AbstractPollution is a huge crisis that affects not just us humans but aquatic life as well. In this paper we will take a deeper look at how a small crustacean Daphnia magna, react to different chemicals. The aim of this experiment was to demonstrate how the different concentration levels of sodium phosphate and water affect D. magna’s heart rate using a compound microscope. The different concentrations of sodium phosphate used in our study were 0%, 2%, 4%, 6%, 8% and 10%. In this experiment our control was water. The concentrations of each solution were placed on a slide along with the living D. magna. The most concentrated solution of sodium phosphate, which was 10%, received the least amount of heart beats per minute compared to the 0% solution which was the least concentrated but showed the greatest amount of heart beats per minute. Our results indicated that sodium phosphate has a direct impact on the D. magna’s heart rate. As the percentage of sodium phosphate on the wet mount increased the amount of heartbeats per minute decreased for the D. magna. This suggested that a sodium phosphate has impacted D. magna’s heart rate in a negative way. This research is ideal because it is significant to keep in mind how humans are affecting other organisms by polluting their environment with sodium phosphate.IntroductionOur body is made of about 85% of water.Water is a very important nutrient that plays a key role in the survival of both aquatic life and humans. Aquatic pollution is regularly caused when toxic chemicals are thrown in clean water (Espinoza, 2014). These toxic substances are frequently presented as chemicals or wastes. Aquatic pollution not only affects fish, but our organs as well (Williams, 2017). Common organs affected by pollutants in the water are kidneys, the liver and fish gills. These may seem like minor things, but could have possible long term effects on reproduction, survival rate and population changes (Khoshnood, 2017). It is very important to stay hydrated when taking sodium phosphate because it can affect your kidney and lead to dehydration (Green, 1950). The independent variable in this study was sodium phosphate that was used in a variety of different concentrations including 0%, 2%, 4%, 6%, 8%, and 10%. Sodium phosphate is commonly used in foods as an additive. This was a clear compound when placed on the wet mount because it is a water-soluble molecule. Another important component of sodium phosphate is that it is often used to control pH and used as a laxative to help with bowel movement (Winstead, 2012). There are many chemicals that affect the organisms living in the aquatic life. People tend to forget that our world is one big circle and that when you kill one-chain of organisms that affects another group that is feeding off of them (Milne, 2017). Although there aren’t a great deal of studies showing the relation between D. magna and sodium phosphate there are other studies done showing similar relationships. A paper was done measuring whether the exposure of Cd or Zn affects the heart rate of crayfish Procambarus clarkia to copper (Giada et al., 2015). This paper looked at the two different metals pollutants to see how each one would affect the specimen in cross-acclimation. Overall the study showed that there was a direct effect between the two metal pollutants and cross acclimations on the crayfish’s heart rate. Another study was done involving D. magna, Cholorella vulgaris and Lemna gibba, which evaluated the toxicity of the global pollutant perfluerooctane sulfonate (PFOS).This study involved two trials, acute and a life cycle.The acute trial required 48-hour exposure to the pollutant and then immobility was measured by probing D. magna while looking at it under a microscope. The D. magna were not fed in this trial (Boudreu et al., 2002).The second trial was similar to the acute however it required the specimen to be evaluated for 21 one days along with it being fed. In conclusion it was found that D. magna was the most profound creature to the test. It showed higher toxicity values to the PFOS then that of plans (Boudreu et al., 2002). D. magna are very small animals that are sometimes described as water fleas. They are very small, about 1 mm long, and look like a little kidney bean. D. magna only have one large eye that is the dark spot on a microscope along with one little eye (Fig. 1). The typical lifespan of a D. magna depends mainly on its environmental conditions. D. magna play a key role in our environment by eating the dirty algae and making water cleaner and more efficient for our use (Coors et al., 2009). Another important job of D. magna is that they play an vital part in aquatic food web as prey to fishes and invertebrates (Hooper et al., 2008). An interesting study has been done looking at the behavior of D. magna and how they live in groups with no social hierarchy, but when it comes to resources that’s when competition plays a role. D. magna use their long antennae to move them upward through water at night then swim down through the water during the day to avoid predators. Some common similar species of D. magna that you may find are Daphnia pulex and Daphnia longispina. In a lot of organisms, like humans for instance, females live longer than males (Pietrzak et al., 2010), but that’s not the case for D. magna. D. magna males are said to live longer than females (Pietrzak et al., 2010). Humans try to live longer by maintaining a healthy diet, exercising regularly etc, that’s not exactly what D. magna males do. Instead they increase the amount of offspring produced. The male D. magna try to maximize their number of fertilized females, by getting in contact with as many females as they can (Pietrzak et al., 2010). Another method that male’s use is to stay really hidden in the water, so they are far away from any predators. In this experiment, it was hypothesized that as the increase in concentration of sodium phosphate the lower the heart rate of D. magna.This was demonstrated because the more variables added to the D. magna’s environment more likely the heart rate will decrease. Placing one D. magna in different percentages of sodium phosphate tested this experiment. The heartbeats were then calculated and recorded. We compared the final results to see if the D. magna was in danger to the sodium phosphate or not. Methods First two depression slides were used to identify the