased carbon levels deep in the ocean."<ref>{{cite journal |last1=Cornwall |first1=Warren |title=To draw down carbon, ocean fertilization gets another look |journal=Science |date=17 December 2021 |volume=374 |issue=6574 |pages=1424 |doi=10.1126/science.acz9837 |pmid=34914509 |bibcode=2021Sci...374.1424C |s2cid=245315876 |url=https://www.science.org/doi/pdf/10.1126/science.acz9837 |access-date=20 October 2022 |language=en |issn=0036-8075}}</ref>

=== Efficiency ===

Algal cell chemical composition is often assumed to respect a ratio where atoms are 106 [[carbon]]: 16 [[nitrogen]]: 1 [[phosphorus]] ([[Redfield ratio]]<ref name=Falkowski2009>{{cite journal|first1=Paul G.|last1=Falkowski|title=Rationalizing elemental ratios in unicellular algae|url=http://ebme.marine.rutgers.edu/HistoryEarthSystems/HistEarthSystems_Fall2008/Week5b/Falkowski_J_Phycol_2000.pdf|journal=Journal of Phycology|date=2000-02-09|issn=1529-8817|pages=3–6|volume=36|issue=1|doi=10.1046/j.1529-8817.2000.99161.x|bibcode=2000JPcgy..36....3F |s2cid=2185706|access-date=16 August 2018|archive-date=8 August 2017|archive-url=https://web.archive.org/web/20170808115200/http://ebme.marine.rutgers.edu/HistoryEarthSystems/HistEarthSystems_Fall2008/Week5b/Falkowski_J_Phycol_2000.pdf|url-status=live}}</ref>): 0.0001 iron. In other words, each atom of iron helps capture 1,060,000 atoms of carbon, while one nitrogen atom only 6.<ref>P.M. Glibert et al., 2008. Ocean urea fertilization for carbon credits poses high ecological risks. Marine Pollution Bulletin, 56(2008): 1049–1056.</ref>

In large areas of the ocean, such organic growth (and hence nitrogen fixation) is thought to be limited by the lack of iron rather than nitrogen, although direct measures are hard.<ref name=Falkowski2009/>

On the other hand, experimental iron fertilisation in HNLC regions has been supplied with excess iron which cannot be utilized before it is scavenged. Thus the organic material produced was much less than if the ratio of nutrients above were achieved. Only a fraction of the available nitrogen (because of iron scavenging) is drawn down. In culture bottle studies of [[oligotroph]]ic water, adding nitrogen and phosphorus can draw down considerably more nitrogen per dosing. The export production is only a small percentage of the new primary production and in the case of iron fertilization, iron scavenging means that regenerative production is small. With macronutrient fertilisation, regenerative production is expected to be large and supportive of larger total export. Other losses can also reduce efficiency.<ref>{{Cite journal|last=Lawrence|first=Martin W.|title=Efficiency of carbon sequestration by added reactive nitrogen in ocean fertilisation|journal=International Journal of Global Warming|language=en|volume=6|issue=1|pages=15|doi=10.1504/ijgw.2014.058754|year=2014}}</ref>

In addition, the efficiency of carbon sequestration through ocean fertilisation is heavily influenced by factors such as changes in stoichiometric ratios and gas exchange make accurately predicting the effectiveness of ocean feralization projects.<ref>{{Cite journal|last1=Gnanadesikan|first1=Anand|last2=Marinov|first2=Irina|date=2008-07-29|title=Export is not enough: nutrient cycling and carbon sequestration|url=https://www.int-res.com/abstracts/meps/v364/p289-294/|journal=Marine Ecology Progress Series|language=en|volume=364|pages=289–294|doi=10.3354/meps07550|issn=0171-8630|doi-access=free|bibcode=2008MEPS..364..289G |access-date=5 March 2021|archive-date=5 May 2021|archive-url=https://web.archive.org/web/20210505230909/http://www.int-res.com/abstracts/meps/v364/p289-294/|url-status=live|hdl=1912/4452|hdl-access=free}}</ref>

Fertilisation also does not create a permanent carbon sink. "Ocean fertilisation options are only worthwhile if sustained on a millennial timescale and phosphorus addition may have greater long-term potential than iron or nitrogen fertilisation."<ref name="atmos-chem-phys-discuss.net" /> 

