Desal Prize, High School Project
After analyzing the data and observations, it can be concluded that Mozambique Tilapia can successfully survive in a brackish environment with additional chemicals. More specifically, they can survive 100% of UNT’s brine solution. However, it should be noted that the tilapia acclimate better in a gradual manner. Their ability to osmoregulate the chemicals help the tilapia survive, but all other aspects should be attended to before adding the chemicals. The tilapia had signs of low dissolved oxygen and the data supported the observations, and over time we believe the fish would not be able to handle multiple stress factors. The importance of having a biofilter (aquaculture) or implementing an aquaponics is demonstrated in the low DO level. Since the ammonium was not able to be converted to nitrites and then nitrates, the fish waste accumulated and clogged the tubing and could be the source of low DO. In addition, the tank size to fish ratio could have been a factor as well. We strongly recommend that the plants are acclimated to the concentrations at the same time as the fish. However they should be grown prior to purchasing fish and have surpassed juvenile stage. The pH at the beginning proved to show that since the tilapia were still in it’s immature stages that they were gonna be put into additional stress. However, with the chemicals added into the system, it provided the pH to increase due to both the addition of neutral salts and to the released ions from osmoregulation and the chloride cells of the tilapia. The data also suggest there is no relationship between the brine concentrations and temperature, dissolved oxygen, and electrical conductivity. Both the data from the experiment tank and the large tank experienced a decrease in dissolved oxygen. The assumption that the brine concentrations caused this is negligible because the large tank wasn’t exposed to chemicals until phase 3, which is day 24, but still experienced a drop in DO levels. The chemicals also had a minimal effect on electrical conductivity. Before any chemicals were added to the large fish tank, electrical conductivity decreased over time. Even though the experimental tank had brine concentrations added, it still followed the same decrease in EC over time. The EC had a range between 5111-11439 mg/L, which is not close to the estimated salinity, which would’ve been 15000 mg/L. This data suggests that EC was decreased by other factors which we believe to be temperature and the addition of water. As temperatures decreases, so does EC. While we installed heaters into both the BT and the experimental tank, the recorded water temperature had a ±10 degrees difference from the actual heater setting. We believe this could have possibly affected EC, but only in a minuscule way. The drop in EC was caused by our addition of fresh water into the system as water was evaporated . (Fresh water has a lower conductivity.)