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.

Ocean Acidification

Authors

Roberta M. Charles
DeAnne C. Lincoln
Michelle A. Simon

Team Wolves

White Mountain High School
PO Box 69
White Mountain, Alaska 99784

Abstract

Ocean acidification is the decrease of the seawater pH level. Ocean acidification effects the chemistry and biology of the oceans. Several things can be directly and indirectly affected. Our community is located near the Bering Sea. The Bering Sea could be affected by ocean acidification in many ways such as the dissolving of marine calcifier's shells. Some of these organisms, such as the pteropod, are at the base of the food web. The dying out of the pteropods could greatly affect the entire food web of the Bering Sea. Alaska's subsistence lifestyle and the state's economy could be greatly effected if we don't do anything to decrease our carbon emissions. Some helpful solutions to this problem could be: solar power, wind power, hydropower, and taking steps such as carpooling and finding ways to cut back our carbon dioxide emissions.

Disucssion

The oceans on earth take up about 70% of the earth's surface. Approximately 30–50% of carbon dioxide emissions in the atmosphere are being absorbed by the oceans (www.afsc.noaa.gov/HEPR/docs/ocean_acidification_%20research_%20plan.pdf). The oceans will continue to absorb carbon dioxide because they have a large capacity to absorb it. It is estimated that nearly 500 million tons of this gas has been taken up in the oceans since the start of the industrial revolution (McFarling 2006). Humans have been clearing and burning vegetation, and burning fossil fuels, such as coal, oil, and natural gas, which release carbon dioxide and other green house gasses (www.science.org.au/nova/106/106key.htm). Greenhouse gases are carbon dioxide, water vapor, nitrous oxide and ozone. Carbonic acid is created when carbon dioxide is dissolved in the oceans and then the water releases hydrogen ions lowering the pH level. When the oceans have more carbon dioxide in the water, the water is more acidic and therefore have a lower pH level (Figure 1) (www.wunderground.com/climate/acidoceans.asp). Places wherever concentrations are the lowest, carbon dioxide travels through it. When the concentrations are high in the atmosphere the carbon dioxide goes into the oceans (McFarling 2006). The pH level before the industrial revolution was ranging from 8.0 to 8.3 and now it ranges from 7.9 to 8.2 (www.wunderground.com/climate/acidoceans.asp). The pH level has dropped about 0.1 unit since around 1759. The pH level of the oceans could drop about a total of 0.5 units by the end of this century (www.science.org.au/nova/106/106key.htm). The acidity in the water dissolves the calcium carbonate (Sample 2008). Calcium carbonate, a building block is used by many marine organisms to grow their skeletons and create coral reef structures.

With a low level of calcium carbonate in the water, coccolithophores (Figure 2a), single celled algae, cannot form tiny plates or scales on their exterior because they use calcite a form of calcium carbonate to form them. Coccolithophores produce a large amount of oxygen and are a food source for many marine animals. With high levels of ocean acidification in the oceans it could be damaging corals. Coral reefs are homes to fish, shrimps, anemones, microscopic creatures, and many other organisms (Figure 2b). About 25% of the world's marine fish live in or around coral reefs (www.dogoodclub.org/tag/oceans). Ocean acidification will likely impact the ability of corals and mollusks to make shells and skeletons from calcium carbonate. We get some ingredients for medicine from coral reefs. There is a medicine that uses coral ingredients that treats cancer (www.dogoodclub.org/tag/oceans). Coral reefs grow in shallow and mostly warm waters in the oceans. Corals help stop shorelines from being slowly eroded. Corals are constructed with skeletons that are mainly made of calcite. Corals that are already existing are being weakened and this could cause coral bleaching. The corals shells will dissolve. With calcite being reduced it can limit formation of new corals. Corals in tropical and subtropical waters with increasing acidity will grow more slowly. Coral reef building is expected to decrease in the future because of low calcite rates. If the corals are becoming more fragile, the corals can not withstand the pounding waves and will break. About one-third of the coral reefs in the world have already been damaged or destroyed in the past century.

Other organisms such as plankton (Figure 2c) and tiny marine snails have a hard time forming their body parts made of calcite or use calcite to form their body parts. Also crabs, mussels (Figures 2d and 2e) and oysters weaken with increasing ocean acidification. With species that are being affected by the reduced calcium, other fish and marine mammal species can be affected because of the food web. The animals that grow in the shells and skeletons that use calcium to form, grows slowly within the shells.

The ocean can be toxic for the eggs and larvae (Figure 2f) of some species and will not hatch. Animals, such as fast-swimming squid (Figure 2g), require lots of oxygen to breath and therefore tend to suffer from breathing in carbon dioxide (McFarling 2006). Also goose barnacles (Figure 2h), are likely to decline dramatically as acidification levels increase (Sample 2008).

A study around southeast Australia of sea urchins indicates reduced swimming speed and sperm motility of sea urchins (Figure 2i). The researchers have found out that the sperm travels much more slowly in waters with a low pH, and the sperm began failing to meet the eggs (www.oceanacidification.wordpress.com/2008/09/23/rising-ocean-acidity-slows-marine-fertilisation/).

The Bering Sea is the stretch of water extending from Russia to Alaska (Figure 3). It is rich in wildlife and is considered one of the most productive marine environments. It provides home to millions of fish, birds, invertebrates, and marine mammals. Fish and invertebrate species important to the Bering Sea include, walleye pollock, salmon (including coho, sockeye, chum, pink and chinook), cod, pacific halibut, herring, crabs, and shrimp (http://www.defyingoceansend.org/bering_sea.asp). These organisms are an important food and income source for many Alaskan residents. The Bering Sea fisheries are also important to the United States and the rest of the world. They provide over half of the fish for our nation's markets (http://www.defyingoceansend.org/bering_sea.asp). Also many of the fish caught in Alaska waters get sent out to countries all over the world. About one-third of the fish caught commercially worldwide, come from Alaska (Hance 2008). Millions of fish, birds, marine mammals, invertebrates, and even people depend on the resources supplied by the Bering Sea. However, the Bering Sea is going through many changes and is faced with difficulty. The main threats to the Bering Sea include, fisheries mismanagement, pollution, and climate change. Another threat, and the subject of this paper, is ocean acidification. Ocean acidification has just recently been considered, and much research has yet to be done.

When fossil fuels are burned, carbon dioxide enters into the atmosphere. Carbon dioxide has the ability to leave the atmosphere and dissolve into the oceans. The uptake of carbon dioxide into the oceans has been going on for thousands of years. But since the industrial revolution, the oceans have been soaking up massive amounts of carbon dioxide, more than it can sustain. Approximately 30-50% of the global carbon dioxide emissions are absorbed by the world's oceans (Hawks 2007). The dissolved carbon dioxide forms carbonic acid (Figure 4). As the carbonic acid breaks up in seawater, it produces hydrogen ions and bicarbonate (Figure 5). The hydrogen ions then have the capability to bind with carbonate to produce bicarbonate (Figure 6). Acidity is the measure of hydrogen ion concentration in solution. Resulting from the increase of hydrogen ions, the oceans will become more acidic. The world's oceans have an average pH of about 8.1 to 8.2, which is slightly alkaline (Sheldon 2008). The pH of the oceans is predicted to drop by 0.3–0.5 units (Sheldon 2008). Even though this may not seem like it would have a great affect on the oceans, it could cause significant change to the chemistry and biology of the oceans.

The Bering Sea will be one of the first places to be affected by ocean acidification. Throughout the ocean's surface water there is a rich layer of calcium carbonate. The calcium carbonate layer is deeper in warm waters and it is closer to the surface in cold waters. Because calcium carbonate is more unstable in cold waters, the polar oceans will be affected first. Ocean acidification will lower the amount of calcium carbonate in the oceans. Because more carbonate is being used to produce bicarbonate, there will be less carbonate to be used to produce calcium carbonate, which is a crucial building block for the shells of many organisms. Cold waters also have a greater capacity for holding carbon dioxide because cold water has the ability to hold more dissolved gas than warmer water (Devic 2007). Because the Bering Sea is very cold, more carbon dioxide will be able to dissolve into it, and it will result in more acidic water than compared to warmer waters.

Ocean acidification could likely affect marine calcifiers. Marine calcifiers such as corals, pteropods, mollusks and other shellfish depend on carbonate to construct their calcium carbonate shells (http://www.akmarine.org/our-work/address-climate-change/ocean-acidification). The combination of increased acidity and decreased amount of carbonate ions, could cause many organisms to face difficulty. With less amounts of carbonate to be used to produce calcium carbonate, there could be less calcium carbonate for the use of organisms. A lower pH could cause their support structures to dissolve and they could be left to die. While these creatures are beginning to grow, they might not be able to construct their shells in the first place because the acidic water will dissolve away the developing shell.

The pteropod, a free-swimming mollusk, has a calcium carbonate shell (Feely Fabry and Guinotte) (Figure 7). This creature is eaten by a variety of organisms, and it is at the base of the food web. The acidic ocean could dissolve away the pteropod's shell and leave it susceptible to death. When the pteropods die out, the ocean's entire food web could be affected (Sheldon 2008). Tiny creatures such as pteropods are a very important source of food for fish such as juvenile salmon. When the pteropods die from having dissolved shells, salmon will then have a lower food supply and be left to starve. Our community is located next to a river that is abundant in salmon. Many people not only enjoy catching and drying fish, but they are also very dependent on the fish they catch because buying food these days could be very expensive. If the fish's food supply is cut short, we could have less fish to catch and eat and many people could go hungry. Pteropods are also eaten by krill, mackerel, pollock, herring and cod (Feely Fabry and Guinotte).

Organisms such as the king and snow crabs use calcite to harden their exoskeletons (Persselin). The crabs of the Bering Sea are highly commercially valuable. Many people also harvest crab for subsistence. The lower pH of the oceans will negatively affect the survival and growth of the crab larvae. The lower acidity will dissolve away the crab's exoskeleton. That could cause numerous deaths among the crab. Research has shown that fish that are exposed to lower pH values have decreased respiration rates, changes in blood chemistry and changes in enzymatic activity (Cullenbug and Baker 2008).

The communities of cold water corals in the Aleutian Islands are an important habitat to many fish. The corals build their skeletons out of calcium carbonate (Sean Markey 2006). A lower pH level could slow down cacification of the corals and they may build weaker skeletons (Sean Markey 2006).

If we let the carbon uptake of the oceans keep going at the same rate as it is today, the oceans will be more corrosive to calcifying organisms and the food web of the entire ocean could be left at risk. Alaska's subsistence lifestyle and the state's economy could be indirectly affected by ocean acidification.

Many bad things have been done to the ocean, but things can be done to help reduce the ocean acidity. The following paragraph will give some helpful solutions to reduce carbon dioxide emissions. The only way to stop ocean acidification is to lower the amount of carbon dioxide being absorbed by the oceans. Here are some useful ways to help stop ocean acidity.

One way is to use cleaner energy such as using solar power, wind power, and hydropower, which will reduce greenhouse gas emissions. Wind turbines convert wind energy into electricity. They do this by the wind turning the blades that spin a shaft, which connects to a generator that makes electricity (Figure 8) (http:www.weatherinstruments.us/anemometer-636.jpg) (http://www.alliantenergykids.com/wcm/groups/wcm_internet/@int/@aekids/documents/contentpage/022818.pdf). The electricity is sent to a substation and is then later distributed to other places in the community. They have also installed a wind monitor to determine if they were able to have enough wind to install a wind power that would generate electricity. Figure 9 shows a similar wind monitor, as the one they used in Nome, Alaska (http://pics2.city-data.com/w4/wnd718.png). In Nome a wind farm had recently been installed. The wind farm will reduce the community's dependence on diesel-powered electricity. The Dutch have used wind for hundreds of years to power pumps and other machinery. Now we can use this free renewable source to produce electricity using similar equipment. The wind farm in Nome consists of roughly one dozen turbines. Nome's main goal was to save money at the time when fuel oil prices were skyrocketing. The ocean will receive a side benefit as carbon dioxide emissions in this coastal town are reduced with each breath of wind. Other communities should follow this lead and utilize this renewable energy source.

Not everyone lives in a windy place, but the sun shines on everyone. Another way to get those electrons flowing is through the use of solar panels. Thanks to Einstein, we learned about the photoelectric effect. Solar panels use this effect. Photons from the sun knock electrons off of metal plates in the solar panels, these electrons flow through wires and become useful electricity. Also in Nome there has been solar panels installed at the Bering Straits Native Corporation (Figure 10) (http://dwb.adn.com/news/alaska/rural/story/9493939p-9404794c.html).

However, there are many ways to stop ocean acidification. John Martin had an idea of fertilizing the ocean with iron. At the time he was only half joking, yet others took him seriously. He had discovered that if he were to fertilize the ocean with iron in the right location it would activate plankton blooms the size of a small city. Then the billions of cells produced might take in enough heat-trapping carbon dioxide to cool the earth's warming atmosphere. Early experiments recommended that every ton of iron added to the ocean would remove 30,000 to 110,000 tons of carbon from the air (http://www.whoi.edu/oceanus/viewArticle.do?id=34167).

Another solution is to store carbon dioxide in giant bags on the ocean floor in water at least 4,000 meters deep. There the pressure is about 5,880 pounds per square inch. The temperature is about 2°C (http://science.cmax.in/?p=79). The pressure of the sea water would keep the carbon dioxide in liquid form and the bags would prevent ocean currents from transporting the carbon dioxide to other locations. The stored carbon dioxide could some day be useful as humans create new technologies.

For hundreds of years humans have been emitting carbon dioxide into the atmosphere and a lot of damage has been done. If we take the necessary steps to lower our carbon emissions we can help lower the ocean acidity of the ocean and prevent the irreversible damage that will be done.

Figures

graph of ocean carbon dioxide versus ocean pH

Figure 1. The graph shows the rise in carbon dioxide in the waters around the Canary Islands, Hawaii, and Bermuda and the graph on the right shows the pH level decreasing.


coccolithophores

Figure 2a. Coccolithophores

coral reefs and fish

Figure 2b. Coral reefs and fish

plankton

Figure 2c. Plankton

crab

Figure 2d. Crab

mussels

Figure 2e. Mussels

fish eggs

Figure 2f. Fish eggs

squid

Figure 2g. Squid

goose barnacles

Figure 2h. Goose barnacles

sea urchin

Figure 2i. Sea urchins


Bering Sea map

Figure 3. This shows the area that the Bering Sea covers.


Figure 4.
CO2 + H2O ←→ H2CO3
This shows that when carbon dioxide is dissolved into water, it produces carbonic acid.


Figure 5.
H2CO3 ←→ H+ + HCO3-
This shows that carbonic acid has the ability to form hydrogen atoms and bicarbonate.


Figure 6.
H+ + CO32- ←→ HCO3-
This shows that hydrogen atoms have the ability to interact with carbonate to produce bicarbonate.


pteropod

Figure 7. Pteropod.


wind turbine

Figure 8. This show part of a winde turbine.


anemometer

Figure 9. This is an anemometer.


solar panels on a building in Nome, Alaska

Figure 10. This is a picture of the solar panels installed in Nome, Alaska.


References