This paper was written as part of the 2009 Alaska Oceans Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.

The effects of ocean acidification on pink salmon (Oncorhynchus gorbuscha) in Alaska

Authors

Kayla Harrison
Molly Emerson
Tyler Houseweart
Stephen Kubota
Jake Pernula

Team Naughty Nautilli

Juneau-Douglas High School
10014 Crazy Horse Dr
Juneau, Alaska 99801-8529

Abstract

The rapid influx of CO2 into the world ocean due to unprecedented anthropogenic carbon emissions over the last two centuries has led to an observed pH decline of about 0.1 units since the beginning of the Industrial Revolution. This process of ocean acidification results from the chemical interactions of hydrated CO2 and the carbonate system of the ocean. A consequence of this is a decline in the concentration of the carbonate ion, an essential component of CaCO3, the building block of many phyto- and zooplanktonic structures. Additionally, the shoaling of compensation depths makes shell precipitation difficult. Solubility in the cold northern waters of Alaska is greater than elsewhere, and cold upwelled water is already laden with CO2. Thus, Alaska is expected to experience exacerbated effects of ocean acidification and is a primary location for observing influences on marine ecosystems. We believe that if ocean acidification reduces deposition rates of key calciferous zooplankton enough to induce a decline in population, this depression will move up the trophic web to their dependants, including pink salmon (Oncorhynchus gorbuscha), whose diet is mainly comprised of various species of calciferous zooplankton. In 2007 the wholesale value of pink salmon was $123 million. The pink salmon industry is an essential component of the Alaskan economy in respect to the profits it brings to the state, the jobs it provides, and through the support to smaller communities' via processing plants. Potential changes in the trophic web due to ocean acidification may impact pink salmon stock. Many proposals advocating mitigation processes for this phenomenon have been set forth, and it is undeniable that some form of mitigation must be implemented to stave off this shift in the marine environment. Our team believes that further research on the effects of acidification on specific important species of phyto- and zooplankton are necessary. However, it is secondary to the need for action in the form of reducing atmospheric CO2 and thus the impact of ocean acidification.

Introduction

The global carbon cycle is undergoing transformations due to increased anthropogenic carbon emissions from an expanding, carbon dependant global economy. According to the Energy Information Administration (http://www.eia.doe.gov/iea/carbon.html), global anthropogenic carbon dioxide (CO2 (g)) emissions from fossil fuel usage in 2006 amounted to approximately 29,000 million metric tons. The steady state condition of the ocean has regulated the effects of the rapid influx of carbon dioxide by absorbing as much as 50% of the total CO2 (g) released into the atmosphere in the last 200 years (Sabine et al., 2004). However, through a series of equilibrium reactions that form the ocean's carbonate buffer system, these increased concentrations of dissolved carbon dioxide (CO2 (aq)) are changing the chemistry of the ocean environment through the process of ocean acidification. Concentrations of CO2 (g) have risen from pre-industrial levels of ~280 ppm to over 380 ppm, higher than any time in at least 800,000 years; the most conservative projections predict 540-970 ppm by the year 2100 (Orr, 2005; Harley et al., 2006; Royal Society, 2005). The current and projected rate of increasing CO2 (g), and thus CO2 (aq), is more than 100 times faster than any time in the last 650,000 years, with atmospheric concentrations expected to increase by 1% per year (Houghton, 2001; Kleypas et al., 2006). Many numerical projections and comparisons have been offered, but the unanimous conclusion is that "business-as-usual" is posing multiple threats to the world ocean, most noticeably through the process of ocean acidification.

The extreme, abrupt modification of dynamic marine systems is a main cause for concern; radical changes are occurring over short time intervals compared to any previous time in the planet's history, and natural systems do not have time to adjust effectively to changing conditions. Repeat hydrographic and time-series data surveys in the North Pacific Ocean already document a lowered seawater pH due to increased absorption of CO2, an approximate decrease of 0.1 units since the beginning of the industrial revolution (Feely, 2007). If current trends continue, pH of ocean surface waters would decrease by a further 0.2–0.3 units; this deceivingly small drop actually reflects a threefold increase in hydrogen ions (H+) (Riebesell et al., 2000). The projected acidification levels are accompanied by a predicted 50-60% decrease of carbonate ion (CO3-2) concentration (Feely, 2007), the importance of which is the main focus of this paper.

