The Effect of Ocean Acidification and Rising Temperatures on Titlow Marine Preserve
Aidan S. Moore
Bellarmine Preparatory School
Abstract The ocean is both gradually becoming more acidic as carbon dioxide is being absorbed from the atmosphere, and increasing in temperature. This study aimed to find out the extent to which ocean acidification and rising temperatures had affected Titlow Marine Preserve. Water samples were taken from Titlow Marine Preserve, and analyzed for temperature, pH, and levels of dissolved CO2. It was found that over the past 15 years, the water in Titlow has become more acidic, and increased in temperature as dissolved CO2 levels decreased. Results are discussed in terms of implications for the health of Titlow Marine Preserve.
Introduction
Since the mid-18th century, the average pH of ocean water has fallen from 8.2 to 8.1, indicating about a 30% rise in acidity (Brewer and Barry, 2008). This is believed to be caused by an increase in carbon dioxide (CO2) in the atmosphere, which is then absorbed by the oceans. Globally, oceans absorb about 25-30% of carbon dioxide produced, after air and water have mixed near the surface (Bennet and NOAA, 2018). Through this process, more than 530 billion tons of CO2 have been removed from the atmosphere. This is beneficial to life on land, as the atmosphere contains fewer CO2 molecules, but is very dangerous for sea life. The reason for this danger is that when water (H2O) and CO2 combine, they form H2CO3, or Carbonic Acid. This acid then splits into HCO3- (Carbonate Ion) and H+ (Hydrogen Ion). In turn, the pH decreases, as the number of Hydrogen Ions determines the pH level.
The increase in acidity has been particularly detrimental to deep sea animals, animals with shells, and sea life already close to extinction due to other causes, such as coral reefs. More acidic water can cause shells to become thinner, and in extreme cases, even dissolve the shell completely (Busch et al., 2014). Deep sea animals are at risk because they have evolved to be in a very stable environment, and can easily become extinct when that environment is altered, much like what occurred when humans and other animals altered the environment of the Dodo bird. Coral Reefs are likely to become even more damaged, and start dissolving, as they are made of similar materials as the shells of many shelled creatures (Bennet and NOAA, 2018).
This problem is predicted to get worse. The ocean is expected to become even more acidic as time progresses, and the rate of change is expected to increase (Citation needed).
Temperature has also been globally rising. Atmospheric temperature increase has been well-documented, but a part of climate change often neglected is oceanic temperature rise. In the past one hundred years, the average atmospheric temperature has risen by .6o Celsius, in contrast to the increase of only .1o Celsius in average oceanic temperature. This small change might seem insignificant, but studies have shown that marine organisms are much more sensitive to small changes in temperature than land organisms (National Geographic, 2010).
Research showing proof of ocean acidification in parts of the Puget Sound and the Hood Canal has been performed, and showed that even in the deep waters of the Hood Canal, there was a decrease in pH. This study was conducted in the hope of finding a reason for a reduction in oyster larvae found by many oyster hatcheries throughout the Puget Sound and Pacific Northwest (Feely et al., 2008). Despite this, almost no research has been done on Titlow Marine Preserve or other areas in the South Puget Sound. With this study, I intend to fill that gap, and provide insight into this area.
Material and Method
Titlow Marine Preserve is a protected area in Tacoma, Washington, with about one mile of shoreline, managed by the Park District of Tacoma. All commercial fishing, and most recreational fishing, is prohibited by the Washington Department of Fishing and Wildlife, or WDFA. There is also a ban on taking invertebrates or fish, with the exception of salmon, caught with a lure from the shore, or non-motorized watercraft (WDFA, 1994). Water Samples were taken from here in an effort to determine the health of the marine preserve.
Procedure:
A bucket was used to collect a sample from the surface of the water at Titlow Marine Preserve, about 20-30 ft. from shore. From this bucket, individual testing bottles, all of which were airtight and watertight, were filled, and labeled with each measure to be collected (pH, temperature, and dissolved CO2). All bottles contained an very similar sample of water, as the bucket had been thoroughly mixed before sample bottles had been filled. Once back at the lab, the small bottles were analyzed.
