User:Smsalas98/sandbox

Full article can be found: User:Ariel (Wiki Ed)/sandbox

 Environmental Impacts of Deep-Sea Ocean Sequestration 

Researchers are studying how ecosystems are affected before and after injection of liquid carbon dioxide through “process studies, surveys of biogeochemical tracers, and ocean bottom studies." The challenge comes from the spatial range of the ocean and the time-scale at which effects would be taking place, making it difficult to detect these effects precisely. Especially in the deep-sea where there is very limited knowledge as to what organisms and ecosystems exist in this unexplored area and the interdependence of such ecosystems. The following is specifically pertaining to ocean sequestration through dilute dispersion, but touches on alternate methods (injection by towed pipeline, injection by stationary pipeline, use of hydrates). Due to the size of the ocean, the predictions and conclusions regarding the environmental risk of this sequestration process are based off small-scale experiments that have been extrapolated to show possible results on a scale as large as the ocean.

Deep Sea
Ocean sequestration in deep sea sediments has the potential to impact deep sea life. The chemical and physical composition of the deep sea does not undergo changes in the way that surface waters do. Because of its limited contact with the atmosphere, most organisms have evolved with very little physical and chemical disturbance and exposed to minimal levels of carbon dioxide. Light is not able to reach such extreme depths and therefore organisms that inhabit this part of the ocean are heterophic rather than autotrophic. Most of their energy is obtained from feeding off of particulate matter that descends from the surface water of the ocean and its ecosystems. There exist areas within the deep sea, such as hydrothermal vents or submarine volcanoes, where specific species have evolved for 15-500 million years to survive very elevated levels of carbon dioxide content.

Deep sea ecosystems do not have rapid reproduction rates nor give birth to many offspring because of their limited access to oxygen and nutrients. Thus, introducing lethal amounts of carbon dioxide into the environment of such a species can have a serious impact on the population size and will take extensive time to recover, relative to surface water species. In particular, species that inhabit the 2000-3000m deep range of the ocean have small, diverse populations and an intense impact to this area has the potential to wipe out an entire species.

Corporations in favor of ocean sequestration, such as ExxonMobil, argue that the uncertainties involved with such predictions instill much doubt in the conclusions of the research. Supporters of ocean sequestration argue that because of the ocean's size, diluted carbon dioxide injections will not be enough to create an actual impact on ecosystems and that species can evolve to these increased levels of carbon dioxide eventually. Scientific research shows that sites of injection are spatially specific and ecosystems that happen to inhabit the site of injection can suffer immediate consequences. Affected areas will experience acidification, due to the augmented bicarbonate levels, and in turn a decrease in calcium carbonate levels. This will cause sediments and shells of organisms to more quickly dissolve. The capacity of deep-sea organisms to acclimate to the injection of carbon dioxide has not been investigated and the hypothesis that they will evolve in time lacks scientific support.

Effects of pH vs. CO2
Acidification of the environment weakens metabolic processes in organisms; enzymes and ion transportation require specific pH levels to continue functioning properly. However, organisms are not only affected by the acidification of water in the presence of heightened carbon dioxide (CO2) levels. CO2 itself interacts with the physiological function of individual organisms. CO2 enters organisms through diffusion and is then internally accumulated over time. These effects are more damaging than those associated with changes in pH of environment. When CO2 enters organisms, mainly fish, through diffusion across tissue, it becomes internally accumulated which can then cause anesthesia and, depending on the concentration of CO2, death. The internal accumulation will also cause organisms to experience blood acidfication. This weakens organisms' ability to uptake oxygen and consequently weakens their performances. This effect is more so detrimental to more complex and larger species that require a greater exertion of energy to move and perform vital bodily functions.

Long term effects
If deep-sea ocean sequestration becomes a common practice, long term effects will continue to be investigated to predict future scenarios of deep sea impacts by CO2. Ocean sequestration of liquid carbon dioxide would not only impact deep-sea ecosystems, but in the long-run would begin to affect surface-water species and eventually humans. It is estimated that organisms not fit for high CO2 levels will begin to experience permanent effects at levels of 400/500ppm of CO2 and/or shifts of 0.1-0.3 units in pH. These levels of CO2 are predicted to be met soley as a result of atmospheric CO2 acidifying the surface waters over a matter of a century, without considering ocean sequestration effects.

Although the long-term effects are the most relevant to understand, they are also the most difficult to predict accurately due to the scale of the ocean and the diversity in species sensitivity to elevated carbon dioxide levels. Surface sea organisms have been more so studied than deep-sea animals in terms of consequences due to prolonged CO2 exposure and have been proven to experience "reduced calcification" and damage to their skeletons. This more seriously affects shelled animals' mortality and growth rate. Adult fish showed remarkable tolerance to elevated CO2 levels, only when dissolution of CO2 occured at a slow rate. Developing fish showed less tolerance than their adult fish counterparts. Acidification of the blood in these species also results in weakened metabolic rates; this stunts protein formation and thus hinders growth and reproduction of organisms. Although individual physiological effects are known, in order to understand how these individual species are interconnected and dependent of each other, field studies would have to be conducted. Different amounts and concentrations of sequestered CO2 will affect each ecosystem and species differently such that a general, universal limit of CO2 to be sequestered doesn't exist.

Alternate methods
The use of clathrate hydrates can be implemented in order to reduce speed of dissolution of CO2. The hydrates give CO2 a negative buoyancy, allowing injection to occur at surface levels rather than through pipelines. Experiments showed that the use of clathrate hydrates minimized the rate at which the injected CO2 spread throughout the ocean floor. This rate did not prove to be spatially restrictive or slow enough to minimize impact on deep sea organisms. The intactness of the hydrates also relies heavily on the ocean current's magnitude at the site of injection. The carbon dioxide dissolved into surface waters before the hydrate was able to sink to the deep ocean (10%-55% of CO2 remained stuck to the hydrate at depths of 1500m into the ocean). In laboratory experiments, continuous streams of hydrates have not yet been achieved.

Studies show that delivering liquid CO2 by a towed pipeline (attached to boat traveling perpendicular to the current), can minimize "clumps" of highly-concentrated CO2  levels. Delivery by fixed pipe would be confined to a small region of the ocean and in turn instantly kill sensitive species inhabiting the region. Theoretically, if we assume future anthropogenic emissions of CO2 drop drastically and only 0.37 Gt of liquid CO2 were to be injected each year through a towed pipe, only 1% of the ocean would be affected. There is consensus among scientists that ocean sequestration of carbon dioxide is not a long-term plan to be relied on, but may solve immediate atmospheric concerns if implemented temporarily. Scientists believe that it is possible to engineer ways to discharge CO2 at rates that resemble the natural fluctuation of CO2 in the oceans ; no such discovery has been made yet.

Smsalas98 (talk) 18:59, 29 November 2018 (UTC)