As expected through analysis of the chemical equilibria and proved in various experiments, a rise in [H+] is conducive to the drop of [CO3-2] (Millero, 2005; Kleypas et al., 1999). An essential mineral, CO3-2, is used by a vast array of calcifying organisms at the base of many food webs to make shells, skeletons, and tests. This decrease in CO3-2 availability is predicted to strongly impact marine biota and systems, and through these effects potentially shift biogeochemical cycles (Caldeira et al., 2003; Kleypas et al., 2006; Royal Society, 2005).

In the past, rapid losses of calcifying organisms in the marine ecosystem have been largely attributed to similar ocean acidifying events, so our current situation has cause for concern (Feely, 2007). We present an examination of the potential stresses on these vital organisms and sequentially on the higher trophic levels that depend on zooplankton. We emphasize the predicted consequences on the trophic web of several species of susceptible calcifying organisms: pteropods, calanoid copepods, euphausids, and amphipods that indirectly affect the population and industry of the Pacific pink salmon (Oncorhynchus gorbuscha).

We discuss ocean acidification with respect to specific chemical and physical Alaskan features, the impact of this food web on the Alaskan economy, and the organisms' role of transferring carbon from surface waters to storage in the deep ocean will be included to provide a realistic perspective on the present situation. Finally, mitigation strategies will be evaluated and suggestions for future management will be proposed.

Alaska on the Front Lines

Alaskan waters are expected to have amplified ocean acidification. Physical and chemical factors are such that ocean acidification occurs at higher rates. The Gulf of Alaska (GOA) will probably be one of the most affected areas and could serve as a model for other regions.

The dissolution of CO2 (g) is plainly described by the relationship: CO2 (aq) ←→ HCO2 + CO2 (g), where HCO2 is the Henry's Law constant (Sigler et al., 2008). In cold temperature and low salinity water, Henry's constant and thus CO2 (g) solubility increases. The GOA loses heat to the atmosphere during winter, exhibiting surface temperatures of 4–6°C and salinities of 32.5–32.8 ppt (Mundy, 2005). Hence, these waters contain higher [CO2 (aq)] than tropical waters (Sigler et al., 2008). High northern Pacific latitudes have a positive ΔpCO2pCO2 = pCO2(ocean)pCO2(atm)) and are supersaturated with respect to CO2 (aq). With this influx of the CO2 (aq) reactant, Alaskan waters are expected to have amplified ocean acidification.

The upwelling system in the GOA may also contribute to acidification. The circulation in the Gulf is controlled by large scale wind fields that shape the Alaska gyre. There is an average upwelling rate of 10–30 m/yr in the gyre center (Mundy, 2005). In the past, this upwelled water brought CO2 saturated deep water to the surface, venting some CO2 back into the atmosphere and causing a measurable annual CO2 flux between the ocean and atmosphere (Short, pers. comm., 2008). Increased atmospheric [CO2 (g)] both inhibits venting and decreases the efficiency of these waters to act as a carbon sink and absorb additional anthropogenic emissions from the atmosphere (Canadell et al., 2007). Hence, upwelled waters in Alaska will contain CO2 (aq) from the atmosphere of its origin, bacteria fixation, as well as 'new' anthropogenic emissions that are dissolved at the surface (Wing, pers. comm., 2008; Short, pers. comm., 2008).

Carbonate Availability and Saturation Horizons

The hydrolysis of CO2 (g) in seawater is well understood and the reactions can be found in any chemical oceanography textbook (Millero, 2005; Sarmiento and Gruber, 2006). Increased concentration of CO2 (aq) affects the carbonate system by the following net reaction: CO2 (aq) + CO3-2 (aq) + H2O → 2HCO3-(aq). This reaction is driven by decreased pH and serves to decrease [CO3-2] (Caldeira et al., 2005; Orr et al., 2005). This decrease of CO3-2 is known to have strong effects on calcifying organisms, as they use the mineral ion to precipitate shells, skeletons, and tests of calcium carbonate (CaCO3) (Riebesell et al., 2000; Feely, 2007; Hays et al., 2005; Orr et al., 2005; Kleypas et al., 2006; Royal Society, 2005; Harley et al., 2006; Sigler et al., 2008).

