Ocean fertilization

A visualization of bloom populations in the North Atlantic and North Pacific oceans from March 2003 to October 2006. The blue areas are nutrient deficient. Green to yellow show blooms fed by dust blown from nearby landmasses.^[1]

Ocean fertilization or ocean nourishment is a type of geoengineering based on the purposeful introduction of nutrients to the upper ocean^[2] to increase marine food production^[3] and to remove carbon dioxide from the atmosphere. A number of techniques, including fertilization by iron, urea and phosphorus have been proposed. Another possible objective of ocean fertilization is to produce more sulfate aerosol in the atmosphere and so increase the amount of sunlight being reflected by clouds, cooling the Earth. There has been commercial interest in using these techniques to reduce carbon dioxide concentrations.

Techniques and motivation

CO₂ sequestration in the ocean

The marine food chain is based on photosynthesis by marine phytoplankton which combine carbon with inorganic nutrients to produce organic matter. The production of organic matter is limited in general by the availability of nutrients, most commonly nitrogen or iron. Numerous experiments^[4] have been carried out demonstrating how iron fertilization can increase phytoplankton productivity. Nitrogen is a limiting nutrient over much of the ocean and can be supplied by from a number of 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.

Ocean fertilization offers the prospect of both reducing the concentration of atmospheric greenhouse gases with the aim of avoiding dangerous climate change and at the same time increasing the sustainable fish stocks. It promises to do this by increasing the ocean primary production.

Ocean fertilization may be a way of creating low cost protein in sufficient quantity to supply the needs of the additional two billion people expected to populate the earth before the population stabilizes at values near eight billion.^{[citation needed]} While manipulation of the land ecosystem in support of agriculture for the benefit of humans has long been accepted it is a new concept to enhance the large scale ocean productivity and so creates some apprehension.

Iron fertilization

In large areas of ocean, there are very few phytoplankton, despite there being high levels of nutrients. John Martin, director of the Moss Landing Marine Laboratories, came up with a hypothesis that the low levels of phytoplankton in these regions are due to a lack of iron. To test this hypothesis (known as the Iron Hypothesis) he arranged an experiment where samples of clean water from Antarctica were collected. To some of these samples iron was added but not to others. They were then left for several days and the phytoplankton in the samples with added iron grew much more than in the untreated samples. This lead Martin to speculate that increased iron concentrations in the oceans could partly explain past ice ages.^[5] This experiment was followed up by a much larger field experiment (IRONEX I) where 445 kg of iron was added to a patch of ocean near the Galápagos Islands. The levels of phytoplankton increased three times in the area where the iron had been added.^[6] The success of this experiment and others has led to proposals to use this technique to remove carbon dioxide from the atmosphere on a commercial basis.^[7]

Sperm whales act as agents of iron fertilisation when they 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 faeces into surface waters of the Southern Ocean. The iron rich faeces causes phytoplankton to grow and take up more carbon from the atmosphere. When the phytoplankton dies, it sinks to the deep ocean and takes the atmospheric carbon with it. By reducing the abundance of sperm whales in the Southern Ocean, whaling has resulted in an extra 2 million tonnes of carbon remaining in the atmosphere each year.^[8]

Phosphorus fertilization

This technique can give 0.83W/m² of globally averaged negative forcing,^[9] which is sufficient to reverse the warming effect of about half the current levels of anthropogenic CO₂ emissions. It is notable, however, that CO₂ levels will have risen by the time this could be achieved.

Nitrogen fertilization

This technique (proposed by Ian Jones) suggests fertilizing the ocean with urea, a nitrogen rich substance, to encourage phytoplankton growth.^{[citation needed]} and has also been considered by Karl.^[10]

An Australian company, Ocean Nourishment Corporation (ONC), plans to sink hundreds of tonnes of urea into the ocean, in order to boost the growth of CO₂-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.^[11]

This technique can give 0.38W/m² of globally averaged negative forcing,^[9] which is sufficient to reverse the warming effect of current levels of around a quarter of anthropogenic CO₂ emissions. It is notable, however, that CO₂ levels will have risen by the time this could be achieved.

