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 in Prince William Sound
Team Visceral Mass
Cordova's ecosystem has a varied and diverse population that greatly depends on pink salmon and other species like it. During the summer, the waters teem with life, as creatures of all shapes and sizes reap the bounty of the warm, productive months. Different species of fishes, mammals and birds all crowd around schools of pink salmon to get their fill. These large organisms are also accompanied by their smaller counterparts, microorganisms. As sea lions and seals are subjected to falling pink salmon returns, being secondary consumers, they will immediately be negatively affected by their loss of a food source. Dog sharks and other species of salmon will also be directly affected by the loss of one of their main dietary supplements. Even the people who live here will lose an important aspect to their diets. As the size of individual pink salmon and the size of pink salmon schools decrease, the economic prosperity that they support in Cordova will also diminish.
Cordovans rely on pink salmon more than any other type of fish as the primary source of income. The summertime fisheries are the only thing keeping this town going, without the surplus of the summer the winter deficit would be too great to overcome. During the summer, fishermen work long hours to bring the salmon back to town where hundreds of people await their return, and their catch. With four different canneries and many more small businesses related to the fishing industry, Cordova's summer economy could not rely more heavily on the continued health of wild pink salmon stocks. After the short season many people leave Cordova. These seasonal workers miss the bleak winter and bleaker winter economy of Cordova. With few jobs to be had and too many people to have them, many people are left to coast on their summer earnings until the salmon return once again. If the size or strength of the pink salmon run became endangered, Cordova itself would be in danger. Without the pink salmon runs as we know them today, the survival of this town would not be guaranteed.
Interactions Leading to Decreased Ocean pH
The ocean's interaction with the atmosphere plays a key part in ocean acidification. Throughout the industrial revolution the ocean has acted as a sink for 30% of the world's anthropogenic carbon dioxide (CO2) (Raven, 2002). This interaction includes the transfer of CO2 between the ocean and the atmosphere as well as acidic precipitation into the oceans.
The transfer of carbon dioxide between the ocean surface layers and the atmosphere is the main driving force of acidification. This transfer takes place through two processes: the biological pump and the solubility pump. The biological pump is driven by the photosynthesis of marine algae and phytoplankton. Carbon dioxide is taken in and then converted and stored as plant biomass. When organisms die, they sink to the bottom and carbon is lost from the surface. The solubility pump encompasses carbon dioxide being absorbed by the water through physio-chemical processes. An important feedback loop in the solubility pump relates to the fact that solubility of carbon dioxide is an inverse function of seawater temperature. As average global temperature increases, the ability of the oceans to absorb carbon dioxide decreases. Although this causes decreased ocean acidification, it reduces the ocean's ability to buffer greenhouse gas accumulation in the atmosphere.
Research has shown that excess CO2 emissions can increase atmospheric temperatures, resulting several negative environmental consequences. The warmer temperatures of the planet work to melt the polar ice-caps and other forms of ice. As this ice melts, the albedo of the Earth is diminished, causing what is called the ice-albedo positive feedback loop. This in turn increases the speed at which global warming occurs as incoming solar radiation is absorbed rather than reflected. Fresh water from melting ice and other runoff tend to have a lower pH level than sea water. This will also cause an increase in acidity of the ocean water. Over the entirety of the ocean this is a meager change, however, where it is concentrated along coastlines and near the polar regions, the change can be large enough to have effects on the local ecosystem.
An additional consequence of warmer global temperatures is the release of iron particles from melting ice. Iron particles blown over glaciers and ice caps long ago will be released into the ocean more rapidly as. As shown through studies conducted by John Martin (1988), iron is a limiting factor for phytoplankton growth. When iron levels increase in an area phytoplankton will increase too. This will increase CO2 uptake through the biological pump (Martin, 1988). Because of the high CO2 absorption in cold waters, the input of iron, and low pH water input, the ocean around the ice caps will be the first areas to be hit hard by ocean acidification.