Aragonite and calcite precipitation rates are dependent on the saturation levels (symbolized by Ω, defined in Kleypas et al., 1999) in the water. Shell formation is favored in areas where the Ω ›1.0; when Ω ‹1.0 the water is corrosive and dissolution will occur (Feely, 2007). Aragonite is 1.5 times more soluble than calcite in equal pH conditions, and organisms that utilize aragonite (i.e., pteropods and hermatypic corals) are most at risk to increased dissolution (Sigler et al., 2008). The amount of effort necessary to utilize aqueous material is linked to saturation, organisms precipitate shells more easily in supersaturated water, but dissolution may still occur in supersaturated conditions (Takahashi, 2004; Orr et al., 2005). It is predicted that some polar and sub-polar surface waters will become under-saturated with respect to aragonite within the next 50 years (Orr et al., 2005). The intermediate waters of the North Pacific already show evidence of under-saturation at depths between 200 and 1000m where CaCO3 dissolution rates are seven times faster than middle and deep water (about 0.051 μmol/kg/y); these areas are extremely affected by anthropogenic emissions because they are beneath the photic zone and thus have no primary production to reduce concentrations of CO2 (aq) (Feely et al., 2002; Feely et al., 2004).

Fabry (1990) and Orr (2005) have done studies on pteropods using estimates of acidification levels generated by the IPCC. Fabry (1990) found slower growth rates when CaCO3 became less available, and Orr (2005) discovered that within 48 hours, active dissolution occurred under the 2100 pH level predictions made by the IPCC. Calcification will probably become more difficult as [CO2 (aq)] rise, and this may be expressed by lower populations of calcifying organisms and their predators.

Potential Shifts in Carbon Cycle and Nutrient Availability/Uptake

The upward migration of saturation horizons, as well as observed increases in airborne CO2 emissions, suggest that the ocean's ability to act as a sink and take up anthropogenic CO2 (g) may be declining (Feely et al., 2002; Canadell et al., 2007). The warming of waters reduces CO2 (g) uptake and is predicted to lead to a 10% reduction of the ocean sink by the year 2100 (Fasham, 2003). Many ocean models predict substantial increases of upper layer stratification (resulting from freshening upper latitudes and warmer waters) that would further reduce vertical exchange and uptake of CO2 (g) by the ocean, altering of the 'carbonate pump', and nutrient circulation (Sarmiento and Gruber, 2006). The carbonate pump is the precipitation of CaCO3 in pelagic ocean zones, and the dissolution in deep ocean waters (due to increased pH from increased CO2 (aq) from microbial respiration). It comprises an important facet of the carbon cycle, responsible for transferring carbon to the deep ocean waters for storage, and is an important component of thermohaline circulation. If the density-driven ocean circulation is affected, nutrient cycles will also be altered. The nutrient supply to the GOA is derived mainly from marine sources and depends on surface mixing by storms and upwelling (Mundy, 2005). With a reduced rate of circulation, nutrient supply and thus primary production would probably decline.

Ocean acidification has a direct effect on nutrient uptake according to actual pH level; both phosphorous and nitrogen, key macronutrients, are pH sensitive (Turley et al., 2006). A pH change from 8.1 to 7.8 shifts the ratio of ammonia (NH3) to ammonium (NH4+) by decreasing NH3 and increasing NH4+ (Short, pers. comm., 2008; Turley et al., 2006). Also, acidification may inhibit microbial nitrification with reduced nitrogen fixation rates and decreased marine concentrations of NO3- (Turley et al., 2006). Lower pH also reduces the availability of phosphate (PO4-3) (Turley et al., 2006).