Advantages

The Ocean Nourishment Corporation has claimed that in the long run, beyond the Sulu Sea trials, “One Ocean Nourishment plant will remove approximately 5-8 million tonnes of CO2 from the atmosphere for each year of operation, equivalent to offsetting annual emissions from a typical 1200 MW coal-fired power station or the short-term sequestration from one million hectares of new growth forest”.^[12]

Disadvantages

Nitrogen fertilization is not as efficient as iron fertilization.

Algal cell chemical composition is 106 carbon: 16 nitrogen: 1 phosphorus: 0.0001 iron. In other words for each atom of iron there are 1060000 atoms of carbon are captured, however for one nitrogen atom only 6 atoms of carbon are captured.^[13]

Urea fertilization may not benefit fisheries

It has been said that addition of urea to the ocean can cause blooms of phytoplankton that is source of food of fish. However, if cyanobactaria and dinoflagellates dominate phytoplankton assemblages that are considered poor quality food for fish then fish quantity cannot be counted as rising. Another disadvantage is the fact that fossil fuels are used to produce urea. The fossil fuels contain buried CO2, so using them is not benign from the environmental point of view.^[14]

Sulu sea biodiversity

The Tubbataha Reef in the Sulu Sea has marine biodiversity which is virtually unparalleled by any other area in the world today^[15] and nitrogen loading in coral reef areas can lead to community shifts towards algal overgrowth of corals and ecosystem disruption.^[16] This makes the Sulu Sea area an unlikely candidate for urea fertilization experiment.

Volcanic ash as a nutrient source

Volcanic ash adds nutrients to the surface ocean. This is most apparent in areas that are nutrient limited. Considerable research has been done on the effects of anthropogenic and eolian iron addition to the ocean surface, but some research suggests that nutrient-limited areas benefit most from a combination of nutrients provided by anthropogenic, eolian, and volcanic deposition.^[17] Some nutrient-limited oceanic areas are limited in more than one nutrient, so the biological community is more likely to thrive from adding multiple nutrients like P, N, and Fe, than if only Fe were added to the system. Volcanic ash has the potential to add these multiple nutrients to the system, allowing the biota to thrive, but excess metal ions can be harmful to systems limited by nutrients. The positive impacts of volcanic ash deposition are potentially outweighed by their potential to do harm.^{[citation needed]}

There is clear evidence for the presence of as much as 45 percent by weight of ash in some deep marine sediments.^[18][19] In the Pacific Ocean, the largest ocean basin covering half of the Earth's surface area, estimates have shown that (on a millennial-scale) the atmospheric deposition of air-fall volcanic ash has been as high as the deposition of desert dust.^[20] This indicates the potential of volcanic ash being a significant source of iron in the surface ocean.

In August 2008 an eruption in the Aleutian Islands, Alaska, deposited ash in the nutrient limited North-East Pacific. There is strong evidence that this ash and iron deposition resulted in one of the largest phytoplankton blooms observed in the subarctic.^[21]

Ocean nourishment and International Law

From the perspective of international law there are some dilemmas around iron, urea, or phosphorus fertilization of the ocean. On one hand the United Nations Framework Convention on Climate Change (UNFCCC 1992) has accepted mitigation actions.^{[citation needed]} On the other hand, the UNFCCC and its revisions currently only recognise forestation and reforestation projects as carbon sinks^{[citation needed]} and international law protects and preserves the marine environment.^{[citation needed]} Some commercial companies like Climos and GreenSea Ventures, and the Australian based Ocean Nourishment Corporation, plan to engage in urea and iron fertilization projects. These companies invite green co-sponsors to finance their activities in return for provision of carbon credits to offset investors’ CO2 emissions.^[22]

In June 2007 the 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'.^[23] but the term 'large scale' was not defined. It is believed that large scale would refer to operations on the scale then planned by Planktos.^{[citation needed]} Planktos is a USA-based company, which abandoned its plans to conduct 6 fertilzation cruises from 2007 to 2009, each of which would have dissolved up to 100 tons of iron over a 10,000 km² area of ocean. The plans were abandoned because their ship Weatherbird II was refused entry to the port of Las Palmas in the Canary Islands where it was to take on provisions and scientific equipment.^[24] In 2008, the convention issued a non-binding resolution which states that ocean fertilization activities, other than legitimate scientific 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".^[25]