=== Side effects ===
Beyond biological impacts, evidences suggests that plankton blooms can affect the physical properties of surface waters simply by absorbing light and heat from the sun. Watson added that if fertilization is done in shallow coastal waters, a dense layer of phytoplankton clouding the top 30 metres or so of the ocean could hinder corals, kelps or other deeper sea life from carrying out photosynthesis (Watson et al. 2008). In addition, as the bloom declines, nitrous oxide is released, potentially counteracting the effects from the sequestering of carbon.<ref>{{Cite journal|last=Law|first=C. S.|date=2008-07-29|title=Predicting and monitoring the effects of large-scale ocean iron fertilization on marine trace gas emissions|url=https://www.int-res.com/abstracts/meps/v364/p283-288/|journal=Marine Ecology Progress Series|language=en|volume=364|pages=283–288|doi=10.3354/meps07549|issn=0171-8630|doi-access=free|bibcode=2008MEPS..364..283L |access-date=5 March 2021|archive-date=6 May 2021|archive-url=https://web.archive.org/web/20210506002137/http://www.int-res.com/abstracts/meps/v364/p283-288/|url-status=live}}</ref>

==== Algal blooms ====
Toxic algal blooms are common in coastal areas. Fertilization could trigger such blooms. Chronic fertilization could risk the creation of [[Dead zone (ecology)|dead zones]], such as [[Gulf of Mexico#Pollution|the one in the Gulf of Mexico]].<ref name="Live Science 2017">{{Cite news |title=Could Fertilizing the Oceans Reduce Global Warming? |work=Live Science |url=http://www.livescience.com/21684-geoengineering-iron-fertilization-climate.html |url-status=live |access-date=2017-06-02 |archive-url=https://web.archive.org/web/20161127100143/http://www.livescience.com/21684-geoengineering-iron-fertilization-climate.html |archive-date=27 November 2016}}</ref>

==== Impact on fisheries ====

Adding urea to the ocean can cause phytoplankton blooms that serve as a food source for [[zooplankton]] and in turn feed for fish. This may increase fish catches.<ref>{{Cite journal |last1=Jones |first1=I |first2=M |last2=Renilson |year=2011 |title=Using Ocean Nourishment to increase fishing effectiveness |url=http://www.journalofoceantechnology.com/ |journal=The Journal of Ocean Technology – One Voice for the World's Oceans Community |issue=6 |pages=30–37 |language=en-US |access-date=2017-06-03 |archive-date=17 August 2018 |archive-url=https://web.archive.org/web/20180817092326/https://www.journalofoceantechnology.com/ |url-status=live }}</ref> However, if [[cyanobacteria]] and [[dinoflagellates]] dominate phytoplankton assemblages that are considered poor quality food for fish then the increase in fish quantity may not be large.<ref>{{cite journal|year=2008|title=Ocean urea fertilization for carbon credits poses high ecological risks|url=http://www.whoi.edu/science/cohh/whcohh/publications/WHCOHH_publications/Glibert_etal_2008_MPB_urea-fert.pdf|journal=Marine Pollution Bulletin|volume=56|issue=6|pages=1049–1056|doi=10.1016/j.marpolbul.2008.03.010|pmid=18439628|pmc=5373553|last=Glibert|first=P M.|bibcode=2008MarPB..56.1049G |access-date=2012-08-27|display-authors=etal|archive-date=29 October 2013|archive-url=https://web.archive.org/web/20131029211503/http://www.whoi.edu/science/cohh/whcohh/publications/WHCOHH_publications/Glibert_etal_2008_MPB_urea-fert.pdf|url-status=live}}</ref> Some evidence links iron fertilization from volcanic eruptions to increased fisheries production.<ref name="Parsons 2012"/><ref name="Olgun 2013" /> Other nutrients would be metabolized along with the added nutrient(s), reducing their presence in fertilized waters.<ref name="Oceanus Fertilizing">{{Cite web|url=https://www.whoi.edu/oceanus/feature/fertilizing-the-ocean-with-iron|title=Fertilizing the Ocean with Iron|website=Oceanus Magazine|language=en|access-date=2017-06-01|archive-date=26 May 2017|archive-url=https://web.archive.org/web/20170526084600/http://www.whoi.edu/oceanus/feature/fertilizing-the-ocean-with-iron|url-status=live}}</ref>