The solubility and availability of the essential micronutrient iron (Fe) is likely to increase with acidification, which may increase primary productivity since it is a key limiting factor (Royal Society, 2005; Turley et al., 2006). With a pH of 8.1, the saturation concentration of Fe+3 in seawater is around 5.0x10-18 moles per liter, compared with 2.5x10-12 moles per liter at a pH of 7.8, a two million-fold increase (Short, pers. comm., 2008). While increased nutrient availability might be considered a positive impact of acidification, it is unknown how dramatic shifts in primary production would manifest in the food webs.

Biological Impacts on the Pink Salmon

It is our expectation that a lowering of pH in the Gulf of Alaska will decrease survivability rates of calcifying organisms primarily through increased shell dissolution rates. Reductions in Arctic calciferous zooplankton may decrease pink salmon stocks, if food were to become a limiting factor. Fish populations depend on net primary production and its passage through the food chain (Brander, 2007). Therefore, acidified waters could threaten pink salmon through decreased growth rates and fecundity due to reduced numbers of the juvenile's main prey.

The feeding habits of salmon during migration differ by location and timing of zooplankton blooms. As fry enter Prince William Sound (PWS) during April and May, consumption of calanoid copepods dominate their diet, while on the coastal GOA, copepods, lavaeceans, and pteropods serve as primary contributors in July and August (Cross et al., 2004). During the fall, euphausids, crab megalopae, and amphipods are primarily consumed (Cross et al., 2004).

Prey selection by pink salmon is governed by zooplankton availability. In PWS, the most dominant prey in pink salmon stomachs were the blooming plankton species (Cooney et al., 2001; Cross et al., 2004). Calcareous organisms (i.e., copepods, pteropods, euphausids, and amphipods) are the most significant contributor to the diet (Cooney et al., 2001; Cross et al., 2004; Willette, 2001; Sturdevant pers. comm., 2008). Therefore, fundamental energy sources utilized by pink salmon may be at risk from the rising aragonite and calcite saturation horizons.

The pelagic snail (Limacina helicina) is potentially at the greatest risk because pteropods use aragonite to strengthen their shell (Wing, pers. comm., 2008; Fabry 1990). Although the drop in significance of pteropods as a food source to pink salmon in 2001 (from ~60% to ~15%) was not linked to population decreases from acidity (Armstrong et al., 2005), the deductions drawn from the ensuing shift in the salmon's diet may provide predictions for the future feeding habits of the salmon. When the abundance of pteropods in the stomachs of juvenile pink salmon dropped, calanoid copepods and euphausids took its place (Willette et al., 2001). We anticipate that a decrease in population size of L. helicina due to complete shoaling of the aragonite saturation horizon will most likely yield the same results.

These replacement prey items would be similarly impacted by ocean acidification if the calcite saturation horizon reaches the surface. This could be a significant change as copepods compose nearly 60% of the zooplankton biomass in some years (Cooney et al., 2001). In addition, it is not fully known exactly how salmon would react to a drastic shift in food sources, so we cannot assume there could be a seamless transition. For example, a Bristol Bay experiment found that even though substantial plankton was present, salmon were still starving. This was because the available organisms were too small (‹1mm) as opposed to the salmon's preferred sized (›3mm) (Wing, pers. comm., 2008).

The presence of zooplankton also aids O. gorbuscha in survival by sheltering them from predation. Willette (2001) found that the July bloom of pteropods decreased predation by providing another food source to higher trophic levels preying upon pink salmon. Without the presence of these blooms, pink salmon are more susceptible to predators.

Decreased prey and thus growth rate is associated with increased mortality because more energy is used to forage (Cross et al., 2004). In 1991 and 1992, the pink salmon fishery declined in the GOA due to a low recruitment rate, this is now attributed to the reduced zooplankton populations (Willette et al., 2001).

A decreased growth rate may affect the overall reproductive success of pink salmon because fecundity of fish is decreased when spawning organisms are younger or below average in size (Cross, 2004; Cooney, 2001). Decreased growth rate also causes increased mortality indirectly as the result of increased predation (Willette, 2001). Pollock (Theragra chalcogramma) and herring (Clupea pallasi) are the greatest predators on juvenile O. gorbuscha. Small pink salmon with a slow growth rate may thus be subject to extended vulnerability to size selective pisciverous organisms (Willete et al., 2001; Armstrong et al., 2005).