specimen with, so we could examine it more precisely. A pipette was used to obtain one D. magna. The stereomicroscope was placed on 4x with a total magnification of 400, with no cover slip. We then set the slides on the stage of the microscope and adjusted the focus. We recorded two minutes with a stopwatch; to let the D. Magna adjust to its new environment. After the two minutes we used the same stopwatch to count the heartbeats for fifteen seconds. All of these steps were then duplicated with the same D. magna. This was done for a total of six time and one being the control, which was the water. After the steps were all completed, we placed D. magna back in the recovery tank. The recovery tank is very important for D. magna because they were able to get back into a semi-normal environment. For the second part of this experiment, we obtained a new D. magna to compare the effects of the different concentration of sodium phosphate solutions (2%, 4%, 6%, 8%, 10%) on its heart rate. We created a wet mount and wiped off any excess material with a Kimwipe carefully not to harm the D. magna. If the Kimwipe touched the D. magna at all it would die immediately. D. magnas’ heartbeats were counted for fifteen seconds and then multiplied by four. This was done to obtain our beats per minute. We started with the lowest concentration of 0% and then slowly increased our way up to 2%, 4% and so on until we reached our goal of 10%. Although we were required to use the same D. magna for all the trials, unfortunately ours died at 6% and 8%. This was done for three trials. After we gathered all our data we then calculated all the means and standard deviations. The standard deviations values gave us accurate error bars to demonstrate the significance between the different trials. Results The results indicated that the increase in concentration of sodium phosphate had a significant effect on the D. magna s’ heart rate. We used the control, which were the water and the sodium phosphate to compare the means of four different trials. Table 1 demonstrates the effect of water on D. magna’s heart rate and Table 2 shows the same findings but with sodium phosphate. As you can see on Table 2 with the sodium phosphate, the maximum beats per minute were at 0% concentration and the lowest were found to be at 10%. We then gathered this data to make a line graph to display the control and sodium phosphate. The control stated consistent throughout the experiment compared to the sodium phosphate that fluctuated (Fig. 1.). The higher the concentration of the sodium phosphate the lower the heart rate dropped. The overlap between the error bars shows the significance difference between the trials. With that being said the 10% concentration did not show this result. Table 1: The effect of water on D. magna heart rateTrial:Heart rate (BPM)Heart rate (BPM)Heart rate (BPM)Heart rate (BPM)MeanStandard DeviationTrial 1Trial 2Trial 3Trial 4Drop 122026029225625729.46Drop 220426030024825339.51Drop 325630428026427621.16Drop 4 24026828424025821.78Drop 521225228826425431.74Drop 6 268244280N/a26418.33Table 2: The effect of sodium phosphate on D. magna heart rate% of Sodium Phosphate Heart rate (BPM) Heart rate (BPM) Heart rate (BPM) Heart rate (BPM) MeanStandard Deviation Trial1 Trial 2Trial 3Trial 40%26027628424426617.742%15612432856166115.84%132240336116206102.686%12020432421221583.748%10011230072146104.0310%721202604012397.07ConclusionThe hypothesis of this experiment was that as the concentration of sodium phosphate increased it lowered D. magna’s heart rate. Our data provides evidence that D. magna is affected by sodium phosphate in a negative way, as it lowered its heart rate. The only time that the sodium phosphate was significantly different from the control was at 10% concentration because the error bars do not overlap (Fig. 1.) Our hypothesis was mainly supported for the 10% concentration that showed the greatest decline in beats per minute. Overall, we can state that sodium phosphate affected our D. magna and needs to be regulated so this does not disturb other organisms in the environment. This is very important because D. magna play a key role in keeping our environment stable and clean (Ebert, 2005). When examining our results we can conclude that high concentration of sodium phosphate is harmful to D. magna. The sodium phosphate consists of salt, which can lead to dehydration. When D. magna was placed in the 10% concentration of sodium phosphate the salt could have caused it to dehydrate causing a decrease in the heartbeats per min. It’s interesting to see how various chemicals can affect the heart rate of D. magna. A study was done involving the effects of ethanol and caffeine on D. magna’s heart rate. The study indicated that the 0.1 % concentration of caffeine increased D. magna’s beats per minute, (Corotto et al., 2010) however comparing this to when D. magna was exposed to the 50mM of nicotine for 30 minutes (Vinson et al., 2010), which had the opposite effect and decreased the heart rate. These results were similar to our data and demonstrate a correlation between the different levels of concentrations on the rate of beats per minute for the D. magna.A possible future experiment could be for someone to filter the water the D. magna swim in and make sure to check the temperature of the water. By filtering the water they can eliminate the oil sands that are usually stored in ponds (Lari et al., 2017). A study was done on the oil sands processed dirty water (OSPW) determined that the effect of OSPW activity affects the D. magna’s respiratory and circulatory systems (Lari et al., 2017). Too much exposure to OSPW in the D. magna body decreased its hemoglobin. This data is important for future researches to read because it provides us with a variety of factors that affect D. magna’s heart rate besides the one we assessed in class. Other research that would be beneficial for D. magna would be to take a deeper look how the weight of D. magna is affected by the sodium phosphate. Another research topic of interest could be to examine the heart rate of D. magna in colder or dry seasons. Their population is said to decrease during those times (Jalal et al., 2013), so it would be interesting to examine what their heart rates are in colder climates compared to warmer. This could be a variable that might have played a role in our experiment done in class. We are not exactly sure.