[[Krill]] populations have declined dramatically since whaling began.<ref name="Live Science 2017" /> [[Sperm whale|Sperm]] [[whales]] transport iron from the deep ocean to the surface during prey consumption and defecation. Sperm whales have been shown to increase the levels of primary production and carbon export to the deep ocean by depositing iron-rich [[Feces|faeces]] into surface waters of the Southern Ocean. The faeces causes phytoplankton to grow and take up carbon. The phytoplankton nourish krill. Reducing the abundance of sperm whales in the Southern Ocean, whaling resulted in an extra 2&nbsp;million tonnes of carbon remaining in the atmosphere each year.<ref>{{Cite journal|last1=Lavery|first1=Trish J.|last2=Roudnew|first2=Ben|last3=Gill|first3=Peter|last4=Seymour|first4=Justin|last5=Seuront|first5=Laurent|last6=Johnson|first6=Genevieve|last7=Mitchell|first7=James G.|last8=Smetacek|first8=Victor|date=2010-11-22|title=Iron defecation by sperm whales stimulates carbon export in the Southern Ocean|journal=Proceedings of the Royal Society of London B: Biological Sciences|language=en|volume=277|issue=1699|pages=3527–3531|doi=10.1098/rspb.2010.0863|issn=0962-8452|pmc=2982231|pmid=20554546}}</ref>

==== Ecosystem disruption ====

Many locations, such as the [[Tubbataha Reef]] in the [[Sulu Sea]], support high marine [[biodiversity]].<ref>Mission, G., 1999. [http://gina.ph/CyberDyaryo/features/cd1999_0930_005.htm WWF's marine police: saving Sulu Sea] {{Webarchive|url=https://web.archive.org/web/20100825223949/http://www.gina.ph/CyberDyaryo/features/cd1999_0930_005.htm |date=25 August 2010 }}</ref> Nitrogen or other nutrient loading in [[coral reef]] areas can lead to community shifts towards [[Algae|algal]] overgrowth of [[coral]]s and ecosystem disruption, implying that fertilization must be restricted to areas in which vulnerable populations are not put at risk.<ref>{{cite journal|url=https://scholarspace.manoa.hawaii.edu/handle/10125/616|last2=Kimmerer|first2=W.J.|last3=Laws|first3=E.A.|last4=Brock|first4=R.E.|last5=Walsh|first5=T.W.|year=1981|title=Kaneohe Bay sewage diversion experiment: perspectives on ecosystem responses to nutritional perturbation|journal=Pacific Science|volume=35|last1=Smith|first1=S.V.|pages=279–395|hdl=10125/616 |access-date=2017-06-04|archive-date=8 September 2015|archive-url=https://web.archive.org/web/20150908001317/http://scholarspace.manoa.hawaii.edu/handle/10125/616|url-status=live}}</ref>

As the phytoplankton descend the water column, they decay, consuming oxygen and producing greenhouse gases [[methane]] and [[nitrous oxide]]. Plankton-rich surface waters could warm the surface layer, affecting circulation patterns.<ref name="Oceanus Fertilizing" />

==== Cloud formation ====
Many phytoplankton species release [[dimethyl sulfide]] (DMS), which escapes into the atmosphere where it forms [[sulfate]] [[aerosol]]s and encourages cloud formation, which could reduce warming.<ref name="Oceanus Fertilizing" /> However, substantial increases in DMS could reduce global rainfall, according to [[General circulation model|global climate model]] simulations, while halving temperature increases as of 2100.<ref>{{Cite journal|last1=Grandey|first1=B. S.|last2=Wang|first2=C.|date=2015-08-21|title=Enhanced marine sulphur emissions offset global warming and impact rainfall|journal=Scientific Reports|language=en|volume=5|issue=1|pages=13055|doi=10.1038/srep13055|issn=2045-2322|pmc=4543957|pmid=26293204|bibcode=2015NatSR...513055G}}</ref><ref>{{Cite news|url=https://news.mit.edu/2015/fertilize-ocean-cool-planet-0908|title=Fertilize the ocean, cool the planet?|work=MIT News|access-date=2017-06-02|archive-date=8 September 2019|archive-url=https://web.archive.org/web/20190908005609/http://news.mit.edu/2015/fertilize-ocean-cool-planet-0908|url-status=live}}</ref>