A smaller calciferous prey population is expected to impact the growth, mortality, and recruitment rates of pink salmon populations (Fivelstad et al., 1998; Fivelstad et al., 2007; Martens et al., 2006). These negative effects would serve as an impact to the most profitable Alaska salmon fishery, as well as a precursor of other strains on biological systems and mariculture industries worldwide as the pH of the ocean drops and primary productivity declines.

Economic Aspect

Last November, the Marine Stewardship Council (MSC) recertified Alaska's commercial fishing industry as sustainable. Alaska's management policies have been modeled worldwide and since the shift to state management authority for all salmon, herring, and shellfish fisheries in 1959, these natural resources have remained stable (http://www.sf.adfg.state.ak.us/fedaidpdfs/sp05-09.pdf 07/07/08).

Alaska harvests nearly 95% of all commercially caught salmon in the U.S. and work associated with commercial fishing provides 47% of private sector jobs in the state (http://www.cf.adfg.state.ak.us/geninfo/finfish/salmon/). The SE seining industry represents over 2,000 well paying jobs to the state (McDowell Group, 2008). It is forecasted that for the FY2008, the state will receive a total of approximately $48.7 million in restricted and unrestricted taxes from the commercial fishing industry (http://www.tax.alaska.gov/programs/documentviewer/viewer.aspx?1338f 07/07/08). The pink salmon fishery is of special importance, as it is, by total weight and quantity harvested, Alaska's most productive salmon fishery (http://csfish.adfg.state.ak.us/bluesheets/bluewebreport.php 06/11/08). Pinks compose an average 75% of the SE Alaska Seine fleet harvest tonnage since 1985 (McDowell Group, 2008).

The value of Alaska pink salmon is predicted to increase in value as dynamics of global product demand shift (Fleming, pers. comm., 2008). The demand for higher-quality frozen and fresh head and gutted (H&G) fish and pink roe has risen substantially. This is seen in the increase of ex-vessel price from $0.21 per pound in 2005 to $0.26 in 2008. The first wholesale value is up $0.41 per pound in 2003 to $0.90 in early 2008 (McDowell Group, 2008). Comparing 2006 to 2007, sales rose from (in thousands of pounds) 32,834 to 50,456; 2,882 to 3,778; and 3,722 to 6,435, of H&G frozen, H&G fresh, and roe, respectively (McDowell Group, 2008). Pink salmon are being processed and marketed in new ways that increase the quality and value of the product.

Until 2003, SE's pink harvest has been consistently and substantially larger than those of the two other major pink producing regions: the PWS and Kodiak districts. Since 2005, PWS harvests have surpassed SE in both odd and even years. This may be attributed to the success of fish hatcheries in PWS, or of an unknown hindrance on the SE population. In the PWS district 80.3% (10,010 thousand fish) of pinks harvested in 2006 were of hatchery origin while in SE hatchery fish accounted for 2.6% (299 thousand fish) of the total harvest (White, 2006).

Monitoring and further investigations of this concern should be looked into; analyses of hatchery release and return data to determine whether decreased survivability rates of juveniles is a factor would be extremely valuable. Further research of hatchery and aquaculture efficiency is important because if future conditions prove detrimental to wild populations, preservation of species through aquaculture may prove necessary. By 2030 aquaculture production is predicted to equal 'wild' capture production, as, at least 70% of world fish stocks are estimated to be fully exploited, overexploited, or recovering from a period of depletion (Brander, 2007).