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 is probably over-estimated by current studies and that other potential adverse effects have not yet been fully studied.^[26]

Law of sea issues

According to United Nations Convention on the Law of the Sea(LOSC 1982), all states are obliged to take individually and jointly all measures necessary to prevent, reduce and control pollution of the marine environment, to prohibit the transfer, either directly or indirectly, of damage or hazards from one area to another, and to prohibit the transformation of one type pollution to another. Without further research it is not clear that fertilization of the oceans is a safe way to reduce carbon dioxide concentrations in the air.^[27]

Solar radiation management

As well as carbon sequestration, ocean fertilization may also create sulfate aerosols which reflect sunlight and modify the Earth's albedo, this creating a cooling effect which reduces some of the effects of climate change. Enhancing the natural sulfur cycle in the Southern Ocean^[28] by fertilizing a small portion with iron in order to enhance dimethyl sulfide production and cloud reflectivity may achieve this. The goal is to slow Antarctic ice from melting and raising sea level.^[29][30]

See also

• Carbon dioxide sink
• Geoengineering
• Planetary engineering

References

Aquatic ecosystems – general and freshwater components General Aquatic ecosystems Acoustic ecology Agent-based models Algal bloom Anoxic waters Aquatic adaptation Aquatic animals Aquatic biodiversity research Aquatic biomonitoring Aquatic insects Aquatic layers Aquatic mammals Aquatic plants Aquatic predation Aquatic respiration Aquatic science Aquatic toxicology Benthos Bioluminescence Biomass Cascade effect Colored dissolved organic matter Dead zone Ecohydrology Eutrophication Fisheries science Food chain Food web GIS and aquatic science Hydrobiology Hypoxia Isotope analysis Microbial ecology Microbial food web Microbial loop Nekton Neuston Particle Photic zone Phytoplankton Plankton Pleuston Productivity Ramsar Convention Schooling Sediment trap Siltation Spawning Substrate Thermal pollution Trophic level Underwater camouflage and mimicry Water column Zooplankton More... Freshwater Freshwater ecosystems Brackish marsh Freshwater biology Freshwater biomes Freshwater fish Freshwater marsh Freshwater swamp forest Hyporheic zone Lake ecosystems Landscape limnology Limnology Lake stratification Macrophyte Pond Fish pond Rheotaxis River ecosystems Stream bed Stream pool Trophic state index Upland and lowland Water garden Wetland Environmental quality More... Ecoregions Freshwater ecoregions List of freshwater ecoregions Marine ecoregions List of marine ecoregions Ecology of the Everglades Ecology of the San Francisco Estuary Ecosystem of the North Pacific Subtropical Gyre Freshwater ecology of Maharashtra   Aquatic ecosystems – marine components Marine Marine ecosystem f-ratio Iron fertilization Iron Hypothesis Large marine ecosystem Marine biology Marine chemistry Marine snow Ocean nourishment Oceanic physical-biological process Ocean turbidity Photophore Thorson's rule Upwelling Whale fall More... Marine life forms Census of Marine Life Coastal fish Coral reef fish Deep sea communities Deep sea creature Deep sea fish Deep-water coral Demersal fish Marine bacteriophage Marine invertebrates Marine larval ecology Marine mammal Marine reptile Marine vertebrate Paradox of the plankton Pelagic fish Seabird Seashore wildlife Wild fisheries Marine habitats Bay mud Black smokers Coastal biogeomorphology Cold seeps Coral reefs Davidson Seamount Estuaries Intertidal ecology Intertidal wetlands Kelp forests Hydrothermal vents Lagoons Mangroves Marine biomes Marine habitats Mudflats Rocky shores Salt marshes Salt pannes and pools Seagrass meadows Sponge reefs Tide pools Issues Ecological values of mangrove Fisheries and climate change HERMIONE Marine conservation Marine conservation activism Marine pollution Marine Protected Area