== Reactions ==
In 2007 Working Group III of the [[United Nations]] [[Intergovernmental Panel on Climate Change]] examined ocean fertilization methods in its fourth assessment report and noted that the field-study estimates of the amount of carbon removed per ton of iron was probably over-estimated and that potential adverse effects had not been fully studied.<ref>{{cite book |title=Climate Change 2007: Working Group III: Mitigation of Climate Change |publisher=Cambridge University Press |year=2007 |editor1=B. Metz |chapter=11.2.2 |access-date=2012-08-27 |editor2=O.R. Davidson |editor3=P.R. Bosch |editor4=R. Dave |editor5=L.A. Meyer |chapter-url=http://www.ipcc.ch/publications_and_data/ar4/wg3/en/ch11s11-2-2.html |archive-url=https://web.archive.org/web/20100329093235/http://www.ipcc.ch/publications_and_data/ar4/wg3/en/ch11s11-2-2.html |archive-date=29 March 2010 |url-status=live}}</ref>

In June 2007 the [[Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter|London Dumping Convention]] issued a statement of concern noting 'the potential for large scale ocean iron fertilization to have negative impacts on the marine environment and human health',<ref>{{cite web |title=Scientific Groups cautious over iron fertilization of the oceans to sequester CO<sub>2</sub> |url=http://www.imo.org/blast/mainframe.asp?topic_id=1472&doc_id=8214 |url-status=live |archive-url=https://web.archive.org/web/20130828102841/http://www.imo.org/blast/mainframe.asp?topic_id=1472&doc_id=8214 |archive-date=28 August 2013 |access-date=2012-08-27}}</ref> but did not define 'large scale'. It is believed that the definition would include operations.{{citation needed|date=August 2012}}

In 2008, the London Convention/London Protocol noted in resolution LC-LP.1 that knowledge on the effectiveness and potential environmental impacts of ocean fertilization was insufficient to justify activities other than research. This non-binding resolution stated that fertilization, other than research, "should be considered as contrary to the aims of the Convention and Protocol and do not currently qualify for any exemption from the definition of dumping".<ref>{{cite book |url=http://www.imo.org/blast/blastDataHelper.asp?data_id=24337&filename=LC-LP1%2830%29.pdf |title=RESOLUTION LC-LP.1 (2008) ON THE REGULATION OF OCEAN FERTILIZATION |date=31 October 2008 |publisher=London Dumping Convention |access-date=9 August 2012 |archive-url=https://web.archive.org/web/20130828015637/http://www.imo.org/blast/blastDataHelper.asp?data_id=24337&filename=LC-LP1(30).pdf |archive-date=28 August 2013 |url-status=live}}</ref>

In May 2008, at the [[Convention on Biological Diversity]], 191 nations called for a ban on ocean fertilization until scientists better understand the implications.<ref>{{Cite journal |last=Tollefson |first=Jeff |date=2008-06-05 |title=UN decision puts brakes on ocean fertilization |journal=Nature |volume=453 |issue=7196 |pages=704 |doi=10.1038/453704b |issn=0028-0836 |pmid=18528354 |doi-access=free}}</ref>

In August 2018, [[Germany]] banned the sale of ocean seeding as [[carbon sequestration]] system<ref>{{cite news |date=2018-08-09 |title=Europe mulls stripping carbon from the skies |newspaper=POLITICO |url=https://www.politico.eu/article/geoengineering-CO<sub>2</sub>-paris-agreement-carbon-europe-mulls-stripping-from-the-skies/ |access-date=2018-08-16 |quote=In early August, Germany decided that ocean seeding will only be allowed for research purposes and under strict conditions. }}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> while the matter was under discussion at EU and [[EASAC]] levels.<ref>{{cite news |last1=Chestney |first1=Nina |title=CO<sub>2</sub> removal 'no silver bullet' to fighting climate change-scientists |newspaper=Reuters |url=https://www.reuters.com/article/us-climatechange-emissions/CO%3Csub%3E2%3C/sub%3E-removal-no-silver-bullet-to-fighting-climate-change-scientists-idUSKBN1FK3CF |access-date=2018-08-16}}{{dead link|date=July 2021|bot=medic}}{{cbignore|bot=medic}}</ref>

== International law ==

International law presents some dilemmas for ocean fertilization.{{Citation needed|date=May 2021}} The [[United Nations Framework Convention on Climate Change]] (UNFCCC 1992) has accepted mitigation actions.{{citation needed|date=August 2012}} 