Mitigations Review

Given the possible effects ocean acidification would have on the ecological and economical aspects of our local area, as well as the world, mitigation measures must be initiated. The present decline in ocean pH is the result of increasing anthropogenic carbon dioxide emissions. The most effective way to halt ocean acidification is to drastically reduce carbon emissions, either through utilization of renewable energy sources, increased efficiency of existing methods, or power source change. These methods are feasible because they allow the natural processes of the Earth to balance CO2 (g) levels. Although with these processes, it would take more than 1,000 years to reach this state (Short, pers. comm., 2008). Moreover, this mitigation is accompanied by huge economic effects. In 2007, the United States energy statistics of fossil fuels was approximately 40% petroleum, 23% natural gasses, and 22% coal; only 7% of energy consumption was renewable (http://eia.doe.gov/cneaf/alternate/page/renew_energy_consump/reec_080514.pdf). The logistics of reframing the global energy sources are extremely daunting but possible in the long run, however the cost is the primary detriment to this mitigation.

Reducing emissions quickly is not likely, therefore many mitigation measures are being researched and proposed. These can be dangerous because they attempt to fix human alteration by trying to manipulate the environment further. Current, mitigation strategies are designed to prevent or slow damage, by using processes such as sequestration and buffering.

It has been suggested that photosynthetic organisms could be used as a carbon sink to trap or sequester the carbon from CO2 in the ocean. One method would be to cultivate species of plants specifically for use as a carbon sink. Sweden uses this method to fulfill its commitments under the Kyoto Protocol. A study on Swedish willow plantations showed that an experimental, well-managed willow plantation took up twice the amount of carbon as a normally managed willow plantation (Grelle et al., 2007). It is important to select organisms with a long life span, otherwise they will die quickly and release the stored carbon back into the atmosphere.

Another form of biological sequestration, first proposed by John Martin, is the "Iron Hypothesis." Much of the ocean contains high nutrient and low chlorophyll (HNLC) water. Seeding HNLC areas with iron may stimulate phytoplankton growth and biologically sequester CO2. In small scale studies in the southern ocean (Southern Ocean Iron Experiment—SOFeX) this method has been shown to be viable. When iron was added to the water, nitrate and CO2 concentrations decreased significantly, indicating increased photosynthetic activity; diatoms were found to have the highest increased growth rate (Coale et al., 2004). Problems with this method include: tests have only been done on small scales; phytoplankton would not provide a permanent sink for CO2; upon death, the CO2 would be re-released back into surface waters or into the water column; iron seeding could result in a switch in the dominant plankton of an ecosystem; and the low solubility of iron in seawater, could to problems with mining, processing, and transportation (Short, pers. comm., 2008).

Photosynthetic organisms can also be used to mitigate ocean acidification by injecting industrial flue gas (the emission of smoke stacks, containing a high percentage of CO2) into the water surrounding certain organisms such as eelgrass or kelp. Eelgrass and kelp are CO2-limited (Palacios et al., 2007; Thom, 1996). Studies showed that increased presence of CO2 increased net productivity and growth rates of eelgrass and bull kelp (Thom, 1996). Palacios (2007) showed that enrichment with CO2 (from flue gas) increased reproductive output, belowground biomass, and vegetative proliferation of new shoots in eelgrass. Pending more research, carbon sequestration through utilization of industrial flue gas may be found to be a viable option.

In another mitigation, CO2 is captured directly from its source and deposited in a natural or artificial storage facility. This can be done by solvent "scrubbing", adsorption, gas separating membranes, and cryogenic sequestration. Storing CO2 has already been used to increase oil mining productivity by sequestering CO2 to displace oil upwards (Verma, 2008). Problems with this mitigation include the current inefficiency of CO2 capture technology, the unavailability of machinery that is compatible with current CO2 producing factories, the potential for dangerous leaks or breakdowns, and the unknown geological effects could put a dangerous strain on underground faults (http://manhaz.cyf.gov.pl/manhaz/links/COAL_BASED_NEW_TECHNOLOGIES/e2003-30.pdf).

Adding a buffer directly into the ocean from calcium carbonate (limestone) rock by, for example, mining the Cliffs of Dover, has also been proposed (Royal Society, 2005). However, this method is not realistic because of insufficient CaCO3 resources, unknown ecological impact by carbonate materials, the high cost, and that alkaline material will not necessarily react with the surface waters and carbonic acid at the desired speed (Royal Society, 2005; House et al., 2007).