Acid rain is also a factor in ocean acidification. Rain is by nature slightly acidic from the formation of carbonic acid from atmospheric carbon dioxide. The extra acidity in acid rain comes mostly from sulfur oxides and nitrogen oxides. These pollutants combine with water to form strong acids such as sulfuric and nitric acid. Acid rain contributes little to ocean acidification on a global scale but in localized, shallow areas it can have an impact. In the Adirondack Mountains of New York, many lakes experience episodic acidification, brief periods where pH levels decrease due to heavy rain or snow melt. This can kill fish, insects, and other marine life (http://www.epa.gov/acidrain/effects/surface_water.html).
As ocean pH decreases, the amount of calcium carbonate in the world's oceans also decreases. Because coral is a calcium carbonate-based life form, a decrease in the availability of this compound would cause coral populations to decrease dramatically. Calcifying macroalgae are also critical to the ecology of coral reefs. In addition to being important food sources for sea urchins, parrot fish and some mollusks, calcifying macroalgae contribute sediment to reef systems and produce high-magnesium calcite that acts as cement that holds coral reefs together. Because high-magnesium calcite is more soluble than calcite or aragonite, calcifying macroalgae, and therefore the coral reefs they stabilize, are at an increased risk from ocean acidification (Guinotte, 2008).
The affects of coral depletion would disrupt the food web and could have very serious repercussions for almost all marine species. Coral reefs are an important habitat for an extensive variety of fish and other marine organisms. Without the protection and habitat provided by coral, many fishes will be more susceptible to predation and other dangers. Some species, such as the parrot fish which feeds on coral, would face a diminished source of food and would likely die of starvation if unable to find alternative food sources.
Meroplankton are also affected by ocean pH. Meroplankton are organisms that are planktonic for part of their life cycles, usually their larval or egg stages. They are free floating until they develop into nekton or benthic organisms. Ocean acidification could have a damaging effect on meroplankton and disrupt the life cycle of many marine organisms. This could affect most fish including flatfish and cod, which have free floating eggs, and crustaceans such as crabs and barnacles, which have planktonic larval forms, as well as other organisms. Crustacean larva in particular could be affected because their complex chitinous skeletons may not develop correctly when exposed to increased levels of CO2. In addition, a highly acidic environment could break down the membranes of some eggs. A study conducted by Haruko Kurihara at Nagasaki University (2007) artificially fertilized Pacific Oyster (Crassotrea gigas) eggs in seawater acidified to pH 7.4. Only 5% of the eggs developed into normal larvae (Figure 1) as compared with 68% in the control group (Kurihara, 2007).
Another negative impact of the gradual lowering of pH throughout the oceans is "acidosis." Acidosis is a physiologic effect that occurs when carbonic acid builds up in the body fluids of marine organisms, the effects of which can be devastating. It can lead to lowered immune response, metabolic decline, and reproductive or respiratory difficulties, leading to decreased fish populations and quality. Acidosis is important to note as it directly affects larger organisms because it pertains to the organism's ability to maintain homeostasis.
Most Critical Challenge
Thecosomata are a calcareous zooplankton. This makes them subject to the effects of a rising carbonate compensation depth (CCD). As the CCD rises, the levels of carbonate in the surface layers will drop to a level of undersaturation. At this point the shells of Thecosomata will be vulnerable to dissolution. One experiment showed Thecosomata shell dissolution within 48 hours of being subjected to the carbonate undersaturation levels projected for the year 2100 in the Southern Ocean surface waters under the IS92a emissions scenario (Orr, 2005).
The first step to bringing about change to reduce the causes of ocean acidification is to raise awareness of the situation. In Cordova's case, the fishing population is most impacted because the industry is directly related to the health of the ocean ecosystem. Our team surveyed local fisherman in order to find the best way to impact them. The results showed that the most effective way to reach out to fishermen is through trade magazines and local agencies such as the Alaska Department of Fish & Game and Cordova District Fishermen United. We have concluded that these agencies have the potential to effectively distribute informational media to members of the commercial fishing industry, who would then have the resources and knowledge to invent and advocate various solutions and conduct and support further research.