=== Law of the sea ===

According to [[United Nations Convention on the Law of the Sea]] (LOSC 1982), all states are obliged to take all measures necessary to prevent, reduce and control pollution of the marine environment, to prohibit the transfer of damage or hazards from one area to another and to prohibit the transformation of one type pollution to another. How this relates to fertilization is undetermined.<ref>Mayo-Ramsay, J P, Climate Change Mitigation Strategies: Ocean Fertilisation, The Argument For & Against (2012)</ref>

== Solar radiation management ==
{{Main|Solar radiation management}}

Fertilization may create [[sulfate aerosols]] that reflect sunlight, modifying the Earth's [[albedo]], creating a cooling effect that reduces some of the effects of climate change. Enhancing the natural [[sulfur cycle]] in the [[Southern Ocean]]<ref>{{Cite journal|last1=Wingenter|first1=Oliver W.|last2=Elliot|first2=Scott M.|last3=Blake|first3=Donald R.|date=2007-11-01|title=New Directions: Enhancing the natural sulfur cycle to slow global warming|journal=Atmospheric Environment|volume=41|issue=34|pages=7373–7375|doi=10.1016/j.atmosenv.2007.07.021|bibcode=2007AtmEn..41.7373W|s2cid=43279436 |url=https://escholarship.org/uc/item/3t2791f1|access-date=7 September 2020|archive-date=13 August 2020|archive-url=https://web.archive.org/web/20200813061020/https://escholarship.org/uc/item/3t2791f1|url-status=live}}</ref> by fertilizing with [[iron]] in order to enhance [[dimethyl sulfide]] production and cloud [[reflectivity]] may achieve this.<ref>{{cite web|url= http://www.climos.com/news/articles/slowingglobal.htm|title= Slowing Global Warming by Enhancing the Natural Sulfur Cycle|url-status= dead|archive-url= https://web.archive.org/web/20110708164838/http://www.climos.com/news/articles/slowingglobal.htm|archive-date= 8 July 2011}}</ref><ref>{{cite journal |author1=Coale, K. H. |author2=Johnson, K. S. |author3=Buesseler, K. |author4=Sofex Group |title=SOFeX: Southern Ocean Iron Experiments. Overview and Experimental Design |journal=AGU Fall Meeting Abstracts |volume=2002 |pages=OS22D–01 |bibcode=2002AGUFMOS22D..01C|year=2002 }}</ref>

== See also ==

* [[Carbon dioxide sink]]
* [[Climate engineering]]
* [[Effects of climate change on oceans]]
* [[Iron fertilization]]
* [[Planetary engineering]]
* [[Fertilizer|Soil fertilization]]

== References ==
{{reflist}}

== External links ==
* {{Cite journal|last1=Williamson|first1=Phillip|last2=Wallace|first2=Douglas W. R.|last3=Law|first3=Cliff S.|last4=Boyd|first4=Philip W.|last5=Collos|first5=Yves|last6=Croot|first6=Peter|last7=Denman|first7=Ken|last8=Riebesell|first8=Ulf|last9=Takeda|first9=Shigenobu|date=2012-11-01|title=Ocean fertilization for geoengineering: A review of effectiveness, environmental impacts and emerging governance|url=http://www.psep.ichemejournals.com/article/S0957-5820(12)00119-X/fulltext|journal=Process Safety and Environmental Protection|language=en|volume=90|issue=6|pages=475–488|doi=10.1016/j.psep.2012.10.007|bibcode=2012PSEP...90..475W |issn=0957-5820}} 
*  {{cite web|url=https://environs.law.ucdavis.edu/volumes/32/2/dean.pdf|title=Iron Fertilization: A Scientific Review with International Policy Recommendations|last=Dean|first=Jennie |year=2009 |access-date=2017-06-04}}
*{{Cite web|date=January 2021|title=Ocean fertilization|url=https://www.geoengineeringmonitor.org/wp-content/uploads/2021/04/ocean-fertilization.pdf|website=geoengineeringmonitor.org}}
{{aquatic ecosystem topics|expanded=marine}}

[[Category:Aquatic ecology]]
[[Category:Fisheries science]]
[[Category:Planetary engineering]]
[[Category:Articles containing video clips]]
[[Category:Oceanographical terminology]]
[[Category:Climate engineering]]
[[Category:Carbon dioxide removal]]

[[de:Eisendüngung]]