A mitigation that improves upon the slow reaction rate of carbonic acid is a process proposed by Harvard scientist called "engineered weathering." This process, which removes a hydrogen ion from carbonic acid (H2CO3), a weak acid, to form a stronger hydrochloric acid (HCl), can be done in a variety of ways. Hydrochloric acid can be electrolytically removed from purified seawater or brine, mined halite minerals, or directly from seawater. This HCl is then neutralized by reacting it with materials like mined silicate minerals. The resulting products can be placed into surface ocean water to increase its alkalinity. The idea behind this process is that it imitates natural silicate weathering, accelerated due to the use of HCl. This process causes atmospheric CO2 to be stored into the ocean without further acidifying it. All reactions, apart from the creation of HCl, are spontaneous (House et al., 2007). Although this process is feasible, a localized increase in pH can have unknown effects on local organisms. Efficient technology that can convert HCl directly from seawater is not yet available because untreated seawater can clog machinery. Electrolysis done with seawater has the possibility of producing halogenated organics as a byproduct—some forms can be the volatile, ozone depleting compounds (House et al., 2007).

The biggest obstacle to preventing damage from CO2 emissions is money and practicality. Any mitigation will most likely require a huge investment. The only environmentally safe prevention of ocean acidification is greatly reducing carbon emissions. However, it is not practical to hope that we can drastically cut our emissions in a short amount of time; therefore these other mitigations should continue to be explored. That does not mean that we should invest all of our resources on one such mitigation, to successfully prevent further damage from ocean acidification, all possible mitigations should be researched in addition to reducing carbon emissions.

Conclusion/Proposal

As discussed previously, the Alaska ocean ecosystems will be impacted by ocean acidification, including southeast Alaska pink salmon and the fishery there. We believe that both state and federal agencies should pursue any measures that reduce CO2 emissions, including potential impacts, the establishment of incentives for corporations to voluntarily reduce emissions, as well as pursuing legal means to force unwilling participants. For example, the Alaska Constitution states that fisheries should be kept sustainable under Article 8 clause 4. Some may argue that this applies to harvest guidelines only, however, we believe that this section could be interpreted to encompass the overall conservation of affected fisheries.

The federal government could potentially use the Endangered Species Act to force mitigation. For example, the endangered humpback whale (Megaptera novaenglia) is a baleen whale and therefore an opportunistic filter feeder; prey of small fish and zooplankton compose most of their diet. The most abundant zooplankton in southeast Alaska waters are copepods, euphausids, pteropods, and larvaceans (Sturdevant pers. comm., 2008). This demonstrates that ocean acidification threatens the survival of humpback whales (by way of ocean acidification impacts on prey), therefore, mitigations could be imposed by using the Environmental Species Act (ESA, 1973) to address ocean acidification causal factors.

It is clear to us that CO2 emissions must be reduced in any long-term plan. We feel a strategy similar to that proposed by researchers at Princeton University (carbon wedges) is appropriate. This proposal includes six broad strategies: energy efficiency, fuel shift, CO2 capture and storage, nuclear energy, renewable energy, and agriculture. These strategies are broken down into "wedges". One wedge is a 50 year plan that progressively reduces global carbon emissions over a 50 year period (http://www.princeton.edu/~cmi/research/ghgt/ghgt-7_poster_color_figures_7-1-04.pdf). By choosing seven of these wedges, this plan theoretically reduces our global CO2. One wedge, regardless of strategy, is equal to any other in amount of CO2 mitigation; therefore any 7 out of 14 can be chosen. The plan consists of technology we already use today, but using them on a global scale.

We recognize that the high dependence on carbon emitting energy is such that atmospheric levels will remain high for quite some time. Therefore, short-term mitigations should also be explored in addition to reducing CO2 emissions. Of all the mitigations we explored in this paper, we feel that underground sequestration is the most practical. Plans such as this one will only be effective if implemented on a global scale. We must protect the ocean and its ecosystems if the health of the ocean and fisheries, such as the pink salmon fishery in Alaska, are to remain viable.

References Cited