Cordovan students, working with the school board, teachers and community members, have created an effective way to test proposed ways to deal with Cordova's energy supply and correlating carbon footprint. With a facility dedicated to energy conservation research, Cordova has become one of the more economically responsible communities in the Prince William Sound. One way in which people and businesses around the world could try to reduce carbon dioxide emissions, thereby slowing down the effects ocean acidification, would be to implement a cap-and-trade system. Cap-and-trade is an emission trading system in which entities that produce carbon dioxide can work to counteract their carbon footprint. Companies can buy a certain amount of credits not exceeding a cap for the amount of carbon dioxide they give off. The money that is received for the emissions is then invested into some sort of venture that will counteract the carbon dioxide emissions, such as planting trees. One problem that can be seen with this system at present is that it is purely voluntary and that there is no widely accepted regulatory committee.
Along with increased public awareness and education about ocean acidification, more research is needed to learn more about the effects of ocean acidification on marine ecosystems and ways to mitigate it. This necessitates increased funds and a larger workforce. Continued investigation into ocean acidification is extremely important to understanding how to deal with global and regional climate change, ocean acidification, and the adverse effects on marine ecosystems.
The United States government has acknowledged the issue of ocean acidification by introducing House Bill 4174 or the Federal Ocean Acidification Research and Monitoring Act of 2008, (FOARAM Act). This bill establishes an ocean acidification research and monitoring plan within the National Oceanic and Atmospheric Administration (NOAA). It is sponsored by Rep. Thomas Allen of Maine. The bill was introduced in November 14, 2007 and was passed in the House of Representatives on July 9, 2008. The act defines ocean acidification as the decrease in pH of the Earth's oceans and changes in ocean chemistry caused by chemical inputs from the atmosphere, including carbon dioxide. It gives $96 million over four years to NOAA and the National Science Foundation, (NSF) to monitor and conduct research on the processes and consequences of ocean acidification. It will also research adaptation strategies for effectively conserving marine ecosystems as they cope with ocean acidification and make an assessment of socioeconomic impacts of increased ocean acidification. It also provides merit-based grants for research on the ecological and socioeconomic effects of ocean acidification. The bill will also ensure that National Aeronautics and Space Administration's (NASA) space-based monitoring assets are used in as productive a manner as possible for monitoring ocean acidification and it's impacts. Most importantly, the bill recognizes ocean acidification as a significant threat to the marine ecosystem, the national economy, and that gaps in funding, coordination, and outreach have impeded national progress in addressing ocean acidification. The bill is currently being reviewed in the Senate. House Bill 4174 will help the United States react to ocean acidification; it needs to be passed as smoothly and expediently as possible (http://www.govtrack.us/congress/bill.xpd?bill=h110-4174).
- Environmental Protection Agency: "Effects of Acid Rain—Surface Waters and Aquatic Animals." 8 June 2007. United States. http://www.epa.gov/acidrain/effects/surface_water.html Accessed 5 November 2008.
- Guinotte, J.M., and V.J. Fabry. 2008. "Ocean Acidification and Its Potential Effects on Marine Ecosystems." Annals of the New York Academy of Sciences. The Year in Ecology and Conservation Biology 2008 1134(1):320–42.
- Govtrack.Us. H.R. 4174—110th Congress (2007): Federal Ocean Acidification Research and Monitoring Act of 2008. 2008. GovTrack.us (database of federal legislation) http://www.govtrack.us/congress/bill.xpd?bill=h110-4174 Accessed 26 November 2008.
- Kurihara, H., S. Kato, and A. Ishimatsu. 2007. "Effects of Increased Seawater CO2 on Early Development of the Oyster Crassostrea Gigas." Aquatic Biology 1:91–98.
- Martin, J.H. and S.E. Fitzwater. 1988. Iron deficiency limits phytoplankton growth in the north-east Pacific subarctic. Nature 331:341–343.
- Orr, J.C., et al. 2005. "Anthropogenic Ocean Acidification over the Twenty-First Century and Its Impact on Calcifying Organisms." Nature 437:681–86.
- Raven, J.A., and P.G. Falkowski. 2002. "Oceanic sinks for atmospheric CO2." Plant, Cell & Environment 22(6):741–55. Wiley InterScience. 1 March 2002. http://www3.interscience.wiley.com/journal/119087640/abstract Accessed 6 November 2008.