1. Ocean pH on Development on the Shells of
Ocean pH on Development on the Shells of
Turbo fluctuosa Mexican Snails
Discussion
Statement of Problem
Materials and Methods
The investigative question is: To what intensity does ocean pH affect the size of shells in the saltwater Turbo fluctuosus?
The goal of this project was to compare the growth of shells in pre-industrial ocean pH, 8.2, to that of pH predicted in 2040, 8.0, and that of the predicted pH in the year 2100, 7.8.
Materials
Mexican Turbo Snails (18), five gallon tanks (3), 30 gallons of aquarium salt water, 10 gallons pure water, aquarium sand, large rocks with holes for hiding (3), Jebo 502 aquarium filters (3), Aqueon 10W aquarium heaters (3), digital aquarium thermometer (Celsius), digital scale (g), Omega One Super Veggie green seaweed, digital pH meter, digital caliper (mm), API saltwater calcium test, API saltwater ammonia test, hydrometer, distilled white vinegar (5% acetic acid), API Proper pH 8.2 buffer, small net.
Methods
Set up each aquarium with water, sand, rocks, a filter, and a heater.
The temperature was set to be between 20 and 28 degrees Celsius and the snails were slowly introduced. A drastic change in temperature, pH and environment could be harmful to their health.
The calcium levels were next measured to ensure that they were between 350 and 450 ppm. Then I measured the preliminary pH of all three tanks and manipulated them to reach 8.2, 8.0, and 7.8. To do this I added a full scoop of the 8.2 buffer to the first tank, a half scoop to the second tank, and nothing to the third.
Over time as the pH fluctuated I would add vinegar to the third tank gradually and more buffer to the first two tanks. Each day I would check that the tanks had a steady temperature and that they were all within a degree of each other.
Before the snails were introduced to the tanks, I labeled them all with a drop of nail polish and took preliminary measurements.
Once the environments were established I began measuring each snail each week. I measured them in millimeters by length and by width (see figure 1). I also weighed them in grams. For feeding I would rip up about ½ a sheet of seaweed into multiple pieces and stick it to the side of the tank, near the surface. I did this daily. About twice a week I measured calcium levels, temperature, and pH. If any numbers were off I would make the appropriate adjustments. Before I measured the snails each week, I scooped up poop and any excess uneaten seaweed on the side of the tank. Halfway through experimentation I did a full water change and cleaning. I also replaced the filters at that halfway mark.
The ideal pH for the Turbo fluctosa species is a pH between 8.1 and 8.4; and most previous experiments show best survival in a normal pH of 8.2. Therefore it would have been expected that the snails in the control tank would have thrived while the snails in the last tank would have not.
The hypothesis was, “the snails living in the environment of 8.2 pH will have the highest growth rates while the snails of the 8.0 pH will have lower growth rates and the snails of the 7.8 pH will have the lowest growth rates”. However, as both graph 1 and table 1 show, the tank with the pH of 8.2 had the slowest growth rate meaning that the hypothesis was not supported.
The variables that could have played a role in these results are numerous. The first idea is that simply, the pH meter could have been unreliable and been reporting incorrect ph. However, it was re-calibrated a few times throughout the project with a solution with a set pH.
Another variable could be that one of the snails, originally was far smaller and less active than the rest. From day 1, this specific snail, snail #5 was sitting at the bottom and hiding in the rocks while all the other snails were eating and climbing the walls. This snail was also the first to die, which could have meant that it carried some disease that spread throughout the population of six snails.
Another idea is that this snail could have caused death in the other snails simply by dying. The chemicals released after dying, such as ammonia, can be very harmful to the survival of other organisms. Snail #5 was monitored daily, so it was removed quickly after its death, hopefully minimizing chances of ammonia release. After its death, the ammonia levels were measured and looked to be minimal. However, to be safe, I followed with a water change to try and eliminate the harmful effects of one snail dying.
Introduction
Ocean pH is decreasing and becoming more acidic as anthropogenic CO2 is being absorbed by the ocean. Pre-industrial levels appear to be about 0.1 units higher than current levels, which translates to about 30% change in H+ ions over the past 200 years.
The pH is projected to decrease about 0.5 more units by 2100 if the rate of CO2 absorption continues on the same trend. It is believed that the ocean has absorbed about 48% of man-made CO2.
As this CO2 is absorbed, it bonds with H2O to form carbonic acid (H2CO3) and this carbonic acid releases H+ ions into the water, dropping ocean pH. The H+ ions bond to carbonate to form bicarbonate.
Shell-building marine animals use carbonate to build shells by combining a calcium ion with it to form calcium carbonate. However, they cannot use carbonate bonded to H+ ions in the shell building process. When they cannot properly build their shells, they become weaker and smaller and budget more energy to shell building rather than eating and reproduction.
The hypothesis was that the snails living in the environment of 8.2 pH would have the highest growth rates while the snails of the 8.0 pH would have lower growth rates and the snails of the 7.8 pH would have the lowest growth rates. .
Results
Figure 2: Average Growth Rate Over Time
Table 1: Average Growth Rate
Week
pH 8.2
pH 8.0
pH7.8
1 to 2
6.28
6.65
9.28
2 to 3
0.44
0.32
0.63
3 to 4
0.3
0.22
0.12
4 to 5
-0.03
-0.07
5 to 6
-1.22
0.07
0.02
1 to 6
0.17
1.39
1.33
Future Implications
To continue this research, I would run this experiment again. As of right now, with my research, I could make the conclusion that snails thrive in water with a pH of 8.0 and even in a pH of 7.8.
With this information it would be assumed that the acidification of the ocean in a controlled setting is beneficial in survival to the species Turbo fluctuosa. I would want to retest a new set of snails in order to verify my conclusion or in order to prove my conclusion wrong.
The snails in the first tank seemed to be smaller, weaker, and less active; the snails in the other two tanks were extremely active, strong, and large.
The snails in the second tank, pH of 8.0, were measured to have the quickest average growth rate of 1.39.
The snails in the third tank, pH 7.8, were measured to have the next quickest average growth rate of 1.33, and the snails in the first tank, pH 8.2, were measured to have the slowest average growth rate of 0.17.
Figure 1: PUT A CAPTION HERE. All photos taken by author.