One bottle was tested for pH using a pHep model probe manufactured by HANNA. A second bottle was tested for temperature with a temperature and salinity probe manufactured by YSI. Dissolved CO2 was tested using the following method:
Filled titration bottle with 20 mL of water sample.
Added two drops of Phenolphthalein. If sample turned red, no free CO2 was present. If colorless, went to step 3.
Filled Direct Reading Titrator with Carbon Dioxide Reagent B. Inserted Titrator in hole of titration tube cap.
While gently swirled, added reagent drop by drop until a faint pink color developed (must have persisted at least 30 seconds).
Read where plunger tip met Titrator scale. Recorded as ppm.
Results
Three main data points were collected to determine the effect of ocean acidification: Temperature, pH, and dissolved CO2. The following table shows these values over time at Titlow Marine Preserve.
Average temperature, pH, and dissolved CO2 over 2003-2017.
The average data for 2003 – early 2017 was not collected in this study, but by others using the same method.
Discussion
As shown previously, temperature has been increasing, and dissolved CO2 and pH have been decreasing. In the past 15 years, the South Puget Sound has become warmer, and more acidic, but the levels of dissolved CO2 have decreased.
Temperature, dissolved CO2, and pH over time, where 0 = 2003, and every increment is one year. Orange is temperature in celsius, green is pH, and blue is dissolved CO2. The lines are the predictions for the future using regression equations.
This might seem to be counterintuitive, but as the temperature of a fluid increases, its CO2 solubility decreases. This can be easily demonstrated by leaving a soda out until it warms up and becomes “flat.†As CO2 solubility decreases, the level of free CO2 would also decrease. This would not have an effect on pH because pH is based on products of the decomposition of carbonic acid, as described above.
These changes, if they continue, will have a negative impact on the marine life in Titlow Marine Preserve. For example, many types of shellfish currently living within Titlow, such as oysters and mussels, will face a reduction in mortality rates, as well as reproduction and fertility rates.
As is true in other parts of the Puget Sound, ocean acidification and rising temperatures have affected Titlow Marine Preserve negatively.
Limitations
Our samples were collected much closer to shore than is typical in published research. We collected from about 20 ft. from shore, whereas most are collected in open water. This could have affected the absolute value of any of our data; however, it would not have an effect on the change in each measure over time, assuming previous samples were collected using similar methods.
Future Directions
It’s important to continue collecting this data consistently to get a better idea of general trends, instead of isolated changes in these indicators of marine health. Also, I would advise collecting data from a greater distance to shore, as to compare to other parts of the Puget Sound, and other bodies of water all over the world. In this study, three important indicators were chosen; however there are several other important indicators of marine health, such as dissolved oxygen, salinity, and levels of nitrates and phosphates. I also recommend that future research investigating the health of Titlow Marine Preserve focus on other indicators to gain a more comprehensive picture of its health, as it may be healthy in some measures, and unhealthy in others.
References
Busch, D. Shallin, et al. “Shell Condition and Survival of Puget Sound Pteropods Are Impaired by Ocean Acidification Conditions.†PLOS Medicine, Public Library of Science, 27 Aug. 2014.
Bennett, Jennifer, and NOAA. “Ocean Acidification.†Smithsonian's National Museum of Natural History, 14 May 2018.
Brewer, Peter, and Barry, James. “Rising Acidity in the Ocean: The Other CO2 Problem.†Scientific American, 1 September 2008.
National Geographic. “Sea Temperature Rise.†National Geographic, 27 April 2010.
Feely, Richard. “Ocean Acidification in Pacific Northwest Waters.†Presented at Washington Sea Grant Symposium, 9 November 2011.
Fish and Wildlife, Washington Department of. “WAC 220-302-110†Washington Legislature, 1